---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 06/03/18: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:57 AM - Am I creating a Ground Loop? (speedy11@aol.com) 2. 10:31 AM - Re: Am I creating a Ground Loop? (Robert L. Nuckolls, III) 3. 11:48 AM - Re: Am I creating a Ground Loop? (user9253) ________________________________ Message 1 _____________________________________ Time: 09:57:45 AM PST US From: speedy11@aol.com Subject: AeroElectric-List: Am I creating a Ground Loop? Fellow Aeroelectric Brothers, According to Wikipedia: A ground loop is caused by the interconnection of electrical equipment that results in there being multiple paths to ground, so a closed conductive loop is formed, With that in mind, let me try to describe what I am doing and ask if you think I am creating a ground loop. I am in the midst of removing old EFIS, radio, AP and installing all new. As a sideshow to that effort I decided, since I have everything gutted, to replace the older Whelen strobe/position lights with new Whelen LED strobe/position lights. The old system was effectively two separate systems. The old position lights were grounded at the wingtip. The strobe lights had a central power supply (fuselage mounted) which was grounded at the firewall forest of tabs. The new all-LED strobe/position light was designed with a single ground wire that provides ground for both the position lights and the strobe. I am attempting to use the original wiring as much as possible to avoid running wires to the wingtips again. If I connect the new single ground wire to the wingtip ground, only the position lights work. If I connect the single ground wire to the old strobe power supply ground (firewall) only the strobe works. If I were to splice the wingtip ground wire and the firewall ground wire together so as to have a single ground wire to attach to the new LED unit, am I creating a ground loop? Thanks for your advice, Stan Sutterfield ________________________________ Message 2 _____________________________________ Time: 10:31:13 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Am I creating a Ground Loop? At 11:56 AM 6/3/2018, you wrote: >Fellow Aeroelectric Brothers, > >According to Wikipedia: A ground loop is caused by the >interconnection of electrical equipment that results in there being >multiple paths to ground, so a closed conductive loop is formed, > >With that in mind, let me try to describe what I am doing and ask if >you think I am creating a ground loop. > >I am in the midst of removing old EFIS, radio, AP and installing all >new. As a sideshow to that effort I decided, since I have >everything gutted, to replace the older Whelen strobe/position >lights with new Whelen LED strobe/position lights. > >The old system was effectively two separate systems. The old >position lights were grounded at the wingtip. The strobe lights had >a central power supply (fuselage mounted) which was grounded at the >firewall forest of tabs. > >The new all-LED strobe/position light was designed with a single >ground wire that provides ground for both the position lights and the strobe. > >I am attempting to use the original wiring as much as possible to >avoid running wires to the wingtips again. > >If I connect the new single ground wire to the wingtip ground, only >the position lights work. If I connect the single ground wire to >the old strobe power supply ground (firewall) only the strobe works. > >If I were to splice the wingtip ground wire and the firewall ground >wire together so as to have a single ground wire to attach to the >new LED unit, am I creating a ground loop? > >Thanks for your advice, Review this drawing https://goo.gl/TW8wFF Significant 'ground loops' ONLY involve potential victims which includes but is not limited to audio systems, avionics, engine instrumentation, or any other system that works with and reacts to SMALL signals. This does not involve LARGE signals like the ground currents for landing lights, pitot heat, hydraulic pumps, alternators, etc. In fact, those LARGE signals devices are what creats tiny voltage drops on the AIRFRAME that might affect a SMALL signal system that seeks more than one ground on separate airframe locations. In the figure cited I illustrate a potential problem with the headset ground and grounding of an oil pressure transducer. In fact, improper grounding of both of these items was identified as a source of difficulties here on the List and discussed in my writings. The greatest prophylactic against ground induced noise/interference is the creation of a central ground point for potential victims . . . usually limited to those devices mounted on the panel I suggested fabrication of an instrument panel ground bus https://goo.gl/VX53mE https://goo.gl/rsVefK This can be fabricated from a D-sub connector and mounted at some convenient, central location at the panel. Grounds for all potential victims can be gathered together at this location thus INSURING that all such appliances share a single common ground with NO REMOTE GROUNDS elsewhere on the airframe. A multiple strand grounding bundle is run from this bus to the firewall bus where all the other stuff gets a ground. Suggest you use a 25 or 37 pin connector to fabricate the bus . . . better to have TOO MANY ground locations than to be nearly done and run out of grounds. All that other stuff OFF THE PANEL, ground locally on a metal airplane or take ground return to the firewall bus on a plastic airplane. Bob . . . ________________________________ Message 3 _____________________________________ Time: 11:48:00 AM PST US Subject: AeroElectric-List: Re: Am I creating a Ground Loop? From: "user9253" Since the old position lights were grounded at the wingtip, that implies that the wingtip ground wire was only a few inches long. I do not understand how the wingtip ground wire is in the fuselage. Is this a metal airplane? Regardless, I would connect both ground wires to the firewall. The important thing is to ground all avionics and instruments to one single location. Make sure that audio and Mic jacks are not grounded locally. Mount jacks with insulating washers. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=480612#480612 ------------------------------------------------------------------------------------- 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.