Today's Message Index:
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1. 09:08 AM - Re: Re: wire for mags (Charlie England)
2. 11:45 AM - Re: wire for mags (Richard Pike)
Message 1
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| Subject: | Re: wire for mags |
For some reason, I never got the original poster's message. But for
wiring magnetos ('conventional' aircraft mags):
Suspend normal thought about shields when looking at magnetos.
The shield helps minimize radiated 'noise' (RF energy) from the mag
while it's operating, and is grounded only on the mag itself while
operating. The shield is the return path to short out the mag when the
mag switch is 'off' (note the quotes).
http://www.aeroelectric.com/articles/MagnetoSwitchOptions.pdf
(Note that the .pdf shows many more 'bells&whistles' than are needed to
simply control a magneto; try to mentally strip away all the extra
functions & just look at the wiring to the mags.)
Center conductor to the points in the mag (P lead terminal), shield
grounded to the mag case.
At the other end, center conductor to one terminal of your mag switch,
and the shield to the other terminal. When the switch is *closed*
(continuity across the terminals), the mag is *off*. When the switch is
*open* (off, in normal terminology), the mag is *on*. The other end of
the shield should not be connected to the airframe; only to the 2nd
terminal of your mag switch.
Wire gauge is non-critical; anything 22awg or bigger for center
conductor is fine (smaller is just too mechanically fragile).
Using a 'spare' wire that's in the same sheath as the P lead might work
fine for something like a tach signal. Or it might not. If something's
not working normally, how do you troubleshoot?
*Charlie *
On 1/1/2017 10:43 PM, Richard Pike wrote:
>
> Yes, they do connect to ground. If you plan to use a radio, then you need to
use a shielded cable, the cheapest and sufficient is microphone cable, it is two
insulated wires plus a ground wire inside a metal foil sheath inside a plastic
sheath. If you have dual mags, you can use one insulated wire for one mag
and the other insulated wire for the 2nd mag.
> If you have an older engine with one mag, then you use one insulated wire for
the mag and the other insulated wire for the tach.
> The basis for this is that the ignition pulses are AC, and they will mess up
your radio, so you ground one end of that wire/sheath to either the engine or
the frame, but not both ends. Only one end gets grounded. I am not knowledgeable
enough to explain it, but you don't ground both ends, only one end.
> Now you have 2 insulated wires running through the grounded sheath. If both of
those wire go to your two coils, then you ground those two wires to your two
kill switches and then to ground. If you have an older type engine with only
one ignition system, then you use one of the wires to ground your ignition coil
- kill switch, and use the other one for the tach.
> TL,DR - wires that carry pulsing AC will mess with your radio, and you want them
inside shielded cable, of which one end is grounded.
> If you are planning to use a radio, you have to use shielded cable, one end of
which has to be grounded, but not both ends. As long as you observe this protocol,
you can make your radio work.
>
> --------
> Richard Pike
> Kolb MKIII N420P (420ldPoops)
> Kingsport, TN 3TN0
>
> There are only two kinds of people in the world. Those who say to God; "Thy
will be done."
> And those to whom God says ; "OK then; have it your way."
>
Message 2
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| Subject: | Re: wire for mags |
Good point, my bad. I was only thinking "Rotax." And having only ever wired up
2-cycle Rotax engines, some of what I said might not be right for the 912/etc
versions. Or an HKS. Sorry.
--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
There are only two kinds of people in the world. Those who say to God; "Thy
will be done."
And those to whom God says ; "OK then; have it your way."
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http://forums.matronics.com/viewtopic.php?p=464616#464616
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