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LED Lamps

matt c

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I have a strange issue with some d0mest1c LED lamps.


I bought three Osram LED lamps, dimmable, designed to directly replace normal BC lamps. One is installed in my living room, with a wallplate dimmer, and the other two are in normal on/off fittings.


Recently, the one in the living room started putting out brief, regular, high intensity flashes, in between which it remained at about 50% intensity. All whilst the dimmer is turned up to full.


I changed the lamp to a non dimmed fitting, and it behaves normally. I can also put either a normal incandescent lamp or one of the other LED lamps into the living room, and both behave normal, dimming as expected.


I'm not sure exactly what's failed....


Has anyone else had similar experiences?



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Standard dimmers and LED technology are completely incompatible technologies. And dimmable lamp is usually either a compromise or quite sophisticated to try and work with a normal dimmer.


Has anything else changed, like another lamp on the same dimmed circuit being changed?


It sounds like the dimmers triac may not be latching properly due to insufficient load.

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Not sure David. I'll stick the scope on it.


It's a standard household dimmer, Tom. It's been working just fine for about 6 months, and suddenly started acting up.


Big Clive, they were specifically designed for standard dimmers, so probably had sophisticated electronics in there to work properly. There are no other lamps on the dimmer.


I guess I'll have to have a halogen in there, and put the LED elsewhere...

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Clive is right, even lamps designed for standard dimmers work very poorly on them. There is often trouble with the triac mis-firing or latching on which causes the flashes you describe, or flickering/strobing effects. Often you will find that putting a normal incandescent lamp on the dimmer as well as the LED will help reduce this.


The best dimmers for LED lamps are "reverse phase" or "trailing edge" dimmers (use mosfets rather than triacs) which are available in wallplate format - Varilight is a common brand. I would bet if you swap the dimmer plate to one of these you will have no more trouble.

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Well there's something learnt. I knew trailing edge dimmers are available in theatre land, but I never realised they were also available for domestic applications.


I'll go get a varilight one, and see if it helps.


Thanks for the advice :-)



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Psst! It's not a real Vari*Lite product. :unsure:


Who came first, though? ;p


I have Varilight v-pro Eclique2 dimmers dimming Toshiba LED lamps and they're honestly the best I've ever seen, other than incandescent. They dim down so far that the final snap-off is hardly noticeable at all. I was amazed when I first tried them...


Oh, and the Toshiba lamps are 90+ CRI so colours look right too.



edit: More info

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