RGB led basics


I have some so really basic questions about controlling RGB leds with the arduino. I’m fine with the programming side of things but the electronics are confusing me…

If 3 leds (or the 3 colours of an RGB) are attached to 3 output pins are they in parallel? I’m trying to work out how to calculate the resistors required - do you calculate each output seperately or do you need to work them all out together?

If they are in parallel, how do you work out the resistors required for different colours? All of the calculators I’ve seen seem to work for identical LEDs.

Cheers for any help you can give me.

Also - I’ve created a lamp that uses PWM to cycle a single RGB through all possible colours but it’s not very bright. What is the correct route for me to go down to add extra LEDs?

The only thing the leds of a rgb led has in common is the ground.

Just calculate the resistors as normal.


/\/ == Resistor

More PWM: http://www.arduino.cc/playground/Learning/TLC5940

Thanks. Is that true for common anode RGBs too?

Yes, except ground becomes vcc :wink: [I know you knew, I had to emphesize, just for the record]

That’s great thanks - I’m trying to make sure I ask enough stupid questions now to check I’m not missing the point :slight_smile:

It’s good to ask a lot. No questions are stupid, so just fire at will. :slight_smile: