- Sun Nov 09, 2008 7:51 pm
#58664
I recently acquired a 3W RGB LED http://www.sure-electronics.net/DC,IC%2 ... L007-2.jpg and now I'm trying to figure out a circuit that will allow me to drive it, using PWM from Arduino/AVR.
My first question is how to power the circuit. Would a 5V power supply be a good choice? Something like this http://www.sparkfun.com/commerce/produc ... ts_id=8269 I want to be able to control each color independently with PWM. The blue and green LEDs have an average Vf of 3.4, and the red is 2.4. The max current is 350mA, so I think I would need at least a 5 Ohm resistor for each color [(5-3.4)/.350 = 4.5], with about .5 W dissipated in each resistor. I already have a 9V power supply but it seems that would just waste more power?
As for interfacing with the Arduino, it seems that the Darlington Array is a popular choice. Am I on the right track? I am looking at the ULN2003 and its data sheet says it can handle only 500mA, so would I need 3 of them, one for each color? Also, I am unsure of what resistor values would be appropriate between the Arduino and Darlington.
Lastly, the LED manufacturer recommends a heat sink for running at max current. What type of heat sink would be a good choice and how would I bond the LED to it? The LED mounted on a nickel-sized aluminum board.
Thanks,
Andrew
My first question is how to power the circuit. Would a 5V power supply be a good choice? Something like this http://www.sparkfun.com/commerce/produc ... ts_id=8269 I want to be able to control each color independently with PWM. The blue and green LEDs have an average Vf of 3.4, and the red is 2.4. The max current is 350mA, so I think I would need at least a 5 Ohm resistor for each color [(5-3.4)/.350 = 4.5], with about .5 W dissipated in each resistor. I already have a 9V power supply but it seems that would just waste more power?
As for interfacing with the Arduino, it seems that the Darlington Array is a popular choice. Am I on the right track? I am looking at the ULN2003 and its data sheet says it can handle only 500mA, so would I need 3 of them, one for each color? Also, I am unsure of what resistor values would be appropriate between the Arduino and Darlington.
Lastly, the LED manufacturer recommends a heat sink for running at max current. What type of heat sink would be a good choice and how would I bond the LED to it? The LED mounted on a nickel-sized aluminum board.
Thanks,
Andrew