While this doesn't help you in general, you can stop an LED from blowing out by connecting it in series with a 220 Ohm resistor, if you're just hooking it up to

While this doesn't help you in general, you can stop an LED from blowing out by connecting it in series with a 220 Ohm resistor, if you're just hooking it up to an Arduino. You can vary the resistance up or down a little to get the LED brighter or dimmer. For properly learning what's what, I started out with Lessons in Electric Circuits, which is pretty decent: http://www.ibiblio.org/kuphaldt/electricCircuits/ http://www.ibiblio.org/kuphaldt/electricCircuits/