Let's Make Robots!

Common anode RGB LEDs?

I understand common cathode RGB LEDs: You hook the three anodes to power sources, and then the cathode to the ground.

(excuse the horrible MS Paint image and incorrectly wired ground)

But how would one control a common anode LED with a microcontroller? Is it possible?


I've always had a problem understanding resistors. Perhaps I just need to see an example, but until then, I'm completely stuck.

Say I have 3.3v of power with 40mA of current, and I want to power an LED that requires 2v and 20mA to run. What sort of resistor would I use to make sure I don't blow it out?

I know I can calculate the resistance of the two using Ohm's law, but is that what I'm supposed to do? Where do I go from there?

That time of the year...

My budget this winter is ~$150-$200 USD, and I've decided to delve into robotics; now I just need to figure out what to get.

PING sensor question

Oh hello there! I'm pretty new with robotics and all of that exciting stuff. I'd been wanting a microcontroller for a few years, and when mbed gave out free mbeds, (yay) I got one and messed around with it a bit.