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Am I creating a Ground Loop?

 
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speedy11



Joined: 29 Jun 2015
Posts: 42
Location: Port Orange, FL

PostPosted: Sun Jun 03, 2018 8:57 am    Post subject: Am I creating a Ground Loop? Reply with quote

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


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nuckolls.bob(at)aeroelect
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PostPosted: Sun Jun 03, 2018 9:31 am    Post subject: Am I creating a Ground Loop? Reply with quote

At 11:56 AM 6/3/2018, you wrote:
Quote:
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 . . .


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user9253



Joined: 28 Mar 2008
Posts: 1256
Location: Riley TWP Michigan

PostPosted: Sun Jun 03, 2018 10:47 am    Post subject: Re: Am I creating a Ground Loop? Reply with quote

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.


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Joe Gores
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speedy11



Joined: 29 Jun 2015
Posts: 42
Location: Port Orange, FL

PostPosted: Mon Jun 04, 2018 3:35 pm    Post subject: Am I creating a Ground Loop? Reply with quote

Bob and Joe, Thanks for your responses.
Stan Sutterfield


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