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1. 04:30 AM - Re: Too many Circuit breakers.... (user9253)
2. 05:17 AM - Re: Too many Circuit breakers.... (user9253)
3. 06:04 AM - Re: Re: Too many Circuit breakers.... (Charlie England)
4. 06:36 AM - Re: Re: Too many Circuit breakers.... (Charlie England)
5. 09:02 PM - Re: Too many Circuit breakers.... (andymeyer)
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| Subject: | Re: Too many Circuit breakers.... |
Charlie, Maybe my Busman fuse block was defective or maybe I am too much of a perfectionist.
But the fuses did not require much force to pull out. The spring
contacts only gripped the fuse at one location. I made my own fuse block using
contacts similar to spade connectors which grip the fuse on two edges. See
Mouser part number 534-3522. I have to use a tool to pull a fuse out.
--------
Joe Gores
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| Subject: | Re: Too many Circuit breakers.... |
Andy, read this http://www.aeroelectric.com/articles/avmaster.pdf
An avionics master switch is an unnecessary failure point. If it fails, all avionics
are lost. If not installed, it can not fail.
There are no voltage spikes that can damage avionics during engine starting.
There is a voltage sag during starting that might cause avionics to reboot. But
voltage sag while cranking the engine will not damage avionics.
Some pilots argue that they don't want to wear out individual avionics switches,
so they install an avionics master switch. Actually, switches need to be exercised
to wear away corrosion. Switches are designed to be operated tens of
thousands of times. How many times will you operate avionics switches during
your lifetime?
My airplane does not have an avionics master switch. I leave all avionics turned
on during engine start. I have started my plane hundreds of times over the
past 11 years. All avionics still work fine.
--------
Joe Gores
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| Subject: | Re: Too many Circuit breakers.... |
On Sun, May 8, 2022 at 7:42 AM user9253 <fransew@gmail.com> wrote:
>
> Charlie, Maybe my Busman fuse block was defective or maybe I am too much
> of a perfectionist. But the fuses did not require much force to pull out.
> The spring contacts only gripped the fuse at one location. I made my own
> fuse block using contacts similar to spade connectors which grip the fuse
> on two edges. See Mouser part number 534-3522. I have to use a tool to
> pull a fuse out.
>
> --------
> Joe Gores
>
> This is what the Bussmann looks like inside. (I 'modded' one to have two
buses in one block.)
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| Subject: | Re: Too many Circuit breakers.... |
On Sat, May 7, 2022 at 11:10 PM andymeyer <meyerkc135@gmail.com> wrote:
> >
>
> Alright - I'm down to 7 breakers, plus 4 W31's...
>
> Any thoughts on the Avionics Master? - Yes? No? Either way?
>
> Breakers:
> Alternator
> Ignition 1
> Ignition 2
> Engine Instruments (This is home built so I want to be able to reset if
> needed)
> Transponder (in case I need to go quiet, formation, etc... It's remote
> only - breaker is a fast switch)
> Audio (In case I get a loud squeal or otherwise, I can get it out of the
> system)
> Autopilot (In case it misbehaves)
>
> W31's are switches/breakers for the following - (been in their for the
> same function for ~20 years) All could be switches and if the W31's give up
> the ghost, they will become switches / fuses:
> Pitot Heat
> Nav lights
> Landing Light
> Boost Pump
>
> Thanks for helping me with the simplification - I'm liking this a lot
> better and gaining a lot of comfort!
>
> Andy
My philosophy on stuff that keeps the engine running is that it should be
independent of any a/c bus, just like conventional carb/mags engines are.
What does the electronic engine mfgr say about how to supply power to the
ignitions? There's one full bore controller mfgr (that I'd never consider
using) that advises stuff that's truly scary, but most tell you to run the
ignition supply directly from the battery, ahead of any master contactor,
etc. If you do that, in my mind fusible links (at the battery) are by far
the most bullet-proof system to protect the wire with no chance of a
'nuisance trip'.
If we ignore the fact that you already have the CBs, nothing on that list
would have a breaker in my plane, except the alternator field, and that
only because I'm using crowbar style overvoltage protection.
Almost anything that needs to be switched can be controlled with a switch
that will be cheaper, lighter, and likely more reliable than a CB;
especially a combo switch/breaker.
For me, any decision about an avionics master would be driven by
operational convenience, and whether I need the ability to load-shed, in a
failed alternator situation. In the totally electrically dependent plane
I'm building, I have dual identical alternators, so load shedding isn't an
issue. I therefore have an engine master, that controls the bus that powers
the engine, and an airframe bus, that powers the rest of the plane. I
suppose we could call the airframe bus an 'avionics bus', but it's really
everything except the stuff that keeps the engine running. There's a
bus-tie switch that can power the engine bus from the airframe bus, as
backup if something in the engine master circuit fails.
If you need to shed loads for alternator-out, then putting all
non-essential stuff on a separate switched bus would make sense.
There's also the issue of 'brownout' and rebooting at engine start. If
that's an inconvenience, you can pick between letting everything boot at
master-on and use a brownout booster, or using an avionics master &
powering the avionics after engine start. I only had one thing (an EFIS) in
my current flying a/c that rebooted at engine start, so I made a brownout
booster using a little $5 'boost' regulator, wired to the supply and to a
diode-isolated power input on the EFIS.
I do have an 'essential' bus in the flying a/c that can be left powered up
if I need to turn off the master to conserve battery energy (the flying a/c
has only one alternator). The essential bus makes it basically a one step
operation to shed nonessential loads, instead of having to individually
turn off stuff, which could be overlooked in a stressed environment.
Charlie
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| Subject: | Re: Too many Circuit breakers.... |
Alright...
Down to 4 breakers which may turn into switches... Engine Monitor, Transponder,
Audio panel (remote) and the autopilot. Those are things I feel I must be able
to shut down hard.
My engine monitor so I can reset the thing - didn't design a reset input into the
PCBA, though that may come with the next board turn. Just ordered the PCBA's
2 weeks ago.
My essential bus will be the following - uAvionix AV30 (basic EFIS), GPS Navigator,
and the engine monitor.
Battery bus will be the two Lightspeed ignitions - switch, no breaker, just fuse
links.
Keeping the Avionics bus - bad habits are hard to break.
Because the Avidyne IFD has dual power inputs that are diode or'd, I'll feed one
side from the Avionics and the other from the Essential bus. Other items don't
so I'll put two schottky diodes in to prevent backfeeding. Or, what 20A schottky
diode is recommended that can support my whole essential bus? Can't see
where I can buy the AEC9001-1.
One ignition will have a 3 position switch - middle position will go to a small
standby battery for power in case the world is coming undone. Totally isolated
then except for that switch.
Normal flight - ESS bus off, master on. Electrical stuff goes weird - ESS on and
Master off. Engine quits, IGN1 to middle position.
Charlie, What's your brown-out booster look like?
Getting real close! Thanks!
Andy
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