Shelly 1 behind LED driver causing buzzing when off

  • I've wired a Shelly 1 (with the jumper switched to DC) sit between LED strips and the LED driver in order to on control my kitchen undercabinet leds. It functions fine but causes the LED driver to buzz audibly when the LEDs are off (but presumably the Shelly is still drawing some power). The drivers have always hummed a bit, but it is quite loud now.

    I don't know much about electrics, but I do wonder if the Shelly is drawing beneath the LED driver minimum load

    The driver is rated for 30W and outputs 12V. The LEDs are non-dimmable strips at approx 15W.

    Is this expected behaviour. Any ideas what I can do about this?

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    Is the driver buzzing as well, when you connect nothing at all at the LED driver output? If yes, then it would be an issue with the minimum load. The only possibility would be to exchange the driver by another type.

    If buzzing only with Shelly 1 connected, then it could be that Shelly 1 is drawing pulsed currents which are causing the noise on LED driver side. In this case, an electrolytic capacitor at the output of the LED driver could help, maybe 1000µF/25V, check for correct polarity.

  • Thanks, that's very helpful. You've given me a couple of things to test to work out the solution.

    Edit: do you know what capacitor size I would need for 12v dc?

    Edit2: Ah I get it - 25vdc is the maximum rating. Thanks for your help.

    Edited 2 times, last by euinor ().

  • Yes, max. rating. 25V types are little bit more robust than 16V types, which would be possible theoretically. 1000uF are just a first guess. When it improves the situation, but not good enough, even bigger capacitance values like 4700uF could be tried.

  • I replaced the led driver with one that explicitly stated a range of amps starting from 0 (implying no minimum load). It also had a lower wattage rating (20 watts), as I'm probably under-loading it when the lights are on - my leds only come to 18 watts (including 20% in case the driver is underrated) and the previous driver was 30 watts.

    The replacement led driver has resolved the humming when the lights are on and the whine when the lights are off!

    Thanks for your help :)