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1. 02:36 PM - Re: Ground Power Z-31 (Robert L. Nuckolls, III)
2. 05:43 PM - Re: Ground Power Z-31 (user9253)
Message 1
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| Subject: | Re: Ground Power Z-31 |
At 08:33 AM 8/9/2022, you wrote:
>
>Looking at Z-31, once the ground power relay is energized, its relay coil will
>remain energized, being back fed from the aircraft battery via the ground
>power relay contacts. It will be up to the pilot to open the
>circuit provided
>that he knows enough to do that and remembers. But if he can't remember
>to shut off the master switch, he won't remember to open the ground power
>relay circuit either. One solution is to put a limit switch in
>series with the
>ground power relay coil. The limit switch could be operated by the cover of
>the piper style receptacle.
Yeah, that's a down-side of the simpler, less expensive
Cole-Hersee external power connector. We had some
discussions about that back in the dark ages. The
simplest thing to do would be to add a "GND PWR"
annunciator light across the contactor coil that
illuminates any time it's energized.
We also did some brainstorming on a circuit to put
in series with the contactor coil at the switch
to detect when it had current flowing in it . . .
this would also illuminate an annunciator. Sticky
part was that what ever technology we used, it had
to stand off the fault currents of crowbaring
a breaker open.
That was a long time ago . . . I'll see if I can
dig up the notes. One simple hack would be to fabricate
a current operated relay that would close at anything
above about 0.5A. Use this to light the annunciator.
This would be the easiest thing to incorporate that
would require a MINIMUM of added wires and nothing
going thru the firewall. The current relay could
be fabricated with a coil of wire around a reed
switch capsule. This device would easily stand off
the crowbar trip current.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 2
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| Subject: | Re: Ground Power Z-31 |
I don't know if a reverse voltage or reverse current sensor is available at a reasonable
price.
If so, the sensor could monitor the current or voltage drop on the cable that goes
between the ground power contactor and aircraft battery
contactor and could open the ground-power contactor coil circuit when current
is reversed.
--------
Joe Gores
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http://forums.matronics.com/viewtopic.php?p=507653#507653
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