Today's Message Index:
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1. 08:59 AM - : Re: [AeroElectric-List] Questions about circuit protection (John Burnaby)
2. 03:06 PM - Re: planning (Robert L. Nuckolls, III)
3. 03:06 PM - Re: Reversible electric motors and CBs (Robert L. Nuckolls, III)
4. 03:25 PM - Re: Z-14 Switch Combos (Robert L. Nuckolls, III)
5. 05:54 PM - Electronic Dead Reckoning Distance Calculator (user9253)
6. 06:02 PM - Busbar Protection Coating (MHerder)
Message 1
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| Subject: | : RE: [AeroElectric-List] Questions about circuit protection |
Jay,
You're probably right about noticing changes in normal ops. Certainly so
for the normal ops single fuel pump. The resounding quiet of engine
stoppage is tough to miss ;-). But losing one E-ignition is a barely
noticeable event even during run-up and, as you say, one would not
feel/see/hear any change if one of a dual power source for an EFI
dropped out. I like it that I can test the system, and reset the alarm
feature with the single (MOM) switch. And if the alarm feature fails, I
still have LED's firing up for blown fuses.
When I first assembled an electronics kit, I thought I was in terribly
complex territory. But after I saw how small the finished kit was and
demonstrated its capability to provide a solution, I became hooked! I
frankly don't know what SCR's and some of the other parts are in this
circuit but they're inexpensive and I would guess pretty reliable. The
guy who designed this circuit is in the home/business security biz. He
outlined some possible problems in high electrical noise environments
but, with caveats, didn't think they would crop up in my application.
Here's the thread if you or anybody is interested:
http://forum.allaboutcircuits.com/showthread.php?t=30782
Message 2
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your philosophy that using a properly maintained RG battery is the
simplest way to add reliability to the
electrical system. I also have Slick mags, and with backup batteries
in the EFIS and a handheld gps/radio,
I don't see the electrical system as the most critical system for the
guarantee of a safe landing. I am definitely
willing to change my mind though.
If you're comfy, so be it. The neat thing about Z-13/8 is that
it's an easy step up from Z-11 at any later time giving you
unlimited 8-10A of e-bus loads for a weight penalty that's
a small fraction of the vacuum system that came out (or wasn't
there in the first place).
-------------------------
Plane Power INCLUDES crowbar OV protection on their OBAM
aircraft alternators.
Thank you. Sure enough, the schematic that came with my alternator
says right at the top;
"12 volt 60 amp experimental alternator w/internal voltage regulator
and over voltage protection".
Do you think this system is as good as, not as good, or better than
using an alternator with external regulator
and OV protection? I think I remember you saying in the past that
you tested the Plane Power alternator.
I have not tested any PP products. However I did
talk to one of the techno-wienies there right after
I was made aware of their offering. I confirmed that
they had adopted a crowbar ov protection technique
and avoided the b-lead contactor by going inside
the alternator to bring out the field excitation
supply line. All in all, an elegant solution.
The design goal for the AEC9004 IR alternator controller
is to achieve any time, any conditions, zero-risk pilot
control of an UNMODIFIED internally regulated alternator.
Aside from differences in design goals, I'd judge the
PP products to be entirely suited to the task.
2)The Skytec starter has it's own contactor to engage the gear, and
apply power to the motor. According to Skytec, I don't need a
separate contactor for the starter if I use a 20+amp starter switch,
which I plan to do (toggle mag switches and separate starter switch)
Are there any cautions for not using a separate starter contactor?
No.
I like the simple "NO" answer, however now after doing some more
reading I have a
couple more questions; I came across your Z-22, fix for run on starters with PM
motors, which the Skytec is. You suggest a relay to replace the
contactor. Further
Skytec suggests on their website that if wiring the starter without a
separate contactor,
to put a diode at the start switch to lengthen service life of the
switch. This all
leaves me a little confused. What is the main issue here, protecting the start
switch, or preventing possible damage to the starter or flywheel
gears, or both, or
something else? Should I use a diode or a relay, or both, or neither?
We're getting several issues tangled together here. First,
unless the builder is going to use a robust starter pushbutton
designed for abuse by two-stage contactor/solenoids then
some sort of "buffering" is worth considering.
Assuming you still wish to control the Skytec contactor
directly, then adding a relay per Z-22 is the way to
go about it. Assuming you already have or wish to use
the single stage starter contactor, then you don't want
to "jumper" the Skytec solenoid coil to the main terminal.
This gives rise to the "run on" phenomenon described. In
this case, you take the "I" terminal from the external
single stage contactor over to the Skytec's coil
terminal as suggested by
http://aeroelectric.com/Pictures/Schematics/Vans_Starter_Wiring_Lg.jpg
This has the advantage of (1) reducing stress on the
starter push-button or switch and (2) preventing
delayed disengagement during spin down on a PM
starter. Kinda slick. Wish I'd thought of it.
Now with most contactors, a diode across the
coil is a good thing to contemplate. On Van's drawing
cathode would go to "S" and anode to ground (case).
You could also consider a diode from the Skytec
coil terminal (cathode) to ground (anode).
And another question; I saw your link to the article below. I found
the philosophical discussion very
interesting, I also noticed that in that article you recommend a 70
or 80 amp fuse in the alternator
B-lead which is different than the Z-figures where an ANL 60 curret
limiter is shown. Reading note 10 I
see that the current limiter is a modern upgrade to the fuse or
breaker, but is 60 amps still the
recommended rating (not 70 or 80)?
Yes, there was a bit of a kerfuffle here on the List
about 13 years ago. See:
http://www.aeroelectric.com/articles/fusvbkr2.html
Early on we were pretty stoked up about using
JJN/JSS fuses as lower cost, bolt-on b-lead
protection. That idea proved less than ideal
when a number of builders reported opening their
60A fuse on a 60A alternator (so we up-sized to
70A . . . probably should have jumped to 100A).
Other builder noted that these fuses were not
very robust mechanically . . . they reported
end caps pulling off the fuse body. Sooooooo . . .
the ANL limiters came to the rescue. Their
electrical robustness. See:
http://www.aeroelectric.com/articles/anl/anlvsjjs.html
Note that a 35A ANL would probably take good
care of the b-lead on a 60A alternator . . .
but a 60A is good too. This is NOT a finely tuned
protection task. Fault currents in the b-lead
will be hundreds to perhaps over 1000 amps!
Bob . . .
Message 3
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| Subject: | Reversible electric motors and CBs |
At 01:10 AM 1/8/2010, you wrote:
>
>Actually, what you need is one of these....
>
>http://www.youtube.com/watch?v=Z86V_ICUCD4
Pretty cute. I'll have to get the details on
it. Be a good project for my oldest grandson
this summer. I've got a bucket-load of model
servos left over from a project.
Bob . . .
Message 4
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| Subject: | Z-14 Switch Combos |
At 01:25 PM 1/7/2010, you wrote:
>
>I think I'll have to fuse them anyway. The wire run length from the
>contactor to the panel is pretty lengthy and I'd feel better about
>putting a fuse inline.
>
>What's the purpose of the resistors? Is that to encourage the
>electrons to flow through the coil instead of the LED?
Fuses protect wires . . . but so do the resistors. If your
led calls for say 1000 ohms total resistance in series
to achieve desired brightness, then consider two
510 ohm resistors in series with each lead right
at the contactor. See:
http://www.aeroelectric.com/articles/Homeless/Homeless_Components.htm
The idea is that the resistors (1) take care of
LED requirements and (2) shorting either lead to
the airframe doesn't create a hazard because the
resistors limit the current.
We did a similar thing with the alternator diagnosis
feature of our now discontinued AEC9021 voltmeter/
loadmeter:
http://www.aeroelectric.com/Catalog/AEC/9021/9021-704F.pdf
On pages 6 and 9 you see a 470 ohm resistor tapping
a sample of alternator field voltage. The resistor's
presence is not detrimental to the diagnostic procedure
described on page 2 but eliminates the need for a fuse
by preventing alternator upset if the diagnostic wire becomes
faulted.
Bob . . .
Message 5
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| Subject: | Electronic Dead Reckoning Distance Calculator |
Back in the days before GPS, I carried a circular slide rule in my shirt pocket.
Once the ground speed was set, the slide rule would tell me the time en route
opposite the distance scale. Later in the flight, I would determine the distance
to go by looking at the distance scale opposite the remaining time. Then
I would measure that distance on the chart and try to find a landmark on the
ground that matched the chart. Do not ask me if I ever got lost. :-)
Wouldn't it be nice if there were some way to automatically calculate the distance
to go without having to match up the scales on the circular slide rule?
What I needed was a poor man's DME. I made one utilizing the constant function
of an electronic calculator. Dividing the aircraft ground speed by 1200 gives
the distance traveled in 3 seconds. All I have to do is subtract that 3-second
distance from the total by pushing the EQUALS KEY every 3 seconds. That
is accomplished automatically by the attached circuit that contains a crystal-controlled
oscillator and divider and solid state relay. There are probably
other ICs or microprocessors that will do a better job, but this is the way that
I did it. And of course GPS is much better as long as it works. There might
be other applications for this circuit besides moving vehicles, i.e. anything
that moves at a constant rate.
http://public.bay.livefilestore.com/y1ppOv3v2Wbgtq80VIypr95YNkF1OXb94DIJlAOGJjOaMH01g82rhlsInEKh0RMLu0M2QKEvsMg3eqsaeibksk3Dw/Distance%20Calc.pdf?download
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=280758#280758
Attachments:
http://forums.matronics.com//files/distance_calc_709.pdf
Message 6
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| Subject: | Busbar Protection Coating |
For those of you using bus bars instead of fuse blocks... What are you using to
protect against inadvertent grounding and the sparks that are sure to follow?
I was thinking about coating my bus bars with heat shrink and just cutting
away where I wanted to tie in, but I had second thoughts since if it did spark
the heat shrink could be a good combustible to get a fire going under my panel.
Any thoughts from anyone are appreciated.
Liquid electrical tape?
Is there some tefzel equivlant that could be used to coat the bus bar? I know
many are not insulated, but it just doesn't give me a warm fuzzy feeling.
Thanks in advance.
--------
One Rivet at a Time!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=280761#280761
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