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pmnewlon
Joined: 20 Jan 2011
Posts: 21
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 Posted: Tue Feb 22, 2011 12:01 pm Post subject: a couple questions about Z10/8 diagram |
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Maybe I missed the answer to this question in the text ...I am unfortunately unable to install a backup power source (SD8, SD20) because of how the engine mount on my RV4 comes across the back of the engine hear the vacuum pump pad. That said, I am planning to install a 7AH backup (brownout?) battery on a tray behind my instrument panel. - I am wondering if I would be OK to install a switch in place of the brownout battery relay? My only reason for this is that I have seen relays fail more often than switches in my automation control field. I could be dissuaded.- I ordered the BandC ebus diode on a heat sink based on an older copy of the 'Connection. Now in 12a I see that a Schottky is mentioned. Any reason to abandon the original diode plan?- I plan to use the same PB/Tyco circuit breakers as Composite Designs uses in their power panels. They have a circuit board that the PIDG terminals on the breakers are connected to. My thought is to use a piece of brass and 'forest of terminals' such as the ground plate BandC sells for power distribution to the breakers. The plate would be insulated from the panel and covered to protect inadvertent shorting by 'falling objects'. Does this sound reasonable?Thank you!Phil [quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Tue Feb 22, 2011 2:12 pm Post subject: a couple questions about Z10/8 diagram |
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At 02:49 PM 2/22/2011, you wrote:
| Quote: | Maybe I missed the answer to this question in the text ...
I am unfortunately unable to install a backup power source (SD8,
SD20) because of how the engine mount on my RV4 comes across the
back of the engine hear the vacuum pump pad. That said, I am
planning to install a 7AH backup (brownout?) battery on a tray
behind my instrument panel.
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What equipment are you carrying that drives this
decision?
| Quote: | - I am wondering if I would be OK to install a switch in place of
the brownout battery relay? My only reason for this is that I have
seen relays fail more often than switches in my automation control
field. I could be dissuaded.
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Not here to persuade you of anything . . . but
your worry-bucket seems to be carrying some
issues. It would be helpful to know more about
your equipment list and the reasons that drive
installation of a second battery. What failure
mode do you perceive that loss of the relay would
be a pre-cursor to your own dark-n-stormy-night
story? Things FAIL all the time in airplanes.
The best design goals call for crafting systems
that are failure tolerant.
| Quote: | - I ordered the BandC ebus diode on a heat sink based on an older
copy of the 'Connection. Now in 12a I see that a Schottky is
mentioned. Any reason to abandon the original diode plan?
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No.
| Quote: | - I plan to use the same PB/Tyco circuit breakers as Composite
Designs uses in their power panels. They have a circuit board that
the PIDG terminals on the breakers are connected to. My thought is
to use a piece of brass and 'forest of terminals' such as the ground
plate BandC sells for power distribution to the breakers. The plate
would be insulated from the panel and covered to protect inadvertent
shorting by 'falling objects'. Does this sound reasonable?
|
No. To many parts and joints. Why not use breakers that
are bus-bar friendly?
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Tue Feb 22, 2011 2:13 pm Post subject: a couple questions about Z10/8 diagram |
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| Quote: |
- I ordered the BandC ebus diode on a heat sink . . .
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What are your e-bus loads? Do you NEED a heat-sinked
normal feedpath diode? You're building a metal airplane.
I suspect the bare-foot rectifier assembly can be simply
bolted to some portion of the airplane.
Bob . . .
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pmnewlon
Joined: 20 Jan 2011
Posts: 21
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| Posted: Tue Feb 22, 2011 3:14 pm Post subject: Re: a couple questions about Z10/8 diagram |
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Crud - I had all my answers typed in and forgot to copy/paste to notepad in case I had been automagically logged out. I hit 'preview' and lost all I typed. Back to the keyboard.....
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pmnewlon
Joined: 20 Jan 2011
Posts: 21
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| Posted: Tue Feb 22, 2011 5:13 pm Post subject: Re: a couple questions about Z10/8 diagram |
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Bob - thanks for taking the time to provide feedback! My responses are in-line below. Phil
>> (7AH backup) What equipment are you carrying that drives this decision?
Primarily my electronic ignition, EIS and EFIS
>> your worry-bucket seems to be carrying some issues.
It sure is! I only have one teenager and had some excess space in that bucket 
I've experienced the failed alternator in a production airplane and don't want to be there by my own doing in my homebuilt. The plane I owned was rented with a flight school and I was at the mercy of their maintenance as were those who rented it. It was stranded twice because of a failed alternator that wasn't noticed in a timely fashion. The first sign of a problem was the comm radio no longer transmitted. Short minutes later the nav would quit. Thankfully the problem was never more nerve-wracking than having to abort the flight somewhat short of the intended destination and it never happened while under IFR. My plan is to have a well thought-out and implemented electrical system in my RV that will provide the necessary ability to alert me to an issue then let me continue without any worries for an hour minimum and up to two hours. That gives me lots of options to complete the flight to a ho-hum end; most likely at the intended destination.
>> (switch in place of the brownout battery relay) What failure mode do you perceive that loss of the relay would be a pre-cursor to your own dark-n-stormy-night story?
In hindsight I probably should have left this out. Comparing my auto industry automation where the relays make and break thousands of times before failure compared to fact that the switch that was used to set the machine in motion is actuated one or more orders of magnitude fewer times isn't 'fair'. I had a relay in my BandC shopping cart when I left work, I will just order it tomorrow
>> It would be helpful to know more about your equipment list and the reasons that drive installation of a second battery.
The 'Connection basic list (xponder, nav radio, panel flood, turn coordinator) plus my electronic ignition and a rear pax light. The ignition adds 2A to the basic list, though I am debating putting one on the battery bus and the other on the e-bus which would lighten the load by 1A to just under 4A.
>> What are your e-bus loads? Do you NEED a heat-sinked normal feedpath diode? You're building a metal airplane. I suspect the bare-foot rectifier assembly can be simply bolted to some portion of the airplane.
I already have the diode on a heat sink because I hadn't planned on the shelf behind the panel for a small battery. Now that I am going to have a plate there, the barefoot one would work but I will just stick with the one on a heatsink. I was wondering about the Schottky diode and if there was a benefit to the lower voltage losses when compared to the diode I have already.
>> (PB/Tyco circuit breakers connected to forest of tabs bus) Too many parts and joints. Why not use breakers that are bus-bar friendly?
Size, weight and cost. I'll admit I like the way they look and that I'm not excited about fuse blocks.
>> Maybe I missed the answer to this question in the text ...
I started to ask just one question - the one about the relay - and then just kept adding more. I miss a lot in the text that I pick up when I reread sections. I recently updated from v10 to v12a and I have to start from square two. So much to learn.... Frankly the adventure of rewiring my airplane has been made tremendously easier because of your text and website. I've gone from tentatively engaging to full-on fun with it because of them!
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