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Saturday, September 24, 2011

Lamp 10W Power LED Retrofit

I had a small side-project about power leds.
Received some 10W (advertized) warm and cool white leds. Yeah, it's bright! And hot too.
Then got some cheapo 10W constant current led drivers, which should drive a led with 900mA max (advertized).

But when I put it to the test, I saw just 580mA, sad. So I opened it and done a dirty hack - soldered a little resistor (75 Ohm on picture) across feedback optocoupler. Now, Viper22A (constant current driver ic) sees less feedback current and drives harder, delivering stable 960mA after warming up. It works a lot hotter now, needs ventilation holes at least.

Forgot to mention that my leds max current is 1 Amp (advertized), I don't know really if I'm overdriving these leds.
Then I found unused lamp which was bought to fit CFL inside, but as it turned out there is no place even for small 15w CFL. I removed E27 screw holder, scraped paint in center and polished. Then drill two holed to hold led tight and put led on polished area with some CPU heat grease/paste. Yea, backside of this lamp is made of metal, it acts as somekind of heatsink now. Double holes at top and bottom is for airflow purpose. Hot air goes up, sucking less cooler air from bottom and so on.

Screwed frosted glass lens back.

The glass lens is not that great quality, as you can probably see it has somewhat greenish tint.

Yea, color is not really correct on this picture, but it's a cheapo led afterall =)
Let it work for a night and in the morning it was not that hot (I mean backside), this is good. Driver was naked while test and was pretty hot, so ventilation holes absolutely need. This was warm white led. Next time I'm going to use smaller lamp for retrofitting.