Replies to This Discussion

Permalink Reply by John Austin on October 25, 2013 at 1:53pm

Dave,

Since the LED strobes are essentially low-voltage lighting and you don't have the issue of a high-voltage power supply radiating high voltage through the wiring, it probably matters little if it's shielded or not. That being said, I used shielded wire, too! I think you can ground it at either end, but since the strobe is mounted on the fiberglass wingtip, there's not a convenient ground source. I just continued my shield with a pigtail through a multi-connector and brought it all the way to the power supply's ground bus.

By the way, although it's unlikely I'll ever pull the wings off (except for a repair God forbid!), I used a "Seal-All" connector (Spruce) at the wing root. It is a weather-proof connector with silicon seals. You can get them with about any number of connections. Like I said, I just made a pigtail off the shield and ran the pigtail through the connector.

John

N750A

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Permalink Reply by Mark Maltais on October 25, 2013 at 5:03pm

I also used shielded wire, just 'cause! :D 

I left a length of the shield on and soldered it to make it a bit more solid then I soldered a wire and crimped a terminal onto it and put a bolt into the wing to ground it, along with the shield from the other side of the connection. I did this at each end of the wing and at the fuselage end where the molex is. 

It might be low voltage but I got enough experience to know any ungrounded line can cause some crappy interference that can be hard to isolate down the road.  I'd rather not take a chance. 

In this shot, taken while I was cleaning up the connections, you can see the shields attached to wires and grounded to the red ring terminals.  This was my solution.

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Permalink Reply by John Austin on October 25, 2013 at 5:11pm

Mark,

I don't know if I followed your description correctly, but if you grounded the same shield at the wingtip and at the fuselage, that's a no-no. Shielded wire is grounded at one end only. Otherwise, you can create a noise-inducing ground loop.

As I said before, it probably doesn't make a hill of beans difference in this case since LED wiring is essentially low-voltage lighting, but grounding the shield at one end only is the correct technique.

Please correct me if I misunderstood.

John

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Permalink Reply by Mark Maltais on October 25, 2013 at 6:43pm

Yeah it didn't come across well in the description.  I have a length of wire in the wing and the shield is grounded at the wing tip.  The other length of wire in the fuselage has one end of the shield grounded in the fuselage.  A word smith me not... :)

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Permalink Reply by David J. Beaulieu on October 26, 2013 at 9:14am

John / Mark

 

Thanks for the replies. 

 

John - Good point about the low voltage thru the lines, everything is "stepped up" via the IC boards at the strobe unit on each wingtip. I will have to check out the wiring diagram, but I believe the AeroLED schematic shows the shield grounded at each end of a continuous run of wire from strobe/nav unit to switch.  I placed a call to AeroLED but missed the tech call back so will try to connect next week.  I used a solder seal with a grounding termination wire to affix a ground to the shield and then grounded to the spar/wing tip extension via rivet.  I had planned on continuing the ground thru the quick connect at the root/fuselage into the panel and also ground to a dedicated ground bus behind the panel within the fuselage.

 

Mark - Thanks for the pic.  Seems like you are in agreement with John regarding grounding of the shield.  You are grounding at each individual run of wire but not continuing the shield continuity across your Molex.  Is my understanding correct?

 

 

Will post wht I hear from AeroLED...  Thanks again!

 

Dave

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Permalink Reply by Mark Maltais on October 26, 2013 at 9:24am

Yeah, pretty much it.  You can ground through the molex if you want to make one continuous length but wherever the line ends up just don't ground the other end.  In my case I'm using automotive trailer connections because the little white connections (molex) that came with mine look like absolute junk and I don't think they would last long.  I also wanted something a little more resistant to water/moisture and tougher since I'll be taking off my wings regularly.

Looking forward to hear what AeroLED says...

Mark

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Permalink Reply by John Austin on October 26, 2013 at 10:28am

Mark,

Check out the Seal-All connectors (Spruce) if you want the ultimate in weather resistance.

John

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Permalink Reply by John Austin on October 26, 2013 at 10:27am

Dave,

Using a central grounding point is the modern standard for aircraft wiring. The ground could be either to the spar tip or the power supply ground bus, but shouldn't be both - you'll create a loop! Best practice would be to carry the ground back to a central grounding point, i.e., the dedicated ground bus. Same for the shield - ground at one end only - your choice whether to do this for each wire segment or instead jumper to the next wire and carry all the way back to a central ground.

John

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Permalink Reply by Daniel C Hall on October 26, 2013 at 11:02pm

It's been said already but once again, ground one end of the shield only.  Both ends of the NEGATIVE conductor of course need to be terminated.  

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Permalink Reply by David J. Beaulieu on November 4, 2013 at 7:38pm

Follow-up to the shielded wire question... I talked with Dean Wilkinson,CTO of Aeroled regarding the schematic for grounding the shield...very personable and seems knowledgeable regarding E&M and application. Schematic indicated grounding of the shielded wire at the wing tip in close proximity to the strobe/nav unit and at the other end of the wire run. Based on his experience, he suggested that I adhere to the schematic and ground at both ends.  Only if I have an issue with an on board magnometer should I consider grounding at one end only, and is so, ground inside the fuselage, vice the wing spar tip.  Also did some browsing on the Van's RV site and the EAA site regarding this topic.  Opinion seems to be split down the middle depending if you are shielding to protect comm freqs or different areas of the spectrum?  So for now, I will plan on continuing the ground thru the quick disconnect into the fuselage and ground at the common ground behind the dash.  I guess worse case would be I make an access panel at the wing tip and disconnect the shield ground there.

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