AeroElectric-Archive.digest.vol-ee
March 22, 2005 - March 31, 2005
>Just my 2 cents.
>Cheers,
>Stein.
Cheers here too
Rumen
BTW I love the machined pins I got from you.
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: DC Power Systems Dynamics - Breakers |
>
>You need to read Bobs white paper and consider your comments again as you
>have confused something. Or I have not made myself clear enough.
>
>When Bob says its 7 and the simple math using his numbers comes out 70 its
>a simple math error but that affects his assumptions in other math.
Paul,
I'll suggest that the value was not an assumption but a math error.
The real assumption was that the breaker should be assigned a resistance
based on a specified maximum voltage drop. Better that the real resistance
of the breaker be measured. I did this and found it to be 38 milliohms.
This tracks with practical reality. I would expect the specified voltage
drop and associated resistance value to be end-of-life values and
it's not surprising to find this number to be perhaps twice the factory
new number. It also pushes total of connection and crimp resistances
into a more reasonable realm and eliminates the need to evaluate the
effects of "better wiring" thus eliminating one whole paragraph from
the paper.
>One NEVER uses assumptions and Always uses spec values . . .
Not all assumptions (or extrapolations) are evil if they
rest on reasonable foundation . . .
> . . . and worst case design
>to be sure the design will always meet the design intent with ANY
>conbination of parts. The subject test simply does not do this.
I disagree here and permit me to illustrate the foundation.
If I design and airplane, should the design goal be to
allow assembly with Grade 5 hardware store bolts or is it
more practical and safer to SPECIFY Grade 8 fasteners?
If I kit up a digital voltmeter with a goal of displaying
bus volts to 1% accuracy, can I use 5% tolerance parts in
the voltage dividers?
System performance is often predicated on utilization
of specific parts. Not a new concept in aviation . . . but while
we're free to choose from a wider variation of components in
the OBAM community, I'll suggest that the choices are never
without boundaries.
If I understand your suggestion as to "combinations of parts"
do I deduce correctly that the major variable is the kind
of circuit breaker used? Keep in mind that the test was NOT
an evaluation of any particular part selection but a simple
illustration of a methodology for demonstrating the effects
of parts, wire, connections and battery impedance on the
performance of a system. It's just a collection of simple
tools applicable to investigation of specific installations
on airplanes or any other test setup.
I'll readily admit to not having considered that someone
might purchase a totally unknown quality breaker and combine
it with the crowbar ov module. That didn't occur to me because
we were supplying recommended (but not SPECIFIED) breakers.
I'll see to it that the installation instructions for this
product are modified to SPECIFY recommended parts so as to
prevent a breaker pulled off a garden tractor from finding
its way into somebody's alternator system. In the
mean time, would it be a useful exercise to identify and
caution against breakers with extra-ordinarily long operating
times? I'd be pleased to test/confirm the suitability or
non-suitability of any breaker you suggest.
With respect to exceeding specified limits on the operation
of breakers recommended for this application, I've captured
information off an Eaton/Mechanical Products data sheet
which I've published on my website at:
http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
This breaker is used by the thousands at RAC and is part of
the samples I'm gathering to evaluate in the experiment.
I think the commercial version of this breaker is the one
sold by B&C as MP Model 4200 as opposed to the mil-spec
parts in the bins at RAC.
Sections of the data sheet have been excerpted and added
to the Report which has been updated to Rev -C-
http://www.aeroelectric.com/articles/Crowbar_OV_Protection/DC_Power_System_Dynamics_C.pdf
This revision corrects the math errors previously identified,
adds the data extracted from the breaker specifications
and offers a foundation for what may have been dubbed
assumptions. I'll suggest they are valid interpretations
of the specifications or rational extrapolations from that
data.
Still working on Rev -D-
>The design also overstresses parts under worst case design rules.
Not sure which part you're referring to here: For the SCR?
Yes, the MCR-69 is operating at the ragged edge for short
wires (and way out the roof for zero length wires) but OV
protection is a rare, generally isolated event. Further,
when the installation instructions are modified to recommend
care in selection the companion breaker, we'll also set up
guidelines for minimum total wire length so as to make sure
no-one installs the module right at the breaker.
SCR's used in the L-series controllers are fatter and
much more robust than the MCR-69 and it's TO-220 cousins.
We'll wear out breakers before we push one of those
puppies off the wagon.
If you're referring to the breaker, I'll rely on data
extracted from manufacturer's published literature for
the breaker SPECIFIED in this experiment and for others
to be specified in the installation instructions for a
crowbar OV protected system.
> >
> >> Bob then goes on with "out of the thin air conclusions" :-) that are not
> >> based on any real facts and in fact the available data (again from
> >> various data sheets do not support the conclusions.
> >>
> >> For example:
> >>
> >> From the report:
> >>
> >> ". Battery delta E for 135A load is about 2.4 volts for an internal
> >> impedance of about 17 milliohms.
> >>
> >> About what one would expect from a two year old battery that started out
> >> in the 8 to 10 milliohm."
> >>>
> >> The Panasonic data sheet says approximately 12 milliohm. Approximately is
> >> hardly an engineering term but it's also not 8-10 as Bob suggests for a
> >> new battery.
Approximately is indeed an engineering term. It's often used to
make sure the listener/reader is not lulled into some sense of accuracy
in a value where accuracy is either suspect or the variable in
question is very loose. For the convenience of our readers,
I've posted the Panasonic data sheet at:
http://www.aeroelectric.com/Mfgr_Data/Batteries/Panasonic_1217.pdf
On several occasions I've measured the source impedance of new
1217 batteries and most of the time they're better than 12 millohms
but why are we quibbling about this? The experiment measured and
stated the source impedance as the battery as it was. We further
extrapolated what the performance would be with ANY other battery having
a lower impedance and discovered that battery impedance doesn't
drive the overall performance. If the soggy 17 milliohm
device were replaced with the gold plated 1 millohm device, overall
performance is affected only slightly. The the driving variables are
wiring,
breaker and switch impedances.
> >> When I do the math I get 70 NOT 7 milliohms on the last line (for the CB)
> >> which conflicts with the first line of 62 milliohms total loop
> >> resistance. From this and my earlier comments the entire technical
> analysis is
> >> clearly faulty.
Error noted and corrected. But since the mis-calculated value
was only part of the total, MEASURED loop impedance, the effect
of correcting the error only shifted more resistance to the breaker
and away from terminals and connections. Net change to the conclusions was
zero. How does this make the entire analysis faulty?
> >> I simply do not understand the massive resistance to make an improvement
> >> (even the addition of 1/4 ohm is resisted).
I don't know that there IS "massive" resistance to any changes.
I'm wanting to understand their value and effect. Please don't
interpret a lack of enthusiasm for improvements to be a reluctance
to change. I've sold hundreds of these systems. B&C has sold
thousands of these systems. It's a really good thing to upgrade
the performance of your products when ever it can be shown to
add value. On the other side, if the improvement is made to
correct some shortcoming in the design or recommendations for
installation, we need to partition that off for examination too.
Do I owe thousands of customers a modified instruction sheet?
Are systems in place for nearly a decade at risk? Should
we be recalling product based on discovery of a real screw-up?
When 400-700A crowbar currents are cited as a risk to the users
of this philosophy it gets my attention. It argues with
what I believed was a long held and reasonably solid understanding.
I hope it's clear that I'm intently interested in examining that
understanding to validate, modify or discard as evaluation of the
investigation directs.
This is another reason for carrying on this conversation out
in the open. It has nothing to do with who invented what or
who recommends what . . . our readers need to have confidence
in everyone's recommendations. That cannot be enhanced by deliberating
behind closed doors.
Bob . . .
________________________________________________________________________________
| From: | "Eric Ruttan" <ericruttan(at)chartermi.net> |
, ,
,
| Subject: | Grandsons Aircraft Ride at Pensacola on March 24. |
This question was sent to me at the Canard Aviation Forum. I found it
rather touching, and with David's permission, I am forwarding it to all the
relevant lists I know.
Please reply to David directly. I have no further information.
Thank you,
Eric Ruttan. One of the canardaviationforum.dmt.net admins
P.S.
If this post is so off topic as to harm or offend, I apologize in advance.
The fault is mine not David's.
----- Original Message -----
From: "David Dorris @ Canard Aviation Forum" <ddorris(at)brsm.org>
Subject: Canard Aviation Forum Contact Us Form - Site Feedback
> The following message was sent to you via the Canard Aviation Forum
Contact Us form by David Dorris.
>
> --------------------------------
>
> I know this isn't in your area, maybe, but I have a problem. My grandsons
are coming to Pensacola on March 24 and I have promised to take them up in a
small plane or helicopter. Do you know where I might be able to get in
tough with someone that offers that service.
>
> Thank you very much.
>
> David Dorris
> ddorris(at)brsm.org
> --------------------------------
________________________________________________________________________________
| From: | "Kingsley Hurst" <khurst(at)taroom.qld.gov.au> |
| Subject: | Circuit breaker ratings for OVP |
Paul M,
You said :-
As I have previously suggested there is a simple fix to those who are
using
the crowbar OVP and that is to add a 1/4 ohm resistor in series that
will
limit the current to 50 amps or less and will not prevent the proper and
intended function of the OVP.
What wattage are we talking about here please Paul or doesn't it matter
owing to the small duration of the high current event ?
Regards
Kingsley Hurst in Oz.
________________________________________________________________________________
| From: | <bakerocb(at)cox.net> |
AeroElectric-List message previously posted by: "Bob McDevitt"
<>
2/22/5005
Hello Bob McDevitt, I agree with Bob Nuckolls -- your are seeing the effects
of EMI (Electro Magnetic Interference), sometimes called RF (Radio
Frequency) interference, on the measuring device.
What voltmeter are you using to measure this increase? The one installed in
your panel or a separate handheld meter connected to the bus? If you are
using the meter in the panel, try a separate handheld meter. If you are
using a separate hand held meter try to borrow a different (and maybe
better) one with regard to resisting EMI.
If the problem persists then try the dummy load technique on your radio
transmitter as recommended by Bob Nuckolls. Please let us know how this is
resolved. Thanks.
OC
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: DC Power Systems Dynamics - Breakers |
You have apparently missed my main point. Its not what you or I have done
with a few tests.
We MUST do a worst case analysis of any and all parts used or recommended
and if specific parts are required they need top be specified. You have
specified parts for the OVP but not specified specific CB part #.
If you take a low 'worst case' current and the worst case long open time
from the CB spec of the CB you actually tested there is no way its going to
be less than 100 milliseconds. Reminder the 7274 CB has a 50 amp trip time
of 0.046 to 0.8 amps. This at 25C and what about when its cold it can trip
10% longer with possible cockpit temps in treasonable climes.
As for the SCR I reviewed the specs for the one called out and its also
rated 300 amps at 50 Hz pulses which is lower than My test. I have found the
die attach bond wires are the really weak point in semi's.
As for batteries again what you or I test is NOT what another production run
or another MFGR's battery will test out at.
I disagree on assumptions and really disagree on taking a few samples and
making general conclusions. Good aerospace engineering requires a worst on
worst analysis. Further if a specific part or resistance is required it must
be specified.
I have more embedded comments below
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: AeroElectric-List: Re: DC Power Systems Dynamics - Breakers
>
>
>
>>
>>
>>
>>One NEVER uses assumptions and Always uses spec values . . .
>
> Not all assumptions (or extrapolations) are evil if they
> rest on reasonable foundation . . .
I should not have used 'never' (almost never) but your paper sure led me and
others to assume that for example 400 amps or 100 ms time to open was not
reasonable but a simple worst on worst specification values along with a
range of real wires etc would suggest otherwise.
In the case where you have dual batteries capable of 3000 amps short current
(7 milliohms each and 3.5 in parallel)and 2 ft of #4 and 2 ft of #6 and the
OVP with 1" leads across the CB and right below the main ground return which
is also 2 ft of #6 the wiring resistance is very low in the real world.
The above is a real representation of my acft less the contactor inline
resistance 0.001 ohm measured) from each battery to the main bus.
I suggest your test example was closer to the other maxi wiring and battery
resistance. I did not measure circuit resistance and the testing was quite
consistent over several weeks.
>
>
>> . . . and worst case design
>>to be sure the design will always meet the design intent with ANY
>>conbination of parts. The subject test simply does not do this.
>
> I disagree here and permit me to illustrate the foundation.
> If I design and airplane, should the design goal be to
> allow assembly with Grade 5 hardware store bolts or is it
> more practical and safer to SPECIFY Grade 8 fasteners?
That is not what you have done. I have never seen a worst case analysis.
Grade 5 parts might be ok IF the design was based on that level of strength
and had the proper design margins built in. One never designs to
specification limits but always derates the parts in my engineering world
either mechanical or electrical there is derating or design margins the
included
> If I kit up a digital voltmeter with a goal of displaying
> bus volts to 1% accuracy, can I use 5% tolerance parts in
> the voltage dividers?
>
> > If I understand your suggestion as to "combinations of parts"
> do I deduce correctly that the major variable is the kind
> of circuit breaker used? Keep in mind that the test was NOT
> an evaluation of any particular part selection but a simple
> illustration of a methodology for demonstrating the effects
> of parts, wire, connections and battery impedance on the
> performance of a system. It's just a collection of simple
> tools applicable to investigation of specific installations
> on airplanes or any other test setup.
But it appeared to have, as an objective, a lot of supporting analysis to
suggest the design was good and safe. Again no use of available data sheet
limits but nearly 100% use of measured values which are far from the max in
the data sheets. Not that the design is good and safe but we need something
more than a test and assumptions as proof
> I'll readily admit to not having considered that someone
> might purchase a totally unknown quality breaker and combine
> it with the crowbar ov module. That didn't occur to me because
> we were supplying recommended (but not SPECIFIED) breakers.
I have above pointed out that the breakers suggested can be a lot slower
than your tests. Also I recommend that you either do a worst case analysis
and or specify the breaker brand and or part # as well as the minimum and
maximum wiring from the battery to the OVP etc if the design requires it to
prevent overly long pop times or too high currents.
>
> I'll see to it that the installation instructions for this
> product are modified to SPECIFY recommended parts so as to
> prevent a breaker pulled off a garden tractor from finding
> its way into somebody's alternator system. In the
> mean time, would it be a useful exercise to identify and
> caution against breakers with extra-ordinarily long operating
> times? I'd be pleased to test/confirm the suitability or
> non-suitability of any breaker you suggest.
My only 'real to me' required change to the do it your self OVP is the
addition of a 1/4 ohm resistor to limit the current to 50 amps max. I can
see no down side to this other than the addition to parts in the field. It
eliminates the objections of very high current and resolves any questions of
overcurrent harming the CB.
Frankly I have tested 3 different brands and you have tested a 4th one. All
are commonly used on acft and 3 of the 4 are available thru Aircraft Spruce
etc. ALL have 500-800 ms long times to open at 1000% of rated load (50 amps)
and that is as I have posted the maximum current that you can break and
retain the original CB ratings.
>
> With respect to exceeding specified limits on the operation
> of breakers recommended for this application, I've captured
> information off an Eaton/Mechanical Products data sheet
> which I've published on my website at:
>
> http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
>
> This breaker is used by the thousands at RAC and is part of
> the samples I'm gathering to evaluate in the experiment.
> I think the commercial version of this breaker is the one
> sold by B&C as MP Model 4200 as opposed to the mil-spec
> parts in the bins at RAC.
This is apparently identical in specs to the 77XX breakers we both have
tested and retail the 800 ms max long opening time.
>
>>The design also overstresses parts under worst case design rules.
>
> Not sure which part you're referring to here: For the SCR?
> Yes, the MCR-69 is operating at the ragged edge for short
> wires (and way out the roof for zero length wires) but OV
> protection is a rare, generally isolated event. Further,
> when the installation instructions are modified to recommend
> care in selection the companion breaker, we'll also set up
> guidelines for minimum total wire length so as to make sure
> no-one installs the module right at the breaker.
>
> SCR's used in the L-series controllers are fatter and
> much more robust than the MCR-69 and it's TO-220 cousins.
> We'll wear out breakers before we push one of those
> puppies off the wagon.
I cannot comment on the LR regulators but the Do it your self OVP specified
essentially the same SCR with regard to ratings. Actually I was unable to
apparently damage the specified SCR with currents that exceeded 700 amps in
a couple of tests. Not that I would recommend their use as that would be out
of the specified range.
>
> If you're referring to the breaker, I'll rely on data
> extracted from manufacturer's published literature for
> the breaker SPECIFIED in this experiment and for others
> to be specified in the installation instructions for a
> crowbar OV protected system.
>
>> >
>> >> Bob then goes on with "out of the thin air conclusions" :-) that are
>> >> not
>> >> based on any real facts and in fact the available data (again from
>> >> various data sheets do not support the conclusions.
>> >>
>> >> For example:
>> >>
>> >> From the report:
>> >>
>> >> ". Battery delta E for 135A load is about 2.4 volts for an internal
>> >> impedance of about 17 milliohms.
>> >>
>> >> About what one would expect from a two year old battery that started
>> >> out
>> >> in the 8 to 10 milliohm."
>> >>>
>> >> The Panasonic data sheet says approximately 12 milliohm. Approximately
>> >> is
>> >> hardly an engineering term but it's also not 8-10 as Bob suggests for
>> >> a
>> >> new battery.
>
> Approximately is indeed an engineering term. It's often used to
> make sure the listener/reader is not lulled into some sense of
> accuracy
> in a value where accuracy is either suspect or the variable in
> question is very loose. For the convenience of our readers,
> I've posted the Panasonic data sheet at:
Apprx as used for engineering calculations is new to me. I have never seen
it used to support analysis where the results would or should be used beyond
some simple test of concept.
> On several occasions I've measured the source impedance of new
> 1217 batteries and most of the time they're better than 12 millohms
> but why are we quibbling about this?
Only that you do not require Panasonic and Panasonic does not warrant the
resistance. Thus regardless of how unimportant it is to the analysis its not
good to use data that may not be represent the entire world of possible
batteries. I have a battery post on the many types of batteries available
not mentioning the specialty brands available at the garden shops etc. These
all come in the same size shape and general ratings 12V 160-18AH. If
Panasonic is required specific that only Panasonic be used.
> The experiment measured and
> stated the source impedance as the battery as it was. We further
> extrapolated what the performance would be with ANY other battery
> having
> a lower impedance and discovered that battery impedance doesn't
> drive the overall performance. If the soggy 17 milliohm
> device were replaced with the gold plated 1 millohm device, overall
> performance is affected only slightly. The the driving variables are
> wiring,
> breaker and switch impedances.
>
>> >> When I do the math I get 70 NOT 7 milliohms on the last line (for the
>> >> CB)
>> >> which conflicts with the first line of 62 milliohms total loop
>> >> resistance. From this and my earlier comments the entire technical
>> analysis is
>> >> clearly faulty.
>
> Error noted and corrected. But since the mis-calculated value
> was only part of the total, MEASURED loop impedance, the effect
> of correcting the error only shifted more resistance to the breaker
> and away from terminals and connections. Net change to the conclusions
> was
> zero. How does this make the entire analysis faulty?
>
>> >> I simply do not understand the massive resistance to make an
>> >> improvement
>> >> (even the addition of 1/4 ohm is resisted).
>
> I don't know that there IS "massive" resistance to any changes.
> I'm wanting to understand their value and effect. Please don't
> interpret a lack of enthusiasm for improvements to be a reluctance
> to change. I've sold hundreds of these systems. B&C has sold
> thousands of these systems. It's a really good thing to upgrade
> the performance of your products when ever it can be shown to
> add value. On the other side, if the improvement is made to
> correct some shortcoming in the design or recommendations for
> installation, we need to partition that off for examination too.
I and friends have had reported to us several dozen cases of false tripping
of the 'do it your self' OVP. I have personally (by accident) found a
condition where it false tripped 100% of the time. I then built up a second
unit and it performed the same. Then "US" :-) engineers got together and
found the likely cause in the design is susceptibility to a specific type of
contact bounce as I was using a contactor to connect the Load dump loads of
10 -40 amps. The OVP tripped every time the load was connected while the
alternator was on line.
The OVP module was built on a perf board 1" by 1.5".
Adding 0.1 mfd, and then 10 mfd tant failed to work but adding 1,000 mfd
cured the problem and false tripping went from 100% to 0%. I have not
previously reported this as I feel its an unusual setup but now wonder if
the small number of false trips we have been told about could have been
related to something similar.
>
> Do I owe thousands of customers a modified instruction sheet?
> Are systems in place for nearly a decade at risk? Should
> we be recalling product based on discovery of a real screw-up?
> When 400-700A crowbar currents are cited as a risk to the users
> of this philosophy it gets my attention. It argues with
> what I believed was a long held and reasonably solid understanding.
I do not know. I have demonstrated to myself and others that what I am
measuring IE 400 amp currents is real. I agree its a setup with low
resistance wiring and never expected your large response to the currents. In
the case where there is no electrically dependent engine involved its no big
deal to have a momentary drop in the battery voltage. Where battery voltage
is important its a different matter and should be discussed independently as
its not just a OVP issue.
>
> I hope it's clear that I'm intently interested in examining that
> understanding to validate, modify or discard as evaluation of the
> investigation directs.
>
> This is another reason for carrying on this conversation out
> in the open. It has nothing to do with who invented what or
> who recommends what . . . our readers need to have confidence
> in everyone's recommendations. That cannot be enhanced by deliberating
> behind closed doors.
As you might have noted I disagreed with my east coast partner (Eric) when
He suggested a committee.
However I would hope this could be the end of this discussion between us. We
have both extensively stated our opinions and its time to move on.
As I have said above the addition of a 1/4 ohm resistor is my only remaining
concern ant that is to satisfy the CB mfgrs requirements to replace any CB
that opens under more than 10X rated currents.
Thanks for your participation in this sometimes warm discussion. Fortunately
just smoke no fire (joke that is please other readers) :-)
Paul
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Circuit breaker ratings for OVP |
>
>
>Paul M,
>
>You said :-
>As I have previously suggested there is a simple fix to those who are
>using the crowbar OVP and that is to add a 1/4 ohm resistor in series that
>will limit the current to 50 amps or less and will not prevent the proper and
>intended function of the OVP.
>
>What wattage are we talking about here please Paul or doesn't it matter
>owing to the small duration of the high current event ?
Is your alternator externally regulated? Then keep in mind that adding
resistance in series with the ov protection module will reduce its
ability to pull the field voltage down even BEFORE the breaker trips.
In fact, adding this much resistance insures that the OV event will
continue until the breaker opens. During the trip event, the series
resistor will have to carry about 50A at about 10v for an instantaneous
dissipation level of about 500 watts. Most wirewound resistor folks
will rate their produces at 10x rated power for 5 seconds. So assuming
a 10 watt, 0.25 ohm resistor will safely handle 100 watts for 5 seconds
(current of 20A) this calculates to an Isquared*t value 20*20*5 or
2,000.
Okay, for a 50A event, an Isquared*t of 2000 yields a maximum time
of 2000/2500 or about .8 seconds. This suggests that a 10W resistor
is plenty hefty enough to accomplish the task. A 5W resistor would
be good for .4 seconds . . . also fine.
See ALSR series wirewounds on Digikey at
http://dkc3.digikey.com/PDF/T051/1026.pdf
An ALSR5J-.25-ND (0.25 ohm, 5w) resistor is in stock and would
cost you about $1.50
If your alternator is internally regulated, then the OVM has no immediate
effect on the runaway condition. Increasing the series resistance
the OVM-14 only increases breaker opening time. However, given that
the internally regulated alternator control system operates nicely through
a 2A breaker, all you need to do is replace your existing breaker with
a 2A sub-miniature breaker. See:
http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
These have an internal resistance of well OVER .25 ohms. 0.30 ohms
in fact. This will have the same effect as adding series resistance
to the OVM-14. Either way, the resistor cited above or replacing the
breaker will have the desired effect.
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Ongoing Soap Opera |
>> Please move this off list. When something useful comes of your
discussions,
>> then share it with us. It will be readily received and appreciated.
> Mr. Windhorn, I'd prefer that you move off this list than Bob or Paul.
Gently, gently my friend. Doug's been around here for quite some time
and has been a good citizen of the List. I presume that his attendance
here demonstrates his sense of value for spending the time to join
us. I fully understand how someone who is not interested in lengthy,
detailed dissertations might find it frustrating . . . and he's certainly
entitled to express them. It's helpful of folks who ARE interested in
the work to assist those with limited time and interest to acquire what
they need/want.
There are only 4 reasons for folks to communicate with each other.
To inform (share facts and simple-ideas), entertain (to each his
own but a little humor or the occasional war story is fine by me), to
persuade (only necessary if you're a preacher, politician, or
lawyer) or to inflict discomfort or injury (self explanatory).
May I suggest that you evaluate your words in these contexts and
decide the purpose for which they are offered. I'd really like to
believe that everyone here wants to know the 'good stuff', have a
good time learning it and will craft their activities in support
of that goal.
Bob . . .
________________________________________________________________________________
| From: | Andrew Rowley <arowley(at)ncable.net.au> |
| Subject: | Re: Circuit breaker ratings for OVP |
Robert L. Nuckolls, III wrote:
> If your alternator is internally regulated, then the OVM has no immediate
> effect on the runaway condition. Increasing the series resistance
> the OVM-14 only increases breaker opening time. However, given that
> the internally regulated alternator control system operates nicely through
> a 2A breaker, all you need to do is replace your existing breaker with
> a 2A sub-miniature breaker. See:
>
> http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
>
>
> These have an internal resistance of well OVER .25 ohms. 0.30 ohms
> in fact. This will have the same effect as adding series resistance
> to the OVM-14. Either way, the resistor cited above or replacing the
> breaker will have the desired effect.
Is the location of the resistor in the circuit significant? It seems
like if you put a resistor after the circuit splits between the OVM and
the alternator disconnect contactor, the contactor will stay closed
until after the breaker trips. On the other hand, if the resistor is
before the 2 circuits divide, you are improving the chances of the
contactor opening before the breaker trips, at the cost of having the
contactor current always running through the resistor.
Using the 2A breaker of course gives you the second scenario.
--
Andrew Rowley
arowley(at)ncable.net.au
________________________________________________________________________________
| From: | Andrew Rowley <arowley(at)ncable.net.au> |
| Subject: | Re: Circuit breaker ratings for OVP |
Robert L. Nuckolls, III wrote:
> If your alternator is internally regulated, then the OVM has no immediate
> effect on the runaway condition. Increasing the series resistance
> the OVM-14 only increases breaker opening time. However, given that
> the internally regulated alternator control system operates nicely through
> a 2A breaker, all you need to do is replace your existing breaker with
> a 2A sub-miniature breaker. See:
>
> http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
>
>
> These have an internal resistance of well OVER .25 ohms. 0.30 ohms
> in fact. This will have the same effect as adding series resistance
> to the OVM-14. Either way, the resistor cited above or replacing the
> breaker will have the desired effect.
Is the location of the resistor in the circuit significant? It seems
like if you put a resistor after the circuit splits between the OVM and
the alternator disconnect contactor, the contactor will stay closed
until after the breaker trips. On the other hand, if the resistor is
before the 2 circuits divide, you are improving the chances of the
contactor opening before the breaker trips, at the cost of having the
contactor current always running through the resistor.
Using the 2A breaker of course gives you the second scenario.
--
Andrew Rowley
arowley(at)ncable.net.au
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Circuit breaker ratings for OVP |
Hmmmm . . . I note that the 10x rated limit for surviving repeated trips
seems to be an industry standard practice for most breakers offered.
One might guess that the limits to the plots in the graph I excerpted
at 1000% imply the same thing. I don't find it in words on the Eaton
data sheet like for most others on the 'net. I found some $low$ breakers
out there rated at only 6x for resetable trips.
Interesting. When we crafted the original crowbar system for the Turbine
Bonanza project, we were bound by the Beech spec for 50 ov trips in a row
with the 51st trip having to be as effective as the first.I don't know
how many qual cycles we conducted on various versions using the same 5A
breaker in the fixture . . . with crowbar currents that ran
no less than 200A and sometimes as high as 300A. I'll bet that
one breaker stood up to over 1000 40x to 60x events although . . . I don't
having testing it for trip calibration after that many cycles. The
breaker never failed to reset. I've got a call into my breaker buddy
at Eaton/Cutler-Hammer to see if he can offer any clarification on this
ubiquitous 10x figure. I know I've discussed this system with him several
times over the past 25 years and he didn't raise any flags. You've raised
an interesting question!
Matt's question is interesting too . . . I'll ask around out at RAC
and see what the policy is for maintenance after a hard-fault trips
on a breaker in an airplane. I've never heard of a replace-the-breaker-too
policy but that doesn't mean it isn't doesn't exist. I can find no
reference to the practice in AC43-13 but I seem to recall someone speaking
about it some time back and I'm not even sure it was in an airplane.
Bob . . .
>
>Hi Paul,
>
>You make an interesting point. I wonder, how often we will know that
>a tripped breaker did so within the spec'ed range? In other words, if a
>breaker trips because of a wiring fault, is there any way to know that the
>1000% spec wasn't violated. I suppose what that suggests is that if
>your airplane chafes off a piece of insulation and then pops a breaker,
>the only approved way to return it to service is to repair the wire, chafe
>protect it, AND replace the breaker. Is that right?
>
>
>Regards,
>
>Matt-
>VE N34RD, C150 N714BK
>
> >
> >
> > One of the likely circuit breaker candidates is the W23 5 amp unit. Its
> > reported this is used by 3 major certificated aircraft and is approved
> > by the FAA.
> >
> > This CB, as are all the others I have looked at, define the 'time to
> > open range' at various over current levels up to 1,000% of rating.
> > Interesting that they all stop at 1,000%. That is 50 amps for a 5 amp
> > breaker. Its also 10 times rated current.
> >
> > Now the W23 specification data sheet states the following:
> >
> > Resettable Overload capacity: Ten times rated current.
> >
> > What does this mean??
> >
> > This is defined in the industry as:
> >
> > "RESETTABLE OVERLOAD CAPACITY
> > * Represents the maximum current the circuit protector is capable of
> > interrupting without damaging itself."
> >
> > What does this mean??
> > It means that the CB may not meet specifications if the current being
> > broken exceeds ten times (or in this case 50 amps) its ratings.
> >
> > I checked with a long time IA and he said that means the CB must be
> > replaced if there is a known overcurrent trip on a critical to flight
> > item. The alternator is considered a critical to flight component.
> > Bsically if a part is known to have been subjected to an out of
> > specification condition that might affest its function it must be
> > replaced, testing is not good enough.
> >
> > The only conclusion I can come to is that any crowbar design that is not
> > current limited to 50 amps will require the CB to be replaced if its
> > tripped by and crowbar OVP in a certificated aircraft.
> >
> > For experimental its not the same but who would not want to replace a
> > potentially damaged CB that might not work as specified??
> >
> > As I have previously suggested there is a simple fix to those who are
> > using the crowbar OVP and that is to add a 1/4 ohm resistor in series
> > that will limit the current to 50 amps or less and will not prevent the
> > proper and intended function of the OVP.
> >
> > Both Bob and I have agreed that the typical OVP being discussed has a
> > tripping current in excess of 100 amps, that we disagree on the amount
> > of current over 100 amps is not really important.
> >
> > I do not know if the certified LR-x series of regulators can overcurrent
> > the CB (worst case over 50 amps) but its worth investigating.
> >
> > I can see no reason for not making this improvement and eliminating the
> > potential damage to the CB from being over stressed.
> >
> > Note that the ability of the CB to break up to 2,000 amps is very
> > different from being able to survive this with no damage. Essentially
> > what the mfgr's are saying is that the CB is reusable as a CB up to ten
> > times its ratings and will open under hundreds of times its ratings but
> > then should be treated like a fuse and be replaced.
> >
> >
> > Paul
> >
> >
>
>
>--
>
>
>-- incoming mail is certified Virus Free.
Bob . . .
--------------------------------------------------------
< Throughout history, poverty is the normal condition >
< of man. Advances which permit this norm to be >
< exceeded -- here and there, now and then -- are the >
< work of an extremely small minority, frequently >
< despised, often condemned, and almost always opposed >
< by all right-thinking people. Whenever this tiny >
< minority is kept from creating, or (as sometimes >
< happens) is driven out of a society, the people >
< then slip back into abject poverty. >
< >
< This is known as "bad luck". >
< -Lazarus Long- >
<------------------------------------------------------>
http://www.aeroelectric.com
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: DC Power Systems Dynamics - Breakers |
>
>You have apparently missed my main point. Its not what you or I have done
>with a few tests.
>
>We MUST do a worst case analysis of any and all parts used or recommended
>and if specific parts are required they need top be specified. You have
>specified parts for the OVP but not specified specific CB part #.
Agreed
>If you take a low 'worst case' current and the worst case long open time
>from the CB spec of the CB you actually tested there is no way its going to
>be less than 100 milliseconds. Reminder the 7274 CB has a 50 amp trip time
>of 0.046 to 0.8 amps. This at 25C and what about when its cold it can trip
>10% longer with possible cockpit temps in treasonable climes.
>
>As for the SCR I reviewed the specs for the one called out and its also
>rated 300 amps at 50 Hz pulses which is lower than My test. I have found the
>die attach bond wires are the really weak point in semi's.
Yes . . . the plastic molded parts seem to be more robust than
the formerly popular TO-3 metal cans. The metal parts were always
considered "superior" and in many ways they were . . . but their
die bond wires hung out in space and were a lot faster to fuse than
for the plastic parts. In the extremes, I seem to recall opening
bond wires in metal parts and fusing junctions in plastic parts
>As for batteries again what you or I test is NOT what another production run
>or another MFGR's battery will test out at.
The battery wasn't offered as a spectrum supply but simply an
experimental test source that could be quantified at the measured
17 milliohms. Performance of other batteries could be extrapolated
based solely on a hypothetical source impedance. The point was to
illuminate the effect of battery impedance on the experiment.
>I disagree on assumptions and really disagree on taking a few samples and
>making general conclusions. Good aerospace engineering requires a worst on
>worst analysis. Further if a specific part or resistance is required it must
>be specified.
Absolutely. What conclusions have I drawn in the experiment paper.
>I have more embedded comments below
>
>Paul
>
>----- Original Message -----
>From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
>To:
>Subject: AeroElectric-List: Re: DC Power Systems Dynamics - Breakers
>
>
> >
> >
> >
> >>
> >>
> >>
> >>One NEVER uses assumptions and Always uses spec values . . .
> >
> > Not all assumptions (or extrapolations) are evil if they
> > rest on reasonable foundation . . .
>
>I should not have used 'never' (almost never) but your paper sure led me and
>others to assume that for example 400 amps or 100 ms time to open was not
>reasonable but a simple worst on worst specification values along with a
>range of real wires etc would suggest otherwise.
>
>In the case where you have dual batteries capable of 3000 amps short current
>(7 milliohms each and 3.5 in parallel)and 2 ft of #4 and 2 ft of #6 and the
>OVP with 1" leads across the CB and right below the main ground return which
>is also 2 ft of #6 the wiring resistance is very low in the real world.
>
>The above is a real representation of my acft less the contactor inline
>resistance 0.001 ohm measured) from each battery to the main bus.
>
>I suggest your test example was closer to the other maxi wiring and battery
>resistance. I did not measure circuit resistance and the testing was quite
>consistent over several weeks.
Not sure about "maxi" wiring . . . do you mean maximum loop resistance?
The total lengths of wire in the experiment were 24" of 20AWG (20 mOhms)
and 6" of 10AWG (0.5 mOhms). The point was to craft a minimum wiring
scenario . . . if wired per instructions supplied with the OVM-14 or per
any of the Z-figures, what is the likelihood that any installation would
have LESS resistance than the experiment . . . and what would be the
effects
of varying battery capabilities. The experiment shows that wiring and the
circuit breaker are major contributors and have the greatest effects on
potential fault current thorough the crowbar device.
To achieve a 400A crowbar current, the total loop resistance must be
on the order of 26 milliohms. If you have a 3.5 mohm battery and a
bus feeder of 1 mohm then this leaves one to make the crowbar connections
with zero length leads and to find a breaker that runs 21.5 millohms.
This may indeed represent a worst case but one has to really work
to create it. Airplanes are put together with serviceable chunks of
wire and I believed that the experiment illustrated an exemplar
worst case for the low end of as-installed loop resistance.
> >
> >> . . . and worst case design
> >>to be sure the design will always meet the design intent with ANY
> >>conbination of parts. The subject test simply does not do this.
> >
> > I disagree here and permit me to illustrate the foundation.
> > If I design and airplane, should the design goal be to
> > allow assembly with Grade 5 hardware store bolts or is it
> > more practical and safer to SPECIFY Grade 8 fasteners?
>
>That is not what you have done. I have never seen a worst case analysis.
>Grade 5 parts might be ok IF the design was based on that level of strength
>and had the proper design margins built in. One never designs to
>specification limits but always derates the parts in my engineering world
>either mechanical or electrical there is derating or design margins the
>included
>
> > If I kit up a digital voltmeter with a goal of displaying
> > bus volts to 1% accuracy, can I use 5% tolerance parts in
> > the voltage dividers?
> >
> > > If I understand your suggestion as to "combinations of parts"
> > do I deduce correctly that the major variable is the kind
> > of circuit breaker used? Keep in mind that the test was NOT
> > an evaluation of any particular part selection but a simple
> > illustration of a methodology for demonstrating the effects
> > of parts, wire, connections and battery impedance on the
> > performance of a system. It's just a collection of simple
> > tools applicable to investigation of specific installations
> > on airplanes or any other test setup.
>
>But it appeared to have, as an objective, a lot of supporting analysis to
>suggest the design was good and safe. Again no use of available data sheet
>limits but nearly 100% use of measured values which are far from the max in
>the data sheets. Not that the design is good and safe but we need something
>more than a test and assumptions as proof.
What have I assumed? The purpose of the experiment thus far
is to simply illustrate how DIFFICULT it is to get a 400A
or larger crowbar event and to inquire as to the conditions
that produced measurements you cited. You tell me that the
crowbar device was located right at the breaker . . . still
difficult to drive the loop resistance to the requisite The next steps
will be to discuss
timing dynamics. The last revision shows that a battery
slows down an OV even so much that the protective circuitry
can stop for a cheeseburger and fries before it needs to
pull the plug on the runaway alternator. My OVP designs
come out of a long history of Mil-Std-704 descriptions
of NORMAL transients to expect on a generator only
system . . hence the relatively short time delays for step
response. But as long as a battery is on line, one can just
about run anything from .5 to 2 seconds and not affect the
level of protection. But as soon as you take the battery
out, we need to go back to the original timing but not so
fast that the system nuisance trips.
> > I'll readily admit to not having considered that someone
> > might purchase a totally unknown quality breaker and combine
> > it with the crowbar ov module. That didn't occur to me because
> > we were supplying recommended (but not SPECIFIED) breakers.
>
>I have above pointed out that the breakers suggested can be a lot slower
>than your tests. Also I recommend that you either do a worst case analysis
>and or specify the breaker brand and or part # as well as the minimum and
>maximum wiring from the battery to the OVP etc if the design requires it to
>prevent overly long pop times or too high currents.
Agreed. We'll do that.
> >
> > I'll see to it that the installation instructions for this
> > product are modified to SPECIFY recommended parts so as to
> > prevent a breaker pulled off a garden tractor from finding
> > its way into somebody's alternator system. In the
> > mean time, would it be a useful exercise to identify and
> > caution against breakers with extra-ordinarily long operating
> > times? I'd be pleased to test/confirm the suitability or
> > non-suitability of any breaker you suggest.
>
>My only 'real to me' required change to the do it your self OVP is the
>addition of a 1/4 ohm resistor to limit the current to 50 amps max. I can
>see no down side to this other than the addition to parts in the field. It
>eliminates the objections of very high current and resolves any questions of
>overcurrent harming the CB.
Agreed for the internally regulated alternator. The internally
regulated alternator poses new questions. We're still okay if
the battery stays on line because the increased opening time
of the breaker with the 50A limit is no big deal. If the battery
is off line, then the crowbar's ability to pull down directly on
the alternator (and hopefully stall it) has been compromised with
the .25 rise in load impedance. I'll look at this. My alternator
test stand gets here tomorrow night.
>Frankly I have tested 3 different brands and you have tested a 4th one. All
>are commonly used on acft and 3 of the 4 are available thru Aircraft Spruce
>etc. ALL have 500-800 ms long times to open at 1000% of rated load (50 amps)
>and that is as I have posted the maximum current that you can break and
>retain the original CB ratings.
>
> >
> > With respect to exceeding specified limits on the operation
> > of breakers recommended for this application, I've captured
> > information off an Eaton/Mechanical Products data sheet
> > which I've published on my website at:
> >
> > http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
> >
> > This breaker is used by the thousands at RAC and is part of
> > the samples I'm gathering to evaluate in the experiment.
> > I think the commercial version of this breaker is the one
> > sold by B&C as MP Model 4200 as opposed to the mil-spec
> > parts in the bins at RAC.
>
>This is apparently identical in specs to the 77XX breakers we both have
>tested and retail the 800 ms max long opening time.
> >
> >>The design also overstresses parts under worst case design rules.
> >
> > Not sure which part you're referring to here: For the SCR?
> > Yes, the MCR-69 is operating at the ragged edge for short
> > wires (and way out the roof for zero length wires) but OV
> > protection is a rare, generally isolated event. Further,
> > when the installation instructions are modified to recommend
> > care in selection the companion breaker, we'll also set up
> > guidelines for minimum total wire length so as to make sure
> > no-one installs the module right at the breaker.
> >
> > SCR's used in the L-series controllers are fatter and
> > much more robust than the MCR-69 and it's TO-220 cousins.
> > We'll wear out breakers before we push one of those
> > puppies off the wagon.
>
>I cannot comment on the LR regulators but the Do it your self OVP specified
>essentially the same SCR with regard to ratings. Actually I was unable to
>apparently damage the specified SCR with currents that exceeded 700 amps in
>a couple of tests.
gee . . . I'm still trying to figure out how you get 700 amps.
> > On several occasions I've measured the source impedance of new
> > 1217 batteries and most of the time they're better than 12 millohms
> > but why are we quibbling about this?
>
>Only that you do not require Panasonic and Panasonic does not warrant the
>resistance. Thus regardless of how unimportant it is to the analysis its not
>good to use data that may not be represent the entire world of possible
>batteries. I have a battery post on the many types of batteries available
>not mentioning the specialty brands available at the garden shops etc. These
>all come in the same size shape and general ratings 12V 160-18AH. If
>Panasonic is required specific that only Panasonic be used.
I'm still mystified as to this exchange. I used the 1217 because it
was sitting under the bench and handy. There were larger and
smaller batteries under there that would have sufficed as well
once their effects on the experiment were understood. Only
then could the effects of any other battery could be deduced. Any
battery would have sufficed for the purpose of exploring how one
gets a 400A crowbar event. This wasn't about requiring or specifying
anything, it was about trying to understand how you achieved
numbers you cited.
>I and friends have had reported to us several dozen cases of false tripping
>of the 'do it your self' OVP. I have personally (by accident) found a
>condition where it false tripped 100% of the time. I then built up a second
>unit and it performed the same. Then "US" :-) engineers got together and
>found the likely cause in the design is susceptibility to a specific type of
>contact bounce as I was using a contactor to connect the Load dump loads of
>10 -40 amps. The OVP tripped every time the load was connected while the
>alternator was on line.
Yes, every scr can be triggered with a fast dv/dt event on the
supply line. The early installations of the SD-20 in Bonanzas would
trip when the landing and taxi lights were switched on simultaneously.
Turns out the Potter-Brumfield breaker switches . . .
(See http://www.aeroelectric.com/Pictures/W31_1.jpg )
are about the most gawd-awful bouncers anyone has ever seen. I'd
put the OVM-14 and close cousins into the lab for the DO-160 conducted
spike and noise susceptibility tests but the noise these switches
put out when switching 150 watt halogen lamps far exceeded the
DO-160 limits. We had to modify the regulators to accommodate this
situation. The OVM-14 was modified too to reduce gate-to-cathode
resistor to 10 ohms from 220 ohms like we did in the Bonanza regulators.
>Adding 0.1 mfd, and then 10 mfd tant failed to work but adding 1,000 mfd
>cured the problem and false tripping went from 100% to 0%. I have not
>previously reported this as I feel its an unusual setup but now wonder if
>the small number of false trips we have been told about could have been
>related to something similar.
Good question. I've had a lot of conversations about nuisance
trips over the years. The vast majority have been cured by
installing the spike catcher across an offending relay or
contactor. I've had perhaps a half dozen of the DIY projects
that would trip when a transmitter was keyed. The thing was built
on too large a scale and placed in a plastic box. The production
OVM-14 is quite compact and seems to be immune to RFI problems
and resistant to dv/dt (spike) events after the gate resistor
was dropped to 10 ohms.
I wouldn't have tried to filter off dv/dt effects with anode
to cathode capacitance. The filter has to grunt the noise
source impedance at the bus level. By tying the gate down,
you take advantage of weak coupling of noise through the anode-gate
capacitance. Besides the large parallel capacitance would
drive the initial crowbar trip current out the roof. Is THIS
how you measured 700A in the SCR?
>As I have said above the addition of a 1/4 ohm resistor is my only remaining
>concern ant that is to satisfy the CB mfgrs requirements to replace any CB
>that opens under more than 10X rated currents.
I've noted your concern and I'll research why this didn't bubble
up as an issue a long time ago. I still need to noodle out the
effects of this change as a generic OV protection device and
then make more specific recommendations in our installation
instructions and the Z-figures.
>Thanks for your participation in this sometimes warm discussion. Fortunately
>just smoke no fire (joke that is please other readers) :-)
I'll continue with the development of the white paper with
exploration of suggested changes and repairs to errors noted.
You are invited to comment on the continuing effort or not as you
see fit. Your input to date has been thought provoking and
helpful.
Bob . . .
________________________________________________________________________________
| From: | Robert McCallum <robert.mccallum2(at)sympatico.ca> |
| Subject: | Re: Circuit breaker ratings for OVP |
Bob;
Although the "time to trip" charts stop at 1000% of the breakers rating,
the specifications you have published here
http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
under interrupting capacity at 28 volts state that for a 4200 series
breaker of 5 amp rating, the interrupting capacity is "unlimited" (seems
a bit high?) Certainly more than 10X. Further the same spec sheet says
that a 7.5 amp breaker is capable of interrupting 2000 amps. This is
266X its nominal rating. If you look at a 25 amp it's 80X nominal. I
realize that this doesn't specify the number of times the breaker will
survive these currents, but it does state that they are capable of
taming currents of these magnitudes. How do these figures impact on the
10X theory and where does the 10X information show up in the
specifications? In a parallel but totally different scenario, household
breakers of 15 amp rating, to be certified for use in your home, (at
least here in Canada) must be capable of interrupting 10,000 amps
minimum. That's 667X nominal value. Unrelated, I know, but ----- These
numbers and those stated by Eaton in the charts cited seem to be at odds
with the 10X value. Yes????? No??????
Bob McC
Robert L. Nuckolls, III wrote:
>
>Hmmmm . . . I note that the 10x rated limit for surviving repeated trips
>seems to be an industry standard practice for most breakers offered.
>One might guess that the limits to the plots in the graph I excerpted
>at 1000% imply the same thing. I don't find it in words on the Eaton
>data sheet like for most others on the 'net. I found some $low$ breakers
>out there rated at only 6x for resetable trips.
>
>Interesting.
>Bob . . .
>
>
________________________________________________________________________________
| From: | BobsV35B(at)aol.com |
| Subject: | Re: pitot tube element |
In a message dated 3/23/2005 7:59:17 A.M. Central Standard Time,
jrstone(at)insightbb.com writes:
Does anyone know who can provide the part and or replace the heating element
in a pitot tube?
I've got a surplus AN 5812 unit set up for 115volts, I want to change that
to 12 volts.
I would also be interested if anyone happens to have a 5812-12 unit they
would like to sell, contact me offline.
Thanks for the help,
Jim Stone
Harmon Rocket
Good Morning Jim,
Maybe we should be looking for an engine driven A/C generator system that
would supply that wild frequency 115 volt AC power that 'Lectric Bob has
mentioned?
It would open us up to a whole lot of neat surplus equipment.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Airpark LL22
Downers Grove, IL 60516
630 985-8502
________________________________________________________________________________
| From: | "Jeffrey Steenson" <jsteenson1(at)comcast.net> |
| Subject: | Whelen Flasher RF Interference |
I installed the Whelen flashing beacon atop the fin of my Murphy Rebel Elite
using unshielded wire. There is no stray radiation that my handheld was
able to pick up, but I am getting the distinctive sound of the flasher
firing through the panel radio.
Can this be corrected by using shielded wire from the flasher all the way
forward to the switch? or possibly for only the first portion of that run?
Or is it likely that I will beed a filter at the source.
This must be a very common problem with well established solutions!
Many thanks!
Jeffrey Steenson
ABQ, NM
________________________________________________________________________________
| From: | "Fergus Kyle" <VE3LVO(at)rac.ca> |
| Subject: | It's not soap opera |
hello,
To go on record with an opinion, let the debate continue!
There's a lot to be learned just by scanning the remarks. There is nothing
to be learned by hiding the debate - except a myriad of childish spelling
mistakes and a lot of me-ing. Old Bob and others are right.
For those who cannot comprehend nor abide discussion - use your
DELE button and look for a games website.
Ferg
Europa A064
________________________________________________________________________________
| From: | Ken <klehman(at)albedo.net> |
| Subject: | Re: Points for discussion OVP/todays summary |
Hi Jerry
You are golden and better than 98% of what is out there.
I know I'm happy with a "Spaceship One" although we are gradually
progressing to "Starship Enterprise" design ;)
Seriously there is a chance the OVM might get tweaked a bit to reduce
the chance of false trips and maybe specify a minimun circuit
resistance. Chances are that like me the resistance in you OVM wiring is
at the high end of what has been discussed - so again - no worries at
this point. It may be good practice to not route the OVP wiring too
close to your compass, magnetic sensors or glass instruments, or Hall
Effect current sensors. I'll bet you haven't done that anyway. There is
also a chance that new designs might gravitate towards non crowbar OV
protection but that doesn't mean I'll be removing what I have. Besides
where possible, I prefer a homebuilt device that I can test and repair
rather than a potted device with unknown components.
There is a very small chance that a OVM trip might cause a computer
reset for some specific items such as an aviation electronic ignition
that can't tolerate a momentary voltage drop but I judge that unlikely.
Most computers won't notice the momentary voltage drop that might
accompany a crowbar trip IMO. Some ignitions might miss a spark or fire
a weak spark but I'd be very surprised if the cpu itself noticed the trip.
It may give some peace of mind to add a transorb to any bus or power
input to a computer or expensive avionic device. There hasn't been
convincing need for that presented yet but I'll be doing that when the
weather warms up since it's easy and can be done for the cost of a cup
of Wet Coast designer coffee. Incidently mouser.com has the 5KP18A
devices in stock now although I'm using 1.5KP18A devices.
So far the discussion has re-inforced my happiness with my own
electrically dependant engine architecture that hardwires my alternators
to their respective batteries but I don't think that affects you. It
makes a lot of this discussion irrelevant if you don't have a battery
contactor. You do have a small external VR alternator which again is
good compared to a 100 amp internal VR automotive behemoth. So for the
time being - Motor On and Be Happy!
Ken
Jerry Isler wrote:
>
>As a lowly RV owner with a Vans 35 amp alternator, solid state external
>voltage regulator (VR-166?) and an AeroElectric crowbar overvoltage
>protection device wired in accordance with Bob's recommendation, what does
>all of this mean to me? If I experience an overvoltage condition and the
>crowbar OVP device trips the field breaker, are you saying the system is
>going to experience hundreds of excess amps from my 35 amp alternator for an
>fraction of a second and melt my lovely RV (and me) into oblivion? Obviously
>if there is an overvoltage condition on the system there is already a
>failure of some sort. Are you saying the crowbar OVP will make the failure
>worse?
>
>Jerry Isler
>RV4 N455J
>
>
________________________________________________________________________________
| From: | "Jim Stone" <jrstone(at)insightbb.com> |
| Subject: | Re: pitot tube element |
Good one, but let's not go there.
Jim
----- Original Message -----
From: <BobsV35B(at)aol.com>
Subject: Re: AeroElectric-List: pitot tube element
>
>
> In a message dated 3/23/2005 7:59:17 A.M. Central Standard Time,
> jrstone(at)insightbb.com writes:
>
> Does anyone know who can provide the part and or replace the heating
> element
> in a pitot tube?
> I've got a surplus AN 5812 unit set up for 115volts, I want to change
> that
> to 12 volts.
> I would also be interested if anyone happens to have a 5812-12 unit they
> would like to sell, contact me offline.
> Thanks for the help,
> Jim Stone
> Harmon Rocket
>
>
> Good Morning Jim,
>
> Maybe we should be looking for an engine driven A/C generator system that
> would supply that wild frequency 115 volt AC power that 'Lectric Bob has
> mentioned?
>
> It would open us up to a whole lot of neat surplus equipment.
>
> Happy Skies,
>
> Old Bob
> AKA
> Bob Siegfried
> Ancient Aviator
> Stearman N3977A
> Brookeridge Airpark LL22
> Downers Grove, IL 60516
> 630 985-8502
>
>
>
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: Circuit breaker ratings for OVP |
Bob, et al.
It would seem improbably at best that a circuit breaker could be built to
survive an arbitrarily large overcurrent. As Paul has pointed out, the
addition of a small resistor will put this crowbar back into the barn.
The 1000% limit is what the device can take and still be per spec. The
"unlimited interrupting capacity"
I would like to suggest that some number of glitchy crowbar OVP's are due
to the "inadvertent recalibration" of the 5A circuit breaker--either through
testing (as we say--"to death"), or the use of a badly-treated circuit
breaker whose early life was questionable---perhaps having suffered from
electron abuse.
Some definitions from the industry: Ref:
http://www.trimaxcb.com/catalog/glossary.html
CURRENT RATING ---maximum current a circuit protector can carry continuously
without exceeding its performance limits. [There's the rating on the breaker
or fuse.]
INTERRUPT CAPACITY---the maximum amperage a circuit protector can safely
trip without evidence or risk of fire or electric shock during or after the
application of this maximum amperage. It is acceptable if, at this maximum
amperage, the circuit protector is rendered inoperable, providing it fails
in the open position and the leads or terminals are not damaged. [There's
the unlimited current.]
RESETTABLE OVERLOAD CAPACITY --- the maximum current the circuit protector
is capable of interrupting without damaging itself. [There's that 1000%.]
MUST-TRIP POINT ---Minimum current at which the circuit protector will trip
reliably. It is normally designated as the Must Trip Point and specified
as a percentage of overload versus trip time. [This is the circuit breaker
minimum trip current. It is a function of both current and time.]
I believed there was a need for non-crowbar OVP (called a "Linear OVM").
The one I make at Perihelion Design uses an LTC1696. But builders who want
to roll their own might want some other approach since the LTC part is a
six-legged surface mount IC the size of a grain of pepper.
One of the nice features of the Perihelion Design Linear OVM is that the
reset can be held in to over-ride the trip. I chewed on this for a while
before I decided that the pilot might be grateful for 18V (or so) if that
was what his failed alternator was putting out and if that was all he could
get.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
"Everything you've learned in school as "obvious" becomes
less and less obvious as you begin to study the universe.
For example, there are no solids in the universe. There's
not even a suggestion of a solid. There are no absolute con-
tinuums. There are no surfaces. There are no straight lines."
- R. Buckminster Fuller
________________________________________________________________________________
| From: | "Gary Casey" <glcasey(at)adelphia.net> |
| Subject: | Re: Alternator characteristics |
Paul said:
<>
That's the answer I was looking for - a "runaway" alternator will produce an
over-voltage condition in seconds, not milliseconds. If it were in minutes
then I would consider using the pilot as the over-voltage control (sees the
ov warning light and shuts off the alternator). If it were fractions of a
second then I don't see how the battery could absorb load dump surges. It
looks like the data shows the time available is less than a minute - a
little bit short to expect a pilot to react correctly, probably making
automatic OV protection prudent, but not mandatory. So I assume from all
this that if an OV event occurred and the alternator shut off that after the
battery voltage drooped the alternator could be turned back on and would NOT
immediately create another OV event until the battery became fully charged?
However, I for one am always VERY reluctant to turn something back on when I
don't know the reason it popped the breaker in the first place.
Gary Casey
And thanks to all for the open dialog - I always learn something.
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: DC Power Systems Dynamics - Breakers |
Thanks for everything,
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: DC Power Systems Dynamics - Breakers
>
>
>
>>
>>
>>You have apparently missed my main point. Its not what you or I have done
>>with a few tests.
>>
>>We MUST do a worst case analysis of any and all parts used or recommended
>>and if specific parts are required they need top be specified. You have
>>specified parts for the OVP but not specified specific CB part #.
>
> Agreed
> snipped
> > I'll continue with the development of the white paper with
> exploration of suggested changes and repairs to errors noted.
> You are invited to comment on the continuing effort or not as you
> see fit. Your input to date has been thought provoking and
> helpful.
>
> Bob . . .
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Circuit breaker ratings for OVP |
The maximum breaking current is not the same as the maximum breaking current
with no damage.
10X is the typical specified breaking current with no damage. Above that
level the CB turns into a fuse. Somewhere, in this case, the 5 amp breaker
goed from a 50 amp current interuption to a fuse at 2000 amps interruption.
The purpose is circuit protection even at the expense of the CB sacrificing
its self tn its "final act" of protection.
It the CB good after breaking a 50 amp circuit the mggr says yes. What about
100 amps (20x) perhaps who knows. 2000amps you bet its gone.
Paul
----- Original Message -----
From: "Robert McCallum" <robert.mccallum2(at)sympatico.ca>
Subject: Re: AeroElectric-List: Circuit breaker ratings for OVP
>
>
> Bob;
>
> Although the "time to trip" charts stop at 1000% of the breakers rating,
> the specifications you have published here
>
> http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
>
> under interrupting capacity at 28 volts state that for a 4200 series
> breaker of 5 amp rating, the interrupting capacity is "unlimited" (seems
> a bit high?) Certainly more than 10X. Further the same spec sheet says
> that a 7.5 amp breaker is capable of interrupting 2000 amps. This is
> 266X its nominal rating. If you look at a 25 amp it's 80X nominal. I
> realize that this doesn't specify the number of times the breaker will
> survive these currents, but it does state that they are capable of
> taming currents of these magnitudes. How do these figures impact on the
> 10X theory and where does the 10X information show up in the
> specifications? In a parallel but totally different scenario, household
> breakers of 15 amp rating, to be certified for use in your home, (at
> least here in Canada) must be capable of interrupting 10,000 amps
> minimum. That's 667X nominal value. Unrelated, I know, but ----- These
> numbers and those stated by Eaton in the charts cited seem to be at odds
> with the 10X value. Yes????? No??????
>
> Bob McC
>
> Robert L. Nuckolls, III wrote:
>
>>
>>
>>Hmmmm . . . I note that the 10x rated limit for surviving repeated trips
>>seems to be an industry standard practice for most breakers offered.
>>One might guess that the limits to the plots in the graph I excerpted
>>at 1000% imply the same thing. I don't find it in words on the Eaton
>>data sheet like for most others on the 'net. I found some $low$ breakers
>>out there rated at only 6x for resetable trips.
>>
>>Interesting.
>>Bob . . .
>>
>>
>
>
>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Circuit breaker ratings for OVP |
To me the OVP is only part of the system. As noted my suggestion of a 1/4
ohm resistor has side effects that need attenton. the following concerns are
possible before the addition of the addl resistor and very likely after its
addition.
Consider it takes 3-5 ms for the start of the crowbar in your OVP. OV can be
present during that time and its not clamped by the OVP.
Consider an internal regulated alternator. Here the OVP is unlikely to
completely clamp a OV condition and the internal regulator's OV protection
is typically set above 30 V as the intent is to protect the regulator.
Then consider a fast OVP action and a slow open contactor. After the CB
blows there is time between this event and the end of the opening of the
contactor for the OV to reappear for a short time.
ALL of the above is prevented with the proper application of Transorbs
across the bus on the bus side of the "B" lead contactor. Protection of the
alternator regulator (which seems necessary in the case of the Vans ND
alternators, well how knows?) is covered with a second set of Transorbs just
for the load dump as seen by the alternator internal regulator..
Thus proper use of transorbs and a OVP can cover 100% of any potential OV
condition and resulting tripping of the CB.
The transorbs must be chosen along with the OVP trip voltage so both work as
intended.
16V transorbs can keep the bus voltage to around 20V max and 18V transorbs
keep it to around 23V max. Depends on the current needed dumping etc but not
a unreasonable solution and low cost and simple to do.
I have tested this approach and it worked well in testing.
I agree with Bobs comments below.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: RE: AeroElectric-List: Circuit breaker ratings for OVP
>
>
>
>>
>>
>>Paul M,
>>
>>You said :-
>>As I have previously suggested there is a simple fix to those who are
>>using the crowbar OVP and that is to add a 1/4 ohm resistor in series that
>>will limit the current to 50 amps or less and will not prevent the proper
>>and
>>intended function of the OVP.
>>
>>What wattage are we talking about here please Paul or doesn't it matter
>>owing to the small duration of the high current event ?
>
>
> Is your alternator externally regulated? Then keep in mind that adding
> resistance in series with the ov protection module will reduce its
> ability to pull the field voltage down even BEFORE the breaker trips.
> In fact, adding this much resistance insures that the OV event will
> continue until the breaker opens. During the trip event, the series
> resistor will have to carry about 50A at about 10v for an instantaneous
> dissipation level of about 500 watts. Most wirewound resistor folks
> will rate their produces at 10x rated power for 5 seconds. So assuming
> a 10 watt, 0.25 ohm resistor will safely handle 100 watts for 5 seconds
> (current of 20A) this calculates to an Isquared*t value 20*20*5 or
> 2,000.
>
> Okay, for a 50A event, an Isquared*t of 2000 yields a maximum time
> of 2000/2500 or about .8 seconds. This suggests that a 10W resistor
> is plenty hefty enough to accomplish the task. A 5W resistor would
> be good for .4 seconds . . . also fine.
>
> See ALSR series wirewounds on Digikey at
>
> http://dkc3.digikey.com/PDF/T051/1026.pdf
>
> An ALSR5J-.25-ND (0.25 ohm, 5w) resistor is in stock and would
> cost you about $1.50
>
> If your alternator is internally regulated, then the OVM has no immediate
> effect on the runaway condition. Increasing the series resistance
> the OVM-14 only increases breaker opening time. However, given that
> the internally regulated alternator control system operates nicely through
> a 2A breaker, all you need to do is replace your existing breaker with
> a 2A sub-miniature breaker. See:
>
> http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
>
>
> These have an internal resistance of well OVER .25 ohms. 0.30 ohms
> in fact. This will have the same effect as adding series resistance
> to the OVM-14. Either way, the resistor cited above or replacing the
> breaker will have the desired effect.
>
> Bob . . .
>
>
>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Circuit breaker ratings for OVP |
Bob using a 2 amp CB is a good idea for the "B" lead contactor but when you
use a 2 amp CB the 1/4 ohm that reduces current to 50 amps is no longer
appropriate as the new max current is reduced from 50 amps to 20 amps.
So an additional resistor is still needed.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: RE: AeroElectric-List: Circuit breaker ratings for OVP
>
>
> If your alternator is internally regulated, then the OVM has no immediate
> effect on the runaway condition. Increasing the series resistance
> the OVM-14 only increases breaker opening time. However, given that
> the internally regulated alternator control system operates nicely through
> a 2A breaker, all you need to do is replace your existing breaker with
> a 2A sub-miniature breaker. See:
>
> http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
>
>
> These have an internal resistance of well OVER .25 ohms. 0.30 ohms
> in fact. This will have the same effect as adding series resistance
> to the OVM-14. Either way, the resistor cited above or replacing the
> breaker will have the desired effect.
>
> Bob . . .
________________________________________________________________________________
| From: | "Travis Hamblen" <TravisHamblen(at)cox.net> |
I am using Z-11 plan and have a couple questions that you guys will
definitely know about. First, I am using the suggested steering diode
between the main and essential bus (using the heat sink). The question is
that because of the amperage I am sending through this diode ( < 25a but
sometimes > 20a) I will be using 10awg wire which means I can't use a fast
on terminal because they don't make them for awg that large. SO would a
good alternative be to solder the wires to the fast on connectors on the
diode? If I did this would it be just as secure, I was concerned that with
all the vibration in an RV that the solder could break away after a while.
I would prefer to use a fast on, but haven't been able to find fast ons for
awg smaller than 14awg; if someone has a source for these please let me
know!
The second question is about the fuse that the steering diode calls for.
The diode is only rated up to a max of 25a and this is a perfect match for
my system. However, it also calls for the use of a breaker or fuse on the
two wires going to the main bus. I was thinking of using an automotive
style inline fuse that would use a 30a standard 1/4" blade type fuse. Is
there a better way or will the inline fuse work just fine?
Thanks,
Travis
RV-7A wiring
--
________________________________________________________________________________
| From: | Ken <klehman(at)albedo.net> |
| Subject: | Re: Circuit breaker ratings for OVP |
But is it an arbitrarilly large current at the specified voltages and
with wires that can reasonably be attached to the device? One of the
examples mentioned about 35 miliohms resistance for the breaker. Well if
a 12volt battery is pulled down to say 10 volts then you simply can't
get more than 10 / 0.035 =286 amps even with a zero impedance (at 10
volts) battery and zero resistance wires and connectors! But it would be
less with real wires, real connectors, and a real battery. OK double
that for a 24 volt system but it still isn't arbitrarilly large.
N'other thing worth consideration might be reliability and the failure
modes of OVP devices. A crowbar that does nothing in normal ops might
have a higher probability of failing passively in normal operations
compared to a device that must continuously conduct field curent to keep
the alternator running??
Ken
Eric M. Jones wrote:
>
>Bob, et al.
>
>It would seem improbably at best that a circuit breaker could be built to
>survive an arbitrarily large overcurrent. As Paul has pointed out, the
>addition of a small resistor will put this crowbar back into the barn.
>
>
>snip
________________________________________________________________________________
| Subject: | Re: Diode question |
| From: | "Matt Prather" <mprather(at)spro.net> |
Hi Travis,
A few questions for your questions...
>
>
> I am using Z-11 plan and have a couple questions that you guys will
> definitely know about. First, I am using the suggested steering diode
> between the main and essential bus (using the heat sink). The question
> is that because of the amperage I am sending through this diode ( < 25a
> but sometimes > 20a) I will be using 10awg wire which means I can't use
For what duration does your power budget show that you will be greater
than 20A. What's the biggest consumer in that 20A budget? Actually, do
you have a list of components on the e-buss and what each item consumes?
The reason I am picking this is that 20A seems like a lot.
> a fast on terminal because they don't make them for awg that large. SO
> would a good alternative be to solder the wires to the fast on
> connectors on the diode? If I did this would it be just as secure, I
> was concerned that with all the vibration in an RV that the solder could
> break away after a while. I would prefer to use a fast on, but haven't
> been able to find fast ons for awg smaller than 14awg; if someone has a
> source for these please let me know!
If it turns out that you really need 14awg and can't find the right terminals
for it (aren't the yellow terminals 14-16awg?), with proper strain relief,
soldering
is a good option. My only concern is that you use a good iron and good
technique
so that you don't seriously overheat the package while soldering to it.
Probably
not an issue, but just something to think about.
>
> The second question is about the fuse that the steering diode calls for.
> The diode is only rated up to a max of 25a and this is a perfect match
> for my system. However, it also calls for the use of a breaker or fuse
> on the two wires going to the main bus. I was thinking of using an
> automotive style inline fuse that would use a 30a standard 1/4" blade
> type fuse. Is there a better way or will the inline fuse work just
> fine?
I have never seen an inline style fuse holder that I thought was particularly
neat or secure. They seem barely adequate for adding a CB radio to your
cousin's pickup truck. I probably just haven't seen the right holder. Show
me.
I think this might be a reasonable application for a fusible link.
>
> Thanks,
> Travis
> RV-7A wiring
>
> --
>
Regards,
Matt-
VE N34RD, C150 N714BK
________________________________________________________________________________
| From: | "Matt Prather" <mprather(at)spro.net> |
Hi Travis,
Including some of these items on the e-bus seems like a bit of a deviation
from the philsophy that I understand. Care to share your thoughts on this?
I wonder about the engine monitor, Flaps, Fuel Boost. It doesn't seem that
any of these items contribute very much to enroute capability. The items
needed are those which help keep the airplane right side up, on course, and
out of the rocks. I thought that things required to keep the engine running
go on the battery bus. I say the xponder and com go on the main bus, but
they
are such small consumers that you could go either way with them. Sometimes
it's comforting, quite a bit more convenient, and safer to be able to talk
and take
radar vectors.
None the less, all of this is somewhat academic, since you have already found
components that allow you to wire the system the way you want.
On an RV, do you consider the flaps to be a necessity?
The fuse holder you posted the link to is okay - about what I thought. My
only
gripes are that it doesn't have any mounting lugs, and that since it has
wires
already attached, you have to introduce two extra sets of connections in
order
to wire it up. Can you change the fuse without putting undue strain on
the wire
connections?
Which part of the fusible link don't you like?
Regards,
Matt-
VE N34RD, C150 N714BK
> e-bus is the following:
>
> Dynon EFIS & Engine Monitor
> EKP IV GPS
> XCOM VHF
> Xponder
> Auto Pilot
> Flaps
> Fuel boost
> Trim
> Interior lighting
>
> I know I wouldn't be using half of these things on a constant basis in
> the event of an elec problem, but I have reasons for having each of
> these on the e-bus. As it turns out, I was just able to find some
> faston connectors for 10awg, so I won't have to solder anything. As for
> the inline fuse, I found a very good quality (marine grade) setup that I
> will use; I just don't like the whole fusible link thing, kind of scary
> to me. Check out the below link (link might break or wrap in e-mail):
>
> http://www.go2marine.com/g2m/action/GoBPage/id/85194F/flat_fuse_holder__30_a
> mp_sierra.html
>
> Travis
>
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: Circuit breaker ratings for OVP |
>>
>>It would seem improbably at best that a circuit breaker could be built to
>>survive an arbitrarily large overcurrent. As Paul has pointed out, the
>>addition of a small resistor will put this crowbar back into the barn.
>>snip
>But is it an arbitrarilly large current at the specified voltages and
>with wires that can reasonably be attached to the device? One of the
>examples mentioned about 35 miliohms resistance for the breaker. Well if
>a 12volt battery is pulled down to say 10 volts then you simply can't
>get more than 10 / 0.035 =286 amps even with a zero impedance (at 10
>volts) battery and zero resistance wires and connectors! But it would be
>less with real wires, real connectors, and a real battery. OK double
>that for a 24 volt system but it still isn't arbitrarilly large.
Ken,
I didn't mean infinitely large. I meant some amount over the 1000% limit
specified by the CB manufacturer. The point is that Bob's white paper
assumed you could extend the curves...and well...I don't think you can.
>N'other thing worth consideration might be reliability and the failure
>modes of OVP devices. A crowbar that does nothing in normal ops might
>have a higher probability of failing passively in normal operations
>compared to a device that must continuously conduct field curent to keep
>the alternator running??
Point taken, but the Linear OVP should be as good as the regulator, the ECU,
and the prop bolts. I mention installing a MOM-OFF-ON switch to over-ride
everything if one wants to.
I'd put the Linear OVM reliability up again the crowbar and breaker any
time. Reliability is fundamentally what this argument is about.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
Teamwork: " A lot of people doing exactly what I say."
(Marketing exec., Citrix Corp.)
________________________________________________________________________________
| From: | Ken <klehman(at)albedo.net> |
| Subject: | Re: Diode question |
Yellow PIDG faston terminals are available from digi-key in
(min.quantity 10) and work fine on 10 and 12 awg wire.
Ken
Travis Hamblen wrote:
>
>I am using Z-11 plan and have a couple questions that you guys will
>definitely know about. First, I am using the suggested steering diode
>between the main and essential bus (using the heat sink). The question is
>that because of the amperage I am sending through this diode ( < 25a but
>sometimes > 20a) I will be using 10awg wire which means I can't use a fast
>on terminal because they don't make them for awg that large. SO would a
>good alternative be to solder the wires to the fast on connectors on the
>diode? If I did this would it be just as secure, I was concerned that with
>all the vibration in an RV that the solder could break away after a while.
>I would prefer to use a fast on, but haven't been able to find fast ons for
>awg smaller than 14awg; if someone has a source for these please let me
>know!
>
>The second question is about the fuse that the steering diode calls for.
>The diode is only rated up to a max of 25a and this is a perfect match for
>my system. However, it also calls for the use of a breaker or fuse on the
>two wires going to the main bus. I was thinking of using an automotive
>style inline fuse that would use a 30a standard 1/4" blade type fuse. Is
>there a better way or will the inline fuse work just fine?
>
>Thanks,
>Travis
>RV-7A wiring
>
>
>
________________________________________________________________________________
| From: | "Bill and Marsha" <docyukon(at)ptcnet.net> |
| Subject: | Whelen power supply |
I have a whelen strobe power supply with MS Cannon conectors. Can anyone
tell me the pin out and coler code to connect up to whelen flash tubes?
________________________________________________________________________________
| From: | CardinalNSB(at)aol.com |
| Subject: | Re: led dimmer question |
Hello:
I have been playing with the LM 317 adjustable voltage regulator
12 volt positive input to the LM 317
led positive lead(s) all connected to the output of the LM 317
common ground for led leads to battery negative
The brightness of the light is based on the (adjusted) voltage, whether 1 or
more leds are connected. So, this will dim leds, brightness is stable,
whether 1 or more leds are in the system.
However, my Garmil 300xl outputs 12 volt + per annnciator light so the LM
317 isn't appropriate. I would need a separate LM 317 for each light circuit
and a way to control each LM 317 at the same time.
Is there a similar product that the common ground from the leds would be the
input and the chassis ground would be the output that would maintain the
reduced voltage?
Is this what the LM 137 does?
That is, the 12v+ from the gps box would go to the led, the negative leg of
the various leds would be connected in common to the input of the LM 137, and
the output of the LM 137 would be grounded. Sort of a LM 317 setup but on
the "downside" leg of the leds.
Thanks for the help. Skip Simpson.
________________________________________________________________________________
| From: | drshufly(at)aol.com |
| Subject: | EGT interference |
My Glasair EGT/CHT readings (as read on my RMI Micromonitor) are steady until I
energize the Whelan strobe system and then they jump around several hundred degrees.
I'm wondering if a Radio Shack noise filter on the strobe power supply
might correct this situation. Closest point of approach for any mutual wire
is twelve inches; strobes are the instigator; EGT/CHT is the victim so I wonder
if a filter would do any good. Could the problem be simply RFI coming from
the strobes? Would appreciate comments.
Bob Shumaker in Virginia
Glasair IIS-RG with 600 safe hours
________________________________________________________________________________
| From: | "Joe & Jan Connell" <jconnell(at)rconnect.com> |
| Subject: | Diodes for Master and Strater relays |
Hi Guys,
I've been searching the AeroElectric-List and the RV-list to
get information on which diode to use across these relays.
Can you provide me a diode part number and ratings? I'd
rather not buy the prepackaged solution from Van's...
Thanks.
Joe Connell
Stewartville, MN
RV-9A N95JJ wiring
________________________________________________________________________________
| From: | D Wysong <hdwysong(at)gmail.com> |
| Subject: | Re: led dimmer question |
Hello Skip -
> That is, the 12v+ from the gps box would go to the led, the negative leg of
> the various leds would be connected in common to the input of the LM 137, and
> the output of the LM 137 would be grounded. Sort of a LM 317 setup but on
> the "downside" leg of the leds.
The LM137 expects a negative voltage differential between the Vin and
ground. Maybe if you attach the LED to the -Vout terminal, your
ground to the -Vin terminal, and a positive supply voltage to the
Ground terminal it'll work. Seems upside down and backwards... but
samples are cheap! Give it a try! :-)
There's an application circuit in the LM117/LM317 datasheet for
"Digitally Selected Outputs" that will work with a few mod's (more
parts!). If you put your LEDs inline with those transistors and move
the entire transistor bank from the Adj rail to the Vout rail, you can
attach your annunciator outputs to the transistor Inputs and drive
your parallel-dimmed LEDs that way.
D
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: led dimmer question |
>I have been playing with the LM 317 adjustable voltage regulator
> 12 volt positive input to the LM 317
>led positive lead(s) all connected to the output of the LM 317
>common ground for led leads to battery negative
>The brightness of the light is based on the (adjusted) voltage, whether 1
or
>more leds are connected. So, this will dim leds, brightness is stable,
>whether 1 or more leds are in the system.
>However, my Garmin 300xl outputs 12 volt + per annnciator light so the LM
>317 isn't appropriate. I would need a separate LM 317 for each light
circuit
>and a way to control each LM 317 at the same time.
>Is there a similar product that the common ground from the leds would be
the
>input and the chassis ground would be the output that would maintain the
>reduced voltage? Is this what the LM 137 does?
>That is, the 12v+ from the gps box would go to the led, the negative leg of
>the various leds would be connected in common to the input of the LM 137,
and
>the output of the LM 137 would be grounded. Sort of a LM 317 setup but on
>the "downside" leg of the leds. Thanks for the help. Skip Simpson.
Skip,
It certainly seems reasonable to use a negative regulator in this
application. After all the electrons don't know the difference. But when you
look at the "negative" LM317, the LM137 you find that all is not so simple.
Whereas the LM317 has a positive voltage in and a regulated positive voltage
out, the LM137 would have a ground in and a "regulated" ground out. a
regulated ground is still zero.
Negative voltages are arranged at the power source by grounding the positive
lead of one battery to the negative lead of the other. Then one battery
provides positive, the connection between the batteries is "ground" and the
second battery negative ground terminal becomes "negative". Negative
voltages can also be had by a little IC power supply.
You don't need to consider them--or the negative voltage regulator. Assuming
the Garmin output can't be dimmed (and I'd surely check into this with
Garmin!) then consider controlling the current through the LEDs by using an
NPN transistor with a grounded emitter. Consider using a National
Semiconductor LM395 (can't break it). Group all your LED cathode grounds
together and change the current through the base. Lot's of help online for
the circuit.
Don't be afraid.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
"Then I got married. I thought...well,
I figured that...ahhh. Hell, I don't know WHAT
I was thinking...."
--My friend Victor
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: Diodes across relay coils |
>For decades 99.999% of the engineering world recommended and used the
common rectifier diode across inductors like relay coils to suppress the
inductive spike that happens hen the power to the inductor is interrupted.
Hey, my dad taught me this technique....And he claimed never to be wrong.
Usually.
>I have removed all the simple diodes across relays and replaced them with
by directional transorbs and also supplied parts to the local builders as
well.
>Paul
This posting was really significant but has not been much commented on.
Basically, ALL the suppressor diodes on all coils and relays and contactors
should be changed to bi-directional transorbs or similar. Okay don't panic,
but put it on your list. If you are having problems (sticking contactors?,
better upgrade now). This is a significant change we can all blame Paul
Messinger for.
Read these links-- Yikes....
http://relays.tycoelectronics.com/application.asp
http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
And of course, these are available from me.
http://www.periheliondesign.com/suppressors/SnapJack.pdf Website hasn't
been updated yet.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
"...as we know, there are known knowns; there are things we know we know. We
also know there are known unknowns; that is to say we know there are some
things we do not know. But there are also unknown unknowns - the ones we
don't know we don't know." D. Rumsfeld
________________________________________________________________________________
| Subject: | Re: Diodes across relay coils |
| From: | "Matt Prather" <mprather(at)spro.net> |
Reading both of these messages, it might sound like using a flyback
diode is worse than nothing. Is that the point? Or is it that flyback
diodes
only fix one kind of problem (arcing from the collapsing field caused by
the high dI/dt), but might make a different one worse (somewhat increase
contact bounce by slowing/reversing armature motion)?
Does anyone have data to quantify how much longer the contacts will live
with no protection, vs. diode protection, vs. transorbs? That would be
useful.
Regards,
Matt-
VE N34RD, C150 N714BK
>
>
>
>
>>For decades 99.999% of the engineering world recommended and used the
> common rectifier diode across inductors like relay coils to suppress the
> inductive spike that happens hen the power to the inductor is
> interrupted.
>
> Hey, my dad taught me this technique....And he claimed never to be
> wrong. Usually.
>
>>I have removed all the simple diodes across relays and replaced them
>> with
> by directional transorbs and also supplied parts to the local builders
> as well.
>>Paul
>
> This posting was really significant but has not been much commented on.
> Basically, ALL the suppressor diodes on all coils and relays and
> contactors should be changed to bi-directional transorbs or similar.
> Okay don't panic, but put it on your list. If you are having problems
> (sticking contactors?, better upgrade now). This is a significant change
> we can all blame Paul Messinger for.
>
> Read these links-- Yikes....
>
> http://relays.tycoelectronics.com/application.asp
>
> http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
>
> And of course, these are available from me.
>
> http://www.periheliondesign.com/suppressors/SnapJack.pdf Website
> hasn't been updated yet.
>
> Regards,
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge MA 01550-2705
> Phone (508) 764-2072
> Email: emjones(at)charter.net
>
> "...as we know, there are known knowns; there are things we know we
> know. We also know there are known unknowns; that is to say we know
> there are some things we do not know. But there are also unknown
> unknowns - the ones we don't know we don't know." D. Rumsfeld
>
>
________________________________________________________________________________
| From: | rd2(at)evenlink.com |
| Subject: | Re: Diodes across relay coils |
Eric, thanks for not letting this escape and sink in mailbaskets, be
forgotten, deleted whatever.
Paul, thanks.
I am no engineer but have learned a lot through my hobby, and this list,
and Bob et all. The by-directional transorbs had caught my attention but
the subject had started to fade in the daily streams of incoming info. This
brought it back. Thank you list.
Rumen
_____________________Original message __________________________
(received from Eric M. Jones; Date: 04:15 PM 3/24/2005
-0500)
>For decades 99.999% of the engineering world recommended and used the
common rectifier diode across inductors like relay coils to suppress the
inductive spike that happens hen the power to the inductor is interrupted.
Hey, my dad taught me this technique....And he claimed never to be wrong.
Usually.
>I have removed all the simple diodes across relays and replaced them with
by directional transorbs and also supplied parts to the local builders as
well.
>Paul
This posting was really significant but has not been much commented on.
Basically, ALL the suppressor diodes on all coils and relays and contactors
should be changed to bi-directional transorbs or similar. Okay don't panic,
but put it on your list. If you are having problems (sticking contactors?,
better upgrade now). This is a significant change we can all blame Paul
Messinger for.
Read these links-- Yikes....
http://relays.tycoelectronics.com/application.asp
http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
And of course, these are available from me.
http://www.periheliondesign.com/suppressors/SnapJack.pdf Website hasn't
been updated yet.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
"...as we know, there are known knowns; there are things we know we know. We
also know there are known unknowns; that is to say we know there are some
things we do not know. But there are also unknown unknowns - the ones we
don't know we don't know." D. Rumsfeld
________________________________________________________________________________
| From: | Richard Tasker <retasker(at)optonline.net> |
| Subject: | Re: Diodes across relay coils |
Diodes are much better than nothing, but they fix one problem and make
another worse. Depending on your whole system one or the other could be
worse. Are large negative voltage spikes every time you shut the relay
off worse than the possibility of the relay welding on at some time? I
suspect that, for most of us, the slight potential of welded contacts
are better than spikes.
With the transorbs you sort of have the best of both worlds - you limit
the spike to something more reasonable (whatever the voltage rating of
the transorb is) and you minimize the likelihood of welded contacts due
to the much faster turnoff time.
Unfortunately, it is impossible to meaningfully quantify the difference
in contact life without knowing a whole lot about your specific application.
Dick Tasker
Matt Prather wrote:
>
>Reading both of these messages, it might sound like using a flyback
>diode is worse than nothing. Is that the point? Or is it that flyback
>diodes
>only fix one kind of problem (arcing from the collapsing field caused by
>the high dI/dt), but might make a different one worse (somewhat increase
>contact bounce by slowing/reversing armature motion)?
>
>Does anyone have data to quantify how much longer the contacts will live
>with no protection, vs. diode protection, vs. transorbs? That would be
>useful.
>
>
>Regards,
>
>Matt-
>VE N34RD, C150 N714BK
>
>
>
>
>>
>>
>>
>>
>>
>>
>>>For decades 99.999% of the engineering world recommended and used the
>>>
>>>
>>common rectifier diode across inductors like relay coils to suppress the
>>inductive spike that happens hen the power to the inductor is
>>interrupted.
>>
>>Hey, my dad taught me this technique....And he claimed never to be
>>wrong. Usually.
>>
>>
>>
>>>I have removed all the simple diodes across relays and replaced them
>>>with
>>>
>>>
>>by directional transorbs and also supplied parts to the local builders
>>as well.
>>
>>
>>>Paul
>>>
>>>
>>This posting was really significant but has not been much commented on.
>>Basically, ALL the suppressor diodes on all coils and relays and
>>contactors should be changed to bi-directional transorbs or similar.
>>Okay don't panic, but put it on your list. If you are having problems
>>(sticking contactors?, better upgrade now). This is a significant change
>>we can all blame Paul Messinger for.
>>
>>Read these links-- Yikes....
>>
>>http://relays.tycoelectronics.com/application.asp
>>
>>http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
>>
>>And of course, these are available from me.
>>
>>http://www.periheliondesign.com/suppressors/SnapJack.pdf Website
>>hasn't been updated yet.
>>
>>Regards,
>>Eric M. Jones
>>www.PerihelionDesign.com
>>113 Brentwood Drive
>>Southbridge MA 01550-2705
>>Phone (508) 764-2072
>>Email: emjones(at)charter.net
>>
>>"...as we know, there are known knowns; there are things we know we
>>know. We also know there are known unknowns; that is to say we know
>>there are some things we do not know. But there are also unknown
>>unknowns - the ones we don't know we don't know." D. Rumsfeld
>>
________________________________________________________________________________
| From: | paul wilson <pwilson(at)climber.org> |
| Subject: | Re: Diodes across relay coils |
Eric,
Paul said "directional transorbs"
You said "bi-directional transorbs or similar"
Typo? Or do I need help to understand?
Thanks, Paul
======================
>
>
> >For decades 99.999% of the engineering world recommended and used the
>common rectifier diode across inductors like relay coils to suppress the
>inductive spike that happens hen the power to the inductor is interrupted.
>
>Hey, my dad taught me this technique....And he claimed never to be wrong.
>Usually.
>
> >I have removed all the simple diodes across relays and replaced them with
>by directional transorbs and also supplied parts to the local builders as
>well.
> >Paul
>
>This posting was really significant but has not been much commented on.
>Basically, ALL the suppressor diodes on all coils and relays and contactors
>should be changed to bi-directional transorbs or similar. Okay don't panic,
>but put it on your list. If you are having problems (sticking contactors?,
>better upgrade now). This is a significant change we can all blame Paul
>Messinger for.
>
>Read these links-- Yikes....
>
>http://relays.tycoelectronics.com/application.asp
>
>http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
>
>And of course, these are available from me.
>
>http://www.periheliondesign.com/suppressors/SnapJack.pdf Website hasn't
>been updated yet.
>
>Regards,
>Eric M. Jones
>www.PerihelionDesign.com
>113 Brentwood Drive
>Southbridge MA 01550-2705
>Phone (508) 764-2072
>Email: emjones(at)charter.net
>
>"...as we know, there are known knowns; there are things we know we know.
>We also know there are known unknowns; that is to say we know there are
>some things we do not know. But there are also unknown unknowns - the ones
>we don't know we don't know." D. Rumsfeld
________________________________________________________________________________
| From: | Richard Tasker <retasker(at)optonline.net> |
| Subject: | Re: Diodes across relay coils |
Actually Paul did say bidirectional transorb. He also mentioned if you
use a uni-directional transorb you must also use a series diode with it.
A bi-directional transorb must have a sufficiently high breakdown
voltage so it never turns on with normal battery/alternator voltage
present - i.e. use one with at least a 16V breakdown.
As an exercise for the student, you can "tune" the response by using a
lower voltage transorb with a series diode to get whatever voltage spike
you are comfortable with. I.e., trade off turn-off time with voltage
spike magnitude. :-) Or not...
Dick Tasker
paul wilson wrote:
>
>Eric,
> Paul said "directional transorbs"
> You said "bi-directional transorbs or similar"
> Typo? Or do I need help to understand?
>Thanks, Paul
>======================
>
>
>
>>
>>
>>
>>
>>>For decades 99.999% of the engineering world recommended and used the
>>>
>>>
>>common rectifier diode across inductors like relay coils to suppress the
>>inductive spike that happens hen the power to the inductor is interrupted.
>>
>>Hey, my dad taught me this technique....And he claimed never to be wrong.
>>Usually.
>>
>>
>>
>>>I have removed all the simple diodes across relays and replaced them with
>>>
>>>
>>by directional transorbs and also supplied parts to the local builders as
>>well.
>>
>>
>>>Paul
>>>
>>>
>>This posting was really significant but has not been much commented on.
>>Basically, ALL the suppressor diodes on all coils and relays and contactors
>>should be changed to bi-directional transorbs or similar. Okay don't panic,
>>but put it on your list. If you are having problems (sticking contactors?,
>>better upgrade now). This is a significant change we can all blame Paul
>>Messinger for.
>>
>>Read these links-- Yikes....
>>
>>http://relays.tycoelectronics.com/application.asp
>>
>>http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
>>
>>And of course, these are available from me.
>>
>>http://www.periheliondesign.com/suppressors/SnapJack.pdf Website hasn't
>>been updated yet.
>>
>>Regards,
>>Eric M. Jones
>>www.PerihelionDesign.com
>>113 Brentwood Drive
>>Southbridge MA 01550-2705
>>Phone (508) 764-2072
>>Email: emjones(at)charter.net
>>
>>"...as we know, there are known knowns; there are things we know we know.
>>We also know there are known unknowns; that is to say we know there are
>>some things we do not know. But there are also unknown unknowns - the ones
>>we don't know we don't know." D. Rumsfeld
>>
>
>
________________________________________________________________________________
| From: | paul wilson <pwilson(at)climber.org> |
| Subject: | Re: Diodes across relay coils |
Thanks Dick
Most of the discussion went past me as you noted. I need the inputs to be
pretty short and simple. :-)
Paul W
==========
>
>
>Actually Paul did say bidirectional transorb. He also mentioned if you
>use a uni-directional transorb you must also use a series diode with it.
>
>A bi-directional transorb must have a sufficiently high breakdown
>voltage so it never turns on with normal battery/alternator voltage
>present - i.e. use one with at least a 16V breakdown.
>
>As an exercise for the student, you can "tune" the response by using a
>lower voltage transorb with a series diode to get whatever voltage spike
>you are comfortable with. I.e., trade off turn-off time with voltage
>spike magnitude. :-) Or not...
>
>Dick Tasker
>
>
>paul wilson wrote:
>
> >
> >Eric,
> > Paul said "directional transorbs"
> > You said "bi-directional transorbs or similar"
> > Typo? Or do I need help to understand?
> >Thanks, Paul
> >======================
> >
> >
> >
>
> >>
>
> >>
> >>
> >>
> >>>For decades 99.999% of the engineering world recommended and used the
> >>>
> >>>
> >>common rectifier diode across inductors like relay coils to suppress the
> >>inductive spike that happens hen the power to the inductor is interrupted.
> >>
> >>Hey, my dad taught me this technique....And he claimed never to be wrong.
> >>Usually.
> >>
> >>
> >>
> >>>I have removed all the simple diodes across relays and replaced them with
> >>>
> >>>
> >>by directional transorbs and also supplied parts to the local builders as
> >>well.
> >>
> >>
> >>>Paul
> >>>
> >>>
> >>This posting was really significant but has not been much commented on.
> >>Basically, ALL the suppressor diodes on all coils and relays and contactors
> >>should be changed to bi-directional transorbs or similar. Okay don't panic,
> >>but put it on your list. If you are having problems (sticking contactors?,
> >>better upgrade now). This is a significant change we can all blame Paul
> >>Messinger for.
> >>
> >>Read these links-- Yikes....
> >>
> >>http://relays.tycoelectronics.com/application.asp
> >>
> >>http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
> >>
> >>And of course, these are available from me.
> >>
> >>http://www.periheliondesign.com/suppressors/SnapJack.pdf Website hasn't
> >>been updated yet.
> >>
> >>Regards,
> >>Eric M. Jones
> >>www.PerihelionDesign.com
> >>113 Brentwood Drive
> >>Southbridge MA 01550-2705
> >>Phone (508) 764-2072
> >>Email: emjones(at)charter.net
> >>
> >>"...as we know, there are known knowns; there are things we know we know.
> >>We also know there are known unknowns; that is to say we know there are
> >>some things we do not know. But there are also unknown unknowns - the ones
> >>we don't know we don't know." D. Rumsfeld
> >>
> >
> >
>
>
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: Diodes across relay coils |
>Eric,
> Paul said "directional transorbs"
>You said "bi-directional transorbs or similar"
>Typo? Or do I need help to understand?
>Thanks, Paul
======================
Paul Messinger wrote
> >I have removed all the simple diodes across relays and replaced them with
>>by directional transorbs and also supplied parts to the local builders as
>>well.
> >Paul
But hear Paul did not spel so gud.
Bi-Directional...There is a class of these---Transorbs, Transils, Mosorbs,
etc. all bi-directional Zener Transient Voltage Suppressor Diodes.
"SnapJacks".
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
"I tried being reasonable--I didn't like it!"
--Clint Eastwood
________________________________________________________________________________
| Subject: | Re: Diodes across relay coils |
In a message dated 3/25/2005 12:08:36 A.M. Eastern Standard Time,
retasker(at)optonline.net writes:
Actually Paul did say bidirectional transorb. He also mentioned if you
use a uni-directional transorb you must also use a series diode with it.
A bi-directional transorb must have a sufficiently high breakdown
voltage so it never turns on with normal battery/alternator voltage
present - i.e. use one with at least a 16V breakdown.
Before silicon diodes were common, a neon "grain of wheat" bulb (a
bi-directional device) was used to halt relay bounce and save contacts from abuse.
I
used to find comfort in watching the neons fire knowing that my device was
being saved from unnecessary destruction.
John P. Marzluf
Columbus, Ohio
Kitfox Outback (out back in the garage)
________________________________________________________________________________
| From: | Ken <klehman(at)albedo.net> |
| Subject: | Re: Diodes across relay coils |
Yup!
99.99% of the engineering world also protected their circuitry from 20
volt and highter negative spikes which may have been more imortant to
them. Sensationalist statements may catch attention but there is more to
this story and it seems to me that there are tradeoffs that should
accompany such a claim...
Ken
(in no hurry to remove my diodes)
Matt Prather wrote:
>
>Reading both of these messages, it might sound like using a flyback
>diode is worse than nothing. Is that the point? Or is it that flyback
>diodes
>only fix one kind of problem (arcing from the collapsing field caused by
>the high dI/dt), but might make a different one worse (somewhat increase
>contact bounce by slowing/reversing armature motion)?
>
>Does anyone have data to quantify how much longer the contacts will live
>with no protection, vs. diode protection, vs. transorbs? That would be
>useful.
>
>
>Regards,
>
>Matt-
>VE N34RD, C150 N714BK
>
>
>
>
>>
>>
>>
>>
>>
>>
>>>For decades 99.999% of the engineering world recommended and used the
>>>
>>>
>>common rectifier diode across inductors like relay coils to suppress the
>>inductive spike that happens hen the power to the inductor is
>>interrupted.
>>
>>Hey, my dad taught me this technique....And he claimed never to be
>>wrong. Usually.
>>
>>
>>
>>>snip
>>>
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: Diodes across relay coils |
>Yup!
>99.99% of the engineering world also protected their circuitry from 20
>volt and highter negative spikes which may have been more imortant to
>them. Sensationalist statements may catch attention but there is more to
>this story and it seems to me that there are tradeoffs that should
>accompany such a claim...Ken
Ken,
Science on the march. Please read and comment on the Tyco and Kilovac
references. Potter and Brumfield is synonymous with "relays". They don't
kid around.
It is usually true that the best technology comes just when the technology
is on its way out. Those steam-turbine locomotives were fabulous. So here we
are in a solid state world and they finally figured out how to make relays
work better. Sensationalist? Not me. But I had a customer who had TWO
starter contactors weld closed in his Lancair. I'll bet he'll be changing
the diodes this weekend.
>(in no hurry to remove my diodes)
So don't.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
"A man's got to know his limitations."
(Clint Eastwood's Dirty Harry in Magnum Force, 1973)
________________________________________________________________________________
| From: | "Joe & Jan Connell" <jconnell(at)rconnect.com> |
| Subject: | Fw: Diodes for Master and Starter relays |
Hi Guys,
Thanks for all your discussion on this topic. In review of
http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
it appears the zener-zener method is preferred. After searching
through the Digikey catalog it looks like I should get a pair of zener
diodes, solder the cathode ends together, and connect the anode
ends to relay terminals after covering them with heat-shrink tubing.
Am I in the ball park on this?
Are 5 watt, 16 volt zener diodes acceptible?
Looks like I can do this for a couple of bucks. All I really need are
part numbers, wattages, and voltages. I don't have the background
to process the technical nuances of the various solutions.
Thanks again...
Joe Connell
Stewartville, MN
RV-9A N95JJ wiring
________________________________________________________________________________
| From: | "Ken Simmons" <ken(at)truckstop.com> |
| Subject: | Tyco/Raychem solder sleeves |
Bob,
Do you know of a good source for these that doesn't require a 100's quantity? I
found some from Mouser, but they are the CWT series not the SO96 that you used.
The SO96 seems to be a much better choice.
Thanks.
Ken
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
The bidirectional transorbs clamp the negative spikes to less than 20 volts
and also have no side affects of merit like contact bounce which is hard on
contacts (not to mention making noise and other potentially nasty things).
Lets consider a worst case. Your alternator runs away and the OVP trips the
CB and the "B" lead contactor stays closed due to contact welding.. This
because you usde a simple diode.
I recommend you really read the referenced articles before deciding
anything.
There is no way to tell when of if a contact will weld. Could happen right
away or never. Sure it reduces lifecycle of the contact but there is no
assurance this reduction will still be above 1000 or what ever. Too many
variables including the power thru the contacts vs the contact rating.
Contacts can be damaged from too little power as well as the popular cases
of too much power. AC ratigs do not always convert to DC ratings. Only ONE
hi load current thru a contact typically damages the ability of the contacts
to properly switch low currents.
In aerospace industry way back when we used relays we has contact r/c
networks across every relay contact.
Personally the large contactors are the main concern as their mass is larger
and thus move slower to between with.
Just because most of the world is misusing the common silicon diode as a
coil spike controller does not mean its correct. There is lots of science to
support the references I have quoted as well as Major relay manufacturers,
world wide, that support the notion that a simple diode is not good.
We all know that something must be done about the inductive spike across the
relay coil. The referenced articles simply show that short of nothing the
worst thing you can use is the common diode. Replacing this one part with a
same sized but different type part does the dame job with out the negative
side affects.
The only reason not to use the better part is lack of willingness to redo it
if you have already installed the simple diodes.
New builders should use transorbs and forget considering silicon rectifier
diodes. The cost at mouser for small quantities is under $0.50 each
depending on the brand you pick.
Paul
PS its not me than cannot smell words korekly its my Komputor and mickety
soft smell ckre what cannot tell one word from another amd thus allows
incorrect words to be used out of kontext. :-)
----- Original Message -----
From: "Ken" <klehman(at)albedo.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
> Yup!
> 99.99% of the engineering world also protected their circuitry from 20
> volt and highter negative spikes which may have been more imortant to
> them. Sensationalist statements may catch attention but there is more to
> this story and it seems to me that there are tradeoffs that should
> accompany such a claim...
> Ken
> (in no hurry to remove my diodes)
>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Circuit breaker ratings for OVP |
You are correct IF 35 milliohms was the fixed value you and Bob have used in
calculations.
However 35 milliohms is only the max specified and in my case the measured
value was far less in some cases.
Thus the often asked for and so far never documented worst case analysis.
That is to take both the max and min possible values for every element in
the circuit and use the values minimizing current (for example) and then the
values maximizing current and getting the range of currents.
Bob has suggested that a couple hundred amps is the maximum and I have
demonstrated that over 400 is real. Neither of us has done a worst case
analysis so the real current range is above 400 amps and the minimum is very
likely to be above 100 amps using reasonable wiring etc.
Paul
----- Original Message -----
From: "Ken" <klehman(at)albedo.net>
Subject: Re: AeroElectric-List: Re: Circuit breaker ratings for OVP
>
> But is it an arbitrarilly large current at the specified voltages and
> with wires that can reasonably be attached to the device? One of the
> examples mentioned about 35 miliohms resistance for the breaker. Well if
> a 12volt battery is pulled down to say 10 volts then you simply can't
> get more than 10 / 0.035 =286 amps even with a zero impedance (at 10
> volts) battery and zero resistance wires and connectors! But it would be
> less with real wires, real connectors, and a real battery. OK double
> that for a 24 volt system but it still isn't arbitrarilly large.
>
> N'other thing worth consideration might be reliability and the failure
> modes of OVP devices. A crowbar that does nothing in normal ops might
> have a higher probability of failing passively in normal operations
> compared to a device that must continuously conduct field curent to keep
> the alternator running??
>
> Ken
>
> Eric M. Jones wrote:
>
>>
>>
>>Bob, et al.
>>
>>It would seem improbably at best that a circuit breaker could be built to
>>survive an arbitrarily large overcurrent. As Paul has pointed out, the
>>addition of a small resistor will put this crowbar back into the barn.
>>
>>
> >snip
>
>
>
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes for Master and Strater relays |
>
>
>Hi Guys,
>
>I've been searching the AeroElectric-List and the RV-list to
>get information on which diode to use across these relays.
>Can you provide me a diode part number and ratings? I'd
>rather not buy the prepackaged solution from Van's...
ANY diode will work. There's not a rectifier diode
made that doesn't have sufficient current and voltage
ratings to do the task. My persona favorites are the
1N5400 series devices. You can get them from Radio
Shack in packages of 2 for about $1.50
See:
http://www.aeroelectric.com/Pictures/RS_Diodes.jpg
These have some mechanical robustness that makes them
easier to work with and more resistant to mechanical
failure in service. See:
http://www.aeroelectric.com/Pictures/s701-1l.jpg
http://www.aeroelectric.com/Pictures/s701-2.jpg
You can find some starter contactors having built
in diodes. This was the variety we used to sell.
The contactors we sold said "diode protected"
right on the base. When in doubt, put an external
diode on . . . two diodes doesn't hurt but no
diode can be a problem See:
http://aeroelectric.com/articles/spikecatcher.pdf
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: EGT interference |
>
>My Glasair EGT/CHT readings (as read on my RMI Micromonitor) are steady
>until I energize the Whelan strobe system and then they jump around
>several hundred degrees. I'm wondering if a Radio Shack noise filter on
>the strobe power supply might correct this situation. Closest point of
>approach for any mutual wire is twelve inches; strobes are the instigator;
>EGT/CHT is the victim so I wonder if a filter would do any good. Could
>the problem be simply RFI coming from the strobes? Would appreciate comments.
>Bob Shumaker in Virginia
It's most likely a conducted noise as opposed to radiated
noise problem. Have you tried running the EGT from its
own battery to see if the effect goes away?
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diode question |
If you're needing to really LOAD up the e-bus normal feed
diode this hard, I'm wondering if you have too much 'stuff'
on the e-bus or perhaps the wrong z-figure selected for
your airplane.
Bob . . .
>
>Yellow PIDG faston terminals are available from digi-key in
>(min.quantity 10) and work fine on 10 and 12 awg wire.
>Ken
>
>Travis Hamblen wrote:
>
>
> >
> >I am using Z-11 plan and have a couple questions that you guys will
> >definitely know about. First, I am using the suggested steering diode
> >between the main and essential bus (using the heat sink). The question is
> >that because of the amperage I am sending through this diode ( < 25a but
> >sometimes > 20a) I will be using 10awg wire which means I can't use a fast
> >on terminal because they don't make them for awg that large. SO would a
> >good alternative be to solder the wires to the fast on connectors on the
> >diode? If I did this would it be just as secure, I was concerned that with
> >all the vibration in an RV that the solder could break away after a while.
> >I would prefer to use a fast on, but haven't been able to find fast ons for
> >awg smaller than 14awg; if someone has a source for these please let me
> >know!
> >
> >The second question is about the fuse that the steering diode calls for.
> >The diode is only rated up to a max of 25a and this is a perfect match for
> >my system. However, it also calls for the use of a breaker or fuse on the
> >two wires going to the main bus. I was thinking of using an automotive
> >style inline fuse that would use a 30a standard 1/4" blade type fuse. Is
> >there a better way or will the inline fuse work just fine?
> >
> >Thanks,
> >Travis
> >RV-7A wiring
> >
> >
> >
>
>
>--
>
>
>-- incoming mail is certified Virus Free.
Bob . . .
--------------------------------------------------------
< Throughout history, poverty is the normal condition >
< of man. Advances which permit this norm to be >
< exceeded -- here and there, now and then -- are the >
< work of an extremely small minority, frequently >
< despised, often condemned, and almost always opposed >
< by all right-thinking people. Whenever this tiny >
< minority is kept from creating, or (as sometimes >
< happens) is driven out of a society, the people >
< then slip back into abject poverty. >
< >
< This is known as "bad luck". >
< -Lazarus Long- >
<------------------------------------------------------>
http://www.aeroelectric.com
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Fw: Diodes for Master and Starter relays |
The Zener-Zener is usually called a Transient Voltage Suppressor(TVS). I
use the term transorb that can be likened to Kleenex. (Its two "zeners" back
to back in one package)
Any way, one useful part is the P6KE18CA. The A at the end says its
bidirectional. Its a 600 watt 18V (start of clipping) transorb. Use
www.findchips.com for popular brands and sources. Variety of sources and
brands with suprisingly wide range of pricing.
Personally I prefer the 1.5KE18CA (1,500 watt) because it has larger
diameter leads and should be less likely to break. 600 watt is overkill in
power rating. Its picking a physical size you are comfortable with.
Paul
----- Original Message -----
From: "Joe & Jan Connell" <jconnell(at)rconnect.com>
Subject: AeroElectric-List: Fw: Diodes for Master and Starter relays
>
>
> Hi Guys,
>
> Thanks for all your discussion on this topic. In review of
> http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
> it appears the zener-zener method is preferred. After searching
> through the Digikey catalog it looks like I should get a pair of zener
> diodes, solder the cathode ends together, and connect the anode
> ends to relay terminals after covering them with heat-shrink tubing.
>
> Am I in the ball park on this?
> Are 5 watt, 16 volt zener diodes acceptible?
>
> Looks like I can do this for a couple of bucks. All I really need are
> part numbers, wattages, and voltages. I don't have the background
> to process the technical nuances of the various solutions.
>
> Thanks again...
>
> Joe Connell
> Stewartville, MN
> RV-9A N95JJ wiring
>
>
>
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Circuit breaker ratings for OVP |
>
>
>
> >>
> >>It would seem improbably at best that a circuit breaker could be built to
> >>survive an arbitrarily large overcurrent. As Paul has pointed out, the
> >>addition of a small resistor will put this crowbar back into the barn.
> >>snip
>
> >But is it an arbitrarilly large current at the specified voltages and
> >with wires that can reasonably be attached to the device? One of the
> >examples mentioned about 35 miliohms resistance for the breaker. Well if
> >a 12volt battery is pulled down to say 10 volts then you simply can't
> >get more than 10 / 0.035 =286 amps even with a zero impedance (at 10
> >volts) battery and zero resistance wires and connectors! But it would be
> >less with real wires, real connectors, and a real battery. OK double
> >that for a 24 volt system but it still isn't arbitrarilly large.
>
>Ken,
>
>I didn't mean infinitely large. I meant some amount over the 1000% limit
>specified by the CB manufacturer. The point is that Bob's white paper
>assumed you could extend the curves...and well...I don't think you can.
I've been really tied up on a couple of fire-fights at RAC and
wasn't able to get as much data on this issue as I'd like. Preliminary
discussions with folks in the mil-spec breaker business have failed
to uncover demonstrable reasons for the 1000% "limit" on max interrupt
current for resetability and no degradation of breaker performance.
I've asked about a half dozen of the ol' salts at RAC about this
and it was a new issue to them. As soon as I get at least one of these
fires out, I'll dig into the documentation and history. My favorite
switch/breaker/contactor guru with Eaton/Cutler-Hammer is out of
town until next Monday. I'm going to see what if any foundation
supports what appears to be an industry wide practice.
Bob . . .
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes for Master and Strater relays |
Bob; Your reply does not answer Joe's question. He is responding to the
relay manufacturers position that a simple diode is not the best way, nor
the second best way, nor the third best way etc.
Granted we need to do something but lets forget the widely used and not a
good way to deal with inductive kicks. The delay in opening and potential
welding of contactor contacts is reason enough to change the part from not
so good to best.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Diodes for Master and Strater relays
>
>
>
>>
>>
>>Hi Guys,
>>
>>I've been searching the AeroElectric-List and the RV-list to
>>get information on which diode to use across these relays.
>>Can you provide me a diode part number and ratings? I'd
>>rather not buy the prepackaged solution from Van's...
>
> ANY diode will work. There's not a rectifier diode
> made that doesn't have sufficient current and voltage
> ratings to do the task. My persona favorites are the
> 1N5400 series devices. You can get them from Radio
> Shack in packages of 2 for about $1.50
>
> See:
>
> http://www.aeroelectric.com/Pictures/RS_Diodes.jpg
>
> These have some mechanical robustness that makes them
> easier to work with and more resistant to mechanical
> failure in service. See:
>
> http://www.aeroelectric.com/Pictures/s701-1l.jpg
> http://www.aeroelectric.com/Pictures/s701-2.jpg
>
> You can find some starter contactors having built
> in diodes. This was the variety we used to sell.
> The contactors we sold said "diode protected"
> right on the base. When in doubt, put an external
> diode on . . . two diodes doesn't hurt but no
> diode can be a problem See:
>
> http://aeroelectric.com/articles/spikecatcher.pdf
>
> Bob . . .
>
>
>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Circuit breaker ratings for OVP |
Perhaps this is in the same category of the widespread practice of the use
of rectifier diodes for relay coil spike suppression. Some manufacturers
provide the relates with diodes (or resistors) built in.
This does not mean its the best way but its what customers have demanded.
Back to the CB ratings. In one case I found where the CB had the 10X number
called out in its specification. Thus if you use this device to break more
than 10X its ratings you are exceeding its specifications regardless of any
real or unreal true damage limit.
The foundation for this limit may or may still apply but until the specs are
revised we should always respect the specification limits. Its foolish not
to do so. If there are no limits specified than does not mean we can expect
no damage at the upper current limit for breaking of 2000 amps.
Also the original foundation for any specific limits may have been lost over
time considering these parts have been in production longer than the normal
working life span of most of us.
I for one do not want to use parts outside their ratings regardless of the
validity of such ratings. In any event what I may do personally, I would
never consider recommending the application of any part outside its rating
for use by others.
SO on this list it seems to me we must consider the 10X as a hard number and
have available designs that do not suggest its OK to go outside the
specifications because there is (or may be) no apparent foundation for that
specification number. Also in this case there is simply no reason to do so
as there are designs that do not violate specifications.
Until the specificationis are physically revised, I will never consider
recommending anyone break the spec because we know its not real.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: Circuit breaker ratings for OVP
>
>
>
>>
>>
>>
>>
>> >>
>> >>It would seem improbably at best that a circuit breaker could be built
>> >>to
>> >>survive an arbitrarily large overcurrent. As Paul has pointed out, the
>> >>addition of a small resistor will put this crowbar back into the barn.
>> >>snip
>>
>> >But is it an arbitrarilly large current at the specified voltages and
>> >with wires that can reasonably be attached to the device? One of the
>> >examples mentioned about 35 miliohms resistance for the breaker. Well if
>> >a 12volt battery is pulled down to say 10 volts then you simply can't
>> >get more than 10 / 0.035 =286 amps even with a zero impedance (at 10
>> >volts) battery and zero resistance wires and connectors! But it would be
>> >less with real wires, real connectors, and a real battery. OK double
>> >that for a 24 volt system but it still isn't arbitrarilly large.
>>
>>Ken,
>>
>>I didn't mean infinitely large. I meant some amount over the 1000% limit
>>specified by the CB manufacturer. The point is that Bob's white paper
>>assumed you could extend the curves...and well...I don't think you can.
>
> I've been really tied up on a couple of fire-fights at RAC and
> wasn't able to get as much data on this issue as I'd like. Preliminary
> discussions with folks in the mil-spec breaker business have failed
> to uncover demonstrable reasons for the 1000% "limit" on max interrupt
> current for resetability and no degradation of breaker performance.
>
> I've asked about a half dozen of the ol' salts at RAC about this
> and it was a new issue to them. As soon as I get at least one of these
> fires out, I'll dig into the documentation and history. My favorite
> switch/breaker/contactor guru with Eaton/Cutler-Hammer is out of
> town until next Monday. I'm going to see what if any foundation
> supports what appears to be an industry wide practice.
>
> Bob . . .
>
>
>
________________________________________________________________________________
| From: | "Bob C. " <flyboy.bob(at)gmail.com> |
| Subject: | Re: Diode question |
Bob,
What is the maximum current you suggest for the e-bus?
Thanks,
Bob
wrote:
>
> If you're needing to really LOAD up the e-bus normal feed
> diode this hard, I'm wondering if you have too much 'stuff'
> on the e-bus or perhaps the wrong z-figure selected for
> your airplane.
>
> Bob . . .
>
>
>
> >
> >Yellow PIDG faston terminals are available from digi-key in
> >(min.quantity 10) and work fine on 10 and 12 awg wire.
> >Ken
> >
> >Travis Hamblen wrote:
> >
> >
> > >
> > >I am using Z-11 plan and have a couple questions that you guys will
> > >definitely know about. First, I am using the suggested steering diode
> > >between the main and essential bus (using the heat sink). The question is
> > >that because of the amperage I am sending through this diode ( < 25a but
> > >sometimes > 20a) I will be using 10awg wire which means I can't use a fast
> > >on terminal because they don't make them for awg that large. SO would a
> > >good alternative be to solder the wires to the fast on connectors on the
> > >diode? If I did this would it be just as secure, I was concerned that with
> > >all the vibration in an RV that the solder could break away after a while.
> > >I would prefer to use a fast on, but haven't been able to find fast ons for
> > >awg smaller than 14awg; if someone has a source for these please let me
> > >know!
> > >
> > >The second question is about the fuse that the steering diode calls for.
> > >The diode is only rated up to a max of 25a and this is a perfect match for
> > >my system. However, it also calls for the use of a breaker or fuse on the
> > >two wires going to the main bus. I was thinking of using an automotive
> > >style inline fuse that would use a 30a standard 1/4" blade type fuse. Is
> > >there a better way or will the inline fuse work just fine?
> > >
> > >Thanks,
> > >Travis
> > >RV-7A wiring
> > >
> > >
> > >
> >
> >
> >--
> >
> >
> >-- incoming mail is certified Virus Free.
>
> Bob . . .
>
> --------------------------------------------------------
> < Throughout history, poverty is the normal condition >
> < of man. Advances which permit this norm to be >
> < exceeded -- here and there, now and then -- are the >
> < work of an extremely small minority, frequently >
> < despised, often condemned, and almost always opposed >
> < by all right-thinking people. Whenever this tiny >
> < minority is kept from creating, or (as sometimes >
> < happens) is driven out of a society, the people >
> < then slip back into abject poverty. >
> < >
> < This is known as "bad luck". >
> < -Lazarus Long- >
> <------------------------------------------------------>
> http://www.aeroelectric.com
>
>
>
>
________________________________________________________________________________
| From: | "simon miles" <simon.miles(at)skynet.be> |
| Subject: | All this overvoltage stuff.... |
You guys lost me some time ago with this subject...
I am about to start flying a homebuilt aeroplane fitted with a Rotax 912S
engine equipped with the standard alternator and no other generating device.
I intend to fly VFR only with an anticipated maximum electrical load of less
10 amps. I will fly day-time VFR only. All of my electrical installation has
been made according to Bob's recommendations and I am very happy with the
results - that is, my panel and radios power up without problem - however, I
haven't yet started the engine.
Do I need to worry about installing transorbs etc. or is my aeroplane
unlikely to be affected by the - to me, arcane - multitude of solutions to
potential problems provided by this list?
Simon Miles.
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: All this overvoltage stuff.... |
>Do I need to worry about installing transorbs etc. or is my aeroplane
>unlikely to be affected by the - to me, arcane - multitude of solutions to
>potential problems provided by this list? Simon Miles.
Simon,
Every experiment needs a control sample. Thanks for volunteering. We will be
sending you a box with wires hanging out marked, "PLACEBO". Make sure you
install it per instructions--and don't open it.
Please keep us updated.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
Ring the bells that still can ring
Forget your perfect offering
There is a crack in everything
That's how the light gets in
- - Leonard Cohen
________________________________________________________________________________
| From: | Andrew Rowley <arowley(at)ncable.net.au> |
| Subject: | Re: Circuit breaker ratings for OVP |
Paul Messinger wrote:
> Back to the CB ratings. In one case I found where the CB had the 10X number
> called out in its specification. Thus if you use this device to break more
> than 10X its ratings you are exceeding its specifications regardless of any
> real or unreal true damage limit.
>
> I for one do not want to use parts outside their ratings regardless of the
> validity of such ratings. In any event what I may do personally, I would
> never consider recommending the application of any part outside its rating
> for use by others.
>
> SO on this list it seems to me we must consider the 10X as a hard number and
> have available designs that do not suggest its OK to go outside the
> specifications because there is (or may be) no apparent foundation for that
> specification number. Also in this case there is simply no reason to do so
> as there are designs that do not violate specifications.
As someone already pointed out, circuit breakers are designed to protect
against short circuits, and your argument suggests you should replace a
circuit breaker if it trips and you can't determine whether the current
was within specifications.
The OVP is subjecting the circuit breaker to exactly the use it is
designed for. It is actually unusual in that you CAN determine in
advance the maximum current it will carry. Mostly maximum breaker
current would be determined by the location of the short.
Are you suggesting that in the general case where a breaker trips, if
you can't verify the maximum current was within specs, it should be
replaced? In that case it effectively becomes an expensive fuse.
Regards
--
Andrew Rowley
arowley(at)ncable.net.au
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Circuit breaker ratings for OVP |
You have a point but in this case if the current version of the OVP trips
the CB you are 100% sure its broken a circuit well over the 10X CB spec
value.
If you are not sure perhaps its best to replace it but usually its possible
to estimate the current. Its up to you and / or your A&P.
On the other hand I have seen and heard about many cases of smoke in the
cockpit and never a CB tripping.
A wire in the harness shorting is quite rare.
Bob does not like CB's and this is one rare case where he recommends a CB. I
tend to agree. At least in this case.
Frankly a 100% reliable 0% false tripping OVP might be better coupled with a
Fuse. However I know of many cases of false tripping of this specific OVP
and Bob has acknowledged that it does rarely occur.
If we could be sure the only time the OVP popped the CB it was due to a
valid alternator failure then a fuse is a good choice. An all solid state
OVP can be made to never false trip if it is a part of a SYSTEM design that
takes care of load dumps or other short term transients.
Paul
----- Original Message -----
From: "Andrew Rowley" <arowley(at)ncable.net.au>
Subject: Re: AeroElectric-List: Re: Circuit breaker ratings for OVP
>
>
> Paul Messinger wrote:
>
>> Back to the CB ratings. In one case I found where the CB had the 10X
>> number
>> called out in its specification. Thus if you use this device to break
>> more
>> than 10X its ratings you are exceeding its specifications regardless of
>> any
>> real or unreal true damage limit.
>>
>
>> I for one do not want to use parts outside their ratings regardless of
>> the
>> validity of such ratings. In any event what I may do personally, I would
>> never consider recommending the application of any part outside its
>> rating
>> for use by others.
>>
>> SO on this list it seems to me we must consider the 10X as a hard number
>> and
>> have available designs that do not suggest its OK to go outside the
>> specifications because there is (or may be) no apparent foundation for
>> that
>> specification number. Also in this case there is simply no reason to do
>> so
>> as there are designs that do not violate specifications.
>
> As someone already pointed out, circuit breakers are designed to protect
> against short circuits, and your argument suggests you should replace a
> circuit breaker if it trips and you can't determine whether the current
> was within specifications.
>
> The OVP is subjecting the circuit breaker to exactly the use it is
> designed for. It is actually unusual in that you CAN determine in
> advance the maximum current it will carry. Mostly maximum breaker
> current would be determined by the location of the short.
>
> Are you suggesting that in the general case where a breaker trips, if
> you can't verify the maximum current was within specs, it should be
> replaced? In that case it effectively becomes an expensive fuse.
>
> Regards
>
> --
> Andrew Rowley
> arowley(at)ncable.net.au
>
>
>
________________________________________________________________________________
| From: | "John Allen" <goldcare2(at)comcast.net> |
| Subject: | Re: All this overvoltage stuff.... |
I also have one of Bob's OV setup, and it works. 7 or 8 times it has popped
the 5 amp breaker/switch on my alternator when the output got to about
16.5v. I know what you're thinking. What dummy would keep flying for a month
or so and just keep resetting the breaker when the battery voltage dropper
too low. Well last summer I had this intermittent runaway alternator. It
would work ok for hours in cruse but on climb-out, just go nuts and Bob's OV
did it's thing just fine with no other damage. It wasn't much of a problem
as I only fly day vfr at present in my Volmer amfib. The flooded cell
battery seems to handle it ok and I only have 2 "handhelds" mounted and
wired in to the ships 12v supply. Finally I pulled the Chevy 60 amp
alternator from my custom mount on the aft end of my 0-200 pusher and found
the problem. The down stream side of the cooling system on a pusher gets
very hot, and the heat had softened the insulation in the cheap Radio Shack
shielded twin-lead wire that I used to run to the remote regulator mounted
next to the battery in the bilge.
When folks say they aren't having any problems, is it because the device
hasn't ever activated or did it activate and function properly. Well for me
it did activate several times. I don't know if it could damage other
electronic equipment, but my 2 radios and electronic fuel calculator still
seem ok. John Allen
________________________________________________________________________________
| From: | Ken <klehman(at)albedo.net> |
| Subject: | Re: Diodes across relay coils |
But a diode clamps the negative pulse to about 1 volt. Seems to me that
the difference may be significant to some electronic circuitry that is
sensitive to negative spikes.
Ken
Paul Messinger wrote:
>
>The bidirectional transorbs clamp the negative spikes to less than 20 volts
>and also have no side affects of merit like contact bounce which is hard on
>contacts (not to mention making noise and other potentially nasty things).
>
>snip
>
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diode question |
>
>Bob,
>
>What is the maximum current you suggest for the e-bus?
>
>Thanks,
>Bob
It's not so much "maximum current" as how much stuff do you
need to run in the max endurance mode . . . I.e. main alternator
quits, no second alternator and battery only. Further, what's
your personal philosophy for battery only endurance? I've suggested
(and many builders have achieved) en route max endurance that
equals engine endurance for fuel aboard.
What are your personal desires? Have you reviewed chapter 17 in
the 'Connection?
Bob . . .
________________________________________________________________________________
| From: | rv-9a-online <rv-9a-online(at)telus.net> |
| Subject: | Re: Sigtronics intercom wiring and 12-channel annunciator |
A few weeks ago there was a discussion on wiring a Sigtronics SPA-400
intercom, and how to deal with the 'forest of tabs' that resulted when
wiring.
I had some discussions off-list with a few of the contributors, and
decided to design a product based on their input. Rather than go into
advertorial mode, I'll direct any interested parties to the Vx Aviation
web site for more information:
http://www3.telus.net/aviation/vx see AMX-1A device.
Also, there was a lot of discussion on annuciator light controllers.
Although this discussion quickly evolved into speech synthesize alarms,
the fundamental problem of driving lamps, testing them and dimming them
while sensing active high and active low inputs has been solved for some
time with a 4-channel device (IL-4A). The requirements of the list
seemed to gravitate to a 12-channel controller, so I've made available a
12-channel device, the IL-12A. For more information see:
http://www3.telus.net/aviation/vx see IL-4A & IL-12A devices.
I hope that these products are of benefit to list members... they were
developed specifically to solve problems that have been debated on-list
recently. I try to listen for common problems, develop solutions and
make them available through Vx Aviation when it makes sense. It's a
service to the OBAM community, and allows me to stay involved in
electronics which I love.
Vern Little
--
________________________________________________________________________________
| From: | CardinalNSB(at)aol.com |
| Subject: | Re: Staco led dimmer |
The EDMO flyer said that Staco is now making led replacement bulbs with no
external resistors required for 6 or 12 or 24 volt, to fit their lighted
switches. It also said they are making a led dimmer, but I couldn't find anything
on their website and nobody had any information. Anyone know about this?
skip simpson
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
Technically very correct as one needs to decide what is important.
Contactor contacts welding shut or a long opening time can be the decision
driver. These side affects are real. 20V negative spikes are very unlikely
to be a problem and never a problem in well designed electronics. In fact
many (most nearly all ???) modern solid state devices have built in ESD and
reverse voltage protection built in that works for input energy far far in
excess of the subject 20 V negative spike.
Modern electronics are properly protected to the small negative spike you
are talking about. Also other than the contacts or solid state device doing
the opening of the relay coil there is no reasonable way for anything to
even "see" this spike.
Its a trade off between things to protect.
My point is the industry expert have all spoken and say back to back Zeners
are far and away the best and the dimple rectifier is not very good at all.
As I have often said there are several good solutions and many bad ones.
I feel that the trade off in this case is simple. Contact welding or contact
bounce that produced large current spikes are better stopped than a worry
about a 20 V spike on the coil leads.
What is really important is to know about this and make your own decisions.
How many on this list knew that the relay industry felt so strongly about
diodes were bad and back to back zeners were so good in protecting the
quality of their product??
Paul
----- Original Message -----
From: "Ken" <klehman(at)albedo.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
> But a diode clamps the negative pulse to about 1 volt. Seems to me that
> the difference may be significant to some electronic circuitry that is
> sensitive to negative spikes.
> Ken
>
> Paul Messinger wrote:
>
>>
>>
>>The bidirectional transorbs clamp the negative spikes to less than 20
>>volts
>>and also have no side affects of merit like contact bounce which is hard
>>on
>>contacts (not to mention making noise and other potentially nasty things).
>>
>>snip
>>
>
>
>
________________________________________________________________________________
| From: | "Gary Casey" <glcasey(at)adelphia.net> |
| Subject: | Re: Diodes across relay coils |
In all this talk about diodes it looks like some of the fundamentals have
not been presented (I think you'll find them in Bob's book). The normal
case is for a relay to be connected to the battery through a switch - the
switch in this case is on the "high side". When the switch is opened the
current attempts to keep flowing because of the inductance of the coil.
Because one side of the coil is connected to ground the voltage on the other
side will by necessity (I haven't installed a diode) go to a large negative
value. Something has to give, so in this case there will be a momentary arc
drawn across the switch. So what is the effect of this? The high voltage
transient exists ONLY in the wire between the switch and the relay. It
doesn't exist in any wire that powers anything else. So the inductive spike
is NOT in danger of doing any damage. The relay coil can certainly handle
it and the switch was presumably designed to handle this type of event. The
other outcome of this type of switching is that an radiated EMI event will
be created that could interfere with electronic equipment. Usually this
doesn't matter as the relays in question are generally for the starter or
master and in both cases the operator probably doesn't care if something is
affected. The description of a "low-side" switching arrangement is
basically the same, except that the voltage will go to a large positive
value. If one really wanted to protect the switch, keep the relay working
correctly and eliminate EMI the best approach is probably Zener protection
in parallel with a capacitor. I'm not sure any of this is really necessary
unless there is a relay that is used often during flight (gear motor
contactor?).
Much ado about nothing?
Gary Casey
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: Diodes across relay coils |
>In all this talk about diodes it looks like some of the fundamentals have
not been presented (I think you'll find them in Bob's book).
Gary,
We run the risk of parroting what we have learned and what is in the
textbooks. The point has been made that this has been revised radically by
the people who know. Please review the links previously posted.
>The normal case is for a relay to be connected to the battery through a
switch - the switch in this case is on the "high side". When the switch is
opened the current attempts to keep flowing because of the inductance of the
coil.
Well, because of the collapse of the magnetic field. But not to quibble....
>Because one side of the coil is connected to ground the voltage on the
other side will by necessity (I haven't installed a diode) go to a large
negative value.
Let's put some numbers on this....typically 1000-1500 volts for a 12V coil.
>Something has to give, so in this case there will be a momentary arc drawn
across the switch. So what is the effect of this? The high voltage
transient exists ONLY in the wire between the switch and the relay. It
doesn't exist in any wire that powers anything else. So the inductive spike
is NOT in danger of doing any damage.
We part company here. The spike radiates into space and every wire, circuit
board trace and conductor everywhere. They teach courses on the subject EMI,
EMC, RFI, whatever. Besides the switch has one side attached to a positive
bus that is connected to your pricey video game in your panel.
>The relay coil can certainly handle it and the switch was presumably
designed to handle this type of event. The other outcome of this type of
switching is that an radiated EMI event will be created that could interfere
with electronic equipment. Usually this doesn't matter as the relays in
question are generally for the starter or master and in both cases the
operator probably doesn't care if something is affected.
There you go....
>The description of a "low-side" switching arrangement is basically the
same, except that the voltage will go to a large positive value.
The transient is always negative.
> If one really wanted to protect the switch, keep the relay working
correctly and eliminate EMI the best approach is probably Zener protection
in parallel with a capacitor.
Read the references. Potter and Brumfield says the best solution is a
bi-directional zener-type device.
>I'm not sure any of this is really necessary unless there is a relay that
is used often during flight (gear motor contactor?).
Hell, I didn't need the landing gear anyway.....think I'll practice my belly
landing technique.
>Much ado about nothing? Gary Casey
You decide. That's why they call it experimental.
As was mentioned before---nobody suggests tearing out all your diodes. But
if you are building the electrical system you should carefully consider that
there is an improved way of squashing transients. And if you have had a
problem you might consider trying the new way to see if it solves your
problem.
The reason this was not done a generation ago was, that the technique was
not known, the parts weren't readily available, and the requirements for
"smooth power" were less demanding.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
In theory there is no difference between theory and practice. In practice
there is.
--Yogi Berra
________________________________________________________________________________
| From: | "Joel Jacobs" <jj(at)sdf.lonestar.org> |
| Subject: | Re: Diodes across relay coils |
Couple comments, food for thought...
Rate of change of current in an inductor = VT/L (Delta I)
relay coils contain inductance AND resistance.
Lets assume 12V 120 ohm coil and simple catch diode.
When you first close the switch you have 12v accross the coil and zero
current. The 12V accross the inductance causes the current to increase. As
the current increases there becomes a voltage drop accross the coils
resistance that subtracts from the voltage accross the inductance. Huh?
Yes, When the current stabilizes it is because the whole 12v is dropped
accross the resistance and there is 0 volts across the inductance. See - if
there were still voltage accross the inductance the current would change
right?
In our case if the current stabilized at say 50ms we could say that we
applied 12*.05/2 or .3 volt-seconds to the inductance to energize the coil.
To de-energize the coil will also require .3 volt-seconds in the oppisate
polarity.
When we open the switch the current wants to keep going in the inductance
and will keep going until .3 volt-seconds has been applied by the spike.
With no catch diode the spike is limited by the interwinding capacitance of
the coil. As we see the greater the amplitude of the spike the faster the
inductance resets - if we allowed the spike to go to 1000v the coil would
reset in .3/1000 = 300us - that might be a little hard on the switch though,
but you can see that a higher voltage spike WILL reset the coil faster.
With a simple catch diode it limits the spike to about 1 volt and you would
think it should take .3/1 = 300ms to reset right? I don't think so. See at
the moment you open the switch the diode is clamping the voltage accross the
coil at 1 volt but there is still 100ma flowing through 120 ohms and that
HAS to be 12v. Subtract the 1 volt clamp and it still leaves 11volts across
the inductance to reset the coil. I would suggest that the energizing and
de-energizing times with a simple catch diode may be nearly the same.
Will using a transorb in place of the diode increase the spike and cause the
coil to reset quicker? Absolutely without doubt! Will that decrease
contact opening time? Maybe, maybe not. If the coil resets before the
contacts open then the open time is determined by the spring and the inertia
of the contact. I can't see how resetting the coil faster at this point
could reduce opening time. If the coil is not fully reset when the armature
begins to move then resetting the coil faster would definatly improve open
time as the residual magnetisim would be fighting the spring.
I would ASSUME ( yeah I know) that relay manufacturers would have designed
thier coils so that they would reset before the armature starts moving using
a standard catch diode.
Joel
________________________________________________________________________________
| From: | "Joel Jacobs" <jj(at)sdf.lonestar.org> |
| Subject: | Re: Diodes across relay coils |
----- Original Message -----
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: AeroElectric-List: Re: Diodes across relay coils
> >The description of a "low-side" switching arrangement is basically the
> same, except that the voltage will go to a large positive value.
>
> The transient is always negative.
>
No, it isn't.. It is always oppisate the applied voltage that energized the
coil. In a low side switch, the low side of the coil is negative while the
switch is closed and the spike will be positive when the switch opens.
Joel
________________________________________________________________________________
| From: | sarg314 <sarg314(at)comcast.net> |
| Subject: | Hall effect current sensor (=Van's Ammeter for sale |
)
I made a Hall effect battery current sensor using the Amploc Hall
effect transducer and a DC_DC converter to generate +12 and -12v. Two
relatively cheap parts plus a 1 ohm resistor gives you 1 mv out for each
amp of battery current without breaking the battery cable to insert a
shunt.
It works fine when connected to my Fluke multimeter which has 10 megOhm
input resistance, but when I hooked it up to a Van's ammeter (IE VAM40)
the meter just lays there. Apparently the Van's meter has thousands of
times less input impedance and the Amploc transducer just can't deliver
enough oomf to drive it. I guess I'll have to use a digital LCD panel
meter that has high input impedance.
So..., I have a virtually new Van's meter that I can't use. $20 buys it
and I'll pay the shipping. That's half what you'd pay to buy it from
Vans. Anybody interested?
--
Tom Sargent, RV-6A, engine
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
----- Original Message -----
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: Re: Diodes across relay coils
>> >The description of a "low-side" switching arrangement is basically the
>> same, except that the voltage will go to a large positive value.
>>
>> The transient is always negative.
>>
>No, it isn't.. It is always oppisate the applied voltage that energized
the
>coil. In a low side switch, the low side of the coil is negative while the
>switch is closed and the spike will be positive when the switch opens.
Joel,
We are probably in agreement, I was referring to the coil terminals. The
diode in always in the same direction because the spike is too--opposite the
applied voltage.
Eric
________________________________________________________________________________
| From: | "Joel Jacobs" <jj(at)sdf.lonestar.org> |
----- Original Message -----
From: "Eric M. Jones" <emjones(at)charter.net>
Subject: AeroElectric-List:
>
>>No, it isn't.. It is always oppisate the applied voltage that energized
> the
>>coil. In a low side switch, the low side of the coil is negative while
>>the
>>switch is closed and the spike will be positive when the switch opens.
>
> Joel,
>
> We are probably in agreement, I was referring to the coil terminals. The
> diode in always in the same direction because the spike is too--opposite
> the
> applied voltage.
>
> Eric
>
Hi Eric,
You're right, relative to the other terminal it's the same polarity. High
side vs. low side - the spike occurs on the opposite terminal hence the
polarity reversal. I was considering the spike at the switch referenced to
ground.. We are in agreement.
Joel
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
Your are incorrect in your assumptions and I suggest rereading the
references I originally posted.
For example I tested several contactors communally used in our acft.
With no diode it takes approx 10 milliseconds to open from switch coil
opening.
Add the diode and it takes 50 ms. Both times are to the first opening.
Contact bounce is reasonably short and only one or two bounces with no
diode. With a diode some opening bounces are numerous and include a
spectacular arc at the end.
The energizing times are not affected with any of the devices across the
coil.
The simple diode makes a huge difference. (see the referenced reports.) I
have lots of proof from lab testing and its real.
The coil resetting (as you say) is many times longer than the mechanical
release. 5+ times in my testing.
Relay manufacturers (as in my referenced links) ASSUME you know what you are
doing and NEVER use a simple diode with out knowing the potentially very bad
side effects that go way beyond any lengthen of the release time. That some
relays come with diodes built in is demand not smart engineering.
One thing we can all agree on is SOME type of suppression is required, the
question is what kind. In my OPINION :-) its OK in many cases to use the
diode as the relay contacts are not stressed (small current vs rating) and
are not switching an inductive load.
Paul
----- Original Message -----
From: "Joel Jacobs" <jj(at)sdf.lonestar.org>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
I would suggest that the energizing and
> de-energizing times with a simple catch diode may be nearly the same.
>
> Will using a transorb in place of the diode increase the spike and cause
> the
> coil to reset quicker? Absolutely without doubt! Will that decrease
> contact opening time? Maybe, maybe not. If the coil resets before the
> contacts open then the open time is determined by the spring and the
> inertia
> of the contact. I can't see how resetting the coil faster at this point
> could reduce opening time. If the coil is not fully reset when the
> armature
> begins to move then resetting the coil faster would definatly improve open
> time as the residual magnetisim would be fighting the spring.
>
> I would ASSUME ( yeah I know) that relay manufacturers would have designed
> thier coils so that they would reset before the armature starts moving
> using
> a standard catch diode.
>
> Joel
>
>
>
________________________________________________________________________________
| From: | "Joel Jacobs" <jj(at)sdf.lonestar.org> |
| Subject: | Re: Diodes across relay coils |
Hi Paul,
If your testing has shown that the contacts open before the coil resets then
I totaly agree that a higher voltage clamp will shorten the open times, that
it's has merit and that being the case, I'll use transorbs on my contacters.
From what you describe 50-100v should do nicely don't you think?
The point of my post was not to advocate diodes over transorbs or vise
versa. It was more to point out that a relay coils equivelant circuit is a
series LR network and even with a simple catch diode the coil current decays
at roughly the same rate as it builds. Thats not very intuitive - most
would think it takes much longer to reset because the back emf is limited to
only 1v by the diode.
Joel
----- Original Message -----
From: "Paul Messinger" <paulm(at)olypen.com>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
> Your are incorrect in your assumptions and I suggest rereading the
> references I originally posted.
>
> For example I tested several contactors communally used in our acft.
>
> With no diode it takes approx 10 milliseconds to open from switch coil
> opening.
>
> Add the diode and it takes 50 ms. Both times are to the first opening.
> Contact bounce is reasonably short and only one or two bounces with no
> diode. With a diode some opening bounces are numerous and include a
> spectacular arc at the end.
>
> The energizing times are not affected with any of the devices across the
> coil.
>
> The simple diode makes a huge difference. (see the referenced reports.) I
> have lots of proof from lab testing and its real.
>
> The coil resetting (as you say) is many times longer than the mechanical
> release. 5+ times in my testing.
>
> Relay manufacturers (as in my referenced links) ASSUME you know what you
> are
> doing and NEVER use a simple diode with out knowing the potentially very
> bad
> side effects that go way beyond any lengthen of the release time. That
> some
> relays come with diodes built in is demand not smart engineering.
>
> One thing we can all agree on is SOME type of suppression is required, the
> question is what kind. In my OPINION :-) its OK in many cases to use the
> diode as the relay contacts are not stressed (small current vs rating) and
> are not switching an inductive load.
>
> Paul
>
> ----- Original Message -----
> From: "Joel Jacobs" <jj(at)sdf.lonestar.org>
> To:
> Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>>
>>
>
> I would suggest that the energizing and
>> de-energizing times with a simple catch diode may be nearly the same.
>>
>> Will using a transorb in place of the diode increase the spike and cause
>> the
>> coil to reset quicker? Absolutely without doubt! Will that decrease
>> contact opening time? Maybe, maybe not. If the coil resets before the
>> contacts open then the open time is determined by the spring and the
>> inertia
>> of the contact. I can't see how resetting the coil faster at this point
>> could reduce opening time. If the coil is not fully reset when the
>> armature
>> begins to move then resetting the coil faster would definatly improve
>> open
>> time as the residual magnetisim would be fighting the spring.
>>
>> I would ASSUME ( yeah I know) that relay manufacturers would have
>> designed
>> thier coils so that they would reset before the armature starts moving
>> using
>> a standard catch diode.
>>
>> Joel
>>
>>
>>
>
>
>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
There is no reason to use Transorbs with a higher V rating that 18V. This
clips the spike well under 20v and is high enough to have insignificant
effect on open time. Higher voltages increase of side effects like damage to
the switch contacts controlling the relay coil as well as putting a higher
transient on the wires between switch and relay that can cause noise etc.
On the coil current decay, remember the relay has a much smaller 'hold
closed' voltage. While we apply 12-14V to the relay to close it, it will
remain closed with far less voltage, in some cases as low as 3 +/- volts. So
the circulating current in the coil due to the diode must decay to under 3 v
before the relay considers opening. Most any voltage present in the coil
will slow the initial rate of opening some.
If you are switching an inductive circuit in the ideal world there is a R-C
series circuit across the contacts to suppress arcing there The circuit
values depend on voltage and current so even there there is not one network
that fits all cases. Its a matter of how far to go is necessary and there is
no simple one size fits all solution.
Paul
----- Original Message -----
From: "Joel Jacobs" <jj(at)sdf.lonestar.org>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
> Hi Paul,
> If your testing has shown that the contacts open before the coil resets
> then
> I totaly agree that a higher voltage clamp will shorten the open times,
> that
> it's has merit and that being the case, I'll use transorbs on my
> contacters.
> From what you describe 50-100v should do nicely don't you think?
> The point of my post was not to advocate diodes over transorbs or vise
> versa. It was more to point out that a relay coils equivelant circuit is
> a
> series LR network and even with a simple catch diode the coil current
> decays
> at roughly the same rate as it builds. Thats not very intuitive - most
> would think it takes much longer to reset because the back emf is limited
> to
> only 1v by the diode.
> Joel
>
> ----- Original Message -----
> From: "Paul Messinger" <paulm(at)olypen.com>
> To:
> Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>>
>>
>> Your are incorrect in your assumptions and I suggest rereading the
>> references I originally posted.
>>
>> For example I tested several contactors communally used in our acft.
>>
>> With no diode it takes approx 10 milliseconds to open from switch coil
>> opening.
>>
>> Add the diode and it takes 50 ms. Both times are to the first opening.
>> Contact bounce is reasonably short and only one or two bounces with no
>> diode. With a diode some opening bounces are numerous and include a
>> spectacular arc at the end.
>>
>> The energizing times are not affected with any of the devices across the
>> coil.
>>
>> The simple diode makes a huge difference. (see the referenced reports.) I
>> have lots of proof from lab testing and its real.
>>
>> The coil resetting (as you say) is many times longer than the mechanical
>> release. 5+ times in my testing.
>>
>> Relay manufacturers (as in my referenced links) ASSUME you know what you
>> are
>> doing and NEVER use a simple diode with out knowing the potentially very
>> bad
>> side effects that go way beyond any lengthen of the release time. That
>> some
>> relays come with diodes built in is demand not smart engineering.
>>
>> One thing we can all agree on is SOME type of suppression is required,
>> the
>> question is what kind. In my OPINION :-) its OK in many cases to use the
>> diode as the relay contacts are not stressed (small current vs rating)
>> and
>> are not switching an inductive load.
>>
>> Paul
>>
>> ----- Original Message -----
>> From: "Joel Jacobs" <jj(at)sdf.lonestar.org>
>> To:
>> Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>>
>>
>>>
>>>
>>
>> I would suggest that the energizing and
>>> de-energizing times with a simple catch diode may be nearly the same.
>>>
>>> Will using a transorb in place of the diode increase the spike and cause
>>> the
>>> coil to reset quicker? Absolutely without doubt! Will that decrease
>>> contact opening time? Maybe, maybe not. If the coil resets before the
>>> contacts open then the open time is determined by the spring and the
>>> inertia
>>> of the contact. I can't see how resetting the coil faster at this point
>>> could reduce opening time. If the coil is not fully reset when the
>>> armature
>>> begins to move then resetting the coil faster would definatly improve
>>> open
>>> time as the residual magnetisim would be fighting the spring.
>>>
>>> I would ASSUME ( yeah I know) that relay manufacturers would have
>>> designed
>>> thier coils so that they would reset before the armature starts moving
>>> using
>>> a standard catch diode.
>>>
>>> Joel
>>>
>>>
>>>
>>
>>
>>
>
>
>
________________________________________________________________________________
| Subject: | Re: Diodes across relay coils |
| From: | "John Schroeder" <jschroeder(at)perigee.net> |
OK guys -
I'm beginning to get it - after eons of back-and-forths and mega hundreds
of words - some hot and some cool. Theory is over. Please give me, and I
suspect a hundred more fellow travellers, something we can use.
How about listing all of the "coils" (I'm presuming they are contactors)
one may want to install in an electrical system of an airplane (assume
dual alternators and dual batteries as the top end) and then doing a
wiring diagram of at least one of the coils (I prefer the crossfeed) with
the proper transorb rating, specs, location & brand (if that matters).
Thanks,
John Schroeder
> posted by: "Paul Messinger"
>
> There is no reason to use Transorbs with a higher V rating that 18V. This
> clips the spike well under 20v and is high enough to have insignificant
> effect on open time. Higher voltages increase of side effects like
> damage to the switch contacts controlling the relay coil as well as
> putting a higher transient on the wires between switch and relay that
> can cause noise etc.
>
________________________________________________________________________________
| From: | Walter Tondu <walter(at)tondu.com> |
| Subject: | Vans Fuel Pump issue |
I was doing the first check of the fuel boost pump today. I have
the standard electric pump and filter combo they sell for my IO-360M1B.
Thought I would simply turn it on and off quickly to verify connectivity;
turn it on, hear some noise, turn it off.
Blew a 5A fuse right away. Checked grounds - good. Checked positive
routing - good. Made sure positive and negatives were correct too.
Everything is ok as far as wiring. Wire size is adequate for both
positive and ground as well. And the switch seems to be working fine
as well.
Tried it again, blew another 5A fuse immediately. In each trial,
the pump did not make any noise, just blew the fuse.
Any ideas?
--
Walter Tondu
http://www.rv7-a.com
________________________________________________________________________________
| From: | Frank & Dorothy <frankvdh(at)xtra.co.nz> |
| Subject: | Re: Vans Fuel Pump issue |
Walter Tondu wrote:
>
>Tried it again, blew another 5A fuse immediately. In each trial,
>the pump did not make any noise, just blew the fuse.
>
>
Sounds like the pump is where the fault lies. But you need to isolate
the pump from the rest of the system to prove that.
Take the pump out of the plane and try it on the bench using either a
current-limited supply or a 5A fuse -- no switch, just wires from supply
+12V to fuse to pump, and pump back to supply ground.
Frank
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes across relay coils |
>
>But a diode clamps the negative pulse to about 1 volt. Seems to me that
>the difference may be significant to some electronic circuitry that is
>sensitive to negative spikes.
>Ken
The concerns for "electronic circuitry" being at-risk from
the energy stored on the coil of a contactor is over-blown. Let's
go to the workbench and review the simple ideas:
I wired up a Cole-Hersee battery contactor with a switch and
'scope to capture some of this part's salient performance features.
See: http://www.aeroelectric.com/articles/Spike_Catching/CH_Closing.gif
First, Ch1 of the scope is used to monitor contactor output
and Ch2 watches the voltage across the switch for a closing
event. Note that closing time to stable contacts is about 17
mS. We can observe some effects of bouncing contacts on the
"battery master" switch as well.
See:
http://www.aeroelectric.com/articles/Spike_Catching/CH_Opening_No_Suppression.gif
Here's what the critter does with no suppression on the coil.
Note that it's about a 13 mS device for basic operating speed to
open.
It will generate a 150+ volt spike that lights the fires between
the master switch contacts for about 2 mS. (Ch2) Arc noise reflected
back to the bus on Ch 1 shows some little bits rising up to about
18V.
See: http://www.aeroelectric.com/articles/Spike_Catching/CH_w_1n5400.gif
Now we put a diode across the coil and we find that opening time
rises to about 75 mS the arcing across the switch is gone. One can
observe the coil's attempt to push its negative terminal above
bus voltage. The inflection lasts about 110 mS meaning that
current is still flowing in the coil when the contactor opens. Note
zero inflection of bus voltage due to coil energy dump.
See: http://www.aeroelectric.com/articles/Spike_Catching/CH_w_120_Ohm.gif
Just for grins, let's try one of the cited common suppression techniques
and tie a 120 ohm resistor across the coil. No we see that the voltage
across the "master switch" rises only to about 90 volts. This illustrates
the fact that an energy contained on the coil can not be delivered at any
current greater than that used to energize the coil. (90-13)/120 = 640 mA
. . . just under what the contactor coil was drawing when the switch was
opened. Note that while arcing across the master switch terminals is
still there . . . it is quite small compared to the earlier trace.
See:
http://www.aeroelectric.com/articles/Spike_Catching/CH_Switch_Arcing_No_Sup.gif
and
http://www.aeroelectric.com/articles/Spike_Catching/CH_Bus_Noise_No_Sup.gif
Here we've removed all the suppression again and looked at arcing
across the switch in more detail in the first trace (Ch2). The companion
Ch1 trace is the second figure. Note that while fire and brimstone are
being brought down on the switch contacts, there are only a handfull of
very narrow trash bits on the bus-side of the contactor. One seems to
have pushed its way up to 90 volts. Hmmm . . . 90v volt spike sounds
pretty dangerous, no?
This experiment was conducted on the bench with 4' long leads to a bench
power supply. Not a very low impedance connection to a battery or any
other mitigating device. Okay, let's tack a 0.1 uF capacitor across the
bus input to the contactor . . .
See:
http://www.aeroelectric.com/articles/Spike_Catching/CH_Bus_Noise_w_0p1_Cap.gif
Note that bus noises due to contactor opening are not zero but
they are tiny and, by the way, well inside the industry standards
for bus quality issues in aircraft. This is going on while the
switch is still having to put up with the 300+ volt, unrestrained energy
dump
from the contactor coil. The fact that these bits of energy can be
clipped off with so small a capacitor demonstrates their relatively
small size.
See:
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_2x18v_Transorbs.gif
Okay, here's what happens with a pair of transorbs back-to-back (same
as a bi-directional transorb). These are some 18v devices where
the array clamps to about 25 volts with 700 mA of current. Now,
looking at the trace, we find that batter master switch terminal
jumps up to about 38 volts (25 + 13) while the coil is dumping
energy into the transorbs. Note that the transorbs stop conduction
about 6 mS after switch opens and the contactor opens at 14 mS.
Compare in the last figure cited and:
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_1n5400.gif
and
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_120_Ohm.gif
there are no significant manifestations of energy from coil collapse
reflected back to the bus. I conducted this experiment with a deliberately
"soggy" bus (long leads to power supply) to encourage any stray bits
of coupling to do what it will with bus voltage.
The "spike" energy dumped by de-energizing a starter or battery contactor
is 99.9% used up in an arc across the controlling switch. The AD
against the ACS-510 keyswitch added a diode to reduce abnormal wear-and-tear
on the starter switch contacts within the assembly. Unfortunately, the diode
is in the wrong place. See article at:
http://aeroelectric.com/articles/spikecatcher.pdf
The foregoing illustrates the effects of transorb arc
suppression for reducing contactor dropout time as compared
with the simple diode. Even a 120 ohm resistor lengthened dropout time
from 14 to 22 mS.
This experiment was crafted to illustrate the differences
in contactor performance, stresses on the controlling switch,
and ultimate resting place for inductive energy released
from the contactor coil for four conditions:
(1) no suppression
(2) 120 ohm parallel resistor
(3) plain vanilla diode
(4) bi-directional Transorb
This experiment demonstrates that coil collapse energy
does not propagate to the bus and therefore not a threat
to other system components whether or not the contactor
coil is suppressed.
However, this discussion does not address the magnitude
of benefit realized for replacing the simple diode
with transorbs. That's the topic of the next installment.
Bob . . .
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
If you can wire the diode per Aeroelectric connection than the Transorb is
the same as the diode except there is no band (for polarity) and it works
either way.
Part numbers were in a recent post. P6KE18CA or 1.5KE18CA. The 1.5 part has
heavier leads and easier to work with for some.
www.findships.com and using the above will give you quite a list to choose
from.
Or just Contact Eric Jones for a Kit of parts Transorbs, terminals, and
heatshrink tubing. Not sure if his web site has these yet.
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
Paul
----- Original Message -----
From: "John Schroeder" <jschroeder(at)perigee.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
> OK guys -
>
> I'm beginning to get it - after eons of back-and-forths and mega hundreds
> of words - some hot and some cool. Theory is over. Please give me, and I
> suspect a hundred more fellow travellers, something we can use.
>
> How about listing all of the "coils" (I'm presuming they are contactors)
> one may want to install in an electrical system of an airplane (assume
> dual alternators and dual batteries as the top end) and then doing a
> wiring diagram of at least one of the coils (I prefer the crossfeed) with
> the proper transorb rating, specs, location & brand (if that matters).
>
> Thanks,
>
> John Schroeder
>
>
>> posted by: "Paul Messinger"
>>
>> There is no reason to use Transorbs with a higher V rating that 18V. This
>> clips the spike well under 20v and is high enough to have insignificant
>> effect on open time. Higher voltages increase of side effects like
>> damage to the switch contacts controlling the relay coil as well as
>> putting a higher transient on the wires between switch and relay that
>> can cause noise etc.
>>
>
>
>
________________________________________________________________________________
| From: | Dj Merrill <deej(at)thayer.dartmouth.edu> |
| Subject: | Cessna A-510 ignition switch |
It was a dark and stormy night... Well, actually
it was a bright and sunny day but it still scared me.
While landing my Glasair, about halfway down the runway my engine quit.
I was unable to get the engine restarted again, and after
some limited troubleshooting I think I have traced the
problem down to the ignition key switch. It is a
Cessna key switch model A-510, part # C292501-0105.
Would anyone happen to have a schematic for this
key switch? I think the way it works is that it simply
grounds (connects the p-lead wire to the
p-lead shield which is grounded at the magneto)
when switched to the OFF position, and leaves
the p-lead disconnected (ie, "open") when in the
BOTH position. Referring to Z-26 seems to follow this logic.
Using my multimeter, I was able to
determine that the p-leads for both mags are connected to
the p-lead shield (ie, "grounded") in all four
positions of the key switch, OFF, R, L, and BOTH.
I measured this without removing any wires from
the keyswitch.
Am I on the right track, or should I be
chasing some other gremlin? Should I remove
the wires from the keyswitch and test it separately?
If I do definitely determine that the
keyswitch is the problem, I'm dumping it and replacing it
with two switches and a push button. Seems silly to have
a redundant ignition system tied to a single point of
failure like this, especially after it scared the
cr*p out of me.
Thanks,
-Dj
--
Dj Merrill
deej(at)thayer.dartmouth.edu
"TSA: Totally Screwing Aviation"
________________________________________________________________________________
| From: | mprather <mprather(at)spro.net> |
| Subject: | Re: Cessna A-510 ignition switch |
Hi DJ,
Embedded comments below:
Dj Merrill wrote:
>
> It was a dark and stormy night... Well, actually
>it was a bright and sunny day but it still scared me.
>While landing my Glasair, about halfway down the runway my engine quit.
>I was unable to get the engine restarted again, and after
>some limited troubleshooting I think I have traced the
>problem down to the ignition key switch. It is a
>Cessna key switch model A-510, part # C292501-0105.
>
>
>
Does the engine crank when the key is in the 'start' position. Kind of
irelevant - just curious.
> Would anyone happen to have a schematic for this
>key switch? I think the way it works is that it simply
>grounds (connects the p-lead wire to the
>p-lead shield which is grounded at the magneto)
>when switched to the OFF position, and leaves
>the p-lead disconnected (ie, "open") when in the
>BOTH position. Referring to Z-26 seems to follow this logic.
>
>
That's a correct analysis.
>Using my multimeter, I was able to
>determine that the p-leads for both mags are connected to
>the p-lead shield (ie, "grounded") in all four
>positions of the key switch, OFF, R, L, and BOTH.
>I measured this without removing any wires from
>the keyswitch.
>
>
>
> Am I on the right track, or should I be
>chasing some other gremlin? Should I remove
>the wires from the keyswitch and test it separately?
>
>
>
I think you are using the right ideas, but I think you are missing a
piece of the puzzle. The
thing I suspect that you don't know is that the P-leads are connected to
ground via the magneto
primary winding which has relatively low DC resistance - what your
multimeter measures.
This makes it look like everything is faulted together, which it
probably isn't.
You can check the integrity of the P-leads by disconneting each of them
from the magneto.
Warning!! Once disconnected, the mags are hot, and as such, the engine
could run with very
little disturbance. Don't leave the engine this way! Once
disconnected, you should see that
the P-leads and their shields are not shorted when the mag is in the
'both' position, and both
should be shorted when the key is turned off.
> If I do definitely determine that the
>keyswitch is the problem, I'm dumping it and replacing it
>with two switches and a push button. Seems silly to have
>a redundant ignition system tied to a single point of
>failure like this, especially after it scared the
>cr*p out of me.
>
>
>
Not a bad change to make.
>Thanks,
>
>-Dj
>
>
>
>
Are you sure it isn't a fuel problem? It seems somewhat unlikely that
both ignition leads
would get faulted at the same time at the end of a flight.
Good hunting, and let us know what you find!
Regards,
Matt
VE N34RD, C150 N714BK
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
A question. What were the transorbs you used (specific part # and BRAND).
The ones I have used clamped several AMPS to below 22V. This data was used
to demonstrate that a 40 amp load dump was limited to 24V or under with 3
1.5KE18C transorbs. I do not understand how one transorb allows the voltage
to 25V at 700 ma I would expect a 700 ma pulse to peak well under 21V. But
different brands do vary a surprising amount. Some 18V transorbs did not
really conduct much below 20V.
The P6KECA I recently tested clamped a 1.0 Amp load at under 18.4V This is a
true 18V bidirectional Transorb. Thus my question how how did you get 25V?
I got very different results when looking at what happens on the bus with
the contacts switching tens of amps and the coil was switched on the + side
and the coil returns were isolated from the main contact power. Not that
there was a significant amount of radiated or conducted noise. I was looking
at the load side contact when it interrupted 10 amps for example.
I believe the main difference was the contact bounce and arcing present with
the slower opening that I observed when a simple diode was used.
The other main concern is the use of a diode on the "B" lead contactor can
delay the opening to well past the CB opening and in some cases with hi
current leads to the CB the contactor still has 8+ volts across the coil.
I conducted a test recently that I will document soon to show how this and
400 amps are possible.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>
>>
>>But a diode clamps the negative pulse to about 1 volt. Seems to me that
>>the difference may be significant to some electronic circuitry that is
>>sensitive to negative spikes.
>>Ken
>
>
> Okay, here's what happens with a pair of transorbs back-to-back (same
> as a bi-directional transorb). These are some 18v devices where
> the array clamps to about 25 volts with 700 mA of current. Now,
> looking at the trace, we find that batter master switch terminal
> jumps up to about 38 volts (25 + 13) while the coil is dumping
> energy into the transorbs. Note that the transorbs stop conduction
> about 6 mS after switch opens and the contactor opens at 14 mS.
________________________________________________________________________________
| From: | Dj Merrill <deej(at)thayer.dartmouth.edu> |
| Subject: | Re: Cessna A-510 ignition switch |
mprather wrote:
> Does the engine crank when the key is in the 'start' position. Kind of
> irelevant - just curious.
Yes, cranks over fine, just as fast as normal.
> I think you are using the right ideas, but I think you are missing a
> piece of the puzzle. The
> thing I suspect that you don't know is that the P-leads are connected to
> ground via the magneto
> primary winding which has relatively low DC resistance - what your
> multimeter measures.
> This makes it look like everything is faulted together, which it
> probably isn't.
Yup, that would do it. I need to test the
switch with the p-leads disconnected to be sure.
I thought I might have been missing something, but
I didn't have the extra time to pull the wires off
for a complete test at the time. Figured I'd get some
advice before proceeding... :-)
> Are you sure it isn't a fuel problem? It seems somewhat unlikely that
> both ignition leads
> would get faulted at the same time at the end of a flight.
No, I'm not sure. I only just started trying to
track this down. However, while cranking the engine I
used the primer to put fuel directly into the cylinders,
and I didn't even get a kick out of the engine.
I am getting fuel pressure with the electric boost pump on
(as normal), and I could hear the primer moving the fuel,
so my initial thoughts are that it is not the fuel system
(if it were, putting fuel into the cyls directly should
have at least gotten a kick). My second theory was
the faulty key switch grounding out the mags.
If the switch proves fine, then the next step is
removing the cowling and start getting dirty.
I should mention it was a VERY BUMPY grass strip
that I landed on, and I suspect something got jounced
out of place. The plane has a carburated Lyc O320 150hp
engine installed.
Thanks for the help!
-Dj
--
Dj Merrill
deej(at)thayer.dartmouth.edu
"TSA: Totally Screwing Aviation"
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Cessna A-510 ignition switch |
>
>
> It was a dark and stormy night... Well, actually
>it was a bright and sunny day but it still scared me.
>While landing my Glasair, about halfway down the runway my engine quit.
>I was unable to get the engine restarted again, and after
>some limited troubleshooting I think I have traced the
>problem down to the ignition key switch. It is a
>Cessna key switch model A-510, part # C292501-0105.
>
> Would anyone happen to have a schematic for this
>key switch?
> I think the way it works is that it simply
>grounds (connects the p-lead wire to the
>p-lead shield which is grounded at the magneto)
>when switched to the OFF position, and leaves
>the p-lead disconnected (ie, "open") when in the
>BOTH position. Referring to Z-26 seems to follow this logic.
>Using my multimeter, I was able to
>determine that the p-leads for both mags are connected to
>the p-lead shield (ie, "grounded") in all four
>positions of the key switch, OFF, R, L, and BOTH.
>I measured this without removing any wires from
>the keyswitch.
Your ohmmeter test will read VERY low resistance
whether the switch is on or off and whether the
breaker points are open or closed. Just disconnect
the p-leads from the switch entirely and see if
the engine runs. You can always shut it down with
the mixture control.
> Am I on the right track, or should I be
>chasing some other gremlin? Should I remove
>the wires from the keyswitch and test it separately?
That's what you need to do to use any kind of instrument.
The magneto primary system has very small DC resitances.
This is why you need the ac current buzz-box to set
magneto timing. An ohmmeter just won't do it.
If your switch turns out to be bad and you do decide
to replace it, I'd like to do an autopsy on it.
Bob . . .
________________________________________________________________________________
| From: | Dj Merrill <deej(at)thayer.dartmouth.edu> |
| Subject: | Re: Cessna A-510 ignition switch |
Robert L. Nuckolls, III wrote:
> If your switch turns out to be bad and you do decide
> to replace it, I'd like to do an autopsy on it.
If it turns out to be the problem, I'd be
glad to send it your way! :-)
-Dj
--
Dj Merrill
deej(at)thayer.dartmouth.edu
"TSA: Totally Screwing Aviation"
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Vans Fuel Pump issue |
>
>I was doing the first check of the fuel boost pump today. I have
>the standard electric pump and filter combo they sell for my IO-360M1B.
>
>Thought I would simply turn it on and off quickly to verify connectivity;
>turn it on, hear some noise, turn it off.
>
>Blew a 5A fuse right away. Checked grounds - good. Checked positive
>routing - good. Made sure positive and negatives were correct too.
>Everything is ok as far as wiring. Wire size is adequate for both
>positive and ground as well. And the switch seems to be working fine
>as well.
>
>Tried it again, blew another 5A fuse immediately. In each trial,
>the pump did not make any noise, just blew the fuse.
What kind of pump is this? Is it a Fawcet or some motor
driven device? If motor driven, know that it can have an
inrush current many times that of running current. You may
have to fuse it at a higher level and upsize the wires accordingly.
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes across relay coils |
>
>A question. What were the transorbs you used (specific part # and BRAND).
>The ones I have used clamped several AMPS to below 22V. This data was used
>to demonstrate that a 40 amp load dump was limited to 24V or under with 3
>1.5KE18C transorbs. I do not understand how one transorb allows the voltage
>to 25V at 700 ma I would expect a 700 ma pulse to peak well under 21V. But
>different brands do vary a surprising amount. Some 18V transorbs did not
>really conduct much below 20V.
They are 5KP18 by General Semiconductor. The data sheet calls
for thresholds over a 22.0 to 24.4
>The P6KECA I recently tested clamped a 1.0 Amp load at under 18.4V This is a
>true 18V bidirectional Transorb. Thus my question how how did you get 25V?
These must be running at the top of spec. Add the forward drop
of the second diode and you come out with 25.0
>I got very different results when looking at what happens on the bus with
>the contacts switching tens of amps and the coil was switched on the + side
>and the coil returns were isolated from the main contact power. Not that
>there was a significant amount of radiated or conducted noise. I was looking
>at the load side contact when it interrupted 10 amps for example.
This experiment wasn't looking at contactor performance, just
the coil energy.
>I believe the main difference was the contact bounce and arcing present with
>the slower opening that I observed when a simple diode was used.
Okay. Here's some traces still warm out of the printer.
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_2x18v_25A_Load.gif
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_1N5400_25A_Load.gif
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_1N5400_25A_Load_A.gif
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_1N5400_25A_Load_B.gif
http://www.aeroelectric.com/articles/Spike_Catching/CH_w_1N5400_25A_Load_C.gif
With a 25A load on the contactor and back-to-back transorbs, I get
the first trace. Contacts open cleanly in 15 mS. Putting the diode
back in gives me a variety of results with the approx 12v source (I was
using alligator clip leads and the voltage drops at 25A were significant).
The drop out delay and non-clean break is evident. These traces are
probably not valid for service as b-lead contactor. When opening the
b-lead of an alternator running ball-to-wall . . . voltage rise across
spreading contacts is going to be spectacular. I'm not truly convinced
that the b-lead contactor would survive a real ov event. The fire might
never go out before the field windings burn up . . . but at least all
that snort isn't hard coupled to the rest of the system.
I'm wondering if a second crowbar right across the b-lead isn't called
for. Pull that puppy to ground which no only keeps the fire from building
in the contactor but stalls the alternator as well. It cannot supply
its own field and continue the OV event if there's no output. I'm thinking
the energy dissipated in the b-lead crowbar would be less than that
dissipated
on the contactor coil breaker.
>The other main concern is the use of a diode on the "B" lead contactor can
>delay the opening to well past the CB opening and in some cases with hi
>current leads to the CB the contactor still has 8+ volts across the coil.
How does it matter if there's a battery on line? Whether the ov system
disconnects the alternator in 30 or 200 mS seems of little consequence
at the end of the day.
I'm still not happy with the idea of internally regulated alternators.
If one subscribes to the reliable as prop-bolts scenario for the
regulators, then OV protection can be left out. However, if one of
those "prop-bolts" does break, the pilot has no way to shut it off . . .
without adding the b-lead contactor. If the b-lead contactor is
present, then you can automate the shutdown just as if it were an
externally regulated alternator . . . but now you have issues with
respect to b-lead contactor performance in opening a 100+ volt circuit
and you still can't shut the puppy off completely. A $10 regulator can
crap and take the field winding with it making the whole alternator
pretty much trash.
We can undoubtedly figure out a way to sense OV condition, open a b-lead
contactor -AND- stall the alternator to prevent further damage to the
alternator -AND- the b-lead contactor . . . but that becomes about as
costly as modifying the alternator to bring out the field leads.
Bob . . .
________________________________________________________________________________
| From: | "Denny Mortensen" <dennymortensen(at)cableone.net> |
| Subject: | Vans Fuel Pump issue |
Might also try disconnecting the + wire from the pump and insulate so as
not to short. Then flip your switch to see if it still blows a fuse. If
it does your problem is in the wiring if not then try your pump.
Denny
-----Original Message-----
Sounds like the pump is where the fault lies. But you need to isolate
the pump from the rest of the system to prove that.
Take the pump out of the plane and try it on the bench using either a
current-limited supply or a 5A fuse -- no switch, just wires from supply
+12V to fuse to pump, and pump back to supply ground.
Frank
________________________________________________________________________________
| From: | Harley <harley(at)AgelessWings.com> |
| Subject: | Re: Cessna A-510 ignition switch |
Morning, DJ...
>>I'm dumping it and replacing it with two switches and a push button.<<
Probably a good idea in any case...that's exactly what I'm going to do,
and for the reasons you mentioned...also, judging from the size and
weight of the key switch that I have, two toggles and a push button will
save weight! Not to mention all the weight of that key itself that
resides in the switch when flying!
As far as troubleshooting...since you're going to replace the key switch
anyway, take it right out, and while the wires are disconnected, start
the engine, then ground each mag p-lead just like you do through the
switch during your run up. You should be able to start it with the
wires disconnected from the switch, and see the normal rpm drop when
grounding the p-leads, with a complete shut down with both grounded.
If this is what happens, you won't have to look any further...if you
still have a problem, then follow some of the other suggestions that
have been mentioned.
Keep us informed!
Harley Dixon
Long EZ N28EZ
Canandaigua, NY
Dj Merrill wrote:
>
> It was a dark and stormy night... Well, actually
>it was a bright and sunny day but it still scared me.
>While landing my Glasair, about halfway down the runway my engine quit.
>I was unable to get the engine restarted again, and after
>some limited troubleshooting I think I have traced the
>problem down to the ignition key switch. It is a
>Cessna key switch model A-510, part # C292501-0105.
>
> Would anyone happen to have a schematic for this
>key switch? I think the way it works is that it simply
>grounds (connects the p-lead wire to the
>p-lead shield which is grounded at the magneto)
>when switched to the OFF position, and leaves
>the p-lead disconnected (ie, "open") when in the
>BOTH position. Referring to Z-26 seems to follow this logic.
>Using my multimeter, I was able to
>determine that the p-leads for both mags are connected to
>the p-lead shield (ie, "grounded") in all four
>positions of the key switch, OFF, R, L, and BOTH.
>I measured this without removing any wires from
>the keyswitch.
>
> Am I on the right track, or should I be
>chasing some other gremlin? Should I remove
>the wires from the keyswitch and test it separately?
>
> If I do definitely determine that the
>keyswitch is the problem, I'm dumping it and replacing it
>with two switches and a push button. Seems silly to have
>a redundant ignition system tied to a single point of
>failure like this, especially after it scared the
>cr*p out of me.
>
>Thanks,
>
>-Dj
>
>
>
>
________________________________________________________________________________
| From: | Christopher Stone <rv8iator(at)earthlink.net> |
Eric....
I believe you previousy posted a link to data on TVS (dueling zeners) devices.
I that had them bookmarked... But alas.
Would you repost?
You also had a PDF of the part you were or are going to offer for sale?
Thanks...
Chris Stone
Wiring RV-8, number one
Day/night VFR
________________________________________________________________________________
| From: | "Wayne Berg" <wfberg(at)msn.com> |
| Subject: | Antenna Triplexer |
I have a Comant triplexer that reads very low resistance from each center conductor
to case. Is this normal?
________________________________________________________________________________
| From: | Walter Tondu <walter(at)tondu.com> |
| Subject: | Re: Vans Fuel Pump issue |
On 03/27 9:55, Robert L. Nuckolls, III wrote:
> >I was doing the first check of the fuel boost pump today. I have
> >the standard electric pump and filter combo they sell for my IO-360M1B.
> >
> >Thought I would simply turn it on and off quickly to verify connectivity;
> >turn it on, hear some noise, turn it off.
> >
> >Blew a 5A fuse right away. Checked grounds - good. Checked positive
> >routing - good. Made sure positive and negatives were correct too.
> >Everything is ok as far as wiring. Wire size is adequate for both
> >positive and ground as well. And the switch seems to be working fine
> >as well.
> >
> >Tried it again, blew another 5A fuse immediately. In each trial,
> >the pump did not make any noise, just blew the fuse.
>
> What kind of pump is this? Is it a Fawcet or some motor
> driven device? If motor driven, know that it can have an
> inrush current many times that of running current. You may
> have to fuse it at a higher level and upsize the wires accordingly.
>
> Bob . . .
It's the Airflow Performance pump. I called the manufacturer
this morning to confirm the 5A fuse. Nope, use 10A as it's
initial draw is as high as 7A.
I'll give it a whirl.
Thanks to all who responded.
--
Walter Tondu
http://www.rv7-a.com
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
I understand. I have the same part/mfgr and they do start clamping on the
high side.
This one reason why we (Eric and I) recommend the use of multiple 1.5K
devices because they start at just ober 18 v and you add devices in paralles
based on the amp capacity of the alternator.
Also back to back unidirectional trqansorbs rated at say 18V will clamp at
around 1 V higher than a bidirectional 18V device.
Thanks for the info.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>
>>
>>
>>A question. What were the transorbs you used (specific part # and BRAND).
>>The ones I have used clamped several AMPS to below 22V. This data was used
>>to demonstrate that a 40 amp load dump was limited to 24V or under with 3
>>1.5KE18C transorbs. I do not understand how one transorb allows the
>>voltage
>>to 25V at 700 ma I would expect a 700 ma pulse to peak well under 21V.
>>But
>>different brands do vary a surprising amount. Some 18V transorbs did not
>>really conduct much below 20V.
>
> They are 5KP18 by General Semiconductor. The data sheet calls
> for thresholds over a 22.0 to 24.4
>
>
>>The P6KECA I recently tested clamped a 1.0 Amp load at under 18.4V This is
>>a
>>true 18V bidirectional Transorb. Thus my question how how did you get 25V?
>
>
> These must be running at the top of spec. Add the forward drop
> of the second diode and you come out with 25.0
>
>>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>
>>
>>
>>The other main concern is the use of a diode on the "B" lead contactor can
>>delay the opening to well past the CB opening and in some cases with hi
>>current leads to the CB the contactor still has 8+ volts across the coil.
>
> How does it matter if there's a battery on line? Whether the ov system
> disconnects the alternator in 30 or 200 mS seems of little consequence
> at the end of the day.
It matters if the contactor is still in the process of opening when the OVP
opens the "B" lead. If the contacts of the "B" lead contactor are still
closed the load dump or failure will reappear on the acft bus until the
contacts finally open and when opening spew transients everywhere. The
transients from contact arcing may not be a concern but having 30+ ms of say
60V on the bus sure is a concern. My data of 50 ms to open with your data of
15 ms to open the CB leaves 35 ms of potential OV back on the bus and in
this case very likely a maxi sized load dump.
> I'm still not happy with the idea of internally regulated alternators.
I never was happy and neither were you as I recall. Its hard to plug the
dike today however.
I think we both feel that todays solution of the crowbar may not cover all
the bases and the entire approach needs revisiting and we are both doing
this.
> If one subscribes to the reliable as prop-bolts scenario for the
> regulators, then OV protection can be left out. However, if one of
> those "prop-bolts" does break, the pilot has no way to shut it off . . .
> without adding the b-lead contactor. If the b-lead contactor is
> present, then you can automate the shutdown just as if it were an
> externally regulated alternator . . . but now you have issues with
> respect to b-lead contactor performance in opening a 100+ volt circuit
> and you still can't shut the puppy off completely. A $10 regulator can
> crap and take the field winding with it making the whole alternator
> pretty much trash.
>
> We can undoubtedly figure out a way to sense OV condition, open a b-lead
> contactor -AND- stall the alternator to prevent further damage to the
> alternator -AND- the b-lead contactor . . . but that becomes about as
> costly as modifying the alternator to bring out the field leads.
>
> Bob . . .
>
>
>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
> The drop out delay and non-clean break is evident. These traces are
> probably not valid for service as b-lead contactor. When opening the
> b-lead of an alternator running ball-to-wall . . . voltage rise across
> spreading contacts is going to be spectacular. I'm not truly convinced
> that the b-lead contactor would survive a real ov event. The fire might
> never go out before the field windings burn up . . . but at least all
> that snort isn't hard coupled to the rest of the system.
With a heavy transorb on the alternator side of the "B" lead contactor the
voltage is clamped to reasonable level as far as the contactor contacts are
concerned. This is where the 5KW 18V transorb helps.
Also if the trip is false the alternator regulator is likely protected by
the transorb.
>
> I'm wondering if a second crowbar right across the b-lead isn't called
> for. Pull that puppy to ground which no only keeps the fire from
> building
> in the contactor but stalls the alternator as well. It cannot supply
> its own field and continue the OV event if there's no output. I'm
> thinking
> the energy dissipated in the b-lead crowbar would be less than that
> dissipated
> on the contactor coil breaker.
Not sure I agree here. Remember there are two sources of current to the
field. The internal connection from the "B" lead and the external "field"
connection. This connection actually supplies field power until there is
power produced by the alternator and the field power is switched to the "B"
lead. Thus there is a second source of power to the alternator that needs
attention.
Also stalling the alternator might have interesting side effects on the belt
drive.
That brings up a new question. Assuming there is a real (vs. false trip)
need to shutdown the alternator, the OVP trips but the alt switch on the
panel is still supplying power to the alternator field thru the internal
regulator. Depending on the regulator's fault it seems to me the alternator
can still be generating power. Also there is the possibility that the
internal "B" lead to regulator connection can reverse power the panel
mounted switch (and on to the acft bus) with a 'far too hi' voltage that was
the reason for the OVP action. Sneak path anyone??? Not sure how long the
fuse/CB would take to trip in this case.
Paul
________________________________________________________________________________
| From: | "Leo Corbalis" <leocorbalis(at)sbcglobal.net> |
| Subject: | Re: Diodes across relay coils |
In the real world, if you're using a transistor to control the relay without
a diode it will work ONCE ! Then you put in a new transistor. If you're
using a switch and no diode, the switch contacts will (guaranteed) get
arced. Manufacturers don't test their switch life this way. It will take
longer to kill a switch but you will kill it.
Leo Corbalis
----- Original Message -----
From: "Joel Jacobs" <jj(at)sdf.lonestar.org>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>
> ----- Original Message -----
> From: "Eric M. Jones" <emjones(at)charter.net>
> To:
> Subject: AeroElectric-List: Re: Diodes across relay coils
>
>> >The description of a "low-side" switching arrangement is basically the
>> same, except that the voltage will go to a large positive value.
>>
>> The transient is always negative.
>>
>
> No, it isn't.. It is always oppisate the applied voltage that energized
> the
> coil. In a low side switch, the low side of the coil is negative while
> the
> switch is closed and the spike will be positive when the switch opens.
>
> Joel
>
>
>
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Antenna Triplexer |
>
>I have a Comant triplexer that reads very low resistance from each center
>conductor to case. Is this normal?
Probably. Dead shorts at DC (ohmmeter readings) are
anything but at VHF/UHF frequencies.
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes across relay coils |
>
>I understand. I have the same part/mfgr and they do start clamping on the
>high side.
>
>This one reason why we (Eric and I) recommend the use of multiple 1.5K
>devices because they start at just ober 18 v and you add devices in paralles
>based on the amp capacity of the alternator.
>
>Also back to back unidirectional trqansorbs rated at say 18V will clamp at
>around 1 V higher than a bidirectional 18V device.
>
>Thanks for the info.
>
>Paul
Not sure I embrace the notion of attempting to hold the bus
to 20v or less. This is a quantum shift in philosophy of
power quality limits. We've learned to live comfortably
in the 40v/100us, 20v/1sec world for over nearly 40 years.
I understand there are some new kids on the block that would
like to have that power quality philosophy relaxed . . . but
I'm not convinced this is a good thing for the industry as
a whole. I continue to mull this over . . .
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes across relay coils |
>
>
>----- Original Message -----
>From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
>To:
>Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
> >
> >
>
> > The drop out delay and non-clean break is evident. These traces are
> > probably not valid for service as b-lead contactor. When opening the
> > b-lead of an alternator running ball-to-wall . . . voltage rise across
> > spreading contacts is going to be spectacular. I'm not truly convinced
> > that the b-lead contactor would survive a real ov event. The fire might
> > never go out before the field windings burn up . . . but at least all
> > that snort isn't hard coupled to the rest of the system.
>
>With a heavy transorb on the alternator side of the "B" lead contactor the
>voltage is clamped to reasonable level as far as the contactor contacts are
>concerned. This is where the 5KW 18V transorb helps.
If the alternator is in runaway mode, the transorbs are going to
be toast in seconds.
>Also if the trip is false the alternator regulator is likely protected by
>the transorb.
True . . . this is, I believe, what prompted consideration of a
voltage clamping devices in this location . . . but one still needs to
approach this with caution. As George Braly noted, he was able to
toast some transorbs in this location when breaking the b-lead of
a properly functioning alternator/regulator combination. I'm convinced
that his experience was driven by regulator/alternator dynamics . . . the
load dump produced a longer than average overshoot transient.
> > I'm wondering if a second crowbar right across the b-lead isn't called
> > for. Pull that puppy to ground which no only keeps the fire from
> > building in the contactor but stalls the alternator as well. It
> > cannot supply its own field and continue the OV event if there's
> > no output. I'm thinking
> > the energy dissipated in the b-lead crowbar would be less than that
> > dissipated
> > on the contactor coil breaker.
>
>Not sure I agree here. Remember there are two sources of current to the
>field. The internal connection from the "B" lead and the external "field"
>connection. This connection actually supplies field power until there is
>power produced by the alternator and the field power is switched to the "B"
>lead. Thus there is a second source of power to the alternator that needs
>attention.
Do we KNOW that an EXTERNAL hard source for field power or is it
simply a start up bias on the order of a few hundred milliamps?
The early alternator installations on cars depended on a startup
bias that came through the panel mounted alternator warning light.
If the light bulb burned out, the alternator wouldn't start. Later
systems included a resistor around the lamp so that the alternator
would start even if the bulb is open.
Even if this is a hard-source, I would expect it to be interrupted
by the first crowbar just as it is now . . .
>Also stalling the alternator might have interesting side effects on the belt
>drive.
How so? It's a 60A machine with limited output current. It won't
require much more torque to run it against a dead short than it does
to have it go into an OV condition against the battery.
>That brings up a new question. Assuming there is a real (vs. false trip)
>need to shutdown the alternator, the OVP trips but the alt switch on the
>panel is still supplying power to the alternator field thru the internal
>regulator.
??? Lost you here. Are we talking some configuration other than
Z-24? My intent there was to open the supply through the
control switch -AND- the open the alternator's b-lead. This leaves
the alternator totally disconnected from the rest of the aircraft's
electrical system.
> Depending on the regulator's fault it seems to me the alternator
>can still be generating power.
Absolutely. This is the source of my concern for putting the fire
out between spreading contacts of the b-lead contactor. If no mitigating
transorb is present, the failed alternator output could rise very
rapidly to voltages beyond what plain vanilla contactors are
designed to break. If a transorb is present, it's seems likely that
it will suffer the Braly effect and become toast. If it's a really
robust array of devices, they might just short and take the alternator
down gracefully. Or, they could take the route chosen by most plastic
devices and blow little bits of smoking plastic around the engine
compartment.
Now, this all takes time and the voltage might well stay down long
enough for the b-lead contactor to open and put the fires out between
spreading contacts.
> Also there is the possibility that the
>internal "B" lead to regulator connection can reverse power the panel
>mounted switch (and on to the acft bus) with a 'far too hi' voltage that was
>the reason for the OVP action. Sneak path anyone??? Not sure how long the
>fuse/CB would take to trip in this case.
Only if we're talking about something other than Z-24 . . .
When Z-24 was crafted, I could assume nothing about the internal
configuration of the alternator. If the bus voltage is too high,
it's time to totally unhook the alternator from the system. This
philosophy has functioned well with the few exceptions reported by
Van's . . . and again, I know (and can assume nothing) about Van's
alternators. I promised only to protect the aircraft. The alternator
had to be cut out on its own.
Bob . . .
________________________________________________________________________________
| From: | <bakerocb(at)cox.net> |
| Subject: | Great Leap Backwards? |
3/28/2005
Hello Matt Dralle, I used to be able to go to the bottom of my lists, click
on Search, and get quickly to what I wanted to look for. It was one of the
most useful aspects of your lists.
Now I see something called Navigator at the bottom of my aeroelectric-list
and when I click on it it doesn't work at all. What is going on?
OC
PS: People, what I am searching for is the company that sells specially
designed hardware for installing radio boxes in instrument panels. Can you
please help me? Thanks.
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes across relay coils |
> >>The other main concern is the use of a diode on the "B" lead contactor can
> >>delay the opening to well past the CB opening and in some cases with hi
> >>current leads to the CB the contactor still has 8+ volts across the coil.
> >
> > How does it matter if there's a battery on line? Whether the ov system
> > disconnects the alternator in 30 or 200 mS seems of little consequence
> > at the end of the day.
>
>It matters if the contactor is still in the process of opening when the OVP
>opens the "B" lead. If the contacts of the "B" lead contactor are still
>closed the load dump or failure will reappear on the acft bus until the
>contacts finally open and when opening spew transients everywhere. The
>transients from contact arcing may not be a concern but having 30+ ms of say
>60V on the bus sure is a concern. My data of 50 ms to open with your data of
>15 ms to open the CB leaves 35 ms of potential OV back on the bus and in
>this case very likely a maxi sized load dump.
??? Lost you here. Until the contactor starts to break the b-lead
loose, the alternator is working at max effort to boost bus voltage.
Further, it's been successful to the extent that the ov protection has
sensed the event and started the process of shutting things down.
In the mean time, the battery will do what batteries do best and
keep enough load on the alternator to prevent a hazardous rise on the
bus. In the revision B discussion of the system dynamics paper
http://www.aeroelectric.com/articles/Crowbar_OV_Protection/DC_Power_System_Dynamics_C.pdf
I showed how a good battery will maintain bus voltage at or below
18 volts for hundreds of milliseconds . . . plenty of time for
bringing things to order in spite of stacked delays noted.
It's exactly this condition that drove the DO-160 to recommend that
14v appliances be designed to withstand 20 volts for 1 second . . .
FAR longer than it takes for the most sedentary ov protection system
to do the job.
> > I'm still not happy with the idea of internally regulated alternators.
>
>I never was happy and neither were you as I recall. Its hard to plug the
>dike today however.
I'm not sure we're obligated to "plug the dyke" . . . I'm certainly
interested seeing it we can teach ourselves to live with this
alternative technology. Alternative technologies have bubbled
up from time to time. Some proved to be good value and others
did not. We need to get all the facts together before the jury
is called.
>I think we both feel that todays solution of the crowbar may not cover all
>the bases and the entire approach needs revisiting and we are both doing
>this.
We're certainly marching off in that direction. I looked over the
alternator test stand that I acquired and found that it's too
badly abused to be worth resurrecting. I'm going back to plan-B.
I've got a 2 hp DC motor and drive controller that I'm going to
direct couple to an ND alternator with field leads brought out.
I really like this idea better anyhow because motor current is
directly proportional to output torque. I can observe and record
alternator drive torque under varying conditions. It will take
less time to build from scratch than to repair the other one
(which was fixed speed). Now all I need is more time.
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes across relay coils |
>
>
>In the real world, if you're using a transistor to control the relay without
>a diode it will work ONCE ! Then you put in a new transistor. If you're
>using a switch and no diode, the switch contacts will (guaranteed) get
>arced. Manufacturers don't test their switch life this way. It will take
>longer to kill a switch but you will kill it.
Sure . . . don't think anyone is arguing against inductive
spike suppression. Lots of techniques suffice to specific
task. The tests I did on the bench yesterday illustrated only
three of them.
Bob . . .
________________________________________________________________________________
| From: | <chaztuna(at)adelphia.net> |
| Subject: | DIY Navigation Antenna Questions |
Bob,
Figure 13-12 on page 13-16 of the Aeroelectric Connection book shows a drawing
for making your own Navigation antenna. One section of this antenna calls for
a 90 degree bend in that section of 0.025" aluminum. The section's length is
called out as "convenient L", which I construe to mean a convenient length. The
width is called out as aluminum sheet angle 0.5" X 1.5". I construe this to
mean that the aluminum should be 1.5" wide on it's horizontal surface and 0.5"
on it's vertical (bent) surface.
Are my assumptions correct? Are there any recommended minimum or maximum lengths
for this section of angle? Is the 90 degree bend in this section to achieve
rigidity? Or, is this section of the antenna to be fastened to the outboard wing
rib? Please advise.
Charlie Kuss
RV-8A still wiring
Boca Raton, Florida
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Diodes across relay coils |
> > > I'm still not happy with the idea of internally regulated alternators.
> >
> >I never was happy and neither were you as I recall. Its hard to plug the
> >dike today however.
>
> I'm not sure we're obligated to "plug the dyke" . . .
Hmmm . . . interesting faux pas . . . wrote it only 30 minutes
and can't imagine where that came from!
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Re: Great Leap Backwards? |
>
>3/28/2005
>
>Hello Matt Dralle, I used to be able to go to the bottom of my lists, click
>on Search, and get quickly to what I wanted to look for. It was one of the
>most useful aspects of your lists.
>
>Now I see something called Navigator at the bottom of my aeroelectric-list
>and when I click on it it doesn't work at all. What is going on?
>
>OC
Matt doesn't monitor all the lists on his servers. If you want
to ask him a question, you'll have to direct it specifically to
him. However, the link below works for me in Netscape. Haven't
tried IE.
>PS: People, what I am searching for is the company that sells specially
>designed hardware for installing radio boxes in instrument panels. Can you
>please help me? Thanks.
Not sure what you're looking for here. I have dozens of hardware
catalogs but none that are uniquely "aircraft". What kind of device
are you looking for?
Bob . . .
________________________________________________________________________________
| Subject: | Re: Great Leap Backwards? |
| From: | "Matt Prather" <mprather(at)spro.net> |
I went to the Archive Search Engine:
http://www.matronics.com/searching/ws_script_short.cgi
and entered (after a couple of tries) "radio tray", and it returned a message
that included reference to:
http://www.radiorax.com/
Is that what you are looking for?
Regards,
Matt-
VE N34RD, C150 N714BK
>
> 3/28/2005
>
> Hello Matt Dralle, I used to be able to go to the bottom of my lists,
> click on Search, and get quickly to what I wanted to look for. It was
> one of the most useful aspects of your lists.
>
> Now I see something called Navigator at the bottom of my
> aeroelectric-list and when I click on it it doesn't work at all. What
> is going on?
>
> OC
>
> PS: People, what I am searching for is the company that sells specially
> designed hardware for installing radio boxes in instrument panels. Can
> you please help me? Thanks.
>
>
________________________________________________________________________________
| From: | Dj Merrill <deej(at)thayer.dartmouth.edu> |
| Subject: | Re: Great Leap Backwards? |
bakerocb(at)cox.net wrote:
> Hello Matt Dralle, I used to be able to go to the bottom of my lists, click
> on Search, and get quickly to what I wanted to look for. It was one of the
> most useful aspects of your lists.
>
> Now I see something called Navigator at the bottom of my aeroelectric-list
> and when I click on it it doesn't work at all. What is going on?
>
> OC
Hi OC,
You can get to the same thing by clicking the
"Navigator" link at the bottom of the e-mail.
That will take you to a page with the search
link on it. Matt did this since a bunch of people
were complaining about having the really long
list of links on every single e-mail message, and
this seemed like a good compromise. It amounts to
just one extra click to get to the same things.
fyi
-Dj
--
Dj Merrill
deej(at)thayer.dartmouth.edu
"TSA: Totally Screwing Aviation"
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
I was not clear apparently.
I was simply replying to your test using different 18V transorbs that
allowed 25V.
The 1.5 watt transorbs will clamp to under 22V at 10 amps in testing. They
are soft zeners and I have photos where you can see the voltage rise during
the load dump from internal transorb die heating during the load dump event.
No way was I suggesting revising old standards in this case. I do believe in
improving power quality and I am in process of developing new methods that
do improve things.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>
>>
>>
>>I understand. I have the same part/mfgr and they do start clamping on the
>>high side.
>>
>>This one reason why we (Eric and I) recommend the use of multiple 1.5K
>>devices because they start at just ober 18 v and you add devices in
>>paralles
>>based on the amp capacity of the alternator.
>>
>>Also back to back unidirectional trqansorbs rated at say 18V will clamp at
>>around 1 V higher than a bidirectional 18V device.
>>
>>Thanks for the info.
>>
>>Paul
>
> Not sure I embrace the notion of attempting to hold the bus
> to 20v or less. This is a quantum shift in philosophy of
> power quality limits. We've learned to live comfortably
> in the 40v/100us, 20v/1sec world for over nearly 40 years.
> I understand there are some new kids on the block that would
> like to have that power quality philosophy relaxed . . . but
> I'm not convinced this is a good thing for the industry as
> a whole. I continue to mull this over . . .
>
> Bob . . .
>
>
>
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Diodes across relay coils |
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>
>
>
>>
>>
>>
>>----- Original Message -----
>>From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
>>To:
>>Subject: Re: AeroElectric-List: Re: Diodes across relay coils
>>
>>
>> >
>>
> If the alternator is in runaway mode, the transorbs are going to
> be toast in seconds.
I agree. The transorb was onlt a solution if there was a false trip.
>
>>Also if the trip is false the alternator regulator is likely protected by
>>the transorb.
>
>
> True . . . this is, I believe, what prompted consideration of a
> voltage clamping devices in this location . . . but one still needs to
> approach this with caution. As George Braly noted, he was able to
> toast some transorbs in this location when breaking the b-lead of
> a properly functioning alternator/regulator combination. I'm convinced
> that his experience was driven by regulator/alternator dynamics . . .
> the
> load dump produced a longer than average overshoot transient.
Perhaps George will jump in but the 5KW transorb solution only is good for
14V systems. A 28V system which George also needs to deal with has lots more
energy to absorb.
>> > I'm wondering if a second crowbar right across the b-lead isn't
>> > called
>> > for. Pull that puppy to ground which no only keeps the fire from
>> > building in the contactor but stalls the alternator as well. It
>> > cannot supply its own field and continue the OV event if there's
>> > no output. I'm thinking
>> > the energy dissipated in the b-lead crowbar would be less than that
>> > dissipated
>> > on the contactor coil breaker.
>>
>>Not sure I agree here. Remember there are two sources of current to the
>>field. The internal connection from the "B" lead and the external "field"
>>connection. This connection actually supplies field power until there is
>>power produced by the alternator and the field power is switched to the
>>"B"
>>lead. Thus there is a second source of power to the alternator that needs
>>attention.
>
> Do we KNOW that an EXTERNAL hard source for field power or is it
> simply a start up bias on the order of a few hundred milliamps?
> The early alternator installations on cars depended on a startup
> bias that came through the panel mounted alternator warning light.
> If the light bulb burned out, the alternator wouldn't start. Later
> systems included a resistor around the lamp so that the alternator
> would start even if the bulb is open.
Understand but we simply do not know so I was simply speculating another
possible path of concern.//// SEE mind F*&
later in this post :-)
But also the alternator fuse would pop if the crowbar was in the right place
and might be a good solution but are we getting too complex for a very
unlikely event?
> Even if this is a hard-source, I would expect it to be interrupted
> by the first crowbar just as it is now . . .
>
>>That brings up a new question. Assuming there is a real (vs. false trip)
>>need to shutdown the alternator, the OVP trips but the alt switch on the
>>panel is still supplying power to the alternator field thru the internal
>>regulator.
>
> ??? Lost you here. Are we talking some configuration other than
> Z-24? My intent there was to open the supply through the
> control switch -AND- the open the alternator's b-lead. This leaves
> the alternator totally disconnected from the rest of the aircraft's
> electrical system.
OOPS sorry memory F*&
. My mind was somewhere else; you are right IF one
wires it properly.
My mind is getting as bad as my smelling of words or lack of :-)
You know, perhaps you should simply only support externally regulated
alternators and simply consider the internal regulator as being far more
reliable than a prop failure and worth the risk if the builder is informed.
Builders need to be informed and then when properly informed can make
informed decisions.
There is still the issue of disconnecting the battery and resulting load
dump but that has a very simple fix in Transorbs
Paul
> Bob . . .
________________________________________________________________________________
| Subject: | Great Leap Backwards? |
Are you thinking of Approach Systems that sells wiring hubs and cables?
http://www.approach-systems.com/
Or maybe Radiorax that sells a proprietary rack/rail installation
system?
http://www.radiorax.com/index.php
Regards,
Greg Young - Houston (DWH)
RV-6 N6GY ...project Phoenix
Navion N5221K - just an XXL RV-6A
>
> 3/28/2005
>
> Hello Matt Dralle, I used to be able to go to the bottom of
> my lists, click on Search, and get quickly to what I wanted
> to look for. It was one of the most useful aspects of your lists.
>
> Now I see something called Navigator at the bottom of my
> aeroelectric-list and when I click on it it doesn't work at
> all. What is going on?
>
> OC
>
> PS: People, what I am searching for is the company that sells
> specially designed hardware for installing radio boxes in
> instrument panels. Can you please help me? Thanks.
>
________________________________________________________________________________
| From: | Matt Dralle <dralle(at)matronics.com> |
| Subject: | Re: Great Leap Backwards? |
At 12:42 PM 3/28/2005 Monday, you wrote:
>
>3/28/2005
>
>Hello Matt Dralle, I used to be able to go to the bottom of my lists, click
>on Search, and get quickly to what I wanted to look for. It was one of the
>most useful aspects of your lists.
>
>Now I see something called Navigator at the bottom of my aeroelectric-list
>and when I click on it it doesn't work at all. What is going on?
Whoops, sorry... I am doing maintenance on the Matronics webserver today
and it sounds like you tried to access the new page when it was unavailable...
I had gotten a number of complaints from members about the size of the old
style message trailer. I came up with the new, smaller version in hopes of
making everyone happy.
Do you still have the same complaint, if the line worked...?
PS- The webserver is up right now, but I will be taking it up and down a
few more times today.
Best regards,
Matt Dralle
Matronics Email List Admin
Matt G Dralle | Matronics | PO Box 347 | Livermore | CA | 94551
925-606-1001 V | 925-606-6281 F | dralle(at)matronics.com Email
http://www.matronics.com/ WWW | Featuring Products For Aircraft
________________________________________________________________________________
| From: | B Tomm <fvalarm(at)rapidnet.net> |
| Subject: | electrical questions (long) |
Bob,
On my electrically dependant engine, I'm planning to have two battery
busses (fuse blocks) ala Z-19. The feed wires to these busses are to be
short as they are unfused. The recommended max length is 6 inches. I
assume that the shorter they are, the less likely they are to short to
ground creating trouble. My batteries will be mounted aft of the baggage
area (RV7A). I suppose I could fabricate a panel to mount the fuse block
busses but access would be difficult. The fuse blocks could be mounted
below the baggage floor with a removable cover which would be easier to
service BUT the unprotected feed would pass through a bulkhead. I would
think this is unwise, correct?
Should I fab a mounting bracket next to the batteries and a exterior access
panel to service the fuses?
Better yet, could I mount the battery busses (fuse blocks) behind the
instrument panel with the others buss blocks using a long feed wire from
the rear batteries and a fusible link at the batteries for protection? I
would prefer this method.
I would like to run one set of main battery feed lines from the pair of
rear mounted batteries to the firewall area. Contactors or better yet
(perihelion) solid state power relays would connect the batteries to these
feed lines. Why do some people recommended separate feed lines? I would
think these heavy wires are UNlikely failure points. Much weight can be
saved by eliminating this redundancy.
I'm not clear on how to size the wire for the main battery feed lines.
Some diagrams show 6,4, and even 2 AWG. The largest current draw for all
the electrical loads + starter can be calculated easy enough. The wire
table I have does not show current carrying capacity but resistance,
weight, 10C temp rise current and something called "CMA per amp". I
thought that we sized wire by some healthy factor over that which would
cause the wire to melt under max current draw. Since there is quite a bit
of weight involved here, and critical functions, this is important. Will a
single set of 6AWG be sufficient to start the Subaru?
I seem to recall that electrical wiring is to be kept some distance away
from fuel system components. Does this just apply to power wires. Are we
concerned about a broken live wire contacting a metalic fuel component such
as a fuel tube, or leaking fuel dripping on wires causing a short to
ground. In our small airplanes there will always be a potential for fuel
and fuel vapor contacting electrical components (we have aircooled radios).
Can you elaborate on wiring and fuel systems please or direct me to some
reference..
Your thoughts are appreciated and likely relavent to others as well.
Bevan
RV7A
Planning for H6 Subaru
________________________________________________________________________________
| Subject: | Great Leap Backwards? |
Is this it? http://www.radiorax.com/
Best regards,
Rob Housman
Europa XS Tri-Gear A070
Airframe complete
Irvine, CA
-----Original Message-----
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com]On Behalf Of
bakerocb(at)cox.net
Subject: AeroElectric-List: Great Leap Backwards?
3/28/2005
Hello Matt Dralle, I used to be able to go to the bottom of my lists, click
on Search, and get quickly to what I wanted to look for. It was one of the
most useful aspects of your lists.
Now I see something called Navigator at the bottom of my aeroelectric-list
and when I click on it it doesn't work at all. What is going on?
OC
PS: People, what I am searching for is the company that sells specially
designed hardware for installing radio boxes in instrument panels. Can you
please help me? Thanks.
________________________________________________________________________________
| From: | BobsV35B(at)aol.com |
| Subject: | Re: Great Leap Backwards? |
In a message dated 3/28/2005 4:52:21 P.M. Central Standard Time,
mprather(at)spro.net writes:
PS: People, what I am searching for is the company that sells specially
> designed hardware for installing radio boxes in instrument panels. Can
> you please help me? Thanks.
Good Evening OC,
If you are thinking of using RadioRax, I have installed a set and like them
very much.
_www.radiorax.com_ (http://www.radiorax.com)
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Airpark LL22
Downers Grove, IL 60516
630 985-8502
________________________________________________________________________________
| Subject: | Re: Diodes across relay coils |
| From: | "George Braly" <gwbraly(at)gami.com> |
Bob,
The load dumps that I have experienced on disconnecting 20 or 30 amps (resistive)
from the alternator were done under circumstances where the field was opened
within a couple of tenths of a millisecond (or even much faster) after the over
voltage threshold was crossed.
I'm not sure what regulator/alternator "dynamics" would cause the noted result,
other than just the ordinary load dump from the alternator.
>Also if the trip is false the alternator regulator is likely protected by
>the transorb.
True . . . this is, I believe, what prompted consideration of a
voltage clamping devices in this location . . . but one still needs to
approach this with caution. As George Braly noted, he was able to
toast some transorbs in this location when breaking the b-lead of
a properly functioning alternator/regulator combination. I'm convinced
that his experience was driven by regulator/alternator dynamics . . . the
load dump produced a longer than average overshoot transient.<<
BTW... I have a nice variable speed alternator test stand - - with an ND set
up on it and it is available if you want to fly down some Saturday morning and
see what we can do to blow up some transorbs or other components.
Regards, George
---
________________________________________________________________________________
| From: | <bakerocb(at)cox.net> |
| Subject: | Great Leap Backwards? |
AeroElectric-List message previously posted by: Matt Dralle
<>
3/29/2005
Hello Matt Dralle, Thanks for the quick response.
I apologize. I should have had more patience / faith when I tried Navigator
a couple of times and it did not work. I must have hit it when it was down
for maintenance.
I think that it works fine and have no complaints with the present
configuration. Many thanks for your continuing support to our homebuilder
community.
'OC'
________________________________________________________________________________
| From: | "Mitch Faatz" <mitchf(at)skybound.com> |
I'm looking at the latest Z-11 which shows two 2-5 switches to be used for mag
switches and starter. Is there a reason why the right mag switch is a 2-5 (on)-off-on
switch like the left mag? The momentary position on the left mag switch
is for starter engage, but shouldn't the right mag switch be a 2-3 on-on instead?
No un-used momentary position and half the price. Or am I missing something?
One of these months, I'm going to get my wiring finalized so I can start running
wires...Grrrrr
Mitch Faatz RV-6A Finish Kit Auburn, CA
________________________________________________________________________________
| From: | "Condrey, Bob (US SSA)" <bob.condrey(at)baesystems.com> |
Bob,
I notice that the various Z drawings show different protection schemes for the
SD-20 alternator. Some use an ANL30 and others show fusable link. I'd prefer
to use an ANL type fuse/holder over a fusable link but can't seem to locate them
as small as ANL30. I found some email in the archives that indicated that
they were available through either your website or B&C's but the smallest shown
on B&C's was ANL40. What's the current thinking?
Thanks.
Bob
________________________________________________________________________________
| From: | <chaztuna(at)adelphia.net> |
Bob,
Littelfuse makes a very nice slow blow fuse and completely insulated & covered
fuseholder which will meet your needs. Look at their "Series 498 MidiFuse" fuseholder
& fuse line. See below.
http://www.littelfuse.com/cgi-bin/r.cgi/prod_series.html?LFSESSION=j7vz9gQyVS&SeriesID=153
http://www.littelfuse.com/data/en/Data_Sheets/498.pdf
http://www.littelfuse.com/data/en/Time_Curve/498.tc.pdf
http://www.littelfuse.com/cgi-bin/r.cgi/prod_parts.html?LFSESSION=j7vz9gQyVS&PartID=1726
These fuseholders come with a fully insulated cover, unlike the exposed Amp ANL
series fuse holders. The Series 498 are also physically more compact.
Charlie Kuss
---- "Condrey wrote:
>
> Bob,
>
> I notice that the various Z drawings show different protection schemes for the
SD-20 alternator. Some use an ANL30 and others show fusable link. I'd prefer
to use an ANL type fuse/holder over a fusable link but can't seem to locate
them as small as ANL30. I found some email in the archives that indicated that
they were available through either your website or B&C's but the smallest shown
on B&C's was ANL40. What's the current thinking?
>
> Thanks.
> Bob
>
>
>
>
>
>
________________________________________________________________________________
| From: | "Mike Larkin" <mlas(at)cox.net> |
Mitch,
Not sure I understand the point you are trying to illustrate. But a
little note on starter mag switches. On most light aircraft, the right
mag is isolated during the start to allow the impulse coupling on the
left mag to fire without causing kick back from the right mag during the
start. Hope this helps.
Mike Larkin
-----Original Message-----
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Mitch
Faatz
Subject: AeroElectric-List: Mag switches
I'm looking at the latest Z-11 which shows two 2-5 switches to be used
for mag switches and starter. Is there a reason why the right mag
switch is a 2-5 (on)-off-on switch like the left mag? The momentary
position on the left mag switch is for starter engage, but shouldn't the
right mag switch be a 2-3 on-on instead? No un-used momentary position
and half the price. Or am I missing something?
One of these months, I'm going to get my wiring finalized so I can start
running wires...Grrrrr
Mitch Faatz RV-6A Finish Kit Auburn, CA
--
--
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
I did that so that the "normal", in flight position
for the two ignition switches was the same. Yes, there's
an unused momentary on position on one switch but it seemed
better to have both switches DOWN for OFF and both swtiches
MID for ON . . . it's a human factors thingy.
Bob . . .
>I'm looking at the latest Z-11 which shows two 2-5 switches to be used
>for mag switches and starter. Is there a reason why the right mag
>switch is a 2-5 (on)-off-on switch like the left mag? The momentary
>position on the left mag switch is for starter engage, but shouldn't the
>right mag switch be a 2-3 on-on instead? No un-used momentary position
>and half the price. Or am I missing something?
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
>
>
>Bob,
>
>I notice that the various Z drawings show different protection schemes for
>the SD-20 alternator. Some use an ANL30 and others show fusable
>link. I'd prefer to use an ANL type fuse/holder over a fusable link but
>can't seem to locate them as small as ANL30. I found some email in the
>archives that indicated that they were available through either your
>website or B&C's but the smallest shown on B&C's was ANL40.
The smaller b-lead fuses could also make use of the
MAXI series fuses sold in automotive parts houses.
They also have robust, inline holders for these fuses.
Bob . . .
________________________________________________________________________________
| From: | f1rocket(at)comcast.net |
| Subject: | Re: Mag switches |
Mitch,
I did it with the switches you noted just so the switch positions were the same
for on and off.
Randy
F1 Rocket
www.pflanzer-aviation.com
-------------- Original message --------------
>
> I'm looking at the latest Z-11 which shows two 2-5 switches to be used for mag
> switches and starter. Is there a reason why the right mag switch is a 2-5
> (on)-off-on switch like the left mag? The momentary position on the left mag
> switch is for starter engage, but shouldn't the right mag switch be a 2-3 on-on
> instead? No un-used momentary position and half the price. Or am I missing
> something?
>
> One of these months, I'm going to get my wiring finalized so I can start running
> wires...Grrrrr
>
> Mitch Faatz RV-6A Finish Kit Auburn, CA
>
>
>
>
>
>
Mitch,
I did it with the switches you noted just so the switch positions were the same
for on and off.
Randy
F1 Rocket
www.pflanzer-aviation.com
-------------- Original message --------------
-- AeroElectric-List message posted by: "Mitch Faatz"
I'm looking at the latest Z-11 which shows two 2-5 switches to be used for mag
switches and starter. Is there a reason why the right mag switch is a 2-5
(on)-off-on switch like the left mag? The momentary position on the left mag
switch is for starter engage, but shouldn't the right mag switch be a 2-3 on-on
instead? No un-used momentary position and half the price. Or am I missing
something?
One of these months, I'm going to get my wiring finalized so I can start running
wires...Grrrrr
Mitch Faatz RV-6A Finish Kit Auburn, CA
ist Email Forum -
________________________________________________________________________________
| From: | "John Schroeder" <jschroeder(at)perigee.net> |
Bob -
Z-14 shows a 40 amp ANL, so we installed that. You said it would be OK.
Any change of thought here?
Thanks,
John
>>
>>
>> Bob,
>>
>> I notice that the various Z drawings show different protection schemes
>> for the SD-20 alternator. Some use an ANL30 and others show fusable
>> link. I'd prefer to use an ANL type fuse/holder over a fusable link but
> The smaller b-lead fuses could also make use of the
> MAXI series fuses sold in automotive parts houses.
> They also have robust, inline holders for these fuses.
>
> Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
>
>
>Bob -
>
>Z-14 shows a 40 amp ANL, so we installed that. You said it would be OK.
>Any change of thought here?
>
>Thanks,
>
>John
The sizes of the ANL series limiters is not critical.
They are VERY robust fuses . . . (I think they'll carry
200% of rated indefinitely at room temperature). You need
some protection for the hard fault which these guys will
do. My figure Z-14 shows ANL-30 limiters downstream of
40A alternators. One is advised to adjust the size of the
current protection to best accommodate the size of
the alternator. 60A alternators would take something
larger than an ANL-30, a 40 would probably be fine
and a 60 is a sure bet.
Keep in mind that SIZES of anything called out in Z-figures
are subject to adjustment based on specifics of your
system and should not be taken as suggestions for every/all
cases. These are ARCHITECTURE drawings.
Here are links to data on Bussmann products cited in
this and other posts on this subject:
http://www.aeroelectric.com/temp/MAX_InLine.pdf
http://www.aeroelectric.com/temp/anl.pdf
http://www.aeroelectric.com/temp/maxifuse.pdf
Bob . . .
________________________________________________________________________________
| From: | "Condrey, Bob (US SSA)" <bob.condrey(at)baesystems.com> |
Bob,
Thanks for the additional info on the Maxi line of fuses. I just
thought I was missing something - Z-14 showed them and a search through the
archives found an email that indicated that both your web site and B&C carried
them. But, when neither website or Bussman had them...
Bob
>Bob -
>
>Z-14 shows a 40 amp ANL, so we installed that. You said it would
be OK.
>Any change of thought here?
>
>Thanks,
>
>John
The sizes of the ANL series limiters is not critical.
They are VERY robust fuses . . . (I think they'll carry
200% of rated indefinitely at room temperature). You need
some protection for the hard fault which these guys will
do. My figure Z-14 shows ANL-30 limiters downstream of
40A alternators. One is advised to adjust the size of the
current protection to best accommodate the size of
the alternator. 60A alternators would take something
larger than an ANL-30, a 40 would probably be fine
and a 60 is a sure bet.
Keep in mind that SIZES of anything called out in Z-figures
are subject to adjustment based on specifics of your
system and should not be taken as suggestions for every/all
cases. These are ARCHITECTURE drawings.
Here are links to data on Bussmann products cited in
this and other posts on this subject:
<http://www.aeroelectric.com/temp/MAX_InLine.pdf>
<http://www.aeroelectric.com/temp/anl.pdf>
<http://www.aeroelectric.com/temp/maxifuse.pdf>
Bob . . .
________________________________________________________________________________
| From: | "John Swartout" <jgswartout(at)earthlink.net> |
| Subject: | Making real world sense of the OVP thread |
Bob, Paul, Eric, et al:
I've been following the overvoltage protection/load dump dialogue as
best I can as a non-electrical-engineer. A couple of ideas and
questions come to mind.
First of all, it seems that most electrical devices have at least some
tolerance for momentary aberrations in the supply, if they are users, or
the load, if they are suppliers. I also deduce that part of the idea
behind the crowbar circuit is that when the alternator goes seriously
off the reservation (which, I think I understand, is a regulator
failure, not a failure of the alternator itself) we sacrifice a cheap
device (a fuse) to save the expensive ones (avionics, GPSs, etc.) while
isolating the alternator.
Well, I opted to go with a relatively cheap main alternator (a new
internally-regulated 55 amp NipponDenso-which incidentally turns out to
be not that cheap, because first I need to spend $30 for a bracket; and
then, to run it at a reasonable speed, 2000-5000 rpm, it will cost me
some $20 for a 5"x5" piece of aluminum plate and some $60 to $75 to have
it machined into a 5" pulley; and then a matching plug, if I can find
one, which will not slip off the quarter-inch flat spade terminals; so I
will have some $260 in this "cheap" alternator) and an auxiliary B&C
SD-8. Why? Because even with $700 worth of alternators, it's still
cheaper and lighter than a single certified alternator. And I have
redundancy. And if the main alternator does fail, only the $120
alternator itself has to be replaced.
So let's carry the crowbar philosophy one step further. If a crowbar
sacrifices a fuse to sever the offending alternator from the buss to
protect high-dollar electronics, BUT produces a load dump in the process
which could be potentially as destructive as the OV situation that
triggered it, and so far, this consequence has not been satisfactorily
controlled, let me propose that the second-cheapest device in my
electrical system, after the fuse, is my $120 alternator. If necessary,
I nominate IT as the second victim on the firing line. If I could reach
the wires attached to this alternator with an axe, I believe I could
remove that runaway alternator from the system more or less
instantaneously before the electrons knew what was happening, and to
hell with the alternator. Am I wrong?
Is there an electrical way to wield that axe?
Secondly, from what I've read about alternators, they are probably
better able to take momentary abuse than any other device in my
electrical system-so why not-if there is a way-direct the abuse thither.
Am I missing something?
Bob, your description of linear vs. switching regulators in AEC didn't
convince me that for my application, the linear is superior. Is it
inherently more failsafe? Why exactly are you not fond of internal
regulation? Is it a) because it is a switcher? Or b) because its
quality can't be evaluated? Or both?
Okay, final question. Since our airplane electronic devices are now,
essentially, computers, how about using computer-protection technology
to protect them? Uninterruptible power source (UPS), surge suppressor,
and/or power conditioner type devices and/or architecture. Would they
a) work? and b) meet our high ruggedness standards for airplanes? and c)
be affordable and light weight?
Thanks, men.
John
________________________________________________________________________________
| Subject: | Re: Making real world sense of the OVP thread |
| From: | "Matt Prather" <mprather(at)spro.net> |
Pulley woes solved here?
http://www.rjays.com/Rjays_electrical/alternators-01.htm
If that is cut off, try: http://tinyurl.com/55742
There are others that are commercially available for the Hot
Rod crowd.
Regards,
Matt-
>
>
> Bob, Paul, Eric, et al:
>
>
> I've been following the overvoltage protection/load dump dialogue as
> best I can as a non-electrical-engineer. A couple of ideas and
> questions come to mind.
>
>
> First of all, it seems that most electrical devices have at least some
> tolerance for momentary aberrations in the supply, if they are users, or
> the load, if they are suppliers. I also deduce that part of the idea
> behind the crowbar circuit is that when the alternator goes seriously
> off the reservation (which, I think I understand, is a regulator
> failure, not a failure of the alternator itself) we sacrifice a cheap
> device (a fuse) to save the expensive ones (avionics, GPSs, etc.) while
> isolating the alternator.
>
>
> Well, I opted to go with a relatively cheap main alternator (a new
> internally-regulated 55 amp NipponDenso-which incidentally turns out to
> be not that cheap, because first I need to spend $30 for a bracket; and
> then, to run it at a reasonable speed, 2000-5000 rpm, it will cost me
> some $20 for a 5"x5" piece of aluminum plate and some $60 to $75 to have
> it machined into a 5" pulley; and then a matching plug, if I can find
> one, which will not slip off the quarter-inch flat spade terminals; so I
> will have some $260 in this "cheap" alternator) and an auxiliary B&C
> SD-8. Why? Because even with $700 worth of alternators, it's still
> cheaper and lighter than a single certified alternator. And I have
> redundancy. And if the main alternator does fail, only the $120
> alternator itself has to be replaced.
>
>
> So let's carry the crowbar philosophy one step further. If a crowbar
> sacrifices a fuse to sever the offending alternator from the buss to
> protect high-dollar electronics, BUT produces a load dump in the process
> which could be potentially as destructive as the OV situation that
> triggered it, and so far, this consequence has not been satisfactorily
> controlled, let me propose that the second-cheapest device in my
> electrical system, after the fuse, is my $120 alternator. If necessary,
> I nominate IT as the second victim on the firing line. If I could reach
> the wires attached to this alternator with an axe, I believe I could
> remove that runaway alternator from the system more or less
> instantaneously before the electrons knew what was happening, and to
> hell with the alternator. Am I wrong?
>
>
> Is there an electrical way to wield that axe?
>
>
> Secondly, from what I've read about alternators, they are probably
> better able to take momentary abuse than any other device in my
> electrical system-so why not-if there is a way-direct the abuse thither.
>
>
> Am I missing something?
>
>
> Bob, your description of linear vs. switching regulators in AEC didn't
> convince me that for my application, the linear is superior. Is it
> inherently more failsafe? Why exactly are you not fond of internal
> regulation? Is it a) because it is a switcher? Or b) because its
> quality can't be evaluated? Or both?
>
>
> Okay, final question. Since our airplane electronic devices are now,
> essentially, computers, how about using computer-protection technology
> to protect them? Uninterruptible power source (UPS), surge suppressor,
> and/or power conditioner type devices and/or architecture. Would they
> a) work? and b) meet our high ruggedness standards for airplanes? and c)
> be affordable and light weight?
>
>
> Thanks, men.
>
>
> John
>
>
________________________________________________________________________________
| From: | "Larry Bowen" <Larry(at)BowenAero.com> |
| Subject: | Two impulse mags? |
I'm considering replacing my unreliable Rose elec ign with another slick
mag. Is there any crime in having two impulse mags so I don't have to rely
on the operator to keep the non-impulse mag off while cranking? Or is there
a better way?
Starter and both ignitions are each on toggle switches.
Thanks,
-
Larry Bowen, RV-8/O-360
Larry(at)BowenAero.com
http://BowenAero.com
________________________________________________________________________________
| From: | BobsV35B(at)aol.com |
| Subject: | Re: Two impulse mags? |
In a message dated 3/30/2005 10:06:43 P.M. Central Standard Time,
Larry(at)BowenAero.com writes:
I'm considering replacing my unreliable Rose elec ign with another slick
mag. Is there any crime in having two impulse mags so I don't have to rely
on the operator to keep the non-impulse mag off while cranking? Or is there
a better way?
Good Evening Larry,
The vast majority of Bonanzas and derivative aircraft are equipped with dual
impulse magnetos.
Work just fine.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Airpark LL22
Downers Grove, IL 60516
630 985-8502
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
Oh, yeah. Understand.
>
>
>
> Bob,
>
> Thanks for the additional info on the Maxi line of
> fuses. I just thought I was missing something - Z-14 showed them and a
> search through the archives found an email that indicated that both your
> web site and B&C carried them. But, when neither website or Bussman had
> them...
Oh, now I understand. Hmmmm . . . I've never carried the ANL
series devices and B&C only carries the fuses that support
their STC'd kits. The Bussmann data sheet lists an ANL40 although
they don't graph it.
It's not a common part in the wild. Did a Google search and
found only a few folks offering the ANL40 . . . guess it's
not a big catalog item. In any case, one can select from
other equally suitable fuse products.
Bob . . .
________________________________________________________________________________
| From: | "Larry Bowen" <Larry(at)BowenAero.com> |
| Subject: | Two impulse mags? |
I'm considering replacing my unreliable Rose elec ign with another slick
mag. Is there any crime in having two impulse mags so I don't have to rely
on the operator to keep the non-impulse mag off while cranking? Or is there
a better way?
Starter and both ignitions are each on toggle switches.
Thanks,
-
Larry Bowen, RV-8/O-360
Larry(at)BowenAero.com
http://BowenAero.com
________________________________________________________________________________
| From: | "Tinne maha" <tinnemaha(at)hotmail.com> |
| Subject: | Avionics & Audio Questions |
This list (especially Bob Knuckolls) has been EXTREMEMELY helpful with my
understanding, planning, re-designing & fabricating the electrical system in
my OBAM aircraft. Many thanks for enduring my seemingly silly questions. I
have much more to learn, but am comfortable proceeding with my project &
eager to get in the air. However, I am feeling overwhelmed by my lack of
understanding of avionics & audio systems. I have my simple VFR only panel
layed out & am sure it can be done the way I am envisioning, but have no
idea how to get there. I haven't found info in the connection specific to
this topic. Can someone can point me in the right direction? Is it in The
Connection & I'm just not seeing it or is there another source? Do the
manufacturer's instructions tell how?
Specifically, I am planning to install a Garmin GNC 250 XL panel mounted
GPS/Comm (not purchased yet) with a King, KT-76A transponder & a flightcom
403 intercom (in my posession, but no instructions). That's it for
avionics, but I also hope to install an Ipod mini to keep my passenger
entertained (me too when not talking to ATC)
Any help will again be greatly appreciated.
Thanks again (& in advance),
Grant Krueger
________________________________________________________________________________
| From: | Harley <harley(at)AgelessWings.com> |
| Subject: | Re: Two impulse mags? |
Morning, Larry...
Have you considered replacing it with an e-Mag? An electronic ignition
whose idea has been getting some positive comments here on this list (as
well as others).
It's a drop-in replacement for a magneto, and doesn't cost much more.
And it's electronic! You can use it with an existing magneto, or
replace both mags with them.
http://emagair.com/
Harley Dixon
Long EZ N28EZ
Canandaigua, NY
Larry Bowen wrote:
>
>I'm considering replacing my unreliable Rose elec ign with another slick
>mag. Is there any crime in having two impulse mags so I don't have to rely
>on the operator to keep the non-impulse mag off while cranking? Or is there
>a better way?
>
>Starter and both ignitions are each on toggle switches.
>
>Thanks,
>
>-
>Larry Bowen, RV-8/O-360
>Larry(at)BowenAero.com
>http://BowenAero.com
>
>
>
>
________________________________________________________________________________
| From: | "Gordon or Marge Comfort" <gcomfo(at)tc3net.com> |
| Subject: | Two impulse mags? |
-----Original Message-----
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Larry
Bowen
Subject: AeroElectric-List: Two impulse mags?
I'm considering replacing my unreliable Rose elec ign with another slick
mag. Is there any crime in having two impulse mags so I don't have to
rely on the operator to keep the non-impulse mag off while cranking? Or
is there a better way?
Starter and both ignitions are each on toggle switches.
Thanks,
-
Larry Bowen, RV-8/O-360
Larry: I have two impulse couplings on my 0-320. They are controlled
with toggle switches. System works just fine.
Gordon Comfort
N363GC
________________________________________________________________________________
| From: | "Alex Peterson" <alexpeterson(at)earthlink.net> |
| Subject: | Two impulse mags? |
> I'm considering replacing my unreliable Rose elec ign with
> another slick mag. Is there any crime in having two impulse
> mags so I don't have to rely on the operator to keep the
> non-impulse mag off while cranking? Or is there a better way?
>
> Starter and both ignitions are each on toggle switches.
>
> Thanks,
>
> -
> Larry Bowen, RV-8/O-360
Larry, you could put the non-impulse mag on a three position switch, down
(momentary) for starter, up for run.
Alex Peterson
RV6-A 604 hours
Maple Grove, MN
http://www.home.earthlink.net/~alexpeterson/
________________________________________________________________________________
| From: | Larry Bowen <Larry(at)BowenAero.com> |
| Subject: | Re: Two impulse mags? |
Yes, I have considered it. The thing is, until I get a replacement ignition on
the right side I am grounded. And the last I heard the delivery times
have from
E-mag are up to 60 days. I'm not sure I can last that long!! I've also
considered begging for someone at the front of the E-mag line to trade
delivery
slots with me, but haven't acted upon that idea yet either.......
Thx,
--
Larry Bowen
Larry(at)BowenAero.com
http://BowenAero.com
Quoting Harley :
>
> Morning, Larry...
>
> Have you considered replacing it with an e-Mag? An electronic ignition
> whose idea has been getting some positive comments here on this list (as
> well as others).
>
> It's a drop-in replacement for a magneto, and doesn't cost much more.
> And it's electronic! You can use it with an existing magneto, or
> replace both mags with them.
>
> http://emagair.com/
>
> Harley Dixon
>
> Long EZ N28EZ
> Canandaigua, NY
>
>
> Larry Bowen wrote:
>
>>
>> I'm considering replacing my unreliable Rose elec ign with another slick
>> mag. Is there any crime in having two impulse mags so I don't have to rely
>> on the operator to keep the non-impulse mag off while cranking? Or is there
>> a better way?
>>
>> Starter and both ignitions are each on toggle switches.
>>
>> Thanks,
>>
>> -
>> Larry Bowen, RV-8/O-360
>> Larry(at)BowenAero.com
>> http://BowenAero.com
>>
>>
>>
>>
>
>
________________________________________________________________________________
| From: | Harley <harley(at)AgelessWings.com> |
| Subject: | Re: Two impulse mags? |
Boy, if I had known your predicament about January, I would have sold
you mine and waited for a new one! As it is, I'll probably be
installing it in the next month or so...hopefully .
Harley
Larry Bowen wrote:
>
>Yes, I have considered it. The thing is, until I get a replacement ignition on
>the right side I am grounded. And the last I heard the delivery times
>have from
>E-mag are up to 60 days. I'm not sure I can last that long!! I've also
>considered begging for someone at the front of the E-mag line to trade
>delivery
>slots with me, but haven't acted upon that idea yet either.......
>
>Thx,
>
>
>
________________________________________________________________________________
| From: | "Eric M. Jones" <emjones(at)charter.net> |
| Subject: | Re: Making real world sense of the OVP thread |
John,
>First of all, it seems that most electrical devices have at least some
tolerance for momentary aberrations in the supply, if they are users, or the
load, if they are suppliers. I also >deduce that part of the idea behind
the crowbar circuit is that when the alternator goes seriously off the
reservation (which, I think I understand, is a regulator failure, not a
failure of >the alternator itself) we sacrifice a cheap device (a fuse) to
save the expensive ones (avionics, GPSs, etc.) while isolating the
alternator.
There are many ways to skin this cat. The crowbar does not seem to be the
most efficacious way to do this---the best way is just an electronic switch
to OFF.
>It will cost me some $20 for a 5"x5" piece of aluminum plate and some $60
to $75 to have it machined into a 5" pulley.....
John, you should try round stock for the pulley. Far less vibration.
(humor).
> If I could reach the wires attached to this alternator with an axe, I
believe I could remove that runaway alternator from the system more or less
instantaneously before the electrons >knew what was happening, and to hell
with the alternator. Am I wrong? Is there an electrical way to wield that
axe?
Sure, I am developing a "Aero Beeline Cutter". What this does is:
1) Stops the load dump with onboard suppressors;
2) Replaces the OVP and the B+ contactor;
3) (Maybe) reads the B+ current and send it to the panel;
4) (Probably) has high and low volt alarm outputs;
5) Other features.....
>Okay, final question. Since our airplane electronic devices are now,
essentially, computers, how about using computer-protection technology to
protect them? Uninterruptible >power source (UPS), surge suppressor, and/or
power conditioner type devices and/or architecture.
John, you've got the picture. Your contributions to the effort would be
valuable.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones(at)charter.net
"Here's the plan...just fly it until it smokes and burns up. Then buy a new
one and don't fly quite so far."
--Anon
________________________________________________________________________________
| From: | Charlie Kuss <chaztuna(at)adelphia.net> |
| Subject: | Re: Two impulse mags? |
Larry,
Several Lycoming models come standard this way. The IO-320-B1A is the
first one which comes to mind. Remember, you'll need a second magneto
spacer to add that impulse coupled mag. Look on EBay for a used one.
Charlie Kuss
>
>I'm considering replacing my unreliable Rose elec ign with another slick
>mag. Is there any crime in having two impulse mags so I don't have to rely
>on the operator to keep the non-impulse mag off while cranking? Or is there
>a better way?
>
>Starter and both ignitions are each on toggle switches.
>
>Thanks,
>
>-
>Larry Bowen, RV-8/O-360
>Larry(at)BowenAero.com
>http://BowenAero.com
>
>
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
| Subject: | Two impulse mags? |
>
>
>
>-----Original Message-----
>From: owner-aeroelectric-list-server(at)matronics.com
>[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Larry
>Bowen
>To: aeroelectric-list(at)matronics.com
>Subject: AeroElectric-List: Two impulse mags?
>
>
>I'm considering replacing my unreliable Rose elec ign with another slick
>mag. Is there any crime in having two impulse mags so I don't have to
>rely on the operator to keep the non-impulse mag off while cranking? Or
>is there a better way?
>
>Starter and both ignitions are each on toggle switches.
Gordon, Haven't heard from you in some time my friend.
If you use a pair of 2-5 toggle switches as illustrated in
figure Z-11 of http://aeroelectric.com/articles/Rev10/z10.pdf
then the starter cannot be energized unless the non impulse coupled
magneto is OFF thus preventing the situation you describe.
Have you considered e or p-mags?
Say hi to Marge.
Bob . . .
________________________________________________________________________________
| From: | sportav8r(at)aol.com |
| Subject: | Re: Two impulse mags? |
Larry: definitely go with the second impulse mag as it will add needless weight
and hopefully slow that plane down to speeds where the rest of us SERV members
fly. Heaven help us when you get around to pants and fairings.
-Stormy
-----Original Message-----
From: Robert L. Nuckolls, III <b.nuckolls(at)cox.net>
Subject: RE: AeroElectric-List: Two impulse mags?
>
>
>
>-----Original Message-----
>From: owner-aeroelectric-list-server(at)matronics.com
>[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Larry
>Bowen
>To: aeroelectric-list(at)matronics.com
>Subject: AeroElectric-List: Two impulse mags?
>
>
>I'm considering replacing my unreliable Rose elec ign with another slick
>mag. Is there any crime in having two impulse mags so I don't have to
>rely on the operator to keep the non-impulse mag off while cranking? Or
>is there a better way?
>
>Starter and both ignitions are each on toggle switches.
Gordon, Haven't heard from you in some time my friend.
If you use a pair of 2-5 toggle switches as illustrated in
figure Z-11 of http://aeroelectric.com/articles/Rev10/z10.pdf
then the starter cannot be energized unless the non impulse coupled
magneto is OFF thus preventing the situation you describe.
Have you considered e or p-mags?
Say hi to Marge.
Bob . . .
________________________________________________________________________________
| From: | "P. Van Caulart" <etivc(at)iaw.on.ca> |
| Subject: | Re: Spam Can Architecture |
Bob et al;
Firstly, thanks to all Aeroelectric digest contributors for advancing
our knowledge base. I'm continually humbled and indebted. Electron
wrangling is a mighty task.
Next, I like to ask about spam can electrical architecture, specifically
the Cessna stuff from the late 60's early 70's. My aircraft is a '68 177
150hp fixed gear and prop. It's a simple 4 place cruiser.
Now as it's age is creeping up to 40 years old, I have doubts about the
integrity of the electrical system. Putting obvious certification issues
aside and looking at just flight safety and reliability, what
technologies could be considered to advance the integrity of the
electrical system? Maintenance of items like batteries, switches and
breakers, contactors and wiring seemed to be addressed in the certified
world on a breakdown basis rather than predictive maintenance.
Thanks,
PeterVC
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> thread |
| Subject: | Re: Making real world sense of the OVP |
thread
thread
>
>
>Bob, Paul, Eric, et al:
>
>
>I've been following the overvoltage protection/load dump dialogue as
>best I can as a non-electrical-engineer. A couple of ideas and
>questions come to mind.
>
>
>First of all, it seems that most electrical devices have at least some
>tolerance for momentary aberrations in the supply, if they are users, or
>the load, if they are suppliers. I also deduce that part of the idea
>behind the crowbar circuit is that when the alternator goes seriously
>off the reservation (which, I think I understand, is a regulator
>failure, not a failure of the alternator itself) we sacrifice a cheap
>device (a fuse) to save the expensive ones (avionics, GPSs, etc.) while
>isolating the alternator.
Normally, a circuit breaker and not a fuse are used downstream
of a crowbar ov sensor module.
>Well, I opted to go with a relatively cheap main alternator (a new
>internally-regulated 55 amp NipponDenso-which incidentally turns out to
>be not that cheap, because first I need to spend $30 for a bracket; and
>then, to run it at a reasonable speed, 2000-5000 rpm, it will cost me
>some $20 for a 5"x5" piece of aluminum plate and some $60 to $75 to have
>it machined into a 5" pulley; and then a matching plug, if I can find
>one, which will not slip off the quarter-inch flat spade terminals; so I
>will have some $260 in this "cheap" alternator) and an auxiliary B&C
>SD-8. Why? Because even with $700 worth of alternators, it's still
>cheaper and lighter than a single certified alternator. And I have
>redundancy. And if the main alternator does fail, only the $120
>alternator itself has to be replaced.
>
>
>So let's carry the crowbar philosophy one step further. If a crowbar
>sacrifices a fuse to sever the offending alternator from the buss to
>protect high-dollar electronics, BUT produces a load dump in the process
>which could be potentially as destructive as the OV situation that
>triggered it,
Not so. The OVP system prevents an over-excited alternator from
dumping its energy onto the bus thus protecting all devices
that depend on power from the bus.
The only component at-risk when internally regulated alternators
are wired per Z-24 is the alternator itself. To date, ALL incidents
of damage to the alternator using Z-24 architecture have been
operator induced. I.e., the alternator was turned OFF while
carrying a significant load.
An internally regulated alternator with a b-lead contactor
is at risk for this form of damage irrespective of the form
of OV protection. In this case, the transient that damaged
the alternator was a function of manipulation of controls
. . . the OV protection system was not a participant.
Had the OVP system operated due to a real OV event, then
the regulator (root cause of the OV event) is already
toast so the event that occurs after the b-lead contactor
opens isn't event a load-dump transient . . . unless you
want to consider a climb past 100 volts that continues
until the field windings fry as a "transient".
> and so far, this consequence has not been satisfactorily
>controlled, let me propose that the second-cheapest device in my
>electrical system, after the fuse, is my $120 alternator. If necessary,
>I nominate IT as the second victim on the firing line. If I could reach
>the wires attached to this alternator with an axe, I believe I could
>remove that runaway alternator from the system more or less
>instantaneously before the electrons knew what was happening, and to
>hell with the alternator. Am I wrong?
The b-lead contactor is the electrical equivalent of the
'axe' . . . if and when circumstances call for that contactor
to be opened in flight, the breaker (or series connected OVP
system) opens power to the b-lead contactor and effectively
cuts the wire LONG before bus voltages can rise to hazardous levels
FOR STUFF THAT WILL MEET DO-160 RECOMMENDATIONS (20v for 1 second).
There's interest in fabricating a 'cleaner' electrical environment
so that products not designed to live in the DO-160 environment
can be pressed into service. This is a laudable goal but as
anyone who has followed this thread can deduce, it's NOT EASY.
>Is there an electrical way to wield that axe?
>
>
>Secondly, from what I've read about alternators, they are probably
>better able to take momentary abuse than any other device in my
>electrical system-so why not-if there is a way-direct the abuse thither.
Internally regulated alternators wired per Z-24 are about as
user and owner friendly as you can get irrespective of what
OVP sensor you use. Recently in the discussions I hypothesized
that the rudimentary 12v automotive contactor may not break
the arc the forms between opening contacts in a high voltage
dc switch. But this represents a hazard only to the contactor
and not to the rest of the system. So in the worst case scenario
you have a toasted alternator and toasted b-lead contactor.
The circuit published in Z-24 WILL do the intended task of
protecting your system and as long as you can refrain from
"let's play flip the switches with the engine running" there's
no risk to your alternator either. Further, since we DON'T know
root cause of the failures reported by Vans, we're not really
sure that there is ANY risk to a factory stock, internally
regulated alternator. It's all hypothetical at this point
made worst by Vans denunciation of OV protection systems
in general and hysterical reactions by some in the OBAM
aircraft community when a company who SHOULD know better
makes recommendations based on zero understanding of the
topic under discussion.
>Am I missing something?
>
>
>Bob, your description of linear vs. switching regulators in AEC didn't
>convince me that for my application, the linear is superior. Is it
>inherently more failsafe? Why exactly are you not fond of internal
>regulation? Is it a) because it is a switcher? Or b) because its
>quality can't be evaluated? Or both?
The linear IS superior in one regard only . . . noise. When
the section on regulators was written, glass and plastic
airplanes were king. When we were selecting a design philosophy
for the L-series regulators, we had ZERO experience with
delivering a product to the OBAM aircraft community. Okay,
we KNEW what it took to live in the certified metal airplane
(and switchers had performed well in those aircraft from day-
one) but the SAFE approach was to do the best we knew how to
do with the market as it existed at that time.
Now, the L-series regulators should have been re-evaluated
a long time ago with the idea of reducing manufacturing costs,
reducing parts count and incorporation of what has now become something
on the order of 15 years experience. It's not a 'bad' regulator
but it's a long way from the best we know how to do TODAY based
on what we've learned since the first ones were sold. LR-2
regulators went around the world on Voyager.
>Okay, final question. Since our airplane electronic devices are now,
>essentially, computers, how about using computer-protection technology
>to protect them? Uninterruptible power source (UPS), surge suppressor,
>and/or power conditioner type devices and/or architecture. Would they
>a) work? and b) meet our high ruggedness standards for airplanes? and c)
>be affordable and light weight?
ABSOLUTELY! Except that these things should have been built into
the accessory from day one. This has been the most irritating
aspect of watching all these new gee-whizzies come onto the market
place wherein designers were either ignorant of or choose to ignore
what we've learned over the past 60 years. "What? DO-160? That's
for them OLD radios and stuff. WE are going to concentrate on putting
lots of neat features in our gee-whizzy and let the customer figure
out how to make his airplane coddle our product."
We have a whole line of products that cannot recover gracefully
from a brown-out induced by starter's locked-rotor inrush currents
lasting perhaps 2-3 milliseconds. I understand the Unison Lasar
system is one such product and it's certified. Well . . . if
the FAA will holy-water a certified system with this deficiency
then what's to hold ME to any greater standards?
I expressed some concerns about "capability slip" in a post last
week. As soon as we accept a down-designing of accessories
in power requirements for the sake of exploiting the really neat
software and graphics of the gee-whizzy, what characteristic
are we going to sacrifice next? The OBAM community has an
opportunity to show the certified side how to do it right, do
it better and do it cheaper. This isn't going to happen if
we brush aside the fundamentals that have served us well for
a very long time.
I'm afraid lots of simple-ideas have been stirred into a single pot
of discussion to the extent that we've forgotten how each of these
concepts play together as a system. The only thing 'bad' about a
crowbar ov protection system is that it places a current transient
on the bus perhaps a handful of times in the lifetime of the airplane . . .
Some are of the opinion that they'd like to offer a product that
doesn't do this . . . which is great. But I think I've demonstrated
through the repeatable experiment that this characteristic should not
be real high on anyone's list of concerns.
In ALL of the discussions that have transpired over the past several
months, I perceive no reason for the OBAM community to
stand poised over their projects with wire cutters in had ready
to rip out any offending components. The real risk of carrying on
these discussions in open forum is that some folks will over-react
or at least get worried about the outcome. We've had some feedback
from readers who asked that we "take the discussion off the list
and come back with recommendations when a consensus is reached."
These are the folk who probably worry the most and listening
in on the conversation only makes their stress levels rise. I'm
sorry for their discomfort but good education has never been
inexpensive or easy. I think there will be a consensus reached
but those who have an interest in understanding about how this
stuff works won't need the consensus paper . . . they will have
reached their own conclusions based on personal understanding
instead of waiting for a committee to publish recommendations.
In the mean time, it's your decision as to how you'll protect
the less-than-accommodating devices in your airplane should
you choose to install gee-whizzies that wander off into the
weeds when the power goes off for a few milliseconds or
won't handle 20 volts for one second.
Believe me folks, it's MUCH easier to design the gee-whizzy
to live in the environment we've learned to live with for
60 years. It's difficult to re-design the environment so as to
accommodate designers wanting to break into an OBAM
aircraft market because they know that some of us will
tolerate features that would prevent them from making it
to first base in the certified side.
Bob . . .
________________________________________________________________________________
| From: | "Jim Stone" <jrstone(at)insightbb.com> |
| Subject: | Re: Two impulse mags? |
Hi Larry,
I have the Rose system an curious what type problems you have experienced.
Jim Stone
----- Original Message -----
From: "Larry Bowen" <Larry(at)BowenAero.com>
Subject: AeroElectric-List: Two impulse mags?
>
>
> I'm considering replacing my unreliable Rose elec ign with another slick
> mag. Is there any crime in having two impulse mags so I don't have to
> rely
> on the operator to keep the non-impulse mag off while cranking? Or is
> there
> a better way?
>
> Starter and both ignitions are each on toggle switches.
>
> Thanks,
>
> -
> Larry Bowen, RV-8/O-360
> Larry(at)BowenAero.com
> http://BowenAero.com
>
>
>
________________________________________________________________________________
| From: | emrath(at)comcast.net |
Bob,
What is the hard fault that you reference and how does one protect against it?
Marty
From: "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net>
Subject: Re: AeroElectric-List: ANL-30?
>
>
>Bob -
>
>Z-14 shows a 40 amp ANL, so we installed that. You said it would be OK.
>Any change of thought here?
>
>Thanks,
>
>John
The sizes of the ANL series limiters is not critical.
They are VERY robust fuses . . . (I think they'll carry
200% of rated indefinitely at room temperature). You need
some protection for the hard fault which these guys will
do. My figure Z-14 shows ANL-30 limiters downstream of
40A alternators. One is advised to adjust the size of the
current protection to best accommodate the size of
the alternator. 60A alternators would take something
larger than an ANL-30, a 40 would probably be fine
and a 60 is a sure bet.
<<>>>
Bob . . .
Bob,
What is the hard fault that you reference and how does one protect against it?
Marty
From: "Robert L. Nuckolls, III" b.nuckolls(at)cox.net
Subject: Re: AeroElectric-List: ANL-30?
-- AeroElectric-List message posted by: "Robert L. Nuckolls, III"
b.nuckolls(at)cox.net
-- AeroElectric-List message posted by: "John Schroeder"
jschroeder(at)perigee.net
Bob -
Z-14 shows a 40 amp ANL, so we installed that. You said it would be OK.
Any change of thought here?
Thanks,
John
The sizes of the ANL series limiters is not critical.
They are VERY robust fuses . . . (I think they'll carry
200% of rated indefinitely at room temperature). You need
some protection for the hard fault which these guys will
do. My figure Z-14 shows ANL-30 limiters downstream of
40A alternators. One is advised to adjust the size of the
current protection to best accommodate the size of
the alternator. 60A alternators would take something
larger than an ANL-30, a 40 would probably be fine
and a 60 is a sure bet.
&l
t;snip
Bob . . .
________________________________________________________________________________
| From: | Larry Bowen <Larry(at)BowenAero.com> |
| Subject: | Re: Two impulse mags? |
See these two articles:
http://bowenaero.com/mt3/archives/2004/10/more_ignition_w.html
http://bowenaero.com/mt3/archives/2005/03/electronic_igni.html
Any ideas appreciated...
--
Larry Bowen
Larry(at)BowenAero.com
http://BowenAero.com
Quoting Jim Stone :
>
> Hi Larry,
> I have the Rose system an curious what type problems you have experienced.
> Jim Stone
> ----- Original Message -----
> From: "Larry Bowen" <Larry(at)BowenAero.com>
> To:
> Subject: AeroElectric-List: Two impulse mags?
>
>
>>
>>
>> I'm considering replacing my unreliable Rose elec ign with another slick
>> mag. Is there any crime in having two impulse mags so I don't have to
>> rely
>> on the operator to keep the non-impulse mag off while cranking? Or is
>> there
>> a better way?
>>
>> Starter and both ignitions are each on toggle switches.
>>
>> Thanks,
>>
>> -
>> Larry Bowen, RV-8/O-360
>> Larry(at)BowenAero.com
>> http://BowenAero.com
>>
>>
>>
>
>
________________________________________________________________________________
| From: | "John Swartout" <jgswartout(at)earthlink.net> |
| Subject: | Making real world sense of the OVP thread |
Thank you, Bob, for bringing this all down to a level I can comprehend
and use.
Not knowing if my electronics are DO-160 RECOMMENDATION-compliant, would
you advise shutting off the electronics, or not turning them on, until
after starting the engine?
I think Paul mentioned a load dump from switching off the landing
lights. Should I also shut off electronics before shutting off landing
lights? Would a rheostat be a better device than a toggle switch for
turning landing lights on and off?
Your observation that the discussion of malfunction modes, however rare,
may get exaggerated attention from the more worry-prone among us is a
point well taken. I suspect I am one of those: "constructive worry" is
at the core of my professional life, and it can be difficult to leave
these essential traits at work. But in my defense, I am building a new
airplane, and I want it to be the best it can be--or at least, at the
intersection of technology and expense that I find most harmonious.
Incidentally, I should mention that I will take your advice and install
two P-mags instead of one P-mag and one E-mag. $250 for another level of
single-point redundancy. But for starting and idling, the engine IS
still dependent on the electrical system. P-mag's self-power output is
linearly proportional to rpm and doesn't become completely independent
of bus power until about 1600-1800 rpm.
-----Original Message-----
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of
Robert L. Nuckolls, III thread
Subject: Re: AeroElectric-List: Making real world sense of the OVP
thread
thread
>
>
>Bob, Paul, Eric, et al:
>
>
>I've been following the overvoltage protection/load dump dialogue as
>best I can as a non-electrical-engineer. A couple of ideas and
>questions come to mind.
>
>
>First of all, it seems that most electrical devices have at least some
>tolerance for momentary aberrations in the supply, if they are users,
or
>the load, if they are suppliers. I also deduce that part of the idea
>behind the crowbar circuit is that when the alternator goes seriously
>off the reservation (which, I think I understand, is a regulator
>failure, not a failure of the alternator itself) we sacrifice a cheap
>device (a fuse) to save the expensive ones (avionics, GPSs, etc.) while
>isolating the alternator.
Normally, a circuit breaker and not a fuse are used downstream
of a crowbar ov sensor module.
>Well, I opted to go with a relatively cheap main alternator (a new
>internally-regulated 55 amp NipponDenso-which incidentally turns out to
>be not that cheap, because first I need to spend $30 for a bracket; and
>then, to run it at a reasonable speed, 2000-5000 rpm, it will cost me
>some $20 for a 5"x5" piece of aluminum plate and some $60 to $75 to
have
>it machined into a 5" pulley; and then a matching plug, if I can find
>one, which will not slip off the quarter-inch flat spade terminals; so
I
>will have some $260 in this "cheap" alternator) and an auxiliary B&C
>SD-8. Why? Because even with $700 worth of alternators, it's still
>cheaper and lighter than a single certified alternator. And I have
>redundancy. And if the main alternator does fail, only the $120
>alternator itself has to be replaced.
>
>
>So let's carry the crowbar philosophy one step further. If a crowbar
>sacrifices a fuse to sever the offending alternator from the buss to
>protect high-dollar electronics, BUT produces a load dump in the
process
>which could be potentially as destructive as the OV situation that
>triggered it,
Not so. The OVP system prevents an over-excited alternator from
dumping its energy onto the bus thus protecting all devices
that depend on power from the bus.
The only component at-risk when internally regulated alternators
are wired per Z-24 is the alternator itself. To date, ALL incidents
of damage to the alternator using Z-24 architecture have been
operator induced. I.e., the alternator was turned OFF while
carrying a significant load.
An internally regulated alternator with a b-lead contactor
is at risk for this form of damage irrespective of the form
of OV protection. In this case, the transient that damaged
the alternator was a function of manipulation of controls
. . . the OV protection system was not a participant.
Had the OVP system operated due to a real OV event, then
the regulator (root cause of the OV event) is already
toast so the event that occurs after the b-lead contactor
opens isn't event a load-dump transient . . . unless you
want to consider a climb past 100 volts that continues
until the field windings fry as a "transient".
> and so far, this consequence has not been satisfactorily
>controlled, let me propose that the second-cheapest device in my
>electrical system, after the fuse, is my $120 alternator. If
necessary,
>I nominate IT as the second victim on the firing line. If I could
reach
>the wires attached to this alternator with an axe, I believe I could
>remove that runaway alternator from the system more or less
>instantaneously before the electrons knew what was happening, and to
>hell with the alternator. Am I wrong?
The b-lead contactor is the electrical equivalent of the
'axe' . . . if and when circumstances call for that contactor
to be opened in flight, the breaker (or series connected OVP
system) opens power to the b-lead contactor and effectively
cuts the wire LONG before bus voltages can rise to hazardous levels
FOR STUFF THAT WILL MEET DO-160 RECOMMENDATIONS (20v for 1 second).
There's interest in fabricating a 'cleaner' electrical environment
so that products not designed to live in the DO-160 environment
can be pressed into service. This is a laudable goal but as
anyone who has followed this thread can deduce, it's NOT EASY.
>Is there an electrical way to wield that axe?
>
>
>Secondly, from what I've read about alternators, they are probably
>better able to take momentary abuse than any other device in my
>electrical system-so why not-if there is a way-direct the abuse
thither.
Internally regulated alternators wired per Z-24 are about as
user and owner friendly as you can get irrespective of what
OVP sensor you use. Recently in the discussions I hypothesized
that the rudimentary 12v automotive contactor may not break
the arc the forms between opening contacts in a high voltage
dc switch. But this represents a hazard only to the contactor
and not to the rest of the system. So in the worst case scenario
you have a toasted alternator and toasted b-lead contactor.
The circuit published in Z-24 WILL do the intended task of
protecting your system and as long as you can refrain from
"let's play flip the switches with the engine running" there's
no risk to your alternator either. Further, since we DON'T know
root cause of the failures reported by Vans, we're not really
sure that there is ANY risk to a factory stock, internally
regulated alternator. It's all hypothetical at this point
made worst by Vans denunciation of OV protection systems
in general and hysterical reactions by some in the OBAM
aircraft community when a company who SHOULD know better
makes recommendations based on zero understanding of the
topic under discussion.
>Am I missing something?
>
>
>Bob, your description of linear vs. switching regulators in AEC didn't
>convince me that for my application, the linear is superior. Is it
>inherently more failsafe? Why exactly are you not fond of internal
>regulation? Is it a) because it is a switcher? Or b) because its
>quality can't be evaluated? Or both?
The linear IS superior in one regard only . . . noise. When
the section on regulators was written, glass and plastic
airplanes were king. When we were selecting a design philosophy
for the L-series regulators, we had ZERO experience with
delivering a product to the OBAM aircraft community. Okay,
we KNEW what it took to live in the certified metal airplane
(and switchers had performed well in those aircraft from day-
one) but the SAFE approach was to do the best we knew how to
do with the market as it existed at that time.
Now, the L-series regulators should have been re-evaluated
a long time ago with the idea of reducing manufacturing costs,
reducing parts count and incorporation of what has now become
something
on the order of 15 years experience. It's not a 'bad' regulator
but it's a long way from the best we know how to do TODAY based
on what we've learned since the first ones were sold. LR-2
regulators went around the world on Voyager.
>Okay, final question. Since our airplane electronic devices are now,
>essentially, computers, how about using computer-protection technology
>to protect them? Uninterruptible power source (UPS), surge suppressor,
>and/or power conditioner type devices and/or architecture. Would they
>a) work? and b) meet our high ruggedness standards for airplanes? and
c)
>be affordable and light weight?
ABSOLUTELY! Except that these things should have been built into
the accessory from day one. This has been the most irritating
aspect of watching all these new gee-whizzies come onto the market
place wherein designers were either ignorant of or choose to ignore
what we've learned over the past 60 years. "What? DO-160? That's
for them OLD radios and stuff. WE are going to concentrate on
putting
lots of neat features in our gee-whizzy and let the customer figure
out how to make his airplane coddle our product."
We have a whole line of products that cannot recover gracefully
from a brown-out induced by starter's locked-rotor inrush currents
lasting perhaps 2-3 milliseconds. I understand the Unison Lasar
system is one such product and it's certified. Well . . . if
the FAA will holy-water a certified system with this deficiency
then what's to hold ME to any greater standards?
I expressed some concerns about "capability slip" in a post last
week. As soon as we accept a down-designing of accessories
in power requirements for the sake of exploiting the really neat
software and graphics of the gee-whizzy, what characteristic
are we going to sacrifice next? The OBAM community has an
opportunity to show the certified side how to do it right, do
it better and do it cheaper. This isn't going to happen if
we brush aside the fundamentals that have served us well for
a very long time.
I'm afraid lots of simple-ideas have been stirred into a single pot
of discussion to the extent that we've forgotten how each of these
concepts play together as a system. The only thing 'bad' about a
crowbar ov protection system is that it places a current transient
on the bus perhaps a handful of times in the lifetime of the
airplane . . .
Some are of the opinion that they'd like to offer a product that
doesn't do this . . . which is great. But I think I've demonstrated
through the repeatable experiment that this characteristic should
not
be real high on anyone's list of concerns.
In ALL of the discussions that have transpired over the past several
months, I perceive no reason for the OBAM community to
stand poised over their projects with wire cutters in had ready
to rip out any offending components. The real risk of carrying on
these discussions in open forum is that some folks will over-react
or at least get worried about the outcome. We've had some feedback
from readers who asked that we "take the discussion off the list
and come back with recommendations when a consensus is reached."
These are the folk who probably worry the most and listening
in on the conversation only makes their stress levels rise. I'm
sorry for their discomfort but good education has never been
inexpensive or easy. I think there will be a consensus reached
but those who have an interest in understanding about how this
stuff works won't need the consensus paper . . . they will have
reached their own conclusions based on personal understanding
instead of waiting for a committee to publish recommendations.
In the mean time, it's your decision as to how you'll protect
the less-than-accommodating devices in your airplane should
you choose to install gee-whizzies that wander off into the
weeds when the power goes off for a few milliseconds or
won't handle 20 volts for one second.
Believe me folks, it's MUCH easier to design the gee-whizzy
to live in the environment we've learned to live with for
60 years. It's difficult to re-design the environment so as to
accommodate designers wanting to break into an OBAM
aircraft market because they know that some of us will
tolerate features that would prevent them from making it
to first base in the certified side.
Bob . . .
________________________________________________________________________________
| From: | <gmcjetpilot(at)yahoo.com> |
| Subject: | Re: Making real world sense of the OVP thread (pulley |
woes)
Matt:
Your pulley recommendation has two problems, if you are referring to the 5 OD pulley
at the bottom of your link:
One) 5-inch OD pulleys will not fit under the cowl without a huge blister.
Two) the shaft is for a domestic (Ford as stated) alternator, which has a 17mm
shaft.
ND alternators use a 15mm shaft. There are racing pulleys for the 15mm shaft alternators.
The max dia. (OD) I would recommend it 3-3.23 max.
I recommend the http://www.niagaraairparts.com/ alternator kit (scroll down half way). I bought it, $225 and it comes with everything, 40amp internal regulated ND alternator, brackets, hardware, and electrical connector. I have not flown with it, but it is very good to high quality. The above link shows installation instructions and an optional external OV protection system from Zeftronics. However if you feel you must have external OV protection, I recommend making up your own system using: http://www.periheliondesign.com/LOVM.htm and an OV contactor (relay- same as a continuous duty master relay). Those components will cost about $80. The nice think about this is you are not shorting anything to ground like the crow bar does; it simply opens the "B" lead relay. So any worry of a runaway alternator melting your avionics is negated, since it is disconnected completely from the buss.
I personally will be throwing caution to the wind and only go with the internal
regulation and no OV protection. Crazy I know, but simple, light and from a statistical
stand point very reliable. Failure of the belt is more likely than
an internal regulator fault causing an OV condition. I have proof, and my 1020
page thesis proof, with differential equations, Laplace Transform and fourier
series is too long to print here. (I know this may be blasphemy and the Senate
and Supreme Court will be petitioned to make this illegal.)
Just my opinion so ignore it if you disagree. ;-)
Cheers George
>
>Subject: Re: Making real world sense of the OVP thread
>From: "Matt Prather" <mprather(at)spro.net>
>
>Pulley woes solved here?
>
>http://www.rjays.com/Rjays_electrical/alternators-01.htm
>
>If that is cut off, try: http://tinyurl.com/55742
>
>There are others that are commercially available for the Hot
>Rod crowd.
>
>Regards, Matt-
---------------------------------
---------------------------------
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> |
>
>Bob,
>What is the hard fault that you reference
A conductor taken to ground through failed insulation or
shorted diodes in the alternator . .
> and how does one protect against it?
. . . fuses or breakers. Each fuse or breaker depicted
on a z-figure is placed there to offset the effects of
faults for which the risks are not at or near zero. This
type of protection has always been the domain of some
form of electrically weak link in the conduction chain
located as close as practical to the energy source that
would provide current to burn the wire.
Bob . . .
________________________________________________________________________________
| From: | "Robert L. Nuckolls, III" <b.nuckolls(at)cox.net> thread |
| Subject: | Making real world sense of the OVP |
thread
thread
>
>
>Thank you, Bob, for bringing this all down to a level I can comprehend
>and use.
>
>Not knowing if my electronics are DO-160 RECOMMENDATION-compliant, would
>you advise shutting off the electronics, or not turning them on, until
>after starting the engine?
What electronics? Are any of these items KNOWN to be ignorant
of or non-compliant with DO-160? Engine starting isn't the problem
with respect to damage of an appliance. Cranking the engine places
perturbs the bus voltage by some expected amount. If the appliance
cannot gracefully recover from the perturbation in a way that
restores usefulness quickly, then you as a consumer have to decide
whether you replace it with one that can . . . or modify the working
environment for that appliance such that it's isolated from an
effect it cannot tollerate.
>I think Paul mentioned a load dump from switching off the landing
>lights. Should I also shut off electronics before shutting off landing
>lights? Would a rheostat be a better device than a toggle switch for
>turning landing lights on and off?
Here we have an excellent example of mis-use or misunderstanding
of words. As long as there is a battery on line, there are NO
perturbations of bus voltage due to operation of any accessory
that should be of concern to the builder. A "load dump" in the
contemporary sense is a perturbation of rare and exceedingly
large magnitude that occurs when large load changes are made
on a system that does not have the stabilizing benefits of a battery.
I've often suggested that this event should be called a "battery dump"
event. In the certified airplane world, a "load dump" is just
what Paul described . . . a large reduction in system load. This
happens any time we shut of a 150A Freon compressor, or 200A of
electric tail de-ice. Yes, this produces a perturbation in bus
voltage that we EXPECT and have LEARNED TO TOLERATE by observing
the system behavior based on decades of performance.
>Your observation that the discussion of malfunction modes, however rare,
>may get exaggerated attention from the more worry-prone among us is a
>point well taken. I suspect I am one of those: "constructive worry" is
>at the core of my professional life, and it can be difficult to leave
>these essential traits at work. But in my defense, I am building a new
>airplane, and I want it to be the best it can be--or at least, at the
>intersection of technology and expense that I find most harmonious.
99% of the worries out there right now are unnecessary because
they are founded on misconception and concerns not based on
the physics and practical realities. This is why I've prefaced
all current discussions with experiments that describe what parts
are used and what behaviors they show when operated in a specific
manner. This is hard data that drives good interpretation and
invites anyone to repeat the experiment to either confirm the
results or illuminate errors. This is not a matter persuasiveness
but accuracy.
>Incidentally, I should mention that I will take your advice and install
>two P-mags instead of one P-mag and one E-mag. $250 for another level of
>single-point redundancy. But for starting and idling, the engine IS
>still dependent on the electrical system. P-mag's self-power output is
>linearly proportional to rpm and doesn't become completely independent
>of bus power until about 1600-1800 rpm.
That isn't a big down side. How often do you drop below 1800 rpm
before you begin descent to landing? Even if the power lead to an
p-mag was compromised such that one ignition drops off line in a
low power descent, you would have to have both power supplies
open before it becomes an issue for comfortable completion of
flight and the failure will be caught at the next pre-flight.
Better yet, write a procedure into your shutdown check list to
drop battery power off on one e/p-mag at a time to see that they
run at ramp idle.
With respect to your opening concerns, the vast majority of accessories
you have to choose from are not adversely affected by perturbations
of voltage on the bus for all normal operations. The only perturbations
of significant concern would be failed regulators (persistent and
extreme over voltage) or "load dump" transients brought on by
large reduction of system loads without benefit of a battery. The
first is easily mitigated by an OV protection system teamed with the
bus stabilizing effects of a well-maintained battery. The latter
is not a big concern because the potential for such an event
arises only when a battery contactor has gone open.
That prompts an interesting thought . . . suppose we put a fat diode
across the battery contactor so that the cathode is tied to the battery
side, anode to the bus side. This diode would not interfere with normal
operations of the battery contactor . . . but should the contactor
open because of solenoid failure -or- wiring failure, the bus would
still benefit from the stabilizing effects of the battery for clamping
of positive going transients under the "load dump" scenario. I'll
have to noodle over that one for a bit to see if there's any downside.
A diode/battery combination makes a hell-of-a-transorb capable of holding
the bus at or below 18 volts for quite some time. Certainly for the
duration
of a load dump perturbation.
Bob . . .
________________________________________________________________________________
| From: | "John Swartout" <jgswartout(at)earthlink.net> |
| Subject: | Re: Making real world sense of the OVP thread (pulley |
woes)
George, what cowling are you talking about? I believe there is plenty
of room for a 5" pulley without any blister on my Zenith CH-801. Do you
have a tightly cowled fuel-injected engine?
My 6 lb. alternator came with an output graph that goes up to 6000 rpm.
Using the stock pulley would turn it at 9450 rpm on take-off and 8700
rpm in cruise. I only need about 30 amps at the most, and this
alternator only has to turn 2000 rpm to give that. A 5" pulley will
give me 30 amps at idle.
I considered the Niagara Airparts alternator, and had I known the one I
bought has an oddball mandrel and the pulley would cost as much as the
alternator, I would have gone with the Niagara. But now I have what I
have, I've already ordered the aluminum for a new pulley, and the
shipping cost to return the alternator and the aluminum would equal the
savings if I changed to the Niagara. In retrospect, when I consider the
time I have spent on this little matter, the L40 B&C would have been
cheaper at $660 w/ regulator....
Well, they let us build airplanes "for education and recreation." I'm
certainly getting an education. In fact, if I value my time at a paltry
$10 an hour, the new 180 hp Maule would have been cheaper.
"Experience keeps a dear school, but fools will learn in no other."
--Benjamin Franklin
John 8*)
-----Original Message-----
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of
gmcjetpilot(at)yahoo.com
Subject: AeroElectric-List: Re: Making real world sense of the OVP
thread (pulley woes)
Matt:
Your pulley recommendation has two problems, if you are referring to the
5 OD pulley at the bottom of your link:
One) 5-inch OD pulleys will not fit under the cowl without a huge
blister.
Two) the shaft is for a domestic (Ford as stated) alternator, which has
a 17mm shaft.
ND alternators use a 15mm shaft. There are racing pulleys for the 15mm
shaft alternators. The max dia. (OD) I would recommend it 3-3.23 max.
I recommend the http://www.niagaraairparts.com/ alternator kit (scroll
down half way). I bought it, $225 and it comes with everything, 40amp
internal regulated ND alternator, brackets, hardware, and electrical
connector. I have not flown with it, but it is very good to high
quality. The above link shows installation instructions and an optional
external OV protection system from Zeftronics. However if you feel you
must have external OV protection, I recommend making up your own system
using: http://www.periheliondesign.com/LOVM.htm and an OV contactor
(relay- same as a continuous duty master relay). Those components will
cost about $80. The nice think about this is you are not shorting
anything to ground like the crow bar does; it simply opens the "B" lead
relay. So any worry of a runaway alternator melting your avionics is
negated, since it is disconnected completely from the buss.
I personally will be throwing caution to the wind and only go with the
internal regulation and no OV protection. Crazy I know, but simple,
light and from a statistical stand point very reliable. Failure of the
belt is more likely than an internal regulator fault causing an OV
condition. I have proof, and my 1020 page thesis proof, with
differential equations, Laplace Transform and fourier series is too long
to print here. (I know this may be blasphemy and the Senate and Supreme
Court will be petitioned to make this illegal.)
Just my opinion so ignore it if you disagree. ;-)
Cheers George
>
>Subject: Re: Making real world sense of the OVP thread
>From: "Matt Prather" <mprather(at)spro.net>
>
>Pulley woes solved here?
>
>http://www.rjays.com/Rjays_electrical/alternators-01.htm
>
>If that is cut off, try: http://tinyurl.com/55742
>
>There are others that are commercially available for the Hot
>Rod crowd.
>
>Regards, Matt-
---------------------------------
---------------------------------
________________________________________________________________________________
| Subject: | Re: Making real world sense of the OVP thread (pulley |
woes)
| From: | "Matt Prather" <mprather(at)spro.net> |
Your suggestion looks good, however, John asked for a 5" pulley in
his initial request... Also, as I said, there are other commercially
available
underdrive alternator pulleys (the industry term) for a variety of
alternators,
including ND's.
Regards,
Matt-
VE N34RD, C150 N714BK
>
>
> Matt:
>
> Your pulley recommendation has two problems, if you are referring to the
> 5 OD pulley at the bottom of your link:
>
> One) 5-inch OD pulleys will not fit under the cowl without a huge
> blister.
>
> Two) the shaft is for a domestic (Ford as stated) alternator, which has
> a 17mm shaft.
>
>
> ND alternators use a 15mm shaft. There are racing pulleys for the 15mm
> shaft alternators. The max dia. (OD) I would recommend it 3-3.23 max.
>
>
> I recommend the http://www.niagaraairparts.com/ alternator kit (scroll
> down half way). I bought it, $225 and it comes with everything, 40amp
> internal regulated ND alternator, brackets, hardware, and electrical
> connector. I have not flown with it, but it is very good to high
> quality. The above link shows installation instructions and an optional
> external OV protection system from Zeftronics. However if you feel you
> must have external OV protection, I recommend making up your own system
> using: http://www.periheliondesign.com/LOVM.htm and an OV contactor
> (relay- same as a continuous duty master relay). Those components will
> cost about $80. The nice think about this is you are not shorting
> anything to ground like the crow bar does; it simply opens the "B" lead
> relay. So any worry of a runaway alternator melting your avionics is
> negated, since it is disconnected completely from the buss.
>
>
> I personally will be throwing caution to the wind and only go with the
> internal regulation and no OV protection. Crazy I know, but simple,
> light and from a statistical stand point very reliable. Failure of the
> belt is more likely than an internal regulator fault causing an OV
> condition. I have proof, and my 1020 page thesis proof, with
> differential equations, Laplace Transform and fourier series is too long
> to print here. (I know this may be blasphemy and the Senate and Supreme
> Court will be petitioned to make this illegal.)
>
>
> Just my opinion so ignore it if you disagree. ;-)
>
>
> Cheers George
>
>
>>
>
>>Subject: Re: Making real world sense of the OVP thread
>
>>From: "Matt Prather" <mprather(at)spro.net>
>
>>
>
>>Pulley woes solved here?
>
>>
>
>>http://www.rjays.com/Rjays_electrical/alternators-01.htm
>
>>
>
>>If that is cut off, try: http://tinyurl.com/55742
>
>>
>
>>There are others that are commercially available for the Hot
>
>>Rod crowd.
>
>>
>
>>Regards, Matt-
>
>
> ---------------------------------
>
> ---------------------------------
>
>
________________________________________________________________________________
| From: | "John Swartout" <jgswartout(at)earthlink.net> |
| Subject: | Making real world sense of the OVP thread |
Bob,
>What electronics?
Dynon D-10A EFIS
Grand Rapids Technologies Model 4000 EIS
ICOM A200 Comm Radio
KT76A Transponder
AmeriKing AK-350 encoder
PS Engineering PM1000II Intercom
Dell Axim x50 PDA with some kind of power supply
Teletype GPS receiver
I'd never heard of DO-160 Recommendations until you mentioned them on
this list, and I've never seen any reference to them in the
documentation for the devices I have. I have all of these devices except
the Dynon, the Dell, and the GPS, but they don't yet have an electrical
system to call home--so they won't be tested by me until I have build
the electrical system and fire it up. I am ready to do that right
now--that's why I'm asking so many questions. I want to give them a
good, safe home.
Concerning a fat diode across the battery contactor:
Diodes, if memory serves, allow electricity to pass through them in only
one direction. Is it true that when you open the battery contactor with
a lot of electricity passing through it, the electricity jumps the gap
while it still can, and this is a violent event like a capacitor
discharging or a spark plug firing? And we know in which direction the
spark leaps? And does a momentary reversal of polarity occur? So a
diode could arrest that spike if we know which way the spike wants to
go? How would it do that? Would it convert the electricity to heat? Is
a diode a good heat sink?
Thanks again for your patience.
John
-----Original Message-----
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of
Robert L. Nuckolls, III thread
Subject: RE: AeroElectric-List: Making real world sense of the OVP
thread
thread
>
>
>Thank you, Bob, for bringing this all down to a level I can comprehend
>and use.
>
>Not knowing if my electronics are DO-160 RECOMMENDATION-compliant,
would
>you advise shutting off the electronics, or not turning them on, until
>after starting the engine?
What electronics? Are any of these items KNOWN to be ignorant
of or non-compliant with DO-160? Engine starting isn't the problem
with respect to damage of an appliance. Cranking the engine places
perturbs the bus voltage by some expected amount. If the appliance
cannot gracefully recover from the perturbation in a way that
restores usefulness quickly, then you as a consumer have to decide
whether you replace it with one that can . . . or modify the working
environment for that appliance such that it's isolated from an
effect it cannot tollerate.
>I think Paul mentioned a load dump from switching off the landing
>lights. Should I also shut off electronics before shutting off landing
>lights? Would a rheostat be a better device than a toggle switch for
>turning landing lights on and off?
Here we have an excellent example of mis-use or misunderstanding
of words. As long as there is a battery on line, there are NO
perturbations of bus voltage due to operation of any accessory
that should be of concern to the builder. A "load dump" in the
contemporary sense is a perturbation of rare and exceedingly
large magnitude that occurs when large load changes are made
on a system that does not have the stabilizing benefits of a
battery.
I've often suggested that this event should be called a "battery
dump"
event. In the certified airplane world, a "load dump" is just
what Paul described . . . a large reduction in system load. This
happens any time we shut of a 150A Freon compressor, or 200A of
electric tail de-ice. Yes, this produces a perturbation in bus
voltage that we EXPECT and have LEARNED TO TOLERATE by observing
the system behavior based on decades of performance.
>Your observation that the discussion of malfunction modes, however
rare,
>may get exaggerated attention from the more worry-prone among us is a
>point well taken. I suspect I am one of those: "constructive worry" is
>at the core of my professional life, and it can be difficult to leave
>these essential traits at work. But in my defense, I am building a new
>airplane, and I want it to be the best it can be--or at least, at the
>intersection of technology and expense that I find most harmonious.
99% of the worries out there right now are unnecessary because
they are founded on misconception and concerns not based on
the physics and practical realities. This is why I've prefaced
all current discussions with experiments that describe what parts
are used and what behaviors they show when operated in a specific
manner. This is hard data that drives good interpretation and
invites anyone to repeat the experiment to either confirm the
results or illuminate errors. This is not a matter persuasiveness
but accuracy.
>Incidentally, I should mention that I will take your advice and install
>two P-mags instead of one P-mag and one E-mag. $250 for another level
of
>single-point redundancy. But for starting and idling, the engine IS
>still dependent on the electrical system. P-mag's self-power output is
>linearly proportional to rpm and doesn't become completely independent
>of bus power until about 1600-1800 rpm.
That isn't a big down side. How often do you drop below 1800 rpm
before you begin descent to landing? Even if the power lead to an
p-mag was compromised such that one ignition drops off line in a
low power descent, you would have to have both power supplies
open before it becomes an issue for comfortable completion of
flight and the failure will be caught at the next pre-flight.
Better yet, write a procedure into your shutdown check list to
drop battery power off on one e/p-mag at a time to see that they
run at ramp idle.
With respect to your opening concerns, the vast majority of
accessories
you have to choose from are not adversely affected by perturbations
of voltage on the bus for all normal operations. The only
perturbations
of significant concern would be failed regulators (persistent and
extreme over voltage) or "load dump" transients brought on by
large reduction of system loads without benefit of a battery. The
first is easily mitigated by an OV protection system teamed with
the
bus stabilizing effects of a well-maintained battery. The latter
is not a big concern because the potential for such an event
arises only when a battery contactor has gone open.
That prompts an interesting thought . . . suppose we put a fat
diode
across the battery contactor so that the cathode is tied to the
battery
side, anode to the bus side. This diode would not interfere with
normal
operations of the battery contactor . . . but should the contactor
open because of solenoid failure -or- wiring failure, the bus would
still benefit from the stabilizing effects of the battery for
clamping
of positive going transients under the "load dump" scenario. I'll
have to noodle over that one for a bit to see if there's any
downside.
A diode/battery combination makes a hell-of-a-transorb capable of
holding
the bus at or below 18 volts for quite some time. Certainly for the
duration
of a load dump perturbation.
Bob . . .
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Making real world sense of the OVP thread |
----- Original Message -----
From: "John Swartout" <jgswartout(at)earthlink.net>
Subject: AeroElectric-List: Making real world sense of the OVP thread
>
>
> Bob, Paul, Eric, et al:
>
Well John,
Here is how I think we stand. (Yes I am somewhat upset at recent posts on
this subject suggesting there is nothing wrong with status quo).
There are far more issues STILL to be resolved that we started with. We
started with issues about the current designs and so far I have seen no
solutions to any of the issues brought up.
I have seen many questions asked and +/- 50% are never answered. Perhaps
pocket vetoed as given time things seem to simply fade away.
I initiated this issue (OVP etc) with the results of a sub part of the load
dump testing from last year.
First a load dump is a normal event as far as the alternator is concerned.
We depend on the battery to act as a huge current sink to stabilize things.
ALL current Aeroelectric designs (as far as I can tell) prevent the
emergency mode of "no battery operation" as the OVP (as a standalone
module) or internal to the LR-3 are fast acting and cannot tell the
difference from a 5+ amp load dump and a hard alternator regulator failure
in the case of no battery operation. Why discard this mode of emergency
operation?? We have seen multiple batteries and alternators suggested. In
all cases the alternator only mode of operation is not only ignored, the
parts suggested as required on the alternator to protect for failures so
rare as near impossible to hear of (compared to engine mechanical failures
several times per week or so it seems) actually preclude this otherwise
simple mode of emergency operation. Of course if we define the battery as
never failing (open in this case) it might then make sense. As I have
documented 3 local "fail open" of aircraft certified batteries in the past 3
years it seems that to assume that batteries never fail open is at best
foolish to suggest.
How many failures do we need to protect for. Lets see it must be at least
three as dual batteries and dual alternators seems a good idea :-). Two
batteries, either can fail, and dual alternators so either can recharge the
battery.
What's wrong with no single failure and this can be done with Dual mags and
carb, or one battery and one alternator IF the alternator can run the system
with a failed battery. Been flying with dual mags for 80 years and now we
need more backups for a much more reliable electrical system???
So If you want to have the ability to operate with no battery or operate in
the case of the battery having an open cell (far more likely than an
alternator regulator failure) you must not have either of the above devices
in your aircraft as they are very likely (near 100%) to false trip the
alternator off line. Their design simply does not address the normal load
dump case with no or a failed battery.
A failed alternator and failing high is very different, and here the LR-3
and OVP module act swiftly to short the system bus and open the associated
CB. This process produces huge currents that overload the CB and a single
case results in potential damage to meet specs of the CB. Thus every time
there is an OVP CB trip its necessary to replace the CB per local FAA verbal
comments. Certificated aircraft only to be sure but who wants to rely on a
CB that may not trip properly next time? There is no need for large currents
but the present designs create them (the only debate is what I found and
what Bob found as both were far higher than the max 'no damage' current).
So far a proper resistor to reduce the currents has not been defined that is
not operated out of its specified currents. Special designed resistors are
required designed for hi current surges as compared with their wattage
rating which is not the design driver here.
There has never been a worst case design analysis to prove the present
designs will safely work under all parts types and specifications. This is a
standard engineering design practice and requirement of any design to be
built more than once.
I could go on but I see no point. We are subjected to strange logic and
sample tests of one to support a poor design concept and implementation. I
have never seen the application of a crowbar in this type of design nor have
any of my associates. Gross misapplication of the crowbar approach in every
opinion I got.
The facts as reported to Van's are clear. Van's says 100% of alternators
reported failed last year had some type of OVP protection added and the
failure occurred simultaneous with the OVP tripping. Perhaps it was a valid
trip but that logic is hard to support given that the thousands of no
failures with NO OVP added in. Vans has told me it would seem the adding of
the OVP devices is causing the failures and Vans does not have them on the
factory acft and does not recommend them to builders.
I have asked around the auto repair shops and auto parts stores locally and
NONE had ever had a alternator failure where the failure was a HI voltage
output.
Are we worrying about a failure so rare (and given that I feel the fix is a
poor design) that the fix is causing problems that are not there to begin
with? That its been the "standard for 40 years" and FAA certified is no
proof of quality or good design. The FAA routinely certifies bad designs of
every sort all the time.
I years ago took a different approach. On the load side of every CB I have a
transorb sized so if the alternator runaway with HI voltage the transorb
will clamp the HI voltage and opens that specific CB and thus protect
expensive and or critical equipment. As I have an fully electrically
dependent aircraft I have a backup battery system for the engine that is
independent of the main bus so a fault hi or low on the main bus will not
affect the backup system.
Given the many CB's and associated transorbs there is essentially a OVP
distributed network in the acft wiring. under $10 for the transorbs and
simple to put across the CB. Would work with fuses as well.
Not the only related post planned but this one is already too long and has
too many subjects
Paul
________________________________________________________________________________
| From: | "Paul Messinger" <paulm(at)olypen.com> |
| Subject: | Re: Making real world sense of the OVP thread |
Some of your listed equipment have specific specs that are inside DO-160
(tighter that is).
I have reviewed DO-160 and its mostly toothless. Its full of suggestions and
requirements things work after this test as you define it to work. Or even
more strange requirements that the manufacturers set so in these cases
DO-160 simply applies what ever the manufacturer says.
There are NO requirements to do any of its parts and no requirements in the
industry that I can find that require meeting any part of DO-160. No
requirement to test, just to design to etc.
Nice guidelines but I have my own list of equipment and NONE has been tested
or even inspected by design to meet DO-160 as the mfgrs simple ignore this
document.
Perhaps its a valid and compliant document in the corporate and hi end
avionics world.
A reasonable design with a few properly placed transorbs will keep the 14V
power system clean, at least to the extent required to meet OUR lists of
equipment.
More IMPORTANT embedded comments below.
----- Original Message -----
From: "John Swartout" <jgswartout(at)earthlink.net>
Subject: RE: AeroElectric-List: Making real world sense of the OVP thread
>
>
> Bob,
>>What electronics?
> Dynon D-10A EFIS
> Grand Rapids Technologies Model 4000 EIS
> ICOM A200 Comm Radio
> KT76A Transponder
> AmeriKing AK-350 encoder
> PS Engineering PM1000II Intercom
> Dell Axim x50 PDA with some kind of power supply
> Teletype GPS receiver
>
> I'd never heard of DO-160 Recommendations until you mentioned them on
> this list, and I've never seen any reference to them in the
> documentation for the devices I have. I have all of these devices except
> the Dynon, the Dell, and the GPS, but they don't yet have an electrical
> system to call home--so they won't be tested by me until I have build
> the electrical system and fire it up. I am ready to do that right
> now--that's why I'm asking so many questions. I want to give them a
> good, safe home.
>
> Concerning a fat diode across the battery contactor:
>
> Diodes, if memory serves, allow electricity to pass through them in only
> one direction. Is it true that when you open the battery contactor with
> a lot of electricity passing through it, the electricity jumps the gap
> while it still can, and this is a violent event like a capacitor
> discharging or a spark plug firing? And we know in which direction the
> spark leaps? And does a momentary reversal of polarity occur? So a
> diode could arrest that spike if we know which way the spike wants to
> go? How would it do that? Would it convert the electricity to heat? Is
> a diode a good heat sink?
I must assume Bob is thinking about his position that batteries never fail.
Nice concept but simply not true so the diode here is of no use in 100% of
the cases. A simple low cost transorb works 100% of the time
>
> Thanks again for your patience.
>
> John
>
> -----Original Message-----
> From: owner-aeroelectric-list-server(at)matronics.com
> [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of
> Robert L. Nuckolls, III thread
> To: aeroelectric-list(at)matronics.com
> Subject: RE: AeroElectric-List: Making real world sense of the OVP
> thread
>
> thread
>
>
>>
>>
>>Thank you, Bob, for bringing this all down to a level I can comprehend
>>and use.
>>
>>Not knowing if my electronics are DO-160 RECOMMENDATION-compliant,
> would
>>you advise shutting off the electronics, or not turning them on, until
>>after starting the engine?
>
>
> What electronics? Are any of these items KNOWN to be ignorant
> of or non-compliant with DO-160? Engine starting isn't the problem
> with respect to damage of an appliance. Cranking the engine places
> perturbs the bus voltage by some expected amount. If the appliance
> cannot gracefully recover from the perturbation in a way that
> restores usefulness quickly, then you as a consumer have to decide
> whether you replace it with one that can . . . or modify the working
March 22, 2005 - March 31, 2005
AeroElectric-Archive.digest.vol-ee