Author Topic: LED specific dimmers for LED replacements?  (Read 1342 times)

LED specific dimmers for LED replacements?
« on: 23 October, 2017, 10:45:22 am »
I bought some dimmable leds:

they work OK with the  already fitted leading-edge (TRIAC) dimmers*, but I have seen claims that it might damage the LED-bulbs:

If they are not flickering, I don't see how:
presumably the bulbs rectify and smooth and switch mode power convert whatever weird waveform they get to power the LED(s) then sample the waveform via a different unsmoothed rectifier to work out if and how much to dim.


*Apparently these buzz, but trailing edge buzzers don't.

Re: LED specific dimmers for LED replacements?
« Reply #1 on: 23 October, 2017, 11:33:16 am »
I used a leading edge dimmer switch for maybe 5 years with a 5 LED bulb ceiling lamp.  It did buzz a bit (according to young people with better hearing.....).  Eventually the switch started to misbehave , not dimming, either on or off, generally random behaviour. 

Replaced with one of these recently https://www.screwfix.com/p/varilight-trailing-edge-push-dimmer-1g-1-2w-300w-va/94816.  Seems to be better, no noise and a smoother dimming transition as it turns.  The bulbs were fine (Homebase specials).

That dimmer has gone up nearly a quid since I bought it in July:(

Raise the question again in another 5 years!

Kim

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Re: LED specific dimmers for LED replacements?
« Reply #2 on: 23 October, 2017, 03:25:30 pm »
I bought some dimmable leds:

they work OK with the  already fitted leading-edge (TRIAC) dimmers*, but I have seen claims that it might damage the LED-bulbs:

If they are not flickering, I don't see how:
presumably the bulbs rectify and smooth and switch mode power convert whatever weird waveform they get to power the LED(s) then sample the waveform via a different unsmoothed rectifier to work out if and how much to dim.

The leading-edge waveform means the smoothing capacitor (which is usually near the top of the of the cost-cutting list) sees much higher inrush currents.