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Topic: powering 4x 3w rgbs (Read 1 time) previous topic - next topic


Hey dweenose,

I'm building a lighting set up driven by audio data in max, and i was planning on powering it all from an old PC PSU.

I am driving 4 of these:


with 12 of these:


from the 12v line on the PSU, utilizing the dim pin of the pt4115 on those each of the driver boards with a PWM pin on my mega.

I am planning on cooling each of the LEDs with a CPU heatsink/fan (and thermal paste of course), will that be enough cooling? will the drivers need to be cooled as well? I plan on running this for at most 4 hours a session, not running them at full blast all the time.

Also, will the voltage drop be too much between all of the LEDs for the PSU to handle?

Thanks in advance


Both your driver and LED are typically used inside a lightbulb housing -- no fan but they do use a decent cone of aluminum for the heatsink. A heatsink/fan used for a CPU should be much more than would ever be used in a production bulb.

Not sure what you mean by the voltage drop and the PSU. That shouldn't be a consideration.


nevermind about the drop question.

the red channels run at around 7-8v
while the blue and green are around 10-11

This might seem foolish, but do you think I'll fry it by running it from my PSU 12v line without a resistor? I cant find 3w tolerant resistors anywhere (locally)


A 7-8V string of LEDs with no current limiting resistor or LED driver connected to 12V? Yes, you'll definitely pop it. As to the 10-11V string it's only highly likely that you'll pop it. Depends on how quickly you can shut off the power ;)

If you're looking for a locally-available solution then you should look for a ~1A transistor (google: transistor as switch) and pulse the current to the LEDs with PWM.


bahh yeah kinda figured (mostly really hopeful i could swing it).

but alas! i forgot about 269 electronics (a component store hidden behind a tourist luggage / watch / perfume store in chinatown) which doesn't carry most ICs, but does have a comprehensive line of NTE resistors and caps.  XD

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