Today's Message Index:
----------------------
1. 03:53 AM - LED light bar annunciator panel? (Kevin Horton)
2. 05:10 AM - Re: AeroElectric-List Digest: 29 Msgs - 02/09/04 (BFV25@aol.com)
3. 05:27 AM - Re: Compass shielding (Bruce Gray)
4. 05:39 AM - Re: Capacitive Fuel Gauges (Mark Steitle)
5. 05:56 AM - Re: Compass shielding (Robert L. Nuckolls, III)
6. 06:03 AM - Re: Load dump protection (Gary Casey)
7. 06:08 AM - Re: Compass shielding (Dale Martin)
8. 06:08 AM - Re: Capacitive Fuel Gauges (Robert L. Nuckolls, III)
9. 06:10 AM - Re: Re: AeroElectric-List Digest: 29 Msgs - (Robert L. Nuckolls, III)
10. 06:11 AM - Re: battery / alternator switch (Robert L. Nuckolls, III)
11. 06:19 AM - Re:Re: For Bob, Comment? (Robert L. Nuckolls, III)
12. 06:27 AM - Re: battery / alternator switch (Robert L. Nuckolls, III)
13. 06:29 AM - Re: Battery Charger (Robert L. Nuckolls, III)
14. 06:36 AM - Re: 11153 Santerre (Robert L. Nuckolls, III)
15. 06:37 AM - Re: LED light bar annunciator panel? (Dave Morris)
16. 06:47 AM - Re: AeroElectric-List Digest: 29 Msgs - 02/09/04 (Speedy11@aol.com)
17. 07:30 AM - Re: LED light bar annunciator panel? (John Schroeder)
18. 07:31 AM - Re: Mag/E.I. switches (Dale Martin)
19. 07:46 AM - Re: Re: Load dump protection (Paul Messinger)
20. 07:46 AM - Re: Load dump issues (Robert L. Nuckolls, III)
21. 07:54 AM - Re: Compass shielding (Jerzy Krasinski)
22. 07:54 AM - Re: Re: AeroElectric-List Digest: 29 Msgs - 02/09/04 (Dale Martin)
23. 09:42 AM - Re: Capacitive Fuel Gauges (Mark Steitle)
24. 10:15 AM - Determining Speaker Requirements (Charles Brame)
25. 10:37 AM - Re: LED light bar annunciator panel? (Fiveonepw@aol.com)
26. 10:38 AM - Rotary Spreadsheet (Ed Anderson)
27. 11:15 AM - Re: Determining Speaker Requirements (Richard Tasker)
28. 11:35 AM - Re: Rotary Spreadsheet (Ed Anderson)
29. 12:01 PM - Re: Z12 e-bus questions (Robert L. Nuckolls, III)
30. 12:03 PM - Re: LED light bar annunciator panel? (Jeffrey W. Skiba)
31. 12:18 PM - Re: For Bob, Comment? (Robert L. Nuckolls, III)
32. 12:34 PM - Re: Determining Speaker Requirements (Charlie & Tupper England)
33. 12:39 PM - Re: Load dump protection (Robert L. Nuckolls, III)
34. 01:06 PM - Dynon and EMI (Jeff Point)
35. 01:40 PM - Re: Re: Load dump protection (Dj Merrill)
36. 02:15 PM - Re: Dynon and EMI (Dale Martin)
37. 07:44 PM - Compass shielding (hollandm)
38. 08:50 PM - Re: Z12 e-bus questions (f1rocket@telus.net)
39. 10:13 PM - Re: Compass shielding (Jerzy Krasinski)
40. 10:18 PM - Re: Compass shielding (Bruce Gray)
41. 11:16 PM - Re: Load dump issues (Paul Messinger)
42. 11:20 PM - Load dump protection (Paul Messinger)
43. 11:20 PM - Re: Load dump issues (Paul Messinger)
Message 1
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| Subject: | LED light bar annunciator panel? |
--> AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
I'm seriously considering manufacturing a small annunciator panel
from Stanley LED light bars. These are the ones with part numbers
like MU04-2101 sold by Digikey, etc. I am wondering what options I
would have to put legends on the face of the light bars. What looks
good and lasts a long time? I am also looking for ideas on how to
package the resistors, etc needed to limit the current. Does anyone
have any pictures they could point me too?
Thanks,
--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
Message 2
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| Subject: | Re: AeroElectric-List Digest: 29 Msgs - 02/09/04 |
--> AeroElectric-List message posted by: BFV25@aol.com
Please remove me for your mail list
bfv25@aol.com
Message 3
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| Subject: | Compass shielding |
--> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
If you shield the compass it will no longer be a compass. It has to be
able to sense the magnetic fields.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
hollandm
Subject: AeroElectric-List: Compass shielding
--> AeroElectric-List message posted by: "hollandm"
<hollandm@pacbell.net>
I'm getting interference between an electric turn coordinator and a
compass (about 2 degrees). Before I start moving things around I was
wondering if it would be possible to shield the compass by surrounding
it with some copper screening or the like, sort of mu-metal chamber
approach.
Has anyone tried this and if so did it work?
Thanks
==
==
==
==
Message 4
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| Subject: | Re: Capacitive Fuel Gauges |
--> AeroElectric-List message posted by: Mark Steitle <msteitle@mail.utexas.edu>
At 09:06 PM 2/9/2004 -0600, you wrote:
>--> AeroElectric-List message posted by: Jerzy Krasinski
><krasinski@direcway.com>
>
>I messed around with Jim Weir circuit, but finally I gave up and I made
>it using a circuit commonly used as a converter changing volmeter into
>capacitance meter. Such a circuit is much simpler, it uses a popular
>double timer (556?) and an op amp. Capacitance of my 1 yard long probes
>made of 1/2 and 1/4 tubes is around 114 pF, which I measured by a
>digital multimeter as well as by substitution of the probe by a capacitor.
Jerzy,
So I would guess that my 6 ft. fuel probe, being twice the length of your 3
ft probe, would have roughly twice the capacitance?
Which Jim Weir circuit did you build, early or late version? A friend
built an early version and got it working, but we had mixed results when we
substituted my probe for his aluminum plate capacitor. As a result, I
thought I might try building one of the Rev. 2 circuits. I would have to
search around for someone with a dual-trace scope to help me adjust/tune
the circuit. Nice thing about the Rev. 2 design is the integrated low fuel
warning light & buzzer.
Do you have any pictures of your design? Or, would you be willing to share
the schematic?
Thanks,
Mark S.
Message 5
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| Subject: | Compass shielding |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:26 AM 2/10/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
>
>If you shield the compass it will no longer be a compass. It has to be
>able to sense the magnetic fields.
>
>Bruce
>www.glasair.org
>
>
>-----Original Message-----
>From: owner-aeroelectric-list-server@matronics.com
>[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
>hollandm
>To: aeroelectric-list@matronics.com
>Subject: AeroElectric-List: Compass shielding
>
>
>--> AeroElectric-List message posted by: "hollandm"
><hollandm@pacbell.net>
>
>I'm getting interference between an electric turn coordinator and a
>compass (about 2 degrees). Before I start moving things around I was
>wondering if it would be possible to shield the compass by surrounding
>it with some copper screening or the like, sort of mu-metal chamber
>approach.
>
>Has anyone tried this and if so did it work?
>
>Thanks
Don't shield the victim, shield the antagonist. Cut a strip
of galvanized flashing metal from the lumber yard
so as to wrap around the t/c about 3 times. Secure
in place with tye-wraps, aluminum tape, string, etc.
I believe this has worked for a number of builders.
Let us know how it does for you.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 6
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| Subject: | RE: Load dump protection |
--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<This effort was unsuccessful (at the time) as this is not an issue with
autos, as in
autos the "B" lead is always directly wired to the battery. Thus there is no
"switch" to be accidentally opened to cause load dump action. Also there is
no OVP included as its rare and not a concern in the auto mfgrs mind. At
least a couple of years ago I was unable to find ANY auto mfgr alternator
that protected against load dump...I do not understand the need for
additional testing in this case. The
Boaters have long since solved the problem and so why are we still
investigating it??>>
Load dump protection in autos is still a real thing. There is a "switch"
between the alternator and the battery and it is the battery terminal
itself. The worst case, that is mostly worried about by boat manufacturers,
is a loose connection on the battery terminal that vibrates, repeatedly
opening and closing. The electronics builders for boats find that it has
not been "solved" as you imply, but is almost a normal situation. The usual
scenario is that the boater stores his boat over the winter, then finds the
battery is dead. He removes the battery and charges it for 10 minutes (the
family is waiting) and then puts it in the boat and just pushes the battery
cable on. The loose cable vibrates, the battery is accepting maximum charge
and the voltage transients are incredible - and repeated many times a
second. Also, the battery doesn't have to be disconnected to have a load
dump. Any time a large load is shut off the alternator has to instantly
reduce its output, which it can't do because of the inductance of the field
windings. Of course, having the battery there tames the load dump to a very
manageable amplitude.
Gary Casey
Message 7
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| Subject: | Re: Compass shielding |
--> AeroElectric-List message posted by: "Dale Martin" <niceez@cableone.net>
mount it 8 to 10 inches from any electrical current.
Dale Martin
Lewiston, ID
LEZ-235
----- Original Message -----
From: "Bruce Gray" <Bruce@glasair.org>
Subject: RE: AeroElectric-List: Compass shielding
> --> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
>
> If you shield the compass it will no longer be a compass. It has to be
> able to sense the magnetic fields.
>
> Bruce
> www.glasair.org
>
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> hollandm
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Compass shielding
>
>
> --> AeroElectric-List message posted by: "hollandm"
> <hollandm@pacbell.net>
>
> I'm getting interference between an electric turn coordinator and a
> compass (about 2 degrees). Before I start moving things around I was
> wondering if it would be possible to shield the compass by surrounding
> it with some copper screening or the like, sort of mu-metal chamber
> approach.
>
> Has anyone tried this and if so did it work?
>
> Thanks
>
>
> ==
> ==
> ==
> ==
>
>
Message 8
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| Subject: | Re: Capacitive Fuel Gauges |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 01:37 PM 2/9/2004 -0600, you wrote:
>--> AeroElectric-List message posted by: Mark Steitle
><msteitle@mail.utexas.edu>
>
>Bob,
>I have a pair of 6 ft. Electronics International tube type capacitive fuel
>level probes and would like to build my own fuel level circuit(s) to use
>with these senders. I have a Westach 0-5v dual fuel gauge that I would
>also like to use. A series of articles were printed in Kitplanes magazine
>in mid 2000 describing how to build a CD type circuit
>(http://www.rst-engr.com/kitplanes/index.htm), but it used two flat plates
>as the sender. Do you know if the "Jim Weir" capacitive fuel level design
>should work with these probes. Is there an easy way to determine the
>capacitance of these probes?
>
>Thank you for sharing your knowledge and wisdom with the OBAM community.
>Mark S.
The length of your probe is only part of the equation. Jim's
circuitry is designed to work with a specific change in capacitance
from some total to indicate empty to full. E.g., the probe may have
a range of 150 uF empty to 1000 pF full. You might have a coax connecing
the probe to the electronics that adds another 100 pF. So, the electronics
needs adjusting such that empty is 250 pF and full is 1100 pF.
So, if you have a probe you like and a piece of shielded wire
picked to connect probe to electronics, the task is to mate the
electronics to the probe/cable combination. Jim's schematic includes
empty and full adjust pots. What you need to know is how close
the probe you have comes to the one Jim describes. His circuit
CAN be made to work with about ANY probe.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 9
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| Subject: | Re: AeroElectric-List Digest: 29 Msgs - |
02/09/04
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
02/09/04
At 08:09 AM 2/10/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: BFV25@aol.com
>
>Please remove me for your mail list
>bfv25@aol.com
You need to go to the UN/SUBSCRIBE address cited below
where you can do it yourself.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 10
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| Subject: | Re: battery / alternator switch |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 07:28 PM 2/9/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: "Dale Martin" <niceez@cableone.net>
>
>Seems like Wayne Blackler has one with the tabs coming off in his tool box.
>Each to his own I guess.
>
>Dale Martin
>Lewiston, ID
>LEZ-235
Has he done anything about it? If B&C doesn't want it
back, I'd sure like to see it.
Bob . . .
>----- Original Message -----
>From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>To: <aeroelectric-list@matronics.com>
>Subject: Re: AeroElectric-List: battery / alternator switch
>
>
> > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
><bob.nuckolls@cox.net>
> >
> > At 11:54 AM 2/9/2004 -0800, you wrote:
> > >--> AeroElectric-List message posted by: "Dale Martin"
><niceez@cableone.net>
> > >
> > >Bob asks,
> > >
> > > >One thing I found amazing is how many different places I had ground
>wires
> > > >terminating. I built my own ground bus only because the ones from B&C
>do
> > > >not appear to be mechanically attached to the brass . . .
> > >
> > > How so?
> > >
> > >Mine are riveted on and then soldered. It is the type of -push on
>tabs -two
> > >way, usually found on Terminal blocks (two holes instead of one) to
>connect
> > >female 1/4" push-on connecters.
> > >
> > >I have attached two Jpeg pictures.
> >
> > Attachments don't get forwarded through the list
> > but that's okay. Rivets are fine too but let's take
> > care lest folks begin to worry about solder as a structural
> > material. With a tensile strength on the order of 3Kpsi or
> > better, likelihood of anyone pulling the fast-on tabs from
> > their B&C fabricated ground bus is very remote.
> >
> > Bob . . .
> >
> >
>
>
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 11
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| Subject: | Re: For Bob, Comment? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 04:35 PM 2/9/2004 -0600, you wrote:
>--> AeroElectric-List message posted by: "buck"
><buckaroo_banzai@the-pentagon.com>
>
>Quite often, the installers of a STC system try to take advantage of what's
>already in the aircraft without fully realizing that they may be
>circumventing the intent of the aircraft manufacturer. It's amazing that
>the FAA and JAA are willing to grant the STC at all!
STC's generally cannot be grand-fathered to other airframes.
STC is exactly what the acronym implies . . . SUPPLEMENT
to a TYPE CERTIFICATE. These are not used as plug-n-play
across a range of aircraft.
STC is EXACTLY what those-who-know-more-about-airplanes-than-
we-do like. Treat every installation like it's never been done
before and test the hell out of it. This keeps those who
don't understand what's happening from having to think or
learn anything. It makes sure that some wheels get invented
over and over again. The STC route is relatively low risk
but also expensive because common sense approaches are
neither encouraged or allowed. Everyone is expected to
read and respond to a rule book. Whether or not he/she
understands the system to which the rules are applied
no longer matters.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 12
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| Subject: | Re: battery / alternator switch |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 10:57 AM 2/9/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: "Dale Martin" <niceez@cableone.net>
>
>Bob says,
> > Do you have a vacuum pump pad with nothing mounted on it?
> > For $300 and 4 pounds you can have a SECOND engine driven
> > power source.
> >
> > Bob . . .
>
>I think you mean a Third source. (Battery =1, Alt =2, Second Alt = 3)
>I like the fact that I get 4 horsepower back at cruise RPM that the Vacuum
>pump stole.
Yes, third system source but only the second engine-driven power source.
> > Are you going to 14v or staying 28v?
>
>I will keep 28 v due to the wire size I use are smaller and paid for! And
>have a second full size Alternator on the shelf.
>But to your credit I did consider it but..... then would have to change the
>starter, Alt, Nav-Com 1, landing light, strobe power unit and all the bulbs
>not to mention the LR3. Your talking over $2000 bucks and accepting peanuts
>for some of the equipment I have now.
Understand.
>BTW, I have always started the engine with the Alt off.
Doesn't hurt, but with a well maintained RG battery, probably
has no benefit other than to delay onset of alternator activity.
One might argue that the pilot is watching for effects of the
current action . . . getting the engine started usually concentrates
on things like oil pressure. If the alternator comes up immediately
in a bad mood, it's not likely to be observed as soon as if the
pilot gets the engine started first and then turns on the alternator
while watching instrumentation unique to that activity.
>One thing I think is an error IMHO is not using separate Ignition Switches
>either Guarded or Locking toggle switch for magneto's and especially the
>older LSE electronic ignitions. When the LSE E.I. are turned on they fire
>all the plugs at once - Yikes ! May not be a good idea to do this at any
>RPM. If you were to bump on off in-flight and turn it back on... and it
>fired say 65 BTDC..... That would really mess things up. Klaus warned me
>about it.
I've heard a lot of concerns over the years about "accidental"
switch operation. It's an easy thing to hypothesize but equally
easy to arrange the panel to avoid it too. Hmmm . . . at ANY
RPM? What happens when you do ignition system checks by turning
them off and on one at a time to observe operation of each system
independently?
>On the alternator thread .......
>
>If the C/B on the LR3 field wire were pulled (engine running) is the Alt
>able to still send out power just not regulated? If it does, that is not
>good. I was taught without the field there is no power.
No, with an externally regulated alternator, pulling the field
supply breaker shuts the system down completely. This has always
been the architecture of choice . . . but we'll soon figure out
how to apply internally regulated alternators with equal degree
of comfort.
Bob . . .
Message 13
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| Subject: | Re: Battery Charger |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 11:30 AM 2/9/2004 -0600, you wrote:
>--> AeroElectric-List message posted by: "Ned Thomas" <315@cox.net>
>
>I am looking at buying a float charger for my 24volt spam can. This spam can
>has an always hot battery bus with the the ships clock on it. I was
>concerned about the following marketing statement as to whether it might
>harm the clock. Anyone care to comment?
>
>Thanks,
>Ned
>
> "High-frequency pulse breaks down sulphated crystals that prevent batteries
>from holding a full charge."
This is a battery maintainer combined with a "de-sulfater".
It should be just fine. It won't hurt your clock or anything
else in the airplane.
Bob . . .
Message 14
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| Subject: | Re: 11153 Santerre |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 03:39 AM 2/10/2004 +0000, you wrote:
>Below is the result of your inquiry. It was submitted by
>Kim Santerre (ksanterre@aol.com) on Monday, February 9, 2004 at 19:39:38
>
>Monday, February 9, 2004
>
>Kim Santerre
>
>,
>Email: ksanterre@aol.com
>Comments/Questions: Hi Bob:
>
>One of our Light Plane Maintenance Readers wants to know why starter and
>other high current solenoids seem to so badly designed. He said upon
>dissassembly it is obvious that only small points of the contact surface
>repeatedly contact and arc and subsequently have earlier failures than
>they should. Are there any sources of really good quality stuff. He has a
>Lancair. Thanks. Kim Santerre
The writer doesn't understand the physics of high
current, intermittent duty contacts. Virtually
EVERY automotive starter contactor uses the low
area very high pressure philosophy for making and
breaking current to the starter. Now, if he's
seeing poor contactor life, it may have to do with
issues outside the design of the contacts themselves.
This is very mature technology with thousands of
this style contactor flying in airplanes and millions
in ground based vehicles. His problems may have more
to do with WHO builds the contactor than with the
basic science that's supposed to make it work.
I will invite you to join us on the AeroElectric List
to continue this and similar discussions. It's useful to
share the information with as many folks as possible.
A further benefit can be realized with membership on
the list. There are lots of technically capable folks
on the list who can offer suggestions too. You can
join at . . .
http://www.matronics.com/subscribe/
Thanks!
Bob . . .
--------------------------------------------
( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
--------------------------------------------
Message 15
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| Subject: | Re: LED light bar annunciator panel? |
--> AeroElectric-List message posted by: Dave Morris <dave@davemorris.com>
You can have an entire annunciator panel built for you by Aircraft
Simulators.com
Take a look at this: http://www.aircraftsimulators.com/F16caution.html
They can furnish just the panel or also the LEDs and wiring.
Dave Morris
At 05:44 AM 2/10/2004, you wrote:
>--> AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
>
>I'm seriously considering manufacturing a small annunciator panel
>from Stanley LED light bars. These are the ones with part numbers
>like MU04-2101 sold by Digikey, etc. I am wondering what options I
>would have to put legends on the face of the light bars. What looks
>good and lasts a long time? I am also looking for ideas on how to
>package the resistors, etc needed to limit the current. Does anyone
>have any pictures they could point me too?
>
>Thanks,
>--
>Kevin Horton RV-8 (finishing kit)
>Ottawa, Canada
>http://go.phpwebhosting.com/~khorton/rv8/
>
>
Message 16
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| Subject: | Re: AeroElectric-List Digest: 29 Msgs - 02/09/04 |
--> AeroElectric-List message posted by: Speedy11@aol.com
In a message dated 2/10/04 2:56:55 AM Eastern Standard Time,
aeroelectric-list-digest@matronics.com writes:
<< For $300 and 4 pounds you can have a SECOND engine driven
> power source.
>
> Bob . . .
I think you mean a Third source. (Battery =1, Alt =2, Second Alt = 3) >>
Key word is "engine-driven." It would be the second source and an important
one.
Stan
Message 17
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| Subject: | Re: LED light bar annunciator panel? |
--> AeroElectric-List message posted by: John Schroeder <jschroeder@perigee.net>
Kevin -
Drop Mark Phillips an email. He has a great design for a panel and used
these LED's in his annunciator panel. We plan to use them too, but are not
sure how to do the lettering. There is an outfit that will custom-make a
backlit plexi panel. If we can get it a little more customized, we may go
that route.
Mark: Mark Phillips <ripsteel@edge.net>
Backlit panels: http://www.aircraftsimulators.com/products.html
Cheers,
John
Message 18
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| Subject: | Re: Mag/E.I. switches |
--> AeroElectric-List message posted by: "Dale Martin" <niceez@cableone.net>
> Hmmm . . . at ANY
> RPM? What happens when you do ignition system checks by turning
> them off and on one at a time to observe operation of each system
> independently?
At low RPM (Below 1700) it doesn't seem to effect it. Besides, if you turn
off the magneto to check the E.I.& plugs and turn it back on there is little
sense in turning off the E.I. system when you see the RPM increase when the
magneto is switched on. If the magneto side is fouling plugs running them
is a way to "hopefully" clean an dismiss and carbon deposits. I usually
turn off the E.I. system at 1000 rpm only for a moment and right back on
just after start up. A smooth idle verify's the magneto plugs are firing
and at run-up the mag is switched of to check the amount of RPM drop.
In reality were checking not only magneto operations but just as much
sparkplug operation. With an E.I. system all your checking is plugs unless
you have a variable advance in which case you -Could- check that too.
Flying the same plane all the time allows a "feel" for engine smoothness and
EGT/CHT numbers then back up the feeling.
Those different shaped switches also make it easier to "feel" for the switch
whether light or dark. Electronics can do alot but they can fail at the
point of "when the engineer didn't think of that." I don't like to be
dependant on electronics 100%. They fail and can't adjust withoput adding
more weight to the system. When I fail - I usually loose a little weight
and hopefully I can adjust... And quickly :-))
Regards,
Dale Martin
Lewiston, ID
LEZ-235
Message 19
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| Subject: | Re: RE: Load dump protection |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
I agree that careless owners need protection. There is no way we can protect
against all loose or broken connections but we can add the simple and low
cost Diode (low cost in 'do it your self ' or $30 for a pre made up diode
with lugs attached). The loose/ broken connection is the first fault and our
designs should protect against that fault from causing additional damage
like the Alternator, or worse, avionics/engine systems etc. Thus boaters
have solved the problem but that requires action to impliment as you note.
However I was referring to the add on Load dump diode mentioned in an
earlier post (or the one I suggested that is already tested and qualified
for that purpose) . With that diode added there is protection against what
you say.
Currently that ""switch"" is the fault and that fault propagates to the
alternator and depending on the wiring design to the main electrical bus
etc. The Load Dump diode stops the propagation
There is a simple solution but as you say its not "stock". The designer(s)
need to research the issue and provide the external FIX NOT provided by
"off the shelf alternators". My point is acft have the same problem and the
same solution is available and has been for decades but has been overlooked
in most designs.
Load dump protection exists as an add on and why are we beating it to death
when there is an existing simple proven fix.
On a related subject I had a frayed starter cable (at the starter end so
hard to see). It finally broke and during starting sparked as the engine
torques. This was back before TVS was used on that auto. I destroyed 3
discrete electronic modules that were on the main battery bus from the HV
transients. NONE of the electronics modules that were on the accessory bus
were damaged as they were disconnected by the IGN switch during starting.
AS far as autos are concerned sure the same can happen but I stand by my
statement there are millions of autos with stock electrical systems and they
all depend on a solid battery connection for protection.
I should have said while Load Dump is a concern in autos, the MFGR's are not
concerned about it enough to do anything as the battery is normally
connected solidly at least during the warranty period. Adding a $1 device or
changing a design of a regulator is very costly and that money is not spent
lightly.
Finally as you point out the energy in the alternator windings is already
there and the regulator can only stop new energy not what is already there
so Load dump can be a real concern with external regulators also. Even OVP
do not address current energy just future energy.
Paul
----- Original Message -----
From: "Gary Casey" <glcasey@adelphia.net>
Subject: AeroElectric-List: RE: Load dump protection
> --> AeroElectric-List message posted by: "Gary Casey"
<glcasey@adelphia.net>
>
> <<This effort was unsuccessful (at the time) as this is not an issue with
> autos, as in
> autos the "B" lead is always directly wired to the battery. Thus there is
no
> "switch" to be accidentally opened to cause load dump action. Also there
is
> no OVP included as its rare and not a concern in the auto mfgrs mind. At
> least a couple of years ago I was unable to find ANY auto mfgr alternator
> that protected against load dump...I do not understand the need for
> additional testing in this case. The
> Boaters have long since solved the problem and so why are we still
> investigating it??>>
>
> Load dump protection in autos is still a real thing. There is a "switch"
> between the alternator and the battery and it is the battery terminal
> itself. The worst case, that is mostly worried about by boat
manufacturers,
> is a loose connection on the battery terminal that vibrates, repeatedly
> opening and closing. The electronics builders for boats find that it has
> not been "solved" as you imply, but is almost a normal situation. The
usual
> scenario is that the boater stores his boat over the winter, then finds
the
> battery is dead. He removes the battery and charges it for 10 minutes
(the
> family is waiting) and then puts it in the boat and just pushes the
battery
> cable on. The loose cable vibrates, the battery is accepting maximum
charge
> and the voltage transients are incredible - and repeated many times a
> second. Also, the battery doesn't have to be disconnected to have a load
> dump. Any time a large load is shut off the alternator has to instantly
> reduce its output, which it can't do because of the inductance of the
field
> windings. Of course, having the battery there tames the load dump to a
very
> manageable amplitude.
>
> Gary Casey
>
>
Message 20
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| Subject: | Re: Load dump issues |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:37 AM 2/9/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>I have watched this discussion and am concerned that the
>issue/facts/solution is going off track a little.
>
>Load dump is NOT unique to internally regulated alternators. ANY alternator
>can and will exhibit load dump when wired such that the load can be removed
>from the "B" lead when the alternator is generating power. IE
>internal/external/new/old/rebuilt are all the SAME with regard to Load Dump
>concerns.
That's not what was said. The problem is load-dump tolerance
of the REGULATORS internal to rebuilt alternators Van's sells vis-a-vis
regulators in OEM alternators which MAY be more resistant.
Regulator chips advertised by Onsemi and others call out "load dump
protection."
I mentioned in a post last week that the externally regulated
Bonanza alternators are wired in a way that I could manually
generate a "load-dump" event by manipulation of switches.
>All alternators, regardless of design, need protection or they can dump
>damaging loads either back to the alternator or to the expensive avionics
>depending on what opened and where.
Correct. We've had this discussion before. The risk is predicated
on battery contactor failure (or pilot operation of the contactor
at inappropriate times) while the battery is being charged. After
that, the duration and amplitude of the event is dependent upon many
system variables.
>Designs that disconnect the "B" lead when OVP is detected are great as long
>as there are Zero false trips. Bob has said many times that his OVP can and
>does (while very rare) false trip. This can result in alternator damage due
>to a false trip and not acceptable to me.
Correct . . . and the goal of this activity is to make it acceptable
to you and the rest of the OBAM aircraft community.
But it doesn't seem to be happening except for a limited population
of alternators which at the moment are all Van's rebuilts. We'll be
testing some factory fresh ND alternators in a few weeks. The working
hypothesis of the moment is that it's zero risk to airplane and strong
risk only to those alternators with regulators built with technology
falling short of what ND might do for a factory fresh product.
The same experiments offer an opportunity to put the 'scope on and
gather some real-time, real-life data.
>Alternator damage with a real OVP trip is not an issue as the alternator has
>already failed.
True
>There are more modern OVP I/C's that have provision for not false tripping
>on narrow spikes as they have adjustable delay to trip times. I suggest that
>this design approach be used to prevent a OVP protection device from
>causing damage from a not quite perfect design.
The OVM-14 and derivatives used in the B&C's products are all
adjustable for trip response. After our experience with the
super-noisy Bonanza's I belive nuisance tripping from dv/dt
effects of very low energy, narrow spikes has been resolved.
Thousands of those devices were in service with successful service
histories until Bonanza came along . . . and I believe we've
slain that dragon as well.
The only kind of nuisance trip we expect to see now will be an true
overshoot of the regulator/alternator combination . . . over which
we have no control when our OVM-14 is purchased for combination with
other hardware. Nuisance tripping is not a component of the current
discussion.
>The Linear LTC1696 is inexpensive and is designed to provide reliable OVP
>with minimal additional parts.
>
>Eric Jones has such a OVP design and I highly recommend it IF you are
>concerned about False trips. It's already designed and available to us.
False trips are not the issue. It's manually generated trips
caused by persons at the controls deliberately opening the
alternator control switch while the alternator is loaded.
>http://www.periheliondesign.com/
>
>If the alternator is generating say 50 amps and 40 amps are going to the
>battery and 10 amps to the rest of the system and the battery is
>disconnected the alternator output voltage (and the acft system bus) will
>rise until the 40 amp excess is loaded. This can result in a high voltage
>spike that is not stopped with OVP devices that shut off the regulator (too
>late action). Thus potential damage to avionics etc is likely if there is a
>large enough load dump. The damaging current is already there and thus its
>too late for a working regulator with or without OVP design to stop the
>energy pulse.
<snip - rhetorical repeat of well known and accepted science>
>Bob has suggested that NEW alternators have such protection and so Bob
>please let us know specifically which NEW alternators have such protection
>built in so we can consider them for our use.
I have said no such thing . . . you have mis-characterized my words.
I'm not setting myself up as the great arbiter of suitable and
unsuitable alternators.
>Then there are comments about rebuilt alternators being inferior. Perhaps
>some are but then many are just as good as the original NEW alternator in
>all respects.
This is the working HYPOTHESIS as to why some alternators are failing
and others do not. There was never a blanket statement made to imply
that all rebuilt alternators are inferior in this regard.
>As for testing and evaluation of TVS devices for load dump protection and
>getting your stamp of approval why do it??
Nobody needs or is recommended to wait for my stamp of approval
for anything. It is my intention to do the repeatable experiment
and deduce the science upon which I can make recommendations.
I and several others have been looking over the 'net on the topic
and you can find a few rational pieces but plenty more built on
poor or no measurements.
I'm interested in the energy dissipated by a TVS connected across
a 60A alternator experiencing a load-dump event. I am also interested
in current magnitudes and wave-shapes. If you have measured data
you can share that speaks to this event, I'd appreciate having access
to it.
I'm also going to see how brand new ND alternators behave in this
situation.
You mentioned a fat capacitor across the b-lead as an alternative
technique. Interesting . . . a 22,000 uF cap impressed with a 60A
constant current pulse rises at 2700 volts/second. So if we wanted
to limit the load/battery-dump event to 24 volts max, then
the event duration could not exceed about 3.6 milliseconds. Hmmmm . . .
sounds reasonable. I'm going to look at that too.
>There are such devices available that are designed, tested and industry
>approved for this specific application and rated for the largest alternator
>likely to be found on any acft. The ST LDP24A is one and rated for 500amp.
That 500A figure is completely meaningless when cited out of
context. ALL TVS devices will carry 500A for some duration.
This is a dynamic total energy study where current, voltage and
duration all contribute to the understanding. I object to phrases
like "industry approved" . . . industry is only slightly more useful
than government in bestowing its blessings on things. Processes
and techniques explained with the building blocks that are
simple-ideas of science will stand by themselves and do not gain
value when "approved" by anyone.
>I do not understand the need for additional testing in this case. The
>Boaters have long since solved the problem and so why are we still
>investigating it??
One member of the list noted that the boaters were being offered
a 70-cent TVS for $29.95 . . .that's why. If you have data from
an experiment that tells us whether or not the 70-cent TVS has
been properly sized and you can share it, then I won't have to
do it . . . or can you point me to a published paper that
describes the experiment?
>With all due respect my comments are intended to be helpful.
Factual but off-point. Nuisance trips and damage therefrom
are not the problem that started this thread. The phenomenon
pops up on what we've observed is a limited population of alternators
wired per Z-24 and only when used in a manner outside the
normal operating envelope for aircraft alternators. The testing
is not intended to confirm or deny need for the TVS. I want to
understand the event and validate the selection of a suitable
component.
The catalogs list hundreds of TVS parts each obviously suited
to some kind of task. The LDF24A is just one of many such
parts and may well be the holy grail of load dump defense
but I'd like to know the details. In the mean time, your
recommendations are welcome and can be operated upon by anyone
on the list as they see fit.
Cook-book engineering suffices for 99.9% of the system design
work going on in the world. We're studying application
of a circuit seldom needed but EXTREMELY useful when it is
needed. I'd like to understand more than what the books choose
to tell us.
For example, I'm working a problem right now where a high
quality, 4 amp, Honeywell SM series Microswitch is failing OPEN
after a few hundreds of cycles. The contacts drive a pair of #327
lamps (0.04A each). The switches are clean and not overly
stressed from an environmental perspective. I'm discovering
an ELECTRICALLY driven phenomenon that I've not seen mentioned
in any text to date (that doesn't mean it hasn't been written
about . . . only that I can usually re-discover the problem
faster than I can scan through all of the print literature).
Every time this happens in the airplane, it generates a
$kilo$ maintenance event.
Have another problem where a mil-spec relay is sticking CLOSED
after a relatively short service life in the airplane. Interestingly
enough, BOTH of these cases seem to be related to the same
phenomenon. I'll know more in a couple of weeks. The
knowledge to be gathered is coming off the workbench.
This event also generates a $1,000+ cost to return the aircraft
to service.
I can also tell you that I've had experts from the manufacturers
of these products set across the table from me and suggest
that I must be using their product in a manner outside
their specified operating envelopes . . . but to a person,
not one could describe the experiment to confirm or refute
the hypothesis. What I think I'm zeroing in on is a phenomenon
that few folks bother to control in the design and specification
of switch contacts.
I'm not recommending or suggesting that anyone wait on
me for anything in their decision making processes. I'm
only saying that right now, I don't have enough data
to offer an explanation of the simple-ideas that will ultimately
support any recommendation I might offer in the future.
In the mean time, a very easy answer to the problem is
don't turn the alternator off while the engine is running
except for the obvious case of malfunction.
Bob . . .
Message 21
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| Subject: | Re: Compass shielding |
--> AeroElectric-List message posted by: Jerzy Krasinski <krasinski@direcway.com>
hollandm wrote:
--> AeroElectric-List message posted by: "hollandm" <hollandm@pacbell.net>
I'm getting interference between an electric turn coordinator and a compass (about
2 degrees). Before I start moving things around I was wondering if it would
be possible to shield the compass by surrounding it with some copper screening
or the like, sort of mu-metal chamber approach.
Has anyone tried this and if so did it work?
Thanks
Do not bother with shielding the compass, it will not work. The compass
MUST be exposed to external magnetic field, this is how it finds
directions.
Two degrees is a very small deviation. Do you always hold your heading
with two degrees precision?
The question is if this deviation is caused by the presence of the turn
coordinator, or is it caused by switching the coordinator on. If it is
caused by the current make sure that you do not have a current loop,
i.e. use two twisted wires (power and ground) to power the turn
coordinator, rather than one wire and ground next to the coordinator.
If you use two twisted wires and still get the deviation, you could put
a magnetic screen around the turn coordinator. The best would be
miumetal or European permalloy. If you cant get these use a soft iron
sheet wrapped around the coordinator. Cooper would not work.
If the deviation is not current related you have no problem. Even a
bigger deviation would be within the compass compensator limits. The
compensating screws are somewhere on the compass and are described E-W
and N-S. If your compass does not have the compensation screws you
should throw it away and replace by one with these screws.
Here is one of possible compensation procedures:
1) Point the plane to exactly to the magnetic North using another
external precise compass or or some other method.
(Do not use the compass that you compensate to find North, that
compass will most likely show some deviation.)
Turn N-S screw with a brass screwdriver until the compass of your
plane shows N, i.e. reduce the deviation to zero
2) Swing the plane to the magnetic East established by the external
precise compass
Turn E-W screw until compass shows East, i.e. reduce the deviation
to zero
3) Swing the plane to the magnetic South. Read deviation of the compass.
Turn N-S screw until the deviation is reduced to 1/2 of the
original deviation.
4) Swing the plane to the magnetic West. Read deviation of the compass.
Turn E-W screw until the deviation is reduced to 1/2 of the
original deviation.
Go back to point 1) and repeat the whole procedure again. Pay attention
to the size of the corrections, now they should be much smaller than
those during the first swing.
Go back to point 1) . Swing it around again. This time you should get
almost stable situation.
Go back to point 1) . Swing it around without touching the screws and
write the deviation of the compass as a function of direction. Read it
every 45 degrees. The deviations should be very small, but no compass in
a plane with all the iron around would show exact directions.
Make a graph of the deviation and glue it to the compass, or next to it.
Jerzy
>
>
>
Message 22
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| Subject: | Re: AeroElectric-List Digest: 29 Msgs - 02/09/04 |
--> AeroElectric-List message posted by: "Dale Martin" <niceez@cableone.net>
Only to you Stan,
How important in the engine driven power supply's when the engine quits?
Maybe you have a use for two alternators right about then but I sure don't.
A very good battery or will give my essential bus the power to do the
required thing and maybe even restart the engine. Alternators have never
started an engine for me yet. This is why a running dual E.I. systems is
nuts to me. If you don't have enough energy to run the systems on battery
power it is a special feeling to know the magneto is not dependant on an
alternate source. Unless you have a big system it doesn't make sense to
this systems designer.
It all depends on the size of the project. No one system fits all. And
here I am talking small 2 place airplanes, night flying capable with limited
weather penetration ability.
Systems which allow for a failure of the alternator and then plan for the
pilot to land in the next 30 to 60 minutes are doable. Systems which allow
you to make your desired destination are heavy and add cost.
Dale Martin
Lewiston, ID
LEZ-235
----- Original Message -----
From: <Speedy11@aol.com>
Subject: AeroElectric-List: Re: AeroElectric-List Digest: 29 Msgs - 02/09/04
> --> AeroElectric-List message posted by: Speedy11@aol.com
>
> In a message dated 2/10/04 2:56:55 AM Eastern Standard Time,
> aeroelectric-list-digest@matronics.com writes:
>
> << For $300 and 4 pounds you can have a SECOND engine driven
> > power source.
> >
> > Bob . . .
>
> I think you mean a Third source. (Battery =1, Alt =2, Second Alt = 3) >>
>
> Key word is "engine-driven." It would be the second source and an
important
> one.
> Stan
>
>
Message 23
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| Subject: | Re: Capacitive Fuel Gauges |
--> AeroElectric-List message posted by: Mark Steitle <msteitle@mail.utexas.edu>
>
> So, if you have a probe you like and a piece of shielded wire
> picked to connect probe to electronics, the task is to mate the
> electronics to the probe/cable combination. Jim's schematic includes
> empty and full adjust pots. What you need to know is how close
> the probe you have comes to the one Jim describes. His circuit
> CAN be made to work with about ANY probe.
>
> Bob . . .
Thanks Bob,
I have contacted the manufacturer for this information. Will have to wait
and see what they say. If that fails, I will have to find a way to measure it.
Mark S.
Message 24
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| Subject: | Determining Speaker Requirements |
--> AeroElectric-List message posted by: Charles Brame <charleyb@earthlink.net>
I have a small, nice looking speaker that I would like to install in my
OBAM. However, it has no markings indicating its impedance. My intercom
system specifies a 4 ohm speaker.
How does one determine the impedance of a speaker?
Can I assume an ohmmeter between the speaker terminals will show the
correct impedance?
Charlie
Message 25
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| Subject: | Re: LED light bar annunciator panel? |
--> AeroElectric-List message posted by: Fiveonepw@aol.com
In a message dated 2/10/04 9:31:54 AM Central Standard Time,
jschroeder@perigee.net writes:
> We plan to use them too, but are not
> sure how to do the lettering. There is an outfit that will custom-make a
> backlit plexi panel. If we can get it a little more customized, we may go
> that route.
Hi John-
If you got the AutoCad dwg of the circuit you can see the mask I used to
label the annuciator- I just opened the drawing, selected a print window around
the mask and printed on overhead projection sheets on a laser printer. It's
just taped to the back of the overlay in the correct position. Works great in
7.4 hours of ACTUAL FLYING TIME so far!
8-)
Best wishes-
Mark (ripsteele is dead- long live fiveonepw@aol.com!)
Message 26
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| Subject: | Rotary Spreadsheet |
--> AeroElectric-List message posted by: "Ed Anderson" <eanderson@carolina.rr.com>
Mark
Here is a spread sheet that will calculate engine parameters for a one, two,
three or any (must change cell value to number of rotors you want} number of
rotors. Ihave expanded the results sheet to show air flow in CFM and
lbs/min as well as btu heat factors and other useful parameters. The engine
calculations are within 2-5%. The cooling results are less valid but has
shown good correlation with folks using evaporator cores
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Message 27
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| Subject: | Re: Determining Speaker Requirements |
--> AeroElectric-List message posted by: Richard Tasker <retasker@optonline.net>
No. Measuring with an ohmmeter will only give you the DC resistance of
the speaker windings - this is NOT the rated impedance. There are ways
of determining the rated impedance but it requires more than an ohmmeter
for test equipment. A higher impedance speaker will not hurt your
intercom - it will just make the maximum volume lower. It is unlikely
that the speaker is much lower than 4 ohms.
Dick Tasker, RV9A #90573
Charles Brame wrote:
>--> AeroElectric-List message posted by: Charles Brame <charleyb@earthlink.net>
>
>I have a small, nice looking speaker that I would like to install in my
>OBAM. However, it has no markings indicating its impedance. My intercom
>system specifies a 4 ohm speaker.
>
>How does one determine the impedance of a speaker?
>
>Can I assume an ohmmeter between the speaker terminals will show the
>correct impedance?
>
>Charlie
>
>
Message 28
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| Subject: | Re: Rotary Spreadsheet |
--> AeroElectric-List message posted by: "Ed Anderson" <eanderson@carolina.rr.com>
Sorry, Folks.
Hit the send button before engaging brain
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From: "Ed Anderson" <eanderson@carolina.rr.com>
Subject: AeroElectric-List: Rotary Spreadsheet
> --> AeroElectric-List message posted by: "Ed Anderson"
<eanderson@carolina.rr.com>
>
> Mark
>
> Here is a spread sheet that will calculate engine parameters for a one,
two,
> three or any (must change cell value to number of rotors you want} number
of
> rotors. Ihave expanded the results sheet to show air flow in CFM and
> lbs/min as well as btu heat factors and other useful parameters. The
engine
> calculations are within 2-5%. The cooling results are less valid but has
> shown good correlation with folks using evaporator cores
>
> Ed
>
> Ed Anderson
> RV-6A N494BW Rotary Powered
> Matthews, NC
> ----- Original Message -----
>
>
Message 29
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| Subject: | Re: Z12 e-bus questions |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 10:45 AM 2/9/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: f1rocket@telus.net
>
>Hi all (Bob),
>
>I'm planning on using a Z-12 type system on my Rocket. One battery, two
>alternators.
>
>I notice the e-bus alternate feed is through a 7 A (fuse?) via a 16 AWG wire.
>
>Two questions: For peace of mind would a breaker be the best way to go
>here?
>I'm thinking that I can easily overload the 7 amps just with the e-bus as
>described in Z-11. The plane will be outfitted for night flying, and needs a
>fuel booster pump. So if I end up with more than 7 A (which either I will
>have, or be very close to) when I loose the main power (assuming two dead
>alternators), and throw the switch, at least I can get smart, shed load and
>reset the breaker. For the most part though, I plan on using fuses,
>because I
>too have never reset a breaker were there wasn't a problem that resetting the
>breaker actually helped, and I plan on having each circuit with it's own fuse.
>
>Second question: Why only 7 amp protection device off the batter bus? The
>wire should be able to handle 12 amps? So why not use the protection
>device to
>protect the wire, since each of the devices coming off the e-bus will be
>protected on it's own?
>
>Thanks in advance, and also for all the past advice.
The Z-figures are intended to define the ART of system
design. This is where you pick through the big box of
Erector-Set, Tinker-Toy, and Lego parts to see how they
best fit together in a system that supports your project's
mission. The Z-figures should NOT be taken as verbatim
of the SCIENCE which dictates component selection.
When you "assuming two dead alternators", you're
getting ready to address a REALLY bad day. The likelihood
of dual failures in any single tank of fuel is extremely
remote. Any piece of wire more than 6" long taking a feed
from a bus with high fault current capability (your battery
may well deliver upwards of 500-1000 amps in a hard fault),
then we say it needs protection. If you're e-bus, e-bus
alternate feed and battery bus can be all wired up with
6" pieces of wire, you don't need any fuse or fusible link.
If the wires are longer, then . . . well, shucks. Now,
if you need an e-bus alternate feed exceeding 5A from
the battery (or battery bus) then using a relay as shown
in:
http://www.aeroelectric.com/temp/E-BusFatFeed.gif
seems prudent. This architecture provides a low power
version of a battery contactor to provide at-the-battery
control of a feeder. The same caveat exists for all
feeders from the battery whether e-bus alternate feed
or feeders to goodies that support an electrically
dependent engine. You mentioned a fuel pump . . . I
wouldn't drive this from the e-bus but directly from
the battery bus via it's 5A or less fuse and no relay
or a 7A+ fuse and a relay.
The VERY FIRST documents you need to craft in your
electrical system design are a tabular listing of each
feeder that comes off each bus. The system that feeder
supplies, the size of protection be it a Lego fuse or
Tinker-Toy breaker, size of the wire, then draw 7 columns
where you're going to deduce and add up the current draw
on each feeder under the following headers, (1) preflight,
(2) taxi, (3) takeoff/climb, (4) vfr cruise, (5) ifr cruise,
(6) approach to landing and (7) alternator-out.
Go get this document:
http://www.aeroelectric.com/temp/LoadAnalysisHandOut.pdf
The first page is an example of how to start this task.
The second page is blank so you can fill in what fits for
your project. You need one page for each bus.
Note that this document becomes a list of all the goodies
in your airplane, how much energy each combination takes
for operation. It can also be an index for your page-per-system
documents that will ultimately record how your airplane
is wired.
Bob . . .
Message 30
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| Subject: | LED light bar annunciator panel? |
--> AeroElectric-List message posted by: "Jeffrey W. Skiba" <jskiba@icosa.net>
I would like the AutoCAD file for the Label of the annuciator please.
Thanks
Jeff.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Fiveonepw@aol.com
Subject: Re: AeroElectric-List: LED light bar annunciator panel?
--> AeroElectric-List message posted by: Fiveonepw@aol.com
In a message dated 2/10/04 9:31:54 AM Central Standard Time,
jschroeder@perigee.net writes:
> We plan to use them too, but are not
> sure how to do the lettering. There is an outfit that will custom-make a
> backlit plexi panel. If we can get it a little more customized, we may go
> that route.
Hi John-
If you got the AutoCad dwg of the circuit you can see the mask I used to
label the annuciator- I just opened the drawing, selected a print window
around
the mask and printed on overhead projection sheets on a laser printer. It's
just taped to the back of the overlay in the correct position. Works great
in
7.4 hours of ACTUAL FLYING TIME so far!
8-)
Best wishes-
Mark (ripsteele is dead- long live fiveonepw@aol.com!)
Message 31
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| Subject: | Re: For Bob, Comment? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 03:41 PM 2/9/2004 +0000, you wrote:
>--> AeroElectric-List message posted by: "ivorphillips"
><ivor@ivorphillips.flyer.co.uk>
>
> > There is an upcoming program on Public Broadcasting: NOVA: The Deadly
>Legacy Of Swiss Air 111 that will be airing on February 17th at 8:00 EST.
>It deals with an inflight fire caused by electrical arcing.
> >
>Have seen this program a couple of weeks ago, It make you wonder how a
>commercial aircraft can have its wiring set up in such away that the pilots
>were unable to isolate the entertainment system from the main cockpit Bus!
>No breakers tripped to alleviate the problem, just smoke from behind
>panelling,
>
>I find it hard to believe that circuits are shared without proper regards
>too overload wire protection, Its criminal that so many folk lost their
>lives due to a preventable wiring short circuit.
It's a little more subtle than what you seem to perceive.
The soft-fault condition in wiring has been a design issue
for a number of folks for at least ten years if not longer.
Irrespective of the type of wire (Kapton may be crappy but
Tefzel can be mechanically damaged too) we can have openings
in the insulation that promote the low current arc that doesn't
draw enough current to trip the breaker. The higher the voltage
goes, the bigger the problem becomes. This is a VERY hot (no
pun intended) topic with the 42V car-guys.
The fact that this particular fault happened in the entertainment
system is irrelevant. It could have happened in any system. When
the pilots were confronted with smoke, there was no way they
could know nor would they care which system was having trouble . . .
Eaton and others are working on smart circuit breakers that
can detect the unique current signature of a soft-fault. They've
perceived a really big market opportunity for replacing all the
breakers in a panel . . . while expensive, it's probably cheaper
than rewiring an airplane.
This incident, typical of all accident scenarios, is a joining
of links in the chain. Breaking any link would have averted the accident.
(1) cracks in wires on (2) system voltage high enough to
support a soft-fault arc (3) close proximity of combustible
insulation (4) inaccessible to crew to fight fire (5) and
so rare an event that the crew could not conceive how much
trouble they were in. Had emergency condition behavior
been initiated sooner, etc. There are probably other links
in this deadly chain I've missed.
While I've ranted as much as anyone about Kapton, we cannot
ignore the fact that this single failure did not cause the
accident without the assistance of numerous other conditions
piling on too.
There's plenty of blame to go around.
Bob . . .
Message 32
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| Subject: | Re: Determining Speaker Requirements |
--> AeroElectric-List message posted by: Charlie & Tupper England <cengland@netdoor.com>
Charles Brame wrote:
>--> AeroElectric-List message posted by: Charles Brame <charleyb@earthlink.net>
>
>I have a small, nice looking speaker that I would like to install in my
>OBAM. However, it has no markings indicating its impedance. My intercom
>system specifies a 4 ohm speaker.
>
>How does one determine the impedance of a speaker?
>
>Can I assume an ohmmeter between the speaker terminals will show the
>correct impedance?
>
>Charlie
>
If it's a typical voice coil type speaker (and it almost certainly will
be) then DC resistance measured with an ohm meter will be about 60% to
80% of the actual impedance of the speaker. As long as the DC resistance
is at least 2.5-3 ohms, you will be safe in hooking it up to your
system. If it's an 8 or 16 ohm speaker, it will probably still work. It
might not be quite as loud as a 4 ohm speaker, but there is so much
variation in efficiency among various speakers that yours might end up
being louder than any random 4 ohm speaker you might find.
Charlie
Audio/electronics tech in a previous life
Message 33
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| Subject: | RE: Load dump protection |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 07:46 AM 2/10/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
<snip>
>Load dump protection exists as an add on and why are we beating it to death
>when there is an existing simple proven fix.
I'll suggest we're not "beating it to death." The standard
approach to education is "put tab(A) in slot(B) and trust
me it will work."
It is incumbent upon anyone who aspires to the title of
teacher to figure out ways to explain and better yet,
demonstrate the underlying simple-ideas that support
any design solution. All this discussion has been here
before and will come around again under some new
circumstances in the future. All of this "beating"
is but a couple of weeks out of THIS semester, like
the inimitable Arnie, it WILL "be back."
I've been reluctant to sign up to "stick TVS(a)
into system(b) and trust me it will work" because
until the current discussion, there was no demonstrable
need to protect every accessory in the airplane from
demons not fully characterized. When the demonstrable need
finally presented itself, it may well turn out to be
vulnerability in a component where the manufacturer
deliberately chose to ignore the risk!
E.G. Microair says anything over 16v puts their radios at
risk. Hmmm . . . even the lowly TVS won't help us here.
If I were to dragon-proof the Microair radios, I'd have
to design power conditioning EXTERNAL to the radio that
Microair should have made INTERNAL to the radio.
I agree that a TVS has a 99.9% probability of being
the elegant fix to offset what may be a conscious
decision on the part of a product designer to short-
change his customers. I'd like to know the numbers.
I'm not resisting the idea at all. But I will
understand and be able to explain the simple-ideas
and repeatable experiments that support it before I
integrate it into the curriculum for my seminars.
In the mean time, all this "beating" is healthy
stirring of the floobydust from which we'll sift
the science and elegant solutions.
Bob . . .
Message 34
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--> AeroElectric-List message posted by: Jeff Point <jpoint@mindspring.com>
Made an interesting discovery today while chasing down the source of EMI
from my Dynon. Like many, I have a distinct noise in the headsets,
which goes away when the Dynon is turned off. My electric system is the
main bus/ essential bus, per Lectric Bob. Both the Dynon and Comm are
on the essential bus. While futzing around, I turned the E bus switch
on while leaving the power master on. The noise instantly decreased
about 80%. The battery is getting rather tired from so much ground use,
and the voltage at the Dynon was showing 10.4V. When the E bus was
switched on, the voltage increased by 0.7V (the amount dropped by the
diode feeding the E bus.) Intrigued, I hooked up the battery charger
and tried it again. The voltage at the Dynon was now 12.5V with the E
bus and battery switches on, and the remaining noise decreased by about
half, to a level I consider pretty close to acceptable. In addition,
the strobe noise I was experiencing also disappeared.
For those experiencing EMI on the ground (not yet flying, like me) you
may want to give this a try. I have not had a chance to test this with
the engine running yet, perhaps in a day or two I will have time to do so.
My theory as to why this is, and it is an uneducated SWAG- the noise
filter circuits inside all of the boxes (Dynon, radio and strobe
supplies) are not functioning because of the low voltage, while the
units themselves appear to work. What does anyone think of that?
Jeff Point
RV-6 getting very close
Milwaukee WI
Message 35
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| Subject: | Re: RE: Load dump protection |
--> AeroElectric-List message posted by: Dj Merrill <deej@thayer.dartmouth.edu>
Robert L. Nuckolls, III wrote:
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>
>>Load dump protection exists as an add on and why are we beating it to death
>>when there is an existing simple proven fix.
>
>
>
> I'll suggest we're not "beating it to death." The standard
> approach to education is "put tab(A) in slot(B) and trust
> me it will work."
FWIW, I've found the discussion very interesting
and educational. I certainly didn't know much about the
topic before this. Please, continue as necessary! :-)
I've also learned why the switched labeled
"alt cutoff" in the already-built experimental plane I bought does
nothing once the engine is running.
I have one of those internally regulated alternators
that once it has power, continues to self-excite
regardless of the cut-off switch. Which is why I
am waiting with baited breath to see where this
discussion goes, since I'll likely "fix" the issue.
-Dj
Message 36
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| Subject: | Re: Dynon and EMI |
--> AeroElectric-List message posted by: "Dale Martin" <niceez@cableone.net>
I really appreciate that point as I am getting ready to purchase the Dynon
EFIS. Wonder how it will be affected when the 24 volt battery is low.
Hmmm..... Interesting.
- Dale
----- Original Message -----
From: "Jeff Point" <jpoint@mindspring.com>
Subject: AeroElectric-List: Dynon and EMI
> --> AeroElectric-List message posted by: Jeff Point
<jpoint@mindspring.com>
>
> Made an interesting discovery today while chasing down the source of EMI
> from my Dynon. Like many, I have a distinct noise in the headsets,
> which goes away when the Dynon is turned off. My electric system is the
> main bus/ essential bus, per Lectric Bob. Both the Dynon and Comm are
> on the essential bus. While futzing around, I turned the E bus switch
> on while leaving the power master on. The noise instantly decreased
> about 80%. The battery is getting rather tired from so much ground use,
> and the voltage at the Dynon was showing 10.4V. When the E bus was
> switched on, the voltage increased by 0.7V (the amount dropped by the
> diode feeding the E bus.) Intrigued, I hooked up the battery charger
> and tried it again. The voltage at the Dynon was now 12.5V with the E
> bus and battery switches on, and the remaining noise decreased by about
> half, to a level I consider pretty close to acceptable. In addition,
> the strobe noise I was experiencing also disappeared.
>
> For those experiencing EMI on the ground (not yet flying, like me) you
> may want to give this a try. I have not had a chance to test this with
> the engine running yet, perhaps in a day or two I will have time to do so.
>
> My theory as to why this is, and it is an uneducated SWAG- the noise
> filter circuits inside all of the boxes (Dynon, radio and strobe
> supplies) are not functioning because of the low voltage, while the
> units themselves appear to work. What does anyone think of that?
>
> Jeff Point
> RV-6 getting very close
> Milwaukee WI
>
>
Message 37
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| Subject: | Compass shielding |
--> AeroElectric-List message posted by: "hollandm" <hollandm@pacbell.net>
The disturbance occurs on switching on the TC and appears to be reproducible.
Concerning the suggestion to obtain mumetal for shielding or permalloy, where would
one obtain such materials?
In the mean time I'll get some tin as Bob suggests and get back to the group.
Message 38
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| Subject: | Re: Z12 e-bus questions |
--> AeroElectric-List message posted by: f1rocket@telus.net
Excellent, thanks. Just a couple more questions for the un-informed (me).
See below.
SNIP> If the wires are longer, then . . . well, shucks. Now,
> if you need an e-bus alternate feed exceeding 5A from
> the battery (or battery bus) then using a relay as shown
> in:
>
> http://www.aeroelectric.com/temp/E-BusFatFeed.gif
>
> seems prudent. This architecture provides a low power
> version of a battery contactor to provide at-the-battery
> control of a feeder. The same caveat exists for all
> feeders from the battery whether e-bus alternate feed
> or feeders to goodies that support an electrically
> dependent engine. You mentioned a fuel pump . . . I
> wouldn't drive this from the e-bus but directly from
> the battery bus via it's 5A or less fuse and no relay
> or a 7A+ fuse and a relay.
In both cases you mention going larger than 5A a relay is required? Is this
just because it is driving a motor (pump) or what am I missing here? I don't
need to put a relay in for all loads larger than 5A do I?
>
> The VERY FIRST documents you need to craft in your
> electrical system design are a tabular listing of each
> feeder that comes off each bus. The system that feeder
> supplies, the size of protection be it a Lego fuse or
> Tinker-Toy breaker, size of the wire, then draw 7 columns
> where you're going to deduce and add up the current draw
> on each feeder under the following headers, (1) preflight,
> (2) taxi, (3) takeoff/climb, (4) vfr cruise, (5) ifr cruise,
> (6) approach to landing and (7) alternator-out.
>
> Go get this document:
>
> http://www.aeroelectric.com/temp/LoadAnalysisHandOut.pdf
I had almost done this, at least for the first three columns (I had one more
column for switch required/type). I like your document better and looks as
though it will guide me in a more analytical path.
Jeff
>
> The first page is an example of how to start this task.
> The second page is blank so you can fill in what fits for
> your project. You need one page for each bus.
>
> Note that this document becomes a list of all the goodies
> in your airplane, how much energy each combination takes
> for operation. It can also be an index for your page-per-system
> documents that will ultimately record how your airplane
> is wired.
>
> Bob . . .
>
>
>
>
>
>
>
Message 39
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| Subject: | Re: Compass shielding |
--> AeroElectric-List message posted by: Jerzy Krasinski <krasinski@direcway.com>
Check Goodfellow at www.goodfellow.com. You need a thick foil. I think
they have 0.125 mm. The problem is that they sell this stuff in rolls
and you need much less. Ask them about distributors.
Jerzy
Jerzt
You can find more at this damn long addressL
http://search.netscape.com/ns/boomframe.jsp?query=mu-metal&page=1&offset=0&result_url=redir%3Fsrc%3Dwebsearch%26amp%3BrequestId%3D18de54f3a00ff8ca%26amp%3BclickedItemRank%3D1%26amp%3BuserQuery%3Dmu-metal%26amp%3BclickedItemURN%3Dhttp%253A%252F%252Fwww.goodfellow.com%252Fcsp%252Factive%252Fstatic%252FA%252FNI03.HTML%26amp%3BinvocationType%3D-%26amp%3BfromPage%3DNSCPIndex&remove_url=http%3A%2F%2Fwww.goodfellow.com%2Fcsp%2Factive%2Fstatic%2FA%2FNI03.HTML
hollandm wrote:
>--> AeroElectric-List message posted by: "hollandm" <hollandm@pacbell.net>
>
>The disturbance occurs on switching on the TC and appears to be reproducible.
>
>Concerning the suggestion to obtain mumetal for shielding or permalloy, where
would one obtain such materials?
>
>In the mean time I'll get some tin as Bob suggests and get back to the group.
>
>
>
>
Message 40
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| Subject: | Compass shielding |
--> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
What brand is the T&B? (One of those Chinese knockoff I'll bet)
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
hollandm
Subject: AeroElectric-List: Compass shielding
--> AeroElectric-List message posted by: "hollandm"
<hollandm@pacbell.net>
The disturbance occurs on switching on the TC and appears to be
reproducible.
Concerning the suggestion to obtain mumetal for shielding or permalloy,
where would one obtain such materials?
In the mean time I'll get some tin as Bob suggests and get back to the
group.
==
==
==
==
Message 41
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| Subject: | Re: Load dump issues |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Embedded comments
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 08:37 AM 2/9/2004 -0800, you wrote:
> >--> AeroElectric-List message posted by: "Paul Messinger"
<paulm@olypen.com>
> >
> >I have watched this discussion and am concerned that the
> >issue/facts/solution is going off track a little.
> >
> >Load dump is NOT unique to internally regulated alternators. ANY
alternator
> >can and will exhibit load dump when wired such that the load can be
removed
> >from the "B" lead when the alternator is generating power. IE
> >internal/external/new/old/rebuilt are all the SAME with regard to Load
Dump
> >concerns.
>
> That's not what was said. The problem is load-dump tolerance
> of the REGULATORS internal to rebuilt alternators Van's sells
vis-a-vis
> regulators in OEM alternators which MAY be more resistant.
> Regulator chips advertised by Onsemi and others call out "load dump
> protection."
I was not saying you had said what I was saying. My point is that ALL
alternators internal and external need to be addressed. The fact that Onsemi
has a regulator with internal load dump does not mean the regulator of a
2004 alternator has load dump protection. The I/C mfgrs have been pushing
load dump protection for at last 20 years that I am aware of with limited
success until recently where modern autos can have thousands of dollars of
electronics at risk.
I have not seen any hard evidence that Van supplied regulators are of lesser
quality, circumstantial perhaps but there may be other reasons.
I was trying to point out that the problem may be very widespread (in
potential)and its only recently that its showing up on Vans acft and perhaps
there only because of pilot procedures and the large number of these
experimentals.
>
> I mentioned in a post last week that the externally regulated
> Bonanza alternators are wired in a way that I could manually
> generate a "load-dump" event by manipulation of switches.
Yes and I think that any design that allows of improper use of unguarded
switches results in damage is unacceptable, at least my acft.
I have a friend who has another spam can (high end acft) that blew an
alternator when the master was pulled when smoke in the cockpit was noticed.
The smoke cleared and the master was reset and the alternator was NG. Later
shown to have several diodes shorted presumably due to load dump. There was
an external reg that was unharmed. This acft was wired by the factory that
way
> >All alternators, regardless of design, need protection or they can dump
> >damaging loads either back to the alternator or to the expensive avionics
> >depending on what opened and where.
>
> Correct. We've had this discussion before. The risk is predicated
> on battery contactor failure (or pilot operation of the contactor
> at inappropriate times) while the battery is being charged. After
> that, the duration and amplitude of the event is dependent upon many
> system variables.
I agree but a design that allows a pilot to simply throw the wrong switch
and cause alternator or worse failure is a bad design. Even switch layout on
the panel is not acceptable to me as we are dealing with Private pilots who
can make mistakes.
> >Designs that disconnect the "B" lead when OVP is detected are great as
long
> >as there are Zero false trips. Bob has said many times that his OVP can
and
> >does (while very rare) false trip. This can result in alternator damage
due
> >to a false trip and not acceptable to me.
>
> Correct . . . and the goal of this activity is to make it acceptable
> to you and the rest of the OBAM aircraft community.
>
> But it doesn't seem to be happening except for a limited population
> of alternators which at the moment are all Van's rebuilts. We'll be
> testing some factory fresh ND alternators in a few weeks. The working
> hypothesis of the moment is that it's zero risk to airplane and strong
> risk only to those alternators with regulators built with technology
> falling short of what ND might do for a factory fresh product.
I hope you will test curent production ND NEW alternators to prove your
theory
> >There are more modern OVP I/C's that have provision for not false
tripping
> >on narrow spikes as they have adjustable delay to trip times. I suggest
that
> >this design approach be used to prevent a OVP protection device from
> >causing damage from a not quite perfect design.
>
> The OVM-14 and derivatives used in the B&C's products are all
> adjustable for trip response. After our experience with the
> super-noisy Bonanza's I belive nuisance tripping from dv/dt
> effects of very low energy, narrow spikes has been resolved.
> Thousands of those devices were in service with successful service
> histories until Bonanza came along . . . and I believe we've
> slain that dragon as well.
The following is from a recent post of yours and over the years has been
repeated several times a year. This with regard to the OVP module design you
have provided to all of us. The LTC1696 is specifically designed so you can
set the trip pulse width time to avoid nuisance tripping from short spikes.
This is not possible with your design per your supplied schematic.
"Nuisance tripping of the crowbar ov module is rare but it
HAS happened and at higher rates than real ov tripping.''
>
> The only kind of nuisance trip we expect to see now will be an true
> overshoot of the regulator/alternator combination . . . over which
> we have no control when our OVM-14 is purchased for combination with
> other hardware. Nuisance tripping is not a component of the current
> discussion.
Disagree as we should be addressing every application not just a matched
set from B&C.
As a nuisance trip with out load dump protection can fail the alternator and
this should not only be addressed but mitigated. Failure of a protection
device should never cause failure of the device being protected. Just as
failure to use a specific switching procedure should not damage components.
> >The Linear LTC1696 is inexpensive and is designed to provide reliable OVP
> >with minimal additional parts.
> >
> >Eric Jones has such a OVP design and I highly recommend it IF you are
> >concerned about False trips. It's already designed and available to us.
>
> False trips are not the issue. It's manually generated trips
> caused by persons at the controls deliberately opening the
> alternator control switch while the alternator is loaded.
>
>
> >http://www.periheliondesign.com/
> >
> >If the alternator is generating say 50 amps and 40 amps are going to the
> >battery and 10 amps to the rest of the system and the battery is
> >disconnected the alternator output voltage (and the acft system bus) will
> >rise until the 40 amp excess is loaded. This can result in a high voltage
> >spike that is not stopped with OVP devices that shut off the regulator
(too
> >late action). Thus potential damage to avionics etc is likely if there is
a
> >large enough load dump. The damaging current is already there and thus
its
> >too late for a working regulator with or without OVP design to stop the
> >energy pulse.
>
> <snip - rhetorical repeat of well known and accepted science>
Then why not include every alternator in the discussion ?, not limit it to
Vans rebuilt internal alternators
>
>
> >Bob has suggested that NEW alternators have such protection and so Bob
> >please let us know specifically which NEW alternators have such
protection
> >built in so we can consider them for our use.
>
> I have said no such thing . . . you have mis-characterized my words.
> I'm not setting myself up as the great arbiter of suitable and
> unsuitable alternators.
Recent comment from you I was referring to.
""It is therefore my belief that the very popular 40 Amp Denso bought new
from
Niagra has a regulator which has dump logic in it. ""
> You mentioned a fat capacitor across the b-lead as an alternative
> technique. Interesting . . . a 22,000 uF cap impressed with a 60A
> constant current pulse rises at 2700 volts/second. So if we wanted
> to limit the load/battery-dump event to 24 volts max, then
> the event duration could not exceed about 3.6 milliseconds. Hmmmm . .
.
> sounds reasonable. I'm going to look at that too.
I was simply stating that without a battery some regulators are unstable
and adding a capacitor has been proven to stabilize the regulator. If the
battery charge current (the source of the load dump) is small when the
battery is disconnected the capacitor will dampen the spike. It may not be
of much help with a 50 amp Load dump.
> >There are such devices available that are designed, tested and industry
> >approved for this specific application and rated for the largest
alternator
> >likely to be found on any acft. The ST LDP24A is one and rated for
500amp.
>
> That 500A figure is completely meaningless when cited out of
> context. ALL TVS devices will carry 500A for some duration.
Its not meaningless IF you take the time to look at the data sheet which was
my intent. I never intended to provide all the details, just the link. In
this case the duration is specified at 0.2 second (more than long enough)
and clearly longer with 1/10 the current we are dealing with vs. the rated
500 amps.
Thank you for well thought out replies.
Paul
Message 42
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| Subject: | Load dump protection |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
> Perhaps I should have need more specific with my comment about "beating it
> to death. The industry has decided that the solution to Load dump
protection
> is simply a TVS added to the regulator. Thus I was simply saying The only
> decision is the specific TVS to add to our Alternators.
>
> While some "modern" internally regulated alternators may be protected from
> load dump its unclear how ANY externally regulated alternator will control
> load dump as the protection MUST be across the "B" lead to ground.
>
> As for testing, I am all for it but with the vast number of alternators
and
> regulator combinations internal and external (including the ever popular
low
> cost Ford) it would seem that there is no reasonable way to provide 100%
> assurance. Not that that is a requirement.
>
> My basic point was and is that until proven innocent every alternator
> (internal OR external regulator) needs a "B" lead load dump TVS.
>
> Another concern is the Load dump TVS voltage can be quite high relative to
> 16V during the peak current of the load dump. Thus, equipment not rated
for
> something over 20V should be looked at carefully. As you have often
> suggested not all equipment meets DO-160 but should.
>
> Paul
>
>
> > >--> AeroElectric-List message posted by: "Paul Messinger"
> <paulm@olypen.com>
> >
> > >Load dump protection exists as an add on and why are we beating it to
> death
> > >when there is an existing simple proven fix.
> >
> >
> > I'll suggest we're not "beating it to death." The standard
> > approach to education is "put tab(A) in slot(B) and trust
> > me it will work."
> >
>
>
Message 43
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| Subject: | Re: Load dump issues |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Embedded comments
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 08:37 AM 2/9/2004 -0800, you wrote:
> >--> AeroElectric-List message posted by: "Paul Messinger"
<paulm@olypen.com>
> >
> >I have watched this discussion and am concerned that the
> >issue/facts/solution is going off track a little.
> >
> >Load dump is NOT unique to internally regulated alternators. ANY
alternator
> >can and will exhibit load dump when wired such that the load can be
removed
> >from the "B" lead when the alternator is generating power. IE
> >internal/external/new/old/rebuilt are all the SAME with regard to Load
Dump
> >concerns.
>
> That's not what was said. The problem is load-dump tolerance
> of the REGULATORS internal to rebuilt alternators Van's sells
vis-a-vis
> regulators in OEM alternators which MAY be more resistant.
> Regulator chips advertised by Onsemi and others call out "load dump
> protection."
I was not saying you had said what I was saying. My point is that ALL
alternators internal and external need to be addressed. The fact that Onsemi
has a regulator with internal load dump does not mean the regulator of a
2004 alternator has load dump protection. The I/C mfgrs have been pushing
load dump protection for at last 20 years that I am aware of with limited
success until recently where modern autos can have thousands of dollars of
electronics at risk.
I have not seen any hard evidence that Van supplied regulators are of lesser
quality, circumstantial perhaps but there may be other reasons.
I was trying to point out that the problem may be very widespread (in
potential)and its only recently that its showing up on Vans acft and perhaps
there only because of pilot procedures and the large number of these
experimentals.
>
> I mentioned in a post last week that the externally regulated
> Bonanza alternators are wired in a way that I could manually
> generate a "load-dump" event by manipulation of switches.
Yes and I think that any design that allows of improper use of unguarded
switches results in damage is unacceptable, at least my acft.
I have a friend who has another spam can (high end acft) that blew an
alternator when the master was pulled when smoke in the cockpit was noticed.
The smoke cleared and the master was reset and the alternator was NG. Later
shown to have several diodes shorted presumably due to load dump. There was
an external reg that was unharmed. This acft was wired by the factory that
way
> >All alternators, regardless of design, need protection or they can dump
> >damaging loads either back to the alternator or to the expensive avionics
> >depending on what opened and where.
>
> Correct. We've had this discussion before. The risk is predicated
> on battery contactor failure (or pilot operation of the contactor
> at inappropriate times) while the battery is being charged. After
> that, the duration and amplitude of the event is dependent upon many
> system variables.
I agree but a design that allows a pilot to simply throw the wrong switch
and cause alternator or worse failure is a bad design. Even switch layout on
the panel is not acceptable to me as we are dealing with Private pilots who
can make mistakes.
> >Designs that disconnect the "B" lead when OVP is detected are great as
long
> >as there are Zero false trips. Bob has said many times that his OVP can
and
> >does (while very rare) false trip. This can result in alternator damage
due
> >to a false trip and not acceptable to me.
>
> Correct . . . and the goal of this activity is to make it acceptable
> to you and the rest of the OBAM aircraft community.
>
> But it doesn't seem to be happening except for a limited population
> of alternators which at the moment are all Van's rebuilts. We'll be
> testing some factory fresh ND alternators in a few weeks. The working
> hypothesis of the moment is that it's zero risk to airplane and strong
> risk only to those alternators with regulators built with technology
> falling short of what ND might do for a factory fresh product.
I hope you will test curent production ND NEW alternators to prove your
theory
> >There are more modern OVP I/C's that have provision for not false
tripping
> >on narrow spikes as they have adjustable delay to trip times. I suggest
that
> >this design approach be used to prevent a OVP protection device from
> >causing damage from a not quite perfect design.
>
> The OVM-14 and derivatives used in the B&C's products are all
> adjustable for trip response. After our experience with the
> super-noisy Bonanza's I belive nuisance tripping from dv/dt
> effects of very low energy, narrow spikes has been resolved.
> Thousands of those devices were in service with successful service
> histories until Bonanza came along . . . and I believe we've
> slain that dragon as well.
The following is from a recent post of yours and over the years has been
repeated several times a year. This with regard to the OVP module design you
have provided to all of us. The LTC1696 is specifically designed so you can
set the trip pulse width time to avoid nuisance tripping from short spikes.
This is not possible with your design per your supplied schematic.
"Nuisance tripping of the crowbar ov module is rare but it
HAS happened and at higher rates than real ov tripping.''
>
> The only kind of nuisance trip we expect to see now will be an true
> overshoot of the regulator/alternator combination . . . over which
> we have no control when our OVM-14 is purchased for combination with
> other hardware. Nuisance tripping is not a component of the current
> discussion.
Disagree as we should be addressing every application not just a matched
set from B&C.
As a nuisance trip with out load dump protection can fail the alternator and
this should not only be addressed but mitigated. Failure of a protection
device should never cause failure of the device being protected. Just as
failure to use a specific switching procedure should not damage components.
> >The Linear LTC1696 is inexpensive and is designed to provide reliable OVP
> >with minimal additional parts.
> >
> >Eric Jones has such a OVP design and I highly recommend it IF you are
> >concerned about False trips. It's already designed and available to us.
>
> False trips are not the issue. It's manually generated trips
> caused by persons at the controls deliberately opening the
> alternator control switch while the alternator is loaded.
>
>
> >http://www.periheliondesign.com/
> >
> >If the alternator is generating say 50 amps and 40 amps are going to the
> >battery and 10 amps to the rest of the system and the battery is
> >disconnected the alternator output voltage (and the acft system bus) will
> >rise until the 40 amp excess is loaded. This can result in a high voltage
> >spike that is not stopped with OVP devices that shut off the regulator
(too
> >late action). Thus potential damage to avionics etc is likely if there is
a
> >large enough load dump. The damaging current is already there and thus
its
> >too late for a working regulator with or without OVP design to stop the
> >energy pulse.
>
> <snip - rhetorical repeat of well known and accepted science>
Then why not include every alternator in the discussion ?, not limit it to
Vans rebuilt internal alternators
>
>
> >Bob has suggested that NEW alternators have such protection and so Bob
> >please let us know specifically which NEW alternators have such
protection
> >built in so we can consider them for our use.
>
> I have said no such thing . . . you have mis-characterized my words.
> I'm not setting myself up as the great arbiter of suitable and
> unsuitable alternators.
Recent comment from you I was referring to.
""It is therefore my belief that the very popular 40 Amp Denso bought new
from
Niagra has a regulator which has dump logic in it. ""
> You mentioned a fat capacitor across the b-lead as an alternative
> technique. Interesting . . . a 22,000 uF cap impressed with a 60A
> constant current pulse rises at 2700 volts/second. So if we wanted
> to limit the load/battery-dump event to 24 volts max, then
> the event duration could not exceed about 3.6 milliseconds. Hmmmm . .
.
> sounds reasonable. I'm going to look at that too.
I was simply stating that without a battery some regulators are unstable
and adding a capacitor has been proven to stabilize the regulator. If the
battery charge current (the source of the load dump) is small when the
battery is disconnected the capacitor will dampen the spike. It may not be
of much help with a 50 amp Load dump.
> >There are such devices available that are designed, tested and industry
> >approved for this specific application and rated for the largest
alternator
> >likely to be found on any acft. The ST LDP24A is one and rated for
500amp.
>
> That 500A figure is completely meaningless when cited out of
> context. ALL TVS devices will carry 500A for some duration.
Its not meaningless IF you take the time to look at the data sheet which was
my intent. I never intended to provide all the details, just the link. In
this case the duration is specified at 0.2 second (more than long enough)
and clearly longer with 1/10 the current we are dealing with vs. the rated
500 amps.
Thank you for well thought out replies.
Paul
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