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Do shielded wires still need to be isolated

BLittleton

Active Member
Hello all. I apologize if this has been answered a lot, but I cannot find it here on VAF or at aeroelectric.

I'm using the FlyLED position/strobe lights and LED landing/taxi lights in the wingtips with the Archer VOR antennae. If the LED lights are so low voltage compared to others and use shielded wires, can the shielded LED wires go in the same wing conduit as the Archer VORs with shielded coax?

I think I understand that those with older type bulbs would run all the wires separate to minimize noise from the wig wag or strobes getting into the other wires. Is that still an issue with the lower voltage and shielded wires for LEDs?

If coax and shielded light wires still have to be separated, what is the minimum distance?

What about possible magnetometer wire...can that go in the same conduit as the lights?

Thanks,
 
In principle, you can run them all side by side. In practice, no shield is perfect. If it were me I'd run the coax at least a foot away, or more if possible. But only a test will give you the answer. BTW, many high power LEDs are very rapidly pulsed (too fast for you to see), so they can be sources of RF interference. I was playing with some cheap ones when I noticed that they drove the FM radio on the bench into emitting a lot of noise!
 
But only a test will give you the answer.

Best I could come with is "don't run cables side by side"...:(

Are you using RG-142 (RG-400)? Possible upgrade path if required.

Research:

"RG-58 also doesn’t shield as well, so it’s worth it to use RG-142. I can’t tell you how many ‘noisy’ airplanes we’ve fixed by just using decent coax.
RG-142 is equivalent to RG-400 for our purposes. RG-400 has a stranded center conductor, but for our uses they’re equivalent."

Older quote,

Garet,

The normal snap bushings sent in the wing kit will work for running the coax cable like I have in the picture. I ran mine outside the conduit because I heard that others have had interference on their com radios when the coax is too close to the wire runs for the lighting. I don't think it is too much of a problem with LED lights, but just wanted to play it safe.



Good article HERE!



T.C.
 
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Hi Bradley

I kind of agree with Bob. There's a comfort level somewhere between 'no problem' and 'run wires together at your peril' for everything!

The energy from the Flyleds product is so low I reckon that it doesn't even need shielded wire... could you please test my theory?!
A xenon strobe, on the other hand, is running on pulses of a few hundred volts, so carefully run and terminated shielded wire is a must there.

For the RV-10 that the first kit went into, we ran the Flyleds shielded wire in the same conduit in the wing as everything else, and along with all the other dozens of other wires in the fuselage bundles. We also have an Archer antenna out on one wing, located about a foot behind the Flyleds boards. No problems.

Shielded cables, when terminated as per each system manufacturer's instructions, will not interfere with each other or pick up noise. Oh and spend the money and use RG400 for your antenna runs!

 
Thanks all for the comments. I wound up running RG-400 separate from the conduit for the comfort level. Everything else (lights, AOA, autopilot servos, stall warner, etc) I plan on running in the conduit.

My question now is what happens when wires start to bundle up in the fuse and run close to or cross the coax all heading for the panel? I know folks try to run things on opposite sides of the fuse and stuff. I assume this is not a problem?
 
Be sure to only ground one end of the shielding. Grounding both ends greats a ground loop that will cause more interference.
 
Just for some data, the controller board for mine is about 7 inches from my comm antenna under the floor boards and I have no noise at all.

Paul, lights are working great. Thanks for the help. Everybody that sees them comments on how bright they are and got some good comments at SnF about them.

Bob. Burns
Rv-4 N82rb
 
My question now is what happens when wires start to bundle up in the fuse and run close to or cross the coax all heading for the panel? I know folks try to run things on opposite sides of the fuse and stuff. I assume this is not a problem?

My thoughts...

To reduce electrostatic/magnetically coupled noise keep high powered antagonists such as magneto p-leads, strobes, and any higher voltage, power switching devices away from easily effected victims...I would include the newer high powered transponders (S) squitter boxes and coax cable as a possible interference problem.
Victims include audio wiring, headphone and mic wiring. Possible serial communication wiring. The sensitive weaker circuits.
Wires meeting at a 90 degree angle to each other is not as bad an issue as wires that are run parallel and in close proximity to each other. (bundles)
Remember, distance between possible coupling wiring is your friend! If you have it, use it. Twisting wires, such as power and grounds can be beneficial. Dedicated avionics power and ground wire landing busses are a must.
As eluded to earlier, proper use of shielded wiring, the number of and where to terminate shielding may very a lot with the type of device. Correctly ground all devices. Follow and use the manufactures recommendations!

With best regards,
 
Hello all. I apologize if this has been answered a lot, but I cannot find it here on VAF or at aeroelectric.

I'm using the FlyLED position/strobe lights and LED landing/taxi lights in the wingtips with the Archer VOR antennae.

Thanks,

What did you pair with the FlyLEDs for the landing/taxi light, if I may ask?

Thanks
Charlie
 
I got the Baja Designs Squadron Pro Driving Combo. I completely copied the install idea from other posts here. I think they will work well, and the power is so low I doubt they will be noisy.
 
So I have my ziptips all wired up with shielded MIL-27500 wire….. is it best to ground shields locally in wing tip somewhere or to run a ground wire to panel like rest of grounds?
I was thinking removing small area of primer and screw down a ground screw someplace out on wing
 
I would think that grounding the shielding at your main ground tree under the panel would be preferable. Local grounds can sometimes do quirky things.
 
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So I have my ziptips all wired up with shielded MIL-27500 wire….. is it best to ground shields locally in wing tip somewhere or to run a ground wire to panel like rest of grounds?
I was thinking removing small area of primer and screw down a ground screw someplace out on wing

John, the best advice is to follow the instructions given by the manufacturer of each device.

For Flyleds strobe lights when people start adding extra grounds that's when all the troubles start. Flyleds strobes use "negative switching" to flash the strobes, so additional grounds just jam the strobes on.

I'm guessing that the Ziptip instructions will be different to mine!

 
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