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I had an old leading edge dimmer switch (probably more than 7 years old) below:

The old dimmer switch

The buttons had worn out on the old switch so I decided to get a replacement but from a different brand (which I think is equally good and is from a reputable company that provides 15 year guarantee) - this one. This new switch is trailing edge which apparently is better than leading edge.

The switch controls the LED light strip for the kitchen counter and with the old switch there was no flickering but there is flickering with the new switch. This is the strip:

enter image description here

The LED light strip is connected to an old LED driver which purportedly supports both trailing edge and leading edge below:

enter image description here

I have tried tweaking very slowly at small intervals the fine tune dial at the back of the new switch, which did reduce the flickering but it still flickers.

What should I try to eliminate the flickers?

  1. Should I replace the old LED driver?
  2. Should I try a new dimmer switch?
  3. Are there any dials I can tweak within the old LED driver?
  4. Anything else?

EDIT: something rather strange but delightful happened at the end which is the flickering somehow stopped by itself. My only guess is that the driver took time to "recalibrate" as the driver supports both leading and trailing edge, and I changed my switch from leading to trailing edge but I would be very interested to hear others' thoughts on this.

2 Answers 2

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It's simply a matter that the dimmer and power supply are not compatible. Matching up these things is a black art.

Triac dimming is a dodgy way to dim anyway... it was done with incandescent bulbs because it was cheap, but it barely worked. With LEDs, it's a fiasco. Essentially the LED driver (or in this case the power supply) must reverse engineer the triac waveform to try to figure out what is being requested, then use current control (or in this case PWM) to properly dim the LEDs under its control.

It's a Rube Goldberg hack.

Those low voltage DC LEDs have an excellent dimming scheme available to them called PWM dimming. This is done on the low-voltage side not the AC side. If it were me, I'd convert the AC switch to a plain switch and use a PWM dimmer on the DC side. Most PWM dimmers happily work on both 12V and 24V.

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  • Many thanks for the advice.
    – ld_pvl
    Jan 17, 2023 at 18:08
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The driver does say it is a dimmable unit, and since you did try adjustments without success, I would say you need to try another brand of dimmer.

Also the voltage draw of the LED strip may be below the threshold of the dimmer's capabilities. Compare specs between the new and old dimmers.

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  • By voltage draw, do you mean max load rating? From the spec sheet of both dimmmers, I do not see anything specifying voltage draw, only max load rating which the new dimmer has a wider range: old range is 5w-50w peclights.com/product/… whilst the new dimmer's range is 5w-150w
    – ld_pvl
    Jan 8, 2023 at 20:59
  • One notable difference I found though is the old dimmer is leading edge but the new dimmer is trailing edge (trailing edge is supposed to be apparently) but my current LED driver says that it supports both leading and trailing edge but maybe because the LED driver is old it's not supporting trailing edge very well?
    – ld_pvl
    Jan 8, 2023 at 21:01

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