I'm making a circuit to drive some K2 LED's. They need 3.42V and about 0.5A. I would like to use LM317, but I can't figure out how to calculate the resistor values. Just using a resistor is IMHO waste of power. I was told to use a constant current source by the guy who sold me those K2 LEDs, but that controller he uses costs like 100$ a piece, and that is something I can't afford ;) So does anyone have a good formula I could use to calculate the values for those resistors or maybe a better, more efficient way to solve that problem. Current regulation (up to 1A) would be even better, but That would probably make my circuit a bit harder as big (1A tolerant) pots are hard to find here and cost a fortune.
Thanks in advance