MGL Avionics User Forum

Hello.

I'm having noise issues with these led lights I bought.

https://es.aliexpress.com/item/1005004745613937.html

They are x6 leds with 3 watts each led. I have installed them as landing lights/wigwag lights under each wing.

I control them via arduino and a relays board:

- toggle switch position 1: both lights are constantly ON
- toggle switch position 2: each light alternates every second

When I turn ON either way, I get noise on the headphones.

If I disconnect the lights from the relays board, those relays do not make noise on the headphones when toggle switch is in any position (so arduino + relays card discarded).

If I connect the lights to a dedicated wigwag module (not arduino), the noise appears again.

So I think that lights must include an electronic circuit inside that make that noise appears. I guess the light includes a circuit to feed leds with constant amperage.

The engine is not working yet, power source is just the battery.

Cables from relays board to lights are not shielded. Could cables with shield solve the problem? Where should I connect the shield to?

Thank you. Manolo.

Unfortunately many cheap LED lights radiate a lot of wideband noise. They use high frequency switch mode supplies to supply a constant current to the LEDs or step up the voltage to supply LED strings. Filtering is often poor or even non-existent. Usually the radiation is via the supply wires. If the LED module itself is large it can also radiate significantly from internal connections.
Easiest way to combat this is to loop the LED supply wire several times through a ferrite that has been formulated to work at 100 Mhz or higher. The ferrite must be installed close to the LED so the wire connection from LED to ferrite is as short as possible. You are creating a new antenna using the ferrites - the length of cable between the ferrite and the emissions source in the LED forms an antenna from an RF point of view so make this as short as possible to tune it for a very high frequency - but be aware of both transponder receiver that operates at 1030 Mhz as well as GPS that operates in the 1.5Ghz band so make sure you are not unintentionally moving the interference into any of those regions.

Thank you Rainier.