LED light interference

[rtc183]

Does anyone know of electrical interference won't any non-aircraft led landing lights and radios or other avionics? Lots of new powerful lights out there, and I want to put two in my wingtip.
Bob

[HighWing]

This is an interesting question and I don't know if there is an answer. When building my current flier, there was an article in Kitplanes detailing a power supply for LEDs for the position lights. This might have been six or seven years ago. It was big and bulky and included a choke coil as big as a stack of half dollars. Way overkill strictly from appearance, but quiet as quiet can be. I tried some LED lights with built in power source and noisy to the extent of obliterating any hope of understand a radio transmission - back to the big ugly system. Then the typical cigarette lighter plug in USB charging device, noisy as well. I bought a LED array kit that I installed as a landing/taxi light and it is quiet unless the flash option is triggered, then noisy with pulses as the light flashes. I did find DC to DC power converters at Mouser that are quiet for building a system for feeding the tablet GPS and the Spot tracker. For me it has been sort of a luck of the draw sort of thing. I did try one of the fairly pricey noise reduction units used on certified airplanes, but with no positive effect.

[Timberwolf]

Your post is very hard to understand, but I assume you are asking about LED lights that don't produce noise. If so there's quite a few of us with RV's that have purchased and used these lights https://www.amazon.com/Multipurpose-Tractor-Industrial-Lighting-Landscape/dp/B01NAB4RTV/ref=sr_1_1?ie=UTF8&qid=1485817092&sr=8-1&keywords=PAR36+LED+18W+6000K

They are super bright and produce no noise. I haven't had the same luck with these nav light replacements http://www.aircraftspruce.com/catalog/elpages/navstrobe11374.php?clickkey=4708

I would steer well clear. I have a set that produces so much RF I my radios are unusable. Tried it in both planes with same results. They are Junk

[cubtractor]

Be careful what you get. I tried a 3000 lumen LED for a landing light and it rendered the radio useless. I even hooked it up by itself to a separate battery on the other side of the hanger, no where near the plane and the radio was inop from it. Sounds like the RV guys have it figured out.

[rtc183]

Thanks for the replies. I was looking for exactly the lights shown in the link. Do you have a picture of the mounts on the RV?
Thanks again.

[rtc183]

Just read my original post. Spell checkers are great, so is not proof reading.

[Timberwolf]

Sorry but I don't have any pics of them installed. It fit just fine in the PAR36 housing though I believe these were a tad thicker than the incandescent fixtures that they replaced. They are much brighter to boot.

[jeffbock]

LED lights vs. VHF radio's. Just adding to the mix on this discussion.
I recently attempted talking on my handheld VHF radio from in the house and the unit was totally unusable. When getting about 100ft from the house it worked fine. After a bit of experimenting I discovered that the overhead LED lights were the offending party.
I have been having trouble with my MGL V-6 radio being staticy and have even installed a noise/static suppressor in line prior to all avionics. Still have the problem. Was thinking of converting to an alternator rather than the dynamo on engine but now feel that may not help. JeffB

[efwd]

this is all very interesting. I have Aero LEDs and am aware of others who are flying with them and they have no issues. Is it likely that the LED installation is the issue here? Are the wires shielded and grounded correctly in these problem
scenarios?
Eddie

[jiott]

I also have been using LED, Whelan, lights for 4 years with absolutely no interference problems. Installed them by the book using shielded wire.

[HighWing]

This is what I have learned about LEDs. They are powered by a power supply that monitors amperage rather than volts. If you have a LED listed at 3 volts and use a resistor to reduce the 12 volts in our system to 3 volts it will light the LED. However during the engine run when the charging system has raised the voltage to close to 14 volts, it will over power the LED. Or conversely if the battery is not producing 12 volts the LED will be under-powered. Both these situations will result in a different light output. The "Powers that Be" have determined that LEDs are more efficient with constant current. The circuitry that monitors and adjusts current appear to be very noisy as it apparently produces frequencies in our RF band that we can hear during radio reception.

All the LEDs will produce light using a resistor with no noise, but the light output will not be a consistent brightness. I would expect that the light arrays produced specifically for aviation use have filtering systems built into the power supply that eliminates the high frequency noise we hear in our headsets. That is likely why they are priced as they are.

[PaulSS]

I will be fitting these, eventually, to my aircraft. They are very, very popular on the Eurfox (A220) and I have not heard one mention of interference:

Whelen Strobes (http://www.whelen.com/aviation/product.php?head_id=10&prod_id=188)

Easy install and no boxes to build up enough ummphh for a flash.

I was originally going to use a 3 core shielded cable (power, ground, synch) but following the advice below (from AeroLED) I'm now going to use 2 core, with the shield being used as a ground return. I wasn't even considering using the shield for this purpose but it seems the LED engineer-types reckon it's a good idea and helps eliminate noise:


How To Minimize Strobe Noise

LED strobes operate differently than legacy Xenon strobes.

Legacy Xenon strobes use a flash capacitor that charges up continuously between flashes, pulling a steady amount of current, then dump the charge to the Xenon tube in a single burst.

LED strobes pull their current while the strobes are lit, and pull nearly zero current between flashes.

As a result, the way that the LED strobes are wired will make a huge difference in whether or not audio frequency noise gets into your intercom. Because the current pulses to LED strobes flow in a loop with the outgoing current flowing in the outbound power wire, and the return current flowing in the ground path, there is the potential for the wiring to create time varying magnetic fields that can couple into adjacent wires such as headset jack cables, or even your antenna coax cable.

To prevent this, it is highly recommended that you follow the following wiring recommendations:

1. Use shielded wire, AeroLEDs has 3 conductor 20 gauge shielded wire available for this purpose.

2. Use the shield as the ground return. When the ground current flows immediately adjacent to the power wire, the magnetic field produced by the power wire current is canceled out by the current flowing in the shield. The ground current prefers to stay in the shield rather than flow through structure because generating a magnetic field takes energy, and the current wants to follow the path that takes the least effort because the fields cancel out (called the path of least inductance).

3. Bring the shielded wire run all the way to the panel, where the power wire can go to the switch, and the shield ground can be run to the behind the panel grounding block. If you need to break the wire run at the wing root with a connector or terminal block, that is OK as long as you resume the shielded wire in the fuselage and connect the shield grounds through the interconnect.

4. As much as possible, keep some separation between the strobe wires and sensitive cables such as intercom audio cables, headset jack cables, or antenna coax for the radios.