billy's plans built sonex 1735

[GordonTurner]

It should be obvious that it makes no difference to the appliance whether the positive or ground is switched. Problems with switching the ground include, but are not necessarily limited to:

-it is non-standard, for what that is worth.

-appliances may have a grounding route through the case, in which case your switch is bypassed.

-when you switch off the positive, there is a lot less of the system with potential energy source to short.

-Maybe that ground plane thing with radios, not too sure about that one.

But....it’s your airplane :)

Gordon

[Rofomoto]

I’ve decided no ground side switches. Thanx all.

[Darick]

This could be an interesting discussion with Jim Weir. Conventional wiring is battery positive-switch-appliance-ground which assumes the electron flow is from positive to negative. However in Jim's article in the August issue of Kitplanes, he says "...those electrons are coming from the negative pole of your battery up through the radio and out into the positive bus."
It's black magic to me but I'm sticking to the conventional method of wiring.

[dbdevkc]

Although it is true the electron flow is actually from negative to positive, until I can be convinced otherwise, I agree with Gordon - especially:

"-appliances may have a grounding route through the case, in which case your switch is bypassed.
-when you switch off the positive, there is a lot less of the system with potential energy source to short."

[Area 51%]

Maybe we can get Chris to move this discussion somewhere else so as not to muddy Billy's site further. For what it's worth, my take on the switched ground was to activate relays, not the appliances they drive.

[DCASonex]

Billy, All of your avionics combined are likely only a few amps. Just install an avionics master switch or master breaker switch right after your master switch, breaker or contactor and before any individual breakers or fuses Have mine located right next to the master switch.

David A.

[Arjay]

Waaay back in the days when we were designing missile flight control systems, standard engineering practice was to never put a switch to ground on the low (ground) side of a load (avionics). One of the reasons was it was too easy to make a single failure point because it was highly probable a ground fault could activate the circuit when you didn't want it to activate, possibly with disastrous results. Our goal was reliability up into the high 99's, thus we tried not to allow single failure points in the design.

As far as the direction of current flow is concerned. We were taught that conventional current flows from positive to negative. However, the electrons actually flow in the other direction. Go figure!!

Ron
Legacy Sonex taildragger, internationally know for landing on 25R.
Aerovee with Aerocarb that we finally got dialed in nicely. (ask me how to do it)
Atlanta area

[Rofomoto]

Panel layout

[Rofomoto]

Ignition system to install on the inside of the firewall to keep it out of the heat

[Rofomoto]

Got my fuse block today. 12 circuits. Will panel mount it. Comes with cover