Today's Message Index:
----------------------
1. 03:09 AM - Re: Coil Suppression Techniques (John Cleary)
2. 05:36 AM - Simplicate my all-electric Electronic Fuel Injection (Sam Hoskins)
3. 07:06 AM - Z-19RB - review and simplify? (Sam Hoskins)
4. 07:26 AM - Re: Coil Suppression Techniques (Eric M. Jones)
5. 07:44 AM - Re: Coil Suppression Techniques. (Robert L. Nuckolls, III)
6. 08:22 AM - Re: Previous Master solonoid clicking (Bill Bradburry)
7. 08:36 AM - Re: Re: Coil Suppression Techniques (Bob White)
8. 12:45 PM - Re: Re: Coil Suppression Techniques (Robert L. Nuckolls, III)
9. 05:47 PM - Z-19 hypothetical question (user9253)
10. 06:06 PM - Re: Z-19RB - review and simplify? (user9253)
Message 1
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| Subject: | Coil Suppression Techniques |
Bob,
You are a LEGEND.
Thanks again,
John
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Friday, 23 May 2008 1:33 PM
Subject: RE: AeroElectric-List: Coil Suppression Techniques
<nuckolls.bob@cox.net>
At 08:03 AM 5/23/2008 +1000, you wrote:
<john_rv10@yahoo.com>
>
>Bob,
>
>Reading all these comments, two questions come to mind.
>
>1. Have you done the tests below with a zener-zener or a diode-zener
>combination to see how they compare with their IN 540x cousins?
Absolutely. The the worse case voltage spike occurs with zero
suppression (where all energies are dissipated in the arcing
across spreading switch contacts). The best scenario for arcing
control is the plain vanilla diode where arcing is minimal
because the negative going spike that would normally go -300 volts
plus is clamped off at ground thus limiting the voltage stress
across the switch contacts to 14 volts.
>2. Have you collected data on the effect on the switch controlling the
relay
>to compare the four conditions:-
> No protection
> IN540x protection
> Zener-zerner protection
> Diode-zener protection?
Sure. They all work within the limits of their physics.
Even a plain resistor adds significant value for arc
reduction . . . even if the least efficient of the lot.
A capacitor/resistor combination works too. Recall the
"condenser" across the points on an Kettering ignition
system distributor? There's a LOT of ways each offering
trade offs. But to date, I've discovered no simpler, easier
to implement technique than use of the plain-vanilla
diode.
>The data from question 1 will show us the effects on the relay under the
>various conditions being discussed. The data from Q2 will show us the
>effects on the switch controlling the relay under those same conditions. It
>seems both lots of data are required to determine the best way to protect
>the switch and at the same time protect the relay? - or am I missing
>something in this debate?
I looked at all these variations and quite frankly they
performed well. I thought I had the traces on
my hard drive but I don't find them. If I get time tomorrow,
I'll go plot them again.
I've not included them in my offerings of data because
they are all middle-ground for performance between NO
suppression and the ULTIMATE suppression of a plain-vanilla
diode.
With one exception. At one time I personally embraced low
voltage MOV's as viable contact preservation devices
but discarded them after I went to the bench to check
performance when a reader told me of his own experiments
where visible arcing was not attenuated by any observable
amount with MOVs. I was properly embarrassed and dutiful
in correcting the gaff. It's one of those things that
happens when understanding based on data sheets does
not mesh with real world experiences.
The debate here is not whether the alternative systems
do their job. The debate is whether there is return
on investment for acquiring "specialized"
components sold not upon hard data and repeatable
experiment. The only support is a kind of "new and
improved" marketing hype based on poorly extrapolated
conclusions in a "celebrity" document. In this case,
engineers that published under the Tyco trade name.
It appears Eric is unwilling to be a teacher based on
his personal understanding of the physics supported
by a willingness to explain it. I am saddened by
this. I'll go get the data on the alternative techniques
tomorrow.
Bob . . .
Checked by AVG.
7:06 AM
Checked by AVG.
7:06 AM
Message 2
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| Subject: | Simplicate my all-electric Electronic Fuel Injection |
I'm looking some feedback of my electrical system, based on Z-19RB. You can
get the pdf here:
http://www.mistakeproofing.net/transfer/N202SH-Z-19RB.pdf
This is a retrofit in my 20 year old composite Quickie Q-200. I do a lot of
day VFR cross country with this plane and do some cross country racing.
Since I am converting to "all electric" I would be interested in your
thoughts about my proposed system.
Besides the Dynon FlightDEK 180 the biggest change is the conversion to
electronic fuel injection. I am using the EC-3 controller from Real World
Solutions (RWS). You can see more about the controller here:
http://www.rotaryaviation.com/eficont.html
The EC-3 controller is divided into two sides, A & B. The fuel injector
control and ignition outputs exit the box from a single connector via a
shared relay. The controller can receive either a primary or secondary 12V
power source.
A few bullet points:
- I am using a primary fuel pump and a backup fuel pump. I also have two
transfer pumps.
- I have not yet sized the batteries.
- I have an existing AEC9005-201 low voltage monitor, without the relay
control.
- Output of the ECU will be shown on another page, perhaps later in the
week.
- I have not yet properly sized the fuses or the wires in this drawing.
My concerns:
- By the time I add strobes and position lights, I will have around 14
or 15 switches, which seems like a lot for a 650 lb. (empty weight)
airplane. Is there a way I could minimize the switch count?
- I am thinking about combining the E-buss and the main power bus to
reduce switch count and the number of fuse blocks. I could easily shed the
loads myself.
- There seem to be a lot of components connected to the unswitched
battery busses. I wonder if I should use CBs instead of fuses so I would
have a shutoff during servicing.
Anything else? Your input is very welcome.
Thanks!
Sam Hoskins
Murphysboro, IL
http://samhoskins.blogspot.com/
Message 3
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| Subject: | Z-19RB - review and simplify? |
I'm looking some feedback on my electrical system, based on Z-19RB. You can
get the pdf here:
http://www.mistakeproofing.net/transfer/N202SH-Z-19RB.pdf
This is a retrofit in my 20 year old composite Quickie Q-200. I do a lot of
day VFR cross country with this plane and do some cross country racing.
Since I am converting to "all electric" I would be interested in your
thoughts about my proposed system.
Besides the Dynon FlightDEK 180 the biggest change is the conversion to
electronic fuel injection. I am using the EC-3 controller from Real World
Solutions (RWS). You can see more about the controller here:
http://www.rotaryaviation.com/eficont.html
The EC-3 controller is divided into two sides, A & B. The fuel injector
control and ignition outputs exit the box from a single connector via a
shared relay. The controller can receive either a primary or secondary 12V
power source.
A few bullet points:
- I am using a primary fuel pump and a backup fuel pump. I also have two
transfer pumps.
- I have not yet sized the batteries.
- I have an existing AEC9005-201 low voltage monitor, without the relay
control.
- Output of the ECU will be shown on another page, perhaps later in the
week.
- I have not yet properly sized the fuses or the wires in this drawing.
My concerns:
- By the time I add strobes and position lights, I will have around 14
or 15 switches, which seems like a lot for a 650 lb. (empty weight)
airplane. Is there a way I could minimize the switch count?
- I am thinking about combining the E-buss and the main power bus to
reduce switch count and the number of fuse blocks. I could easily shed the
loads myself.
- There seem to be a lot of components connected to the unswitched
battery busses. I wonder if I should use CBs instead of fuses so I would
have a shutoff during servicing.
Anything else? Your input is very welcome.
Thanks!
Sam Hoskins
Murphysboro, IL
http://samhoskins.blogspot.com/
Message 4
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| Subject: | Re: Coil Suppression Techniques |
> induces a high VOLTAGE which is the opposite polarity of the applied voltage.
The faster the current decreases, the higher the voltage
> spike. The suppression diode gives the current a place to go allowing
> it to decay more slowly, producing a lower voltage, reducing the
> arcing on the switch controlling the relay. The current will never
> exceed the original current flowing in the coil.
>
> Use of the suppression diode delays opening the relay because the
> current continues to flow for a longer time. The important point is
> that the suppression diode protects the switch controlling the relay.
> The effects on the relay contact arcing are secondary.
>
> Bob W.
Actually, Eric is in bed with the cold/flu. And Paul M. keeps calling me up to
rant about politics.....Jeeeze.
Let's clear the air regarding coil suppression.
When the relay is closed (and as I said this is targeted mainly at contactor relays),
the relay coil has a large amount of energy stored in its inductor. When
the relay coil switch is opened, the field collapses and a problematic high
voltage is produced (the voltage depends on the several construction variables).
I think we agree to this point.
Now, it might seem that the current produced by the collapsing field is opposite
its normal direction. This is not so. The coil current is in the same direction,
but the relay coil has changed from being the Load to being the Generator.
If you look at the diode direction, you will see that a current in the opposite
direction could not flow at all, and the diode would serve no purpose.
I agree with Bob W. that the coil suppressor protects the switch and anything else
that provides power to the relay. It also provides other beneficial effect.
However, not having a coil suppressor is not an option.
Indeed, the best way to preserve the contactor's own power contacts is to have
NO coil suppressor and just rip them apart as fast and as far as possible as possible.
But everything else would suffer.
The common (and historic) coil suppression technique that minimized damage to other
components like the on/off switch was to shunt the coil with a reversed bias
diode (a diode arranged so that it does not normally conduct current). Now
when the coil's magnetic field collapses, it induces a
current that is shorted by the diode. The current flows through the coil and stops
in a very short time, lowering the voltage by lengthening the field collapse
time.
This longer field collapse time is deleterious to the power contacts, and (by Tyco
P&B's information) can actually cause momentary re-closure which manifests
as chatter, bouncing, etc. I assume this depends on the load, and the particulars
of the contactor.
But this approach raises some red flags:
1) The diode must not be driven over-current.
2) The delay to opening must be minimized.
3) The suppression device should last longer than the contactor.
4) The ground bounce oscillations should be handled. (for inductive loads)
Now this is where Bob N. and I part company. Bob runs tests and depends on experience,
I just read technical papers and study spec sheets. I claim one should
dump the diode and use a newer approach. Bob N. claims the diode is good enough.
I claim the major purveyors of contactors now use back-to-back zeners or bidirectionals.
Bob N. can show lots of relays that use diodes.
There you go.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=184508#184508
Message 5
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| Subject: | Re: Coil Suppression Techniques. |
At 04:16 PM 5/22/2008 -0700, you wrote:
>Hi Bob, on behalf of myself and many others I'm sure I'd like to thank you
>for - first of all, your restraint, and of course your informative posts
>that make it so easy for the rest of us to click on the links of your
>experiments.
>
>I joined this list probably two years ago and a great deal of what was
>discussed was over my head (and still is!) ... I received the daily emails
>and for the longest time would check out the subject titles and more often
>than not delete the email. Over time I've 'gotten up to speed', read your
>book, and spent the time to learn (whether the particular subject
>concerned my airplane or not).
That's what Richard Feynman describes as "The
Pleasure of Finding Things Out". Virtually every
classroom we all sat in for the first time offered
tons of information sometimes accompanied with
lucid explanation and even real-life connections.
It is not uncommon when "getting a drink from the
fire hose" that certain simple-ideas don't catch
on or fit into the current library of life experiences.
But as you've alluded, there is an osmosis
effect . . . tiny bits of the big drink soak
in. At some point in the future, a sort of
epiphany may take place when one realizes that
"Yeah, I KNOW how that works".
It still happens to me regularly.
>
>It's all too easy to "gold plate the spec" to cover ALL conceivable
>conditions that a particular component may see whether applicable or
>not. It is of GREAT value to me that you repeatedly base your responses
>on OBAM aircraft. Meaning... if age/environmental factors, etc is going
>to kill my component before I or my designed system does then thats
>exactly what I need to know. I have always found your posts and advice to
>be practical in the real world (where most of us live with our little
>homebuilt airplanes) and considerate of my time & money.
To me, being an engineer was the ideal connection
between pure physics and people. I was exceedingly
fortunate in my career to have some good teachers
AND a charter to make my ideas play in the marketplace.
I.e, offer competitive value that was attractive
for performance, price and after-the-sale service.
VERY few of my contemporaries have enjoyed so broad
an experience.
>
>I continue to learn from all the contributors and contributions to the
>site. Best Regards to all and my apologies for feeling the need to
>'waste' bandwidth! ;)
Forgive me but that "wasted bandwidth" canard is
really raises the ol' blood pressure. It seems most
often used by individuals who complain to other
individuals about the use of a communications tool
that is nobody's property . . . a term almost never
used in a exchange that quests for understanding of
simple ideas.
If one wants to bemoan "wasted bandwidth", just
hit any cable channel for an hour and make notes on
what one learns that adds any value to their lives.
I.e., how did the $time$ spent today make one's life
any more enjoyable or confident tomorrow?
I view $time$ spent here as an opportunity to
fine tune my own skills as well as encouragement
to broaden my own understanding. Folks on the List
are not always aware of the $time$ spent to firm
up a foundation for an reply before I post it.
You folks are as useful to me as I hope I am to
all of you. $Time$ and 'bandwidth' used in that
endeavor is never a waste.
Everyone on the List has an opportunity to be both
student and teacher. It has nothing to do with
the total experience of either individual. Any
instance where understanding supported by repeatable
experiment is exchanged, there is opportunity
for growth for everyone who chooses to
participate.
Bob . . .
Message 6
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| Subject: | Previous Master solonoid clicking |
I left out that my plane is wired closely to the Z-19 architecture.
Also the low voltage module is one that I built using one of Bob's boards
from the old model.
Bill B
A while back, I discussed a clicking sound that I heard after I turned the
alternator on when the engine was running.
Today I discovered that my low voltage module was not working and when I
removed it, the clicking went away.
I tested the module by putting +9V on pin 4, grounded pin 5, and looked for
the LED to come on and also for a ground to show up on pin 1. No light, no
ground. Must have crapped out??!!
I also noticed that when the module was disconnected, If I had the main
battery set to "Alternator", and the engine battery set to "ON", I got about
13.4V. If I flipped the engine battery switch to "Auto", the voltage went
up to about 14.6V.
I was at a loss as to why this would be. I didn't try it with the engine
battery set to "OFF", so I don't know what would have happened if I did.
Does anyone have any ideas as to what was happening to cause the clicking if
the module caused it, and why the voltage increase? I at first thought..I
am turning one of the batteries off, so the voltage went up, but then I
thought...why wouldn't the voltage regulator bring it back down in that
case.
Thanks for the help!
Bill B
Message 7
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| Subject: | Re: Coil Suppression Techniques |
On Fri, 23 May 2008 07:23:10 -0700
"Eric M. Jones" <emjones@charter.net> wrote:
>
>
> > induces a high VOLTAGE which is the opposite polarity of the applied voltage.
The faster the current decreases, the higher the voltage
> > spike. The suppression diode gives the current a place to go allowing
> > it to decay more slowly, producing a lower voltage, reducing the
> > arcing on the switch controlling the relay. The current will never
> > exceed the original current flowing in the coil.
> >
> > Use of the suppression diode delays opening the relay because the
> > current continues to flow for a longer time. The important point is
> > that the suppression diode protects the switch controlling the relay.
> > The effects on the relay contact arcing are secondary.
> >
> > Bob W.
>
>
> Actually, Eric is in bed with the cold/flu. And Paul M. keeps calling me up to
rant about politics.....Jeeeze.
>
> Let's clear the air regarding coil suppression.
>
> When the relay is closed (and as I said this is targeted mainly at contactor
relays), the relay coil has a large amount of energy stored in its inductor. When
the relay coil switch is opened, the field collapses and a problematic high
voltage is produced (the voltage depends on the several construction variables).
I think we agree to this point.
>
> **** Now, it might seem that the current produced by the collapsing field is
opposite its normal direction. This is not so. The coil current is in the same
direction, but the relay coil has changed from being the Load to being the Generator.
If you look at the diode direction, you will see that a current in the
opposite direction could not flow at all, and the diode would serve no purpose.
>
> I agree with Bob W. that the coil suppressor protects the switch and anything
else that provides power to the relay. It also provides other beneficial effect.
However, not having a coil suppressor is not an option.
>
> Indeed, the best way to preserve the contactor's own power contacts is to have
NO coil suppressor and just rip them apart as fast and as far as possible as
possible. But everything else would suffer.
>
> The common (and historic) coil suppression technique that minimized damage to
other components like the on/off switch was to shunt the coil with a reversed
bias diode (a diode arranged so that it does not normally conduct current). Now
when the coil's magnetic field collapses, it induces a
> current that is shorted by the diode. The current flows through the coil and
stops in a very short time, lowering the voltage by lengthening the field collapse
time.
>
> This longer field collapse time is deleterious to the power contacts, and (by
Tyco P&B's information) can actually cause momentary re-closure which manifests
as chatter, bouncing, etc. I assume this depends on the load, and the particulars
of the contactor.
>
> But this approach raises some red flags:
> 1) The diode must not be driven over-current.
> 2) The delay to opening must be minimized.
> 3) The suppression device should last longer than the contactor.
> 4) The ground bounce oscillations should be handled. (for inductive loads)
>
> Now this is where Bob N. and I part company. Bob runs tests and depends on experience,
I just read technical papers and study spec sheets. I claim one should
dump the diode and use a newer approach. Bob N. claims the diode is good enough.
I claim the major purveyors of contactors now use back-to-back zeners or
bidirectionals. Bob N. can show lots of relays that use diodes.
>
> There you go.
>
> --------
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge, MA 01550
> (508) 764-2072
> emjones@charter.net
>
>
>
OK, that's better. You have stated the physics correctly.
The only minor point I might make is that the fourth paragraph is not
entirely accurate (marked **** above). I wouldn't expect the current
produced by the collapsing field to be in the opposite direction. What
I did say was that the voltage generated by the collapsing field was
of the opposite polarity to the originally applied voltage. If that
weren't true, the diode wouldn't provide any benefit.
As to the usefulness of a suppression technique more complex than a
diode, it seems to me that Bob N.'s test have shown that the effect on
the contactors used in OBAM aircraft is fairly minor. It's interesting
that the table shown in the PDF you referenced earlier shows the
relationship between various suppression techniques and drop out time
when the important factor is armature velocity. Did the engineers that
wrote this paper take any data on armature velocity? They don't say.
Did they test hundreds of relays to failure? The don't say. A tech
paper needs to be based on experience or it's of little value. Bob's
data shows a reduction in armature velocity. That is consistent with
statements in the PDF. Bob has characterized the reduction and
concluded that it's minor, based on his invaluable experience.
Bob W.
--
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://roblinstores.com/cables/
Message 8
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| Subject: | Re: Coil Suppression Techniques |
At 07:23 AM 5/23/2008 -0700, you wrote:
>
>
> > induces a high VOLTAGE which is the opposite polarity of the applied
> voltage. The faster the current decreases, the higher the voltage
> > spike. The suppression diode gives the current a place to go allowing
> > it to decay more slowly, producing a lower voltage, reducing the
> > arcing on the switch controlling the relay. The current will never
> > exceed the original current flowing in the coil.
> >
> > Use of the suppression diode delays opening the relay because the
> > current continues to flow for a longer time. The important point is
> > that the suppression diode protects the switch controlling the relay.
> > The effects on the relay contact arcing are secondary.
> >
> > Bob W.
>
>
>Actually, Eric is in bed with the cold/flu. And Paul M. keeps calling me
>up to rant about politics.....Jeeeze.
>
>Let's clear the air regarding coil suppression.
>
>When the relay is closed (and as I said this is targeted mainly at
>contactor relays), the relay coil has a large amount of energy stored in
>its inductor. When the relay coil switch is opened, the field collapses
>and a problematic high voltage is produced (the voltage depends on the
>several construction variables). I think we agree to this point.
yes except that "large" is not quantified. We're
talking a handful of millijoules.
>Now, it might seem that the current produced by the collapsing field is
>opposite its normal direction. This is not so. The coil current is in the
>same direction, but the relay coil has changed from being the Load to
>being the Generator. If you look at the diode direction, you will see that
>a current in the opposite direction could not flow at all, and the diode
>would serve no purpose.
>
>I agree with Bob W. that the coil suppressor protects the switch and
>anything else that provides power to the relay. It also provides other
>beneficial effect. However, not having a coil suppressor is not an option.
???? Tens of thousands of aircraft have flown out their
lifetimes (and millions of cars ditto) with no coil
collapse suppression on a variety of inductive loads.
Service life of the controlling devices was perhaps
less than what MIGHT be achieved but running without
it was and still is AN OPTION in numerous antique
vehicles including airplanes.
>Indeed, the best way to preserve the contactor's own power contacts is to
>have NO coil suppressor and just rip them apart as fast and as far as
>possible as possible. But everything else would suffer.
Agreed . . . but "everything else" and "suffering"
are non-identified and non-quantified.
>The common (and historic) coil suppression technique that minimized damage
>to other components like the on/off switch was to shunt the coil with a
>reversed bias diode (a diode arranged so that it does not normally conduct
>current). Now when the coil's magnetic field collapses, it induces a
>current that is shorted by the diode. The current flows through the coil
>and stops in a very short time, lowering the voltage by lengthening the
>field collapse time.
agreed
>This longer field collapse time is deleterious to the power contacts, and
>(by Tyco P&B's information) can actually cause momentary re-closure which
>manifests as chatter, bouncing, etc. I assume this depends on the load,
>and the particulars of the contactor.
I've never seen a spreading contact re-reclose. Have
you some examples of where this has been observed?
Chatter, bouncing . . . yes ALL contacts in switches,
relays and contactors do not close and stay closed
on first contact. I've seen as few as 2 or 3 closures-
before-stable and as many as dozens. I counted over 25
bounces in one of traces I recently published Mercury
wetted relays and solid-state switches are some exceptions.
>But this approach raises some red flags:
>1) The diode must not be driven over-current.
Sure . . . but even the most delicate of silicon
power rectifiers is not at risk for over-current
in situations common to our aircraft.
>2) The delay to opening must be minimized.
Why? There ARE the occasional condition where
TIMING is important. I've wrestled with "relay
races" in circuits where relay-logic combinations
were polluted because relay timing was not consistent
or carefully accommodated.
In every situation we're considering here, the
relay or contactor is manually operated by
crew . . . whether or not the contacts begin
to move 1 mS or 50 mS after the pilot hits
the switch is transparent to both the operator
and to system performance.
>3) The suppression device should last longer than the contactor.
??? Have you seen a contactor kill its own
collapse suppressor? I just measured the inductance
of an S701-1 contactor at 45 mH. LI^2/2 = (.045 x
.9 x .9)/2 = 18 millijoules. The 1N4001
is rated to take 30A (1v drop) for 8.3 mS for
250 millijoles. My favorite diode 1N5400
is good for 200A for 8.3 mS for a spike
catching capability of 1660 millijoules.
I can't imagine where we'd encounter an energy-
stress situation for coil suppression.
>4) The ground bounce oscillations should be handled. (for inductive loads)
Not sure how you're using "ground bounce". Inductance
across a ground system is an issue within devices
where very fast, tiny signals are handled. The
ground system in a vehicle is exceedingly variable,
difficult to control which is why we assume that
products installed in an airplane should be able to
withstand a variety of butt-ugly noises including
"ground bounce". A diode across a relay coil has no
significance to the generation or suppression of
ground bounce as I perceive the phrase. If you
have another perception, I'll need to understand
it before I can intelligently discuss it.
>Now this is where Bob N. and I part company. Bob runs tests and depends on
>experience,
. . . repeatable experiments are the ingredients
that go into recipes for success.
>I just read technical papers and study spec sheets.
the printed word is an exceedingly important
communications tool for teachers with simple-ideas
to explain. At the same time, anyone can write down
ideas that are easily mis-interpreted or are just
plain wrong. One must always be wary of poorly
explained ideas promoted only with convincing words.
No teacher is insulted by honorable skepticism.
> I claim one should dump the diode and use a newer approach. Bob N.
> claims the diode is good enough.
. . . for relays and contactors as WE use them
in OUR airplanes. I will happily use any alternative
technique that improves on performance, reliability
or cost of ownership. Here's an example of arc
suppression added across the contacts of my products
control relay:
http://aeroelectric.com/Pictures/Relays/Relay_with_Arc_Suppression_s.jpg
Here the concern was for the effects of an inductive
load on ME as the controlling device. I had no
control over configuration of load so I had to
cover the bases in the design of my product and
put suppression on not on my coil but my contacts!
> I claim the major purveyors of contactors now use back-to-back zeners or
> bidirectionals. Bob N. can show lots of relays that use diodes.
I don't thing we have "parted company" if you're
agreeing that the diode is . . .
(1) the ultimate transient suppressor from a energy
management perspective, convenience and cost
of ownership and . . .
(2) causes an extended but insignificant
drop-out delay for the ways we use relays
and contactors and . . .
(3) offers an insignificant influence upon
service life for applications under discussion.
I'll go plot the performance characteristics
of 6-8 different ways to manage stored energy
in a contactor coil. I'll also discuss the
fact that selection of arc suppression techniques
depend on the whole suite of design considerations
that may go beyond starter/master switch and starter/
battery contactor service life.
Bob . . .
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| Subject: | Z-19 hypothetical question |
Here is a hypothetical question for you electrical gurus. A pilot is flying on
trip in a plane wired according to schematic Z-19. Shortly after takeoff the
main battery contactor fails open. The pilot does not notice anything wrong
because the engine battery contactor is closed and the alternator is still functioning.
Eventually the main battery discharges due to loads on the main battery
bus, and the pilot notices some things not working. He knows there is a
problem but does not know the cause. Just to be safe, he closes the Endurance-Bus
Alternate-Feed switch. The question is, does the charging current blow a
fuse? (either one or both fuses) The current path is from the Main Power Distribution
Bus, 7A fuse, diode, Endurance Bus, Alternate-Feed switch, fuse, Main
Battery Bus, to the main battery.
If the answer to the above question is yes, then everything on the Endurance Bus
might not work for the remainder of the flight. I think the best solution is
to increase the wire and fuse sizes in the above circuit. What size is required?
Other possible solutions such as another diode or relay create additional
problems.
Joe Gores
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=184591#184591
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| Subject: | Re: Z-19RB - review and simplify? |
Do any of your electronic displays have voltage monitoring and alarm features?
If so, you would not have to use that low voltage module.
I would use fuses. They have several advantages. You will not be servicing equipment
very often and you can pull a fuse.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=184595#184595
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