Today's Message Index:
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1. 02:12 PM - Placement of Switch within Simple Circuits - does it Matter? (wsimpso1)
2. 06:52 PM - Re: Placement of Switch within Simple Circuits - does it Matter? (user9253)
Message 1
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| Subject: | Placement of Switch within Simple Circuits - does it |
Matter?
Is there any reason to put the switch close to the bus, close to the load, or even
on the wire going to the ground bus? We have quite a few circuits in our airplanes
where the switch is simply closing or opening the circuit. On this simplest
of circuits, the function can be effective no matter where we put the switch.
We do have quite a few devices where circuit control is done on the ground side.
EFII injectors and coils are commonly hot from the bus to the device and the
return wire goes to the ECU where it is grounded. So that got me thinking about
where we put our switches.
Taking this design philosophy question a step further, it occurs to me the choice
to fuse the + volt side is because we traditionally have a metal airframe available
for the ground path, and indeed is a spectrum of places where a hot wire
will short back to the battery. In my non-conductive airframe, I am running
a ground wire to a ground bus. It would seem that any place in my circuit could
be shorted to another circuit of opposite polarity, and yet we do not fuse
our ground wires. Is that really OK?
Billski
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=517197#517197
Message 2
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| Subject: | Re: Placement of Switch within Simple Circuits - does |
it Matter?
> and yet we do not fuse our ground wires. Is that really OK?
Yes, in most cases. Suppose that a very large positive wire shorts to a small
negative wire. The fuse protecting the large positive wire might not blow. But
the chances of that happening are pretty small, especially if good workmanship
is practiced. Use lots of wire-ties to prevent relative motion between wires.
Use grommets where wires pass through bulkheads.
Installing a fuse in a negative wire introduces several new failure points.
Future troubleshooters will cuss you out. :-)
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Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=517198#517198
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