Today's Message Index:
----------------------
1. 06:02 AM - Re: Re: Summing up OVP (John Schroeder)
2. 07:10 AM - crowbar method ()
3. 07:30 AM - Re: Re: Summing up OVP (plaurence@the-beach.net)
4. 08:26 AM - traffic scope antenna (rd2@evenlink.com)
5. 08:44 AM - Re: Summing up OVP (Jim Oke)
6. 09:24 AM - Re: traffic scope antenna (Chuck Jensen)
7. 10:39 AM - Re: crowbar method (Ken)
8. 12:18 PM - Re: crowbar method (John Swartout)
9. 12:19 PM - Re: traffic scope antenna (rd2@evenlink.com)
10. 01:53 PM - Re: crowbar method (Eric M. Jones)
11. 02:38 PM - Re: [Bulk] Re: crowbar method (Kevin Horton)
12. 04:00 PM - Re: Re: crowbar method (Ken)
13. 05:20 PM - Re: [Bulk] Re: crowbar method (Charlie England)
14. 06:25 PM - Re: crowbar method (Eric M. Jones)
15. 06:51 PM - Re: crowbar method (Eric M. Jones)
16. 07:26 PM - Re: Re: Paul M. has risen from the dead (Robert L. Nuckolls, III)
17. 07:30 PM - Re: Re: I've got a secret (Robert L. Nuckolls, III)
18. 07:30 PM - Re: Re: crowbar method (Charlie England)
19. 08:08 PM - Re: Diode orientation (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Summing up OVP |
--> AeroElectric-List message posted by: "John Schroeder" <jschroeder@perigee.net>
Tom -
That also has been my understanding of the thread - in much more vague
terms than you so clearly describe. Thanks for the great summary.
John Schroeder
>
> This is my understanding as well. There are really only two "lightning
> rod" issues here:
>
> 1) Crowbar disconnect method VS other methods
>
> a) AEC has recommended the crowbar method for shutting down both
> internally and externally regulated alternators.
> b) Some say that the crowbar method is outdated and that there are
> better ways to implement this function.
> c) Some say that the crowbar method is hazardous due to the low
> internal resistance of modern batteries.
> d) I have yet to see a published schematic for any alternative to the
> AEC crowbar module.
> e) False triggering will be an "issue of scrutiny" with any disconnect
> method.
>
> 2) B-Lead disconnect & load dump issues
>
> a) AEC has recommended a B-lead overvoltage disconnect ONLY for
> internally regulated alternators.
> b) It has been shown that a B-lead disconnect can cause a "load dump"
> event.
> c) It has been shown that a load dump event can damage some
> alternators.
> d) It has been claimed that the installation of Transorbs in the right
> places can mitigate this problem.
>
> Tom Johnson
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> AeroElectric-List message posted by: <bakerocb@cox.net>
AeroElectric-List message previously posted by: "Thomas Johnson"
<trj01@comcast.net>
<<.......skip....... There are really only two "lightning rod" issues
here:
1) Crowbar disconnect method VS other methods......skip.....>>
7/31/2005
Hello Tom, Thanks for your input. The term "crowbar disconnect method" has a
dramatic, violent, attention getting, and definitive connotation to it, but
it is completely non descriptive in terms of what is doing what to what.
I'll bet there are dozens of readers just like me that don't know what the
method actually consists of. Would you, or some other contributor, please
just describe the method in simple layman's terms?
I hesitate to suggest such a disruptive change in the use of a term that,
through repitition, has become engraved in our consciousness, if not our
understanding, but think of the value in increased understanding of using
instead a phrase such as "the frammis on the whoosis" method.
OC
PS: And I really hate to nit pick here, but my layman's brain associates the
term "crowbar method" as just an initiating or multiple step process that
can lead to ending the undesired output of an alternator. To actually
accomplish an alternator disconnect (opening the B lead), however,requires
some additional, and apparently rather controversial, hardware.
PPS: Deliberate or not, I like your "lightning rod" pun.
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Summing up OVP |
--> AeroElectric-List message posted by: plaurence@the-beach.net
On 30 Jul 2005 at 23:30, Thomas Johnson wrote:
> --> AeroElectric-List message posted by: "Thomas Johnson"
> <trj01@comcast.net>
>
> >>
> 1) Crowbar disconnect method VS other methods
>
> a) AEC has recommended the crowbar method for shutting down both
> internally and externally regulated alternators. b) Some say that
> the crowbar method is outdated and that there are better ways to
> implement this function. c) Some say that the crowbar method is
> hazardous due to the low internal resistance of modern batteries. d)
> I have yet to see a published schematic for any alternative to the
> AEC crowbar module. e) False triggering will be an "issue of
> scrutiny" with any disconnect method.
>
>IMHO, there is always more than one method for tackling this problem. However,
I knew nothing about
wiring an airplane until I came across Bob's book a few years ago. As a result,
I have wired a Velocity and
soon my RV9A. Bob at least has attempted to provide me(us) with a method. I can
understand a company
or would be enterprise who is selling a device to "crowbar" an alternator might
not want to share their
schematic with the list. But I think it would be helpful to explain there methodology
and rudimentary circuit
design.
Peter Laurence
Peter Laurence
RV9A wings
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | traffic scope antenna |
--> AeroElectric-List message posted by: rd2@evenlink.com
Hi all,
For a recently purchased traffic scope I would like to install a fixed
antenna.
The airplane already has 2 shark fin antennae (one for the transponder and
one for the DME).
1) Does anyone have a good source of shark fins (meaning good price and
SWR)? I may have to replace one of the existing shark fins (coating
cracked) and add another for the traffic scope.
2) How far from the existing shark fins should I install the antenna for
the traffic scope? Any possible interference (e.g. from the DME?)
3) Is a less expensive solution appropriate (ebay monopole for $16.95 -
http://search.ebay.com/transponder-antenna_W0QQfkrZ1QQfromZR8) ?
Advantages/disadvantages of such monopole?
Rumen
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> AeroElectric-List message posted by: Jim Oke <wjoke@shaw.ca>
Taking a further step back, the OVP "discussion" comes down to a cost vs.
benefit vs. risk analysis.
Thus:
A) most modern OBAM aircraft need a power source to run radios, EFIS, GPS,
engine instruments, etc.
B) the power source is most commonly an engine driven alternator.
C) choices in alternators are low production volume (= high cost)
specialized aviation units vs. mass-produced (= relatively low cost)
automotive units, the latter also often having size/weight advantages as
well.
D) numberous factors go into the cost/benefit analysis of this choice.
E) part of this choice is a risk analysis done to anticipate failue modes(s)
and decide what sorts of protective/back-up devices should be added to the
system to protect against particular modes.
F) the risk analysis involves partly safety of flight issues and partly
dollar costs.
So that's how people have arrived at Case 5 and the "debate" about providing
a cost effective over voltage protection stated in worst "worst case" terms
as Case 6.
Part of case 6 seems to be about protecting the alternator against damage
during a possible "load dump" event during some failures. Given that the
automotive alternators we are talking about are in the $100-$200 cost range,
and that the avionics in some aircraft are approaching the $10,000 range
(Garmin 430s, etc.), then (to myself) the alternator can be regarded as a
throwaway "fuse" to protect the much more costly avionics in a complex OBAM
aircraft.
In my own "built to a budget" aircraft (basic VFR instruments, basic engine
instruments, basic VHF & TPNDR avionics) it made no sense to spend $800 to
power $1500 worth of avionics so I went with a low cost automotive
alternator and spent the $25 to build a "homebrew" OVP device. This was a
sensible cost vs. benefit vs. risk analysis to me. I consider there are no
"safety of flight" alternator failure issues in my plain jane VFR RV-6A.
As in many things in life, you pay your money, you make your choices, and
you live with the associated risks.
Jim Oke
Wpg., MB
RV-6A, RV-3
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ken
> Sent: July 30, 2005 10:13 PM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Summing up OVP
>
> --> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>
> I don't think anyone has spoken of any failure mode that
> would justify case 2. I believe a B-lead contactor has only
> been proposed in conjunction with an internal VR alternator.
> Ken
>
> bakerocb@cox.net wrote:
>
> >--> AeroElectric-List message posted by: <bakerocb@cox.net>
> >
> >AeroElectric-List message previously posted by: Richard Riley
> ><richard@riley.net>
> >
> ><<..........skip.......The problem is X It can occur when using
> >equipment Y, under the following conditions - If you use equipment Z
> >instead, it won't happen......skip.......>>
> >
> >7/30/2005
> >
> >Hello Richard, I think that your questions are right on target. I'd
> >like to take a layman's whack at answering them:
> >
> >A) "The problem is X"
> >
> >The problem is potential damage to an aircraft's electrical,
> avionics,
> >or instrument components from an alternator that is putting out
> >excessive voltage.
> >
> >B) "It can occur when using equipment Y......"
> >
> >It can occur when using either an internally regulated or an
> externally
> >regulated field controlled alternator or a permanent magnet
> alternator.
> >
> >C) "under the following conditions"
> >
> >When the voltage regulator (either external or internal) or the
> >alternator suffers a fault that causes the over voltage condition.
> >
> >D) "If you use equipment Z instead, it won't happen"
> >
> >There is no way to guarantee that, "it", the over voltage condition,
> >will never happen with any type of regulator or alternator. So the
> >discussion moves onto the ongoing thread of how to best protect an
> >aircraft's electrical, avionics, or instrument components from an
> >alternator that is putting out excessive voltage.
> >
> >1) Case one: Use an externally regulated field controlled alternator
> >and a mechanism that when an over voltage conditon is
> detected cuts off
> >the field current to the field controlled alternator.
> >
> >2) Case two: But what if one doesn't feel that just cutting off the
> >field current provides adequate protection? Then put a
> separate cut off
> >mechanism in the externally regulated alternator's output B (for
> >battery) lead that opens up that lead in time to protect the
> components at risk.
> >
> >3) Case three: But what if the voltage gets so high so
> quickly that the
> >separate B lead cut off mechanism cannot do its job in time?
> How high
> >and how quick and the best kind of B lead cut off mechanism
> is what the
> >ongoing thread is all about.
> >
> >4) Case four: Use an internally regulated alternator and depend upon
> >the internal regulator to not permit an over voltage condition.
> >
> >5) Case five: But what if the internal regulator fails to provide
> >adequate protection? Then put a separate cut off mechanism in the
> >internally regulated alternator's output B (for battery) lead that
> >opens up that lead in time to protect the components at risk.
> >
> >6) Case six: But what if the voltage gets so high so quickly
> that the
> >separate B lead cut off mechanism cannot do its job in time?
> How high
> >and how quick and the best kind of B lead cut off mechanism
> is what the
> >ongoing thread is all about.
> >
> >7) Case seven: Use a permanent magnet alternator and put a
> separate cut
> >off mechanism in the permanent magnet alternator's output B (for
> >battery) lead that opens up that lead in time to protect the
> components at risk.
> >
> >8) Case eight: But what if the voltage gets so high so
> quickly that the
> >separate B lead cut off mechanism cannot do its job? How
> high and how
> >quick and the best kind of B lead cut off mechanism is what
> the ongoing
> >thread is all about.
> >
> >So where should one's comfort level reside? Mine stops at
> Case one, but
> >I am not trying to push that down any one's throat.
> >
> >OC
> >
> >
> >
> >
>
>
> Photoshare, and much much more:
>
>
>
>\]
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | traffic scope antenna |
--> AeroElectric-List message posted by: "Chuck Jensen" <cjensen@dts9000.com>
What kind of traffic scope did you buy? If it's a Ryan TCAS, which uses
3 sharkfin antennas, there's no choice but to use theirs. Other brands
may vary.
Chuck
Do Not Archive
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
rd2@evenlink.com
Subject: AeroElectric-List: traffic scope antenna
--> AeroElectric-List message posted by: rd2@evenlink.com
Hi all,
For a recently purchased traffic scope I would like to install a fixed
antenna.
The airplane already has 2 shark fin antennae (one for the transponder
and
one for the DME).
1) Does anyone have a good source of shark fins (meaning good price and
SWR)? I may have to replace one of the existing shark fins (coating
cracked) and add another for the traffic scope.
2) How far from the existing shark fins should I install the antenna for
the traffic scope? Any possible interference (e.g. from the DME?)
3) Is a less expensive solution appropriate (ebay monopole for $16.95 -
http://search.ebay.com/transponder-antenna_W0QQfkrZ1QQfromZR8) ?
Advantages/disadvantages of such monopole?
Rumen
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
I'll take a stab at this. Crowbar just means that when the Overvoltage
trips the SCR, the SCR shorts out the power.( Kind of like throwing a
crowbar across the battery to short things out.) That immediately starts
dropping the voltage (a good thing) and the current flow through the CB
trips the CB to permanently shutdown the alternator.
The SCR causes a significant momentary current flow or pulse from the
battery through the CB. There have been some (unsubstantiated in my
opinion) allegations that it could be harmful in vague ways. No
circuitry to do this any other way has been presented by anyone here as
far as I know however one person here does sell an alternative product
for shutting things down.
I don't think there is much controversy over the method of opening a B
lead connection for an internal VR alternator. We seem to know that a
standard $15. battery contactor is simply not guranteed to do this
reliably as the voltage may climb way above 12 volts and cause contact
arcing.
I'm sticking with the crowbar and the advantage of feedback on its
performance from other list members. So far I have yet to purchase an
aviation related electronic device that hasn't required modification,
repair, or information in addition to what the manufacturer provided so
I put a high value on understanding what I use and feedback from this list.
Ken
bakerocb@cox.net wrote:
>--> AeroElectric-List message posted by: <bakerocb@cox.net>
>
>AeroElectric-List message previously posted by: "Thomas Johnson"
><trj01@comcast.net>
>
><<.......skip....... There are really only two "lightning rod" issues
>here:
>
>1) Crowbar disconnect method VS other methods......skip.....>>
>
>7/31/2005
>
>Hello Tom, Thanks for your input. The term "crowbar disconnect method" has a
>dramatic, violent, attention getting, and definitive connotation to it, but
>it is completely non descriptive in terms of what is doing what to what.
>
>I'll bet there are dozens of readers just like me that don't know what the
>method actually consists of. Would you, or some other contributor, please
>just describe the method in simple layman's terms?
>
>I hesitate to suggest such a disruptive change in the use of a term that,
>through repitition, has become engraved in our consciousness, if not our
>understanding, but think of the value in increased understanding of using
>instead a phrase such as "the frammis on the whoosis" method.
>
>OC
>
>PS: And I really hate to nit pick here, but my layman's brain associates the
>term "crowbar method" as just an initiating or multiple step process that
>can lead to ending the undesired output of an alternator. To actually
>accomplish an alternator disconnect (opening the B lead), however,requires
>some additional, and apparently rather controversial, hardware.
>
>PPS: Deliberate or not, I like your "lightning rod" pun.
>
>
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> AeroElectric-List message posted by: "John Swartout" <jgswartout@earthlink.net>
OC, Jim Weir wrote a nice column explaining what a crowbar circuit does
and how to fashion one in the September '01 KITPLANES. If you don't
have the magazine, you can read the article here:
http://www.rst-engr.com/kitplanes/KP0109/KPtext.pdf
John
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
bakerocb@cox.net
Subject: AeroElectric-List: crowbar method
--> AeroElectric-List message posted by: <bakerocb@cox.net>
AeroElectric-List message previously posted by: "Thomas Johnson"
<trj01@comcast.net>
<<.......skip....... There are really only two "lightning rod" issues
here:
1) Crowbar disconnect method VS other methods......skip.....>>
7/31/2005
Hello Tom, Thanks for your input. The term "crowbar disconnect method"
has a
dramatic, violent, attention getting, and definitive connotation to it,
but
it is completely non descriptive in terms of what is doing what to what.
I'll bet there are dozens of readers just like me that don't know what
the
method actually consists of. Would you, or some other contributor,
please
just describe the method in simple layman's terms?
I hesitate to suggest such a disruptive change in the use of a term
that,
through repitition, has become engraved in our consciousness, if not our
understanding, but think of the value in increased understanding of
using
instead a phrase such as "the frammis on the whoosis" method.
OC
PS: And I really hate to nit pick here, but my layman's brain associates
the
term "crowbar method" as just an initiating or multiple step process
that
can lead to ending the undesired output of an alternator. To actually
accomplish an alternator disconnect (opening the B lead),
however,requires
some additional, and apparently rather controversial, hardware.
PPS: Deliberate or not, I like your "lightning rod" pun.
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | traffic scope antenna |
--> AeroElectric-List message posted by: rd2@evenlink.com
Surecheck's "traffic scope", portable; uses a short rubber stub; can use
any x-ponder/dme antenna
Rumen
_____________________Original message __________________________
(received from Chuck Jensen; Date: 12:22 PM 7/31/2005
-0400)
--> AeroElectric-List message posted by: "Chuck Jensen" <cjensen@dts9000.com>
What kind of traffic scope did you buy? If it's a Ryan TCAS, which uses
3 sharkfin antennas, there's no choice but to use theirs. Other brands
may vary.
Chuck
Do Not Archive
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
rd2@evenlink.com
Subject: AeroElectric-List: traffic scope antenna
--> AeroElectric-List message posted by: rd2@evenlink.com
Hi all,
For a recently purchased traffic scope I would like to install a fixed
antenna.
The airplane already has 2 shark fin antennae (one for the transponder
and
one for the DME).
1) Does anyone have a good source of shark fins (meaning good price and
SWR)? I may have to replace one of the existing shark fins (coating
cracked) and add another for the traffic scope.
2) How far from the existing shark fins should I install the antenna for
the traffic scope? Any possible interference (e.g. from the DME?)
3) Is a less expensive solution appropriate (ebay monopole for $16.95 -
http://search.ebay.com/transponder-antenna_W0QQfkrZ1QQfromZR8) ?
Advantages/disadvantages of such monopole?
Rumen
Message 10
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>I'll take a stab at this. Crowbar just means that when the Overvoltage
trips the SCR, the SCR shorts out the power.( Kind of like throwing a
crowbar across the battery to short things out.) That immediately starts
dropping the voltage (a good thing) and the current flow through the CB
trips the CB to permanently shutdown the alternator.
Correct. However, the circuit breaker is not rated for this abuse. Nor is
adding a small resistor to bring the currents down simple (see earlier
posts), since pulse resistors are a special breed.
>The SCR causes a significant momentary current flow or pulse from the
battery through the CB. There have been some (unsubstantiated in my
opinion) allegations that it could be harmful in vague ways.
Unsubstantiated allegations? The circuit breaker is not rated for the
current. It is the designer's responsibilty to make sure the design meets
the requirement. To use the term "unsubstantiated allegations" seems very
strange when discussing merely technical performance. The "allegations" are
very much substantiated. The circuit breaker won't do the job. Look it up.
>No circuitry to do this any other way has been presented by anyone here as
>far as I know however one person here does sell an alternative product for
>shutting things down.<
I am that person. Since I sell a part called the Linear Over Voltage Module,
I don't want to release the schematic, but I will tell you it uses a LTC1696
available only in an SOT-23-6 package that is not suitable for most builders
to assemble. "Linear" (non-crowbar) OVPs aren't hard to design but they have
5 mosfets and 20 other parts. But the important point is that the LOVM just
cuts off the field current. This is the preferred method. Let me slop a
pearl....nobody has used a crowbar for this application in 30 years.
>I don't think there is much controversy over the method of opening a B lead
>connection for an internal VR alternator. We seem to know that a standard
>$15 battery contactor is simply not guranteed to do this reliably as the
>voltage may climb way above 12 volts and cause contact arcing.<
True. The Kilovac "Czonka III" EV200AAANA is the contactor that will do the
job and has a 100 mA coil as a bonus. (I have a few of these cheap if you
contact me offlist.)
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
"I tried being reasonable, I didn't like it."
---Clint Eastwood
Message 11
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
> --> AeroElectric-List message posted by: "Eric M. Jones"
> <emjones@charter.net>
>
> --> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>
>
>> I'll take a stab at this. Crowbar just means that when the
>> Overvoltage
>>
> trips the SCR, the SCR shorts out the power.( Kind of like throwing a
> crowbar across the battery to short things out.) That immediately
> starts
> dropping the voltage (a good thing) and the current flow through
> the CB
> trips the CB to permanently shutdown the alternator.
>
> Correct. However, the circuit breaker is not rated for this abuse.
> Nor is
> adding a small resistor to bring the currents down simple (see earlier
> posts), since pulse resistors are a special breed.
>
>
>> The SCR causes a significant momentary current flow or pulse from the
>>
> battery through the CB. There have been some (unsubstantiated in my
> opinion) allegations that it could be harmful in vague ways.
>
> Unsubstantiated allegations? The circuit breaker is not rated for the
> current. It is the designer's responsibilty to make sure the design
> meets
> the requirement. To use the term "unsubstantiated allegations"
> seems very
> strange when discussing merely technical performance. The
> "allegations" are
> very much substantiated. The circuit breaker won't do the job. Look
> it up.
>
>
The CB specs provide an envelope of conditions under which the CB
should perform as advertised, repeatedly - i.e. it will trip within a
certain time, at a certain tolerance to the advertised trip current.
But the spec sheet doesn't say what will happen if it is operated at
other conditions. It doesn't say how its performance will be
affected. So how do we know it won't do the job? Is there evidence
that it won't do the job, or is the statement "the circuit breaker
won't do the job" simply an unsubstantiated allegation?
I'd love to see the test results that show the CB in a crowbar OVP
won't do the job. Bob has described tests he has down that show the
CB will do the job, and the only complaints from the field seem to be
some installations that are prone to nuisance trips. The later
variants of the design are reputed to be less prone to nuisance trips.
If we operate the CB outside its rated current repeatedly, this could
possibly affect the current at which the CB will open. But, the
exact value at which it opens isn't important in this application.
Normally there is very little current through the CB. If there is an
overvoltage, and the OVP trips, there will be a very large current
though the CB. We only need the CB to differentiate between a very
small current, and a very large one. It doesn't matter exactly what
its trip point is.
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://www.kilohotel.com/rv8
Message 12
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
This is where we disagree I guess Eric.
Circuit breakers are used to interupt an overcurrent situation. My
opinion is that the most common overcurrent situation is a short
circuit. This is what circuit breakers do. If I didn't think a circuit
breaker was acceptable for this I wouldn't use them anywhere else either
as I'd have to replace the breaker every time it tripped and fuses are
cheaper in that case. Mine still seem to do the job after several dozen
OVM trips fed by modern AGM batteries...
Ken
>Unsubstantiated allegations? The circuit breaker is not rated for the
>current. It is the designer's responsibilty to make sure the design meets
>the requirement. To use the term "unsubstantiated allegations" seems very
>strange when discussing merely technical performance. The "allegations" are
>very much substantiated. The circuit breaker won't do the job. Look it up.
>
>
Message 13
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: Charlie England <ceengland@bellsouth.net>
Kevin Horton wrote:
>--> AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
>
>
>
>>--> AeroElectric-List message posted by: "Eric M. Jones"
>><emjones@charter.net>
>>
>>--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>>
>>
>>
>>
>>>I'll take a stab at this. Crowbar just means that when the
>>>Overvoltage
>>>
>>>
>>>
>>trips the SCR, the SCR shorts out the power.( Kind of like throwing a
>>crowbar across the battery to short things out.) That immediately
>>starts
>>dropping the voltage (a good thing) and the current flow through
>>the CB
>>trips the CB to permanently shutdown the alternator.
>>
>>Correct. However, the circuit breaker is not rated for this abuse.
>>Nor is
>>adding a small resistor to bring the currents down simple (see earlier
>>posts), since pulse resistors are a special breed.
>>
>>
>>
>>
>>>The SCR causes a significant momentary current flow or pulse from the
>>>
>>>
>>>
>>battery through the CB. There have been some (unsubstantiated in my
>>opinion) allegations that it could be harmful in vague ways.
>>
>>Unsubstantiated allegations? The circuit breaker is not rated for the
>>current. It is the designer's responsibilty to make sure the design
>>meets
>>the requirement. To use the term "unsubstantiated allegations"
>>seems very
>>strange when discussing merely technical performance. The
>>"allegations" are
>>very much substantiated. The circuit breaker won't do the job. Look
>>it up.
>>
>>
>>
>>
>
>The CB specs provide an envelope of conditions under which the CB
>should perform as advertised, repeatedly - i.e. it will trip within a
>certain time, at a certain tolerance to the advertised trip current.
>But the spec sheet doesn't say what will happen if it is operated at
>other conditions. It doesn't say how its performance will be
>affected. So how do we know it won't do the job? Is there evidence
>that it won't do the job, or is the statement "the circuit breaker
>won't do the job" simply an unsubstantiated allegation?
>
>I'd love to see the test results that show the CB in a crowbar OVP
>won't do the job. Bob has described tests he has down that show the
>CB will do the job, and the only complaints from the field seem to be
>some installations that are prone to nuisance trips. The later
>variants of the design are reputed to be less prone to nuisance trips.
>
>If we operate the CB outside its rated current repeatedly, this could
>possibly affect the current at which the CB will open. But, the
>exact value at which it opens isn't important in this application.
>Normally there is very little current through the CB. If there is an
>overvoltage, and the OVP trips, there will be a very large current
>though the CB. We only need the CB to differentiate between a very
>small current, and a very large one. It doesn't matter exactly what
>its trip point is.
>
>Kevin Horton RV-8 (finishing kit)
>Ottawa, Canada
>http://www.kilohotel.com/rv8
>
Others have posted on this topic who can speak with much more authority
than I, but it seems to me that saying that a breaker isn't designed to
open a circuit when there's a short flies in the face of all logic. It
seems to me, that's why it's there in the 1st place. It isn't there to
protect some device from moderate over-current; the mfgr of the device
has the responsibility to do that. The breaker is there to protect
downstream wire from melting/burning in the case of gross over-current
conditions (shorts). Would anyone maintain that we should go find some
high tech alternative for our house breakers because they aren't
designed to open the circuit if someone shorts out a circuit by
accidentally cutting into a lamp cord with a pair of scissors?
Aren't the crowbar circuits being discussed designed to short across the
supply to the field winding of the alternator? Following the 'not
designed for the job' argument, is another solution needed for a
traditional alternator field breaker in its traditional role considering
that a wire between the breaker & the alternator might inadvertently rub
against the chassis somewhere & short to ground? If the breaker is
unsuitable for a crowbar circuit, it is just as unsuitable to open the
same circuit if there is an insulation failure on the wire & it touches
a grounded portion of the airframe.
I haven't seen anyone say that repeated trips of the breaker due to hard
shorts is a good thing. Most breakers aren't designed for high cycling
counts; they are just there to protect against the (hopefully) rare
catastrophic event. If there is repeated cycling, the problem needs to
be fixed, not designed around with some high tech circuit. If I have
hundreds of trip events of a circuit breaker & it eventually fails to
protect the circuit, I'm probably getting what I deserve. On the other
hand, if it won't protect against at least a few catastrophic short
events over the life of the a/c, I've wasted my money on that
high-dollar breaker.
Charlie
no technical degrees after my name but a career in consumer & industrial
electronics maintenance behind me
Message 14
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>This is where we disagree I guess Eric.
Circuit breakers are used to interupt an overcurrent situation. My
opinion is that the most common overcurrent situation is a short
circuit. This is what circuit breakers do. If I didn't think a circuit
breaker was acceptable for this I wouldn't use them anywhere else either
as I'd have to replace the breaker every time it tripped and fuses are
cheaper in that case. Mine still seem to do the job after several dozen
OVM trips fed by modern AGM batteries...Ken
Nothing is as simple as it seems. The manufacturers publish specificatons on
what their products are rated to do. But even in the most simple situations
it is just plain wrong to think you can stretch the limits. Maybe you can
get away with it once or twice--but as a design, it is always a mistake to
think you know better than the manufacturer. After all the manufacture would
LOVE to find out their parts work above their design--that their Buna-N
Orings operate at 40 degrees F. It's money in the bank for them. And even
then you risk the manufacturer's right to modify the device while remaining
inside her specifications. This is a common engineer's trap. There are
ALWAYS free-floating specs that the manufacurer won't guarantee. In this
case, the tests haven't been done and the parts aren't specified to do the
job.
If a circuit breaker is called upon to interrupt a current above its
designed rating (volts, amps, temp, time, etc.), the contacts can weld, the
mechanism can blow apart, the materials can change properties, the spacings
may be inadequate, the repeat characteristics can change. Furthermore it is
up to the designer to show the design is right. Even in the case where a new
design requires testing--the tests have to be done and documented.
These alligators....are substantial.
--> AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
>The CB specs provide an envelope of conditions under which the CB
should perform as advertised, repeatedly - i.e. it will trip within a
certain time, at a certain tolerance to the advertised trip current.
But the spec sheet doesn't say what will happen if it is operated at
other conditions. It doesn't say how its performance will be
affected. So how do we know it won't do the job? Is there evidence
that it won't do the job, or is the statement "the circuit breaker
won't do the job" simply an unsubstantiated allegation?
"So how do we know it won't do the job?" We don't. But it's a silly
question to ask. Think about it. Okay, maybe it WILL do the job. Maybe.
>I'd love to see the test results that show the CB in a crowbar OVP
won't do the job. Bob has described tests he has down that show the
CB will do the job, and the only complaints from the field seem to be
some installations that are prone to nuisance trips. The later
variants of the design are reputed to be less prone to nuisance trips.
Paul Messinger has data on the crowbar OVP showing adequate current to trash
the CB. ....but he also has a burr under his saddle. And a stone in his
boot. But he makes the good point and I agree, that it is not up to anybody
else to show the crowbar/CB is suited for the job. That's not how science
works. So don't be too annoyed that he doesn't want to finish the report.
>If we operate the CB outside its rated current repeatedly, this could
possibly affect the current at which the CB will open. But, the
exact value at which it opens isn't important in this application.
Normally there is very little current through the CB. If there is an
overvoltage, and the OVP trips, there will be a very large current
though the CB. We only need the CB to differentiate between a very
small current, and a very large one. It doesn't matter exactly what
its trip point is. Kevin Horton
Kevin...Maybe, but what if you designed this into a real airplane?
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
"The man who carries a cat by the tail learns something that can be learned
in no other way."
- Mark Twain
Message 15
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: Charlie England
ceengland@bellsouth.net
>>Others have posted on this topic who can speak with much more authority
than I, but it seems to me that saying that a breaker isn't designed to
open a circuit when there's a short flies in the face of all logic. It
seems to me, that's why it's there in the 1st place. It isn't there to
protect some device from moderate over-current; the mfgr of the device
has the responsibility to do that. The breaker is there to protect
downstream wire from melting/burning in the case of gross over-current
conditions (shorts). Would anyone maintain that we should go find some
high tech alternative for our house breakers because they aren't
designed to open the circuit if someone shorts out a circuit by
accidentally cutting into a lamp cord with a pair of scissors?
Charlie--A short circuit can produce high currents limited only by the
circuit impedance. This impedance can be very very low. That's the problem.
At 14.5 volts, a short of 0.001 ohms is 14500 amps. Of course your 5A
circuit breaker would emit gamma rays at this current. (I'm not kidding).
Lucky for us, in the real world the circuit breaker will probably not have
to handle such a current, but the crowbar/CB combination WILL suffer damage
as currently designed. Bob and Paul argued the exact current---but in
summary it depends on where the battery is and what the battery is.
>>Aren't the crowbar circuits being discussed designed to short across the
supply to the field winding of the alternator? Following the 'not
designed for the job' argument, is another solution needed for a
traditional alternator field breaker in its traditional role considering
that a wire between the breaker & the alternator might inadvertently rub
against the chassis somewhere & short to ground? If the breaker is
unsuitable for a crowbar circuit, it is just as unsuitable to open the
same circuit if there is an insulation failure on the wire & it touches
a grounded portion of the airframe.
Negatory, the normal length of wire between the CB and the alternator or
regulator will reduce the current by resistance and inductance a little bit,
and that is enough to allow the 5A breaker to work as designed. In the case
of the OVP/CB, this grounding can be a very large current. (but it depends
on layout....). Also real short circuits are rarely "slammed down hard to
ground".
>>I haven't seen anyone say that repeated trips of the breaker due to hard
shorts is a good thing. Most breakers aren't designed for high cycling
counts; they are just there to protect against the (hopefully) rare
catastrophic event. If there is repeated cycling, the problem needs to
be fixed, not designed around with some high tech circuit. If I have
hundreds of trip events of a circuit breaker & it eventually fails to
protect the circuit, I'm probably getting what I deserve. On the other
hand, if it won't protect against at least a few catastrophic short
events over the life of the a/c, I've wasted my money on that
high-dollar breaker.
Correcto. And since breakers don't have "History Recorders" on them, it's
hard to know. Even the first trip can be a problem operated outside of the
manufacturers specs. Maybe you'll get lucky. Or maybe you'll be in
Huatabampo Mexico (a very nice town, but not many replacement parts).
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
Message 16
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Paul M. has risen from the dead |
again!
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
again!
<snip>
>Geez, I see that "Pope Paul M." is once again pontificating. Lord! why
>can't he be excommunicated?
>
>Peter Van Caulart
Folks, I really would like to focus on simple-ideas, repeatable
experiments and to encourage any honorable action that helps
move our craft forward. This kind of response adds nothing
useful to anyone's experience.
I've had a ton of flack from a few who want this discussion
"moved off list" or "burried" etc. etc.
I've encourage folks who are upset by the discussion to
please not read it. There's another group of folks who need
the list deal with "where to I buy" and "how do I hook up"
kinds of questions. For those folks too, I would encourage
you to use the delete key.
For those who are interested in learning how logic, simple-ideas,
and cooperative design review can filter the BS and suggest
ways to make your airplane work better, cost less and be
easier to repair, then keep a finger on the pulse of things.
But if any part of it upsets you for any reason other a
proffering of bad science or a demonstration of bad behavior,
then please don't read it.
Life is too short and your airplane project is taking
too long, you don't need more aggravation. Don't for
a moment think that I'm one bit tense over these discussions.
When I'm tense, I'll make it known and describe the exact
reason why.
Unless you have some specific questions and/or contribution
to the discussions, please don't throw more cabbages and
tomatoes. It doesn't help.
Thanks!
Bob . . .
Message 17
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: I've got a secret |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 11:09 PM 7/29/2005 -0700, you wrote:
>--> AeroElectric-List message posted by: Richard Riley <richard@riley.net>
>
>If you think that's hateful, you must be new to the internet.
>
>Are you capable of summing up this amazingly useless, endless thread
>in one paragraph? Like
>
>The problem is X
>It can occur when using equipment Y, under the following conditions -
>If you use equipment Z instead, it won't happen.
>
>I appreciate the free ice cream that Bob delivers here. It's not
>always my favorite flavor, but it's still free. (That's a metaphor, BTW)
Gentlemen, please. If you're not a participant in seeking solutions,
please don't be part of an unrelated problem. Nobody is guaranteed
an insult free existence . . . but keep in mind that one can only
be insulted if you give someone permission to do it!
Bob . . .
Message 18
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: crowbar method |
--> AeroElectric-List message posted by: Charlie England <ceengland@bellsouth.net>
Eric M. Jones wrote:
>--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
>
>--> AeroElectric-List message posted by: Charlie England
>ceengland@bellsouth.net
>
>
>
>>>Others have posted on this topic who can speak with much more authority
>>>
>>>
>than I, but it seems to me that saying that a breaker isn't designed to
>open a circuit when there's a short flies in the face of all logic. It
>seems to me, that's why it's there in the 1st place. It isn't there to
>protect some device from moderate over-current; the mfgr of the device
>has the responsibility to do that. The breaker is there to protect
>downstream wire from melting/burning in the case of gross over-current
>conditions (shorts). Would anyone maintain that we should go find some
>high tech alternative for our house breakers because they aren't
>designed to open the circuit if someone shorts out a circuit by
>accidentally cutting into a lamp cord with a pair of scissors?
>
>Charlie--A short circuit can produce high currents limited only by the
>circuit impedance. This impedance can be very very low. That's the problem.
>At 14.5 volts, a short of 0.001 ohms is 14500 amps. Of course your 5A
>circuit breaker would emit gamma rays at this current. (I'm not kidding).
>Lucky for us, in the real world the circuit breaker will probably not have
>to handle such a current, but the crowbar/CB combination WILL suffer damage
>as currently designed. Bob and Paul argued the exact current---but in
>summary it depends on where the battery is and what the battery is.
>
>
>
>>>Aren't the crowbar circuits being discussed designed to short across the
>>>
>>>
>supply to the field winding of the alternator? Following the 'not
>designed for the job' argument, is another solution needed for a
>traditional alternator field breaker in its traditional role considering
>that a wire between the breaker & the alternator might inadvertently rub
>against the chassis somewhere & short to ground? If the breaker is
>unsuitable for a crowbar circuit, it is just as unsuitable to open the
>same circuit if there is an insulation failure on the wire & it touches
>a grounded portion of the airframe.
>
>Negatory, the normal length of wire between the CB and the alternator or
>regulator will reduce the current by resistance and inductance a little bit,
>and that is enough to allow the 5A breaker to work as designed. In the case
>of the OVP/CB, this grounding can be a very large current. (but it depends
>on layout....). Also real short circuits are rarely "slammed down hard to
>ground".
>
>
>
>>>I haven't seen anyone say that repeated trips of the breaker due to hard
>>>
>>>
>shorts is a good thing. Most breakers aren't designed for high cycling
>counts; they are just there to protect against the (hopefully) rare
>catastrophic event. If there is repeated cycling, the problem needs to
>be fixed, not designed around with some high tech circuit. If I have
>hundreds of trip events of a circuit breaker & it eventually fails to
>protect the circuit, I'm probably getting what I deserve. On the other
>hand, if it won't protect against at least a few catastrophic short
>events over the life of the a/c, I've wasted my money on that
>high-dollar breaker.
>
>Correcto. And since breakers don't have "History Recorders" on them, it's
>hard to know. Even the first trip can be a problem operated outside of the
>manufacturers specs. Maybe you'll get lucky. Or maybe you'll be in
>Huatabampo Mexico (a very nice town, but not many replacement parts).
>
>Regards,
>Eric M. Jones
>www.PerihelionDesign.com
>113 Brentwood Drive
>Southbridge MA 01550-2705
>(508) 764-2072
>
But Eric, if the crowbar is after the alternator field breaker, all the
wire between the battery & the breaker & load mentioned in your argument
is still there (or not there). If the breaker is in danger from the
crowbar, it follows that it is in danger from an inadvertent short
circuit. Yet alternator field circuit breakers seem to have survived as
a design since the dawn of alternators in a/c.
(If I could be convinced that this 'slam down' technique really is
dangerous, why do I need dozens of extra components to solve the
problem? Why not just use one of those gadgets with inverse temperature
coefficient used to soft start incandescent lamps <sorry; I forget the
name of the device> in series with the crowbar?)
Charlie
Message 19
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Diode orientation |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 10:20 AM 7/30/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: Charlie Brame <chasb@satx.rr.com>
>
>Bob, et al,
>
>My Navaid installation manual recommends a diode between the Navaid pin
>7 and the Comm PTT circuit. The Navaid schematic shows a black and white
>diode with a large white area and a small black stipe on one end. The
>white area is oriented toward the Comm unit and the black stripe
>oriented toward the PTT circuit. However, the diode I received from B&C
>is mostly black with a small grey stripe at one end.
>
>Can I assume that the large black end of the diode equates to the large
>white end on the Navaid schematic?
The descriptions you're making for the parts and wiring
diagram are don't give us a clear image of the instructions.
Most wire lead diodes have a "band" on one end and the color
of the band is insignificant. It will be some color that
contrasts with the body color of the diode itself.
The banded end corresponds to the "cathode". In a diode's
schematic, the "bar" touched by the arrowhead is the
cathode while the arrowhead itself is the anode. Electrons
flow through a diode in opposition to direction of arrow.
See:
http://www.aeroelectric.com/Pictures/Diode_Wiring_2.jpg
Some folks are confused when they see diodes used for two
different tasks like "steering" as shown in -A- and -B-
and spike clipping as shown in -C- and -D-.
Do you have a real schematic of the wiring were the
bar and arrowhead are seen in the classic diode symbol
. . . or is it a comic book wiring diagram that shows
only pictures? Sounds like you're working with the latter.
In this case, go by which end has a band on it irrespective
of color. Do they say what this diode is supposed to do?
I'm mystified by the need hook any part of your comm transceiver
to the autopilot.
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|