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nuckollsr(at)cox.net
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 Posted: Sat Feb 24, 2007 10:17 am Post subject: Shielded wires with modern ignition systems . . . |
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| Quote: | Comments/Questions: Bob,
Please confirm that I have this right or suggest corrections. I am
building a Zenith CH601-HD with Jabiru 3300A using an electrical system
similar to Z-20. However, I am using the Aircraft Spruce A-510-2 Ignition
Switch. Is the following wiring correct? Both mags are connected to the
switch via shielded 20 AWG wire.
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Yes
| Quote: | The mag wires are sheilded with a pigtail only at one end.
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Yes
| Quote: | I chose to ground the pigtails at the switch end because the electronic
mags are in a plastic case.
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Oops, if they're electronic mags, then perhaps shielding
is not necessary. Unlike with a magneto the "p-lead" (primary-
lead) does not carry the gawd-awful high voltage waveform that
makes the classic magneto p-lead a potential noise source.
| Quote: | So the pigtails are attached to the center ground screw on the switch.
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| Quote: | The shielding on the wire to the starter contactor is also grounded to
the same switch screw.
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Why are you shielding this lead?
| Quote: | At the contactor end the shielding is grounded to the lower
stud on the forest of tabs ground block.
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There's no need to shield any wires connected to
the starter contactor . . .
| Quote: | So the p-lead ground goes from the mags to the switch to
the ground block.
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. . . and I'm not convinced that the control lead
to any form of electronic ignition benefits from shielding.
For example, on pages 6 and 22 of E-Mag's installation
manual at:
http://emagair.com/Manual%20L113v29.pdf
The pictures and schematics are notably devoid of shielded
wire . . . and I would be disappointed if they called out
the use of shielded wire.
You'll need to ask the manufacturer for your system as
to the need for shielded wire
| Quote: | Does this work out OK? Thanks ... Jeff Davidson (Novice Electrician)
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Don't think it's at all necessary. Without specific instructions
from your ignition manufacturer my recommendation is that no
shielded wire is necessary and all system ground wires be taken to
a common ground point on the firewall.
P.S. I dug up the installation manual for the 3300 on the 'net. The
wiring diagram DOES NOT call for shielded wire to the ignition controls.
Bob . . .
----------------------------------------
( IF one wishes to be "world class" at )
( anything, what ever you do must be )
( exercised EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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frank.phyllis(at)mindspri
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| Posted: Sat Feb 24, 2007 6:28 pm Post subject: Shielded wires with modern ignition systems . . . |
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The ROTAX 912ULS wiring diagram (with electron mags) shows shielded wire
for the ignition with a ground at both ends. I assume this diagram
should be followed?
Frank
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jetboy
Joined: 22 Jul 2006
Posts: 233
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| Posted: Sat Feb 24, 2007 10:52 pm Post subject: Re: Shielded wires with modern ignition systems . . . |
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The Jabiru mags are not "electronic ignition" as commonly classified. they do have a transistor switch inside.
Although shielding the P lead is not necessary, best practice is to run in shielded lead, ground the shield at mag end to a spare thread hole (on the alternator statorplate will do). At the mag switch end, the shield is connected to the gnd terminal of the switch, but not connected to the airframe here.
during running, there are over 200v of spikes on these lines. Refer to the files section on Yahoo Jabiru/engines group, "radio noise" , look for jab.coil primary - a photo of the trace on the P lead.
http://groups.yahoo.com/group/jabiruengines/files/Radio%20noise/
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_________________
Ralph - CH701 / 2200a |
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