Electronics

gemini · Joined: 08 Nov 2006 Posts: 1 Location: Milwaukee, WI

Trying to build a regulator for 3 Luxeon LEDs in series from a 12.6v (peak) battery using the MINIMUM amount of components.

I have LM317Ts and LM338Ks...

So for 3 of these LEDs in series: http://www.luxeonstar.com/item.php?id=1803&link_str=330&partno=LXK2-PM14-U00 what would be the best way to regulate current and/or voltage?

I used a 5w 1 ohm resistor across the adjust and output of a LM317T and took the Vout off the adjust pin, but that seemed to give me 250ma (if I measured correctly) and made the LM317T burn VERY hot...

I am putting these on a T-Shirt so minimal components and cool components are a must (LEDs already have adequate sinks).

So essentially need to limit the battery output to 11.55v at 1500mA.
I also will be using these: http://www.luxeonstar.com/item.php?id=1822&link_str=330&partno=LXK2-PL12-R00 which would need to run 10.2v at 700mA, so really I'd need 2 circuits (one for 1500mA, one for 700mA). Battery output is 30A at 12.6vdc (when fully charged) at least.

Any ideas as to what components I'll need? I was hoping the 1 ohm resistors and the LM317T would do the trick, guess not?

Thanks in advance...

neon · Joined: 25 Feb 2006 Posts: 590

lm317 IS PERFECT here is what you do decide how much those LEDs need to light up in series then take 1.2v devided by the LED current. now this is the value of the resistor that is neccessary to regulate the current.put this resistor from adj to out. and you will have the exact current to light them up THAT IS SIMPLE.The leds tie to the adj not the output.

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