What am I doing wrong? How can I fix this? Is there a better way to drop voltage from 12v to the required 5v? Thanks!
QuoteWhat am I doing wrong? How can I fix this? Is there a better way to drop voltage from 12v to the required 5v? Thanks!What you are doing wrong is running your led with constant voltage (5vdc) rather then with a constant current source. Higher power leds need to have their current flow controlled, your just applying 5vdc to them and letting the current be whatever it might be depending on the specific PWM value. Now one could with by modified wiring and adding a resistor convert the 7805 voltage regulator to perform as a constant current source maybe. So bottom line your powering method is not up to speed for powering 3 watt leds. You need to look for 3 watt led driver modules for a proper solution.Lefty
Don't forget heatsinks.
Alright, Fungus, I followed your advice and it worked! (as math should)
I replaced the voltage regulator with a 10ohm, 10W ceramic resistor (http://www.radioshack.com/product/index.jsp?productId=12566075), and it works beautifully! With a supply of 12v, the circuit now draws 0.8A, with about 4v across the LED. The LED is just as bright as ever. The resistor does get very hot though (165*F).