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Connecting up a bunch of 1W LEDs Answered

Yet another LED question I'm afraid....

I've have a bunch of 30 cheap 1W LEDs from eBay and plan to use them in my kitchen for under-cabinet lighting. Forward voltage on the LEDs is 3-3.5V, max current 300mA.

I'm trying to figure out how best to power them. I have an old laptop power supply that provides 12V and up to 3A - that would give me up to 36W, enough to power the 30 x 1W LEDs. If I created multiple rings of 4 LEDs in series (giving a 3V drop across each), then connected each of these rings in parallel would that work? Or should I say, would that be a good way of doing things?

When dealing with much lower power LEDs (the typical 30mA or so type), I would usually put a resistor in front of each, but it seems that in the case of 1W LEDs I could end up losing a lot of energy across a resistor (and fry it in the process).

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Downunder35m

3 years ago

The resistor is to limit the current going into the LED.
In other words: it prevents the LED from blowing up if something is not 100% correct.
Since you would like to operate them in series to stay under the nominal voltage for the LED's it should work just fine - in theory.
Problem with LED's is they change their electrical reistance slightly when getting hot.
Here come these dedicated LED drivers into the game.
They provide a set voltage and a set amperage, the later won't go up no matter what happens.
For powerful LED's you need powerful heatsinks and if no dedicated driver is used I would at least include a constant current circuit to protect the LED's - for each set of 4 LED's that is.

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Yonatan24

3 years ago

A 12V Laptop power supply? That's pretty rare...

Sounds good. Just make sure that they don't heat up a lot. Those cheap ones tend to heat up quite a bit...