drive Luxeon Emitter with resistor for testing?

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#1
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Hi guys!

The Luxeon emitters / stars are my choice for lighting, now I'll have to build a test circuit with them. Is it possible without destroying them to limit current with a resistor like with normal LEDs?

I know a switching power regulator is a better idea in terms of wasted power (creating heat) and that will be the way to go once I build the last prototypes and the final modules. But to make it easy for now, I thought resistors will do the trick.

The values I calculated for 5V Vcc are:
2.85V, 350mA LED - 2.15V drop needed - 6.14 Ohms
3.42, 350mA LED - 1.58V drop needed - 4.51 Ohms

So driving them with 6.8 Ohms and 4.7 Ohms should be safe. - Are my calculations correct or will I fry 25 EUR of LEDs if I use resistors?

Edit: I did read both the Emitter and the Star datasheet, there's no big difference to ordinary LEDs except the current, and ordinary LEDs definitely can be driven with resistors...

Markus

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you can test the LEDs, but I wont suggest it for long. also use high wattage resistors!

and read the constant current source thread of mine (the one with 19 pages and counting). I'm trying to achieve a similar thing with my power-LEDs (4x5W K2). and where did you get them for 25€?!? I wouldn't pay over 7€ for a LED (5W one for instance). Mine cost about 6€ a piece....

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25 EUR = 3x7 EUR and shipping/handling. I will use three modules (RGB) and if the resistors are wrong, I'll burn all three of them...

I thought of 2W resistors, should be enough to drive a 1W LED without getting close to limits.

I'm not planning a burn-in test with the resistors. It's just for a few minutes in each test run to see if the colors mix well and the brightness is good enough. Haven't seen those high power LEDs in reality yet and the module I built does work with standard 5mm LEDs (some thousand mcd for testing) quite well.

Markus

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Watch out - high power LEDs like the Luxeons are meant to be operated with a heat sink. Running them "just for a few minutes in each test run" right on your bench will most likely fry them. BTW: there are datasheets available from all LED manufacturers extensively listing the cooling requirements (you may want to look for 'thermal management').

Andreas