---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 08/10/22: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 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 _____________________________________ Time: 02:36:48 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 05:43:11 PM PST US Subject: AeroElectric-List: Re: Ground Power Z-31 From: "user9253" 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 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=507653#507653 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.