how do you calculate the LEDs proper resistor?
And here's another site: http://home.cogeco.ca/~rpaisley4/LEDcalc.html
In general, you want a few milliamps (maybe 2 - 20 mA?) running thorugh your LED. The higher the current, the brigher the LED will be, but the faster it will burn out. To calculate the current passing through your LED you can use Ohm's Law: I = (V - LED voltage drop)/R
Typically LEDs have a voltage drop of between 1 and 3 V, depending on their color (the higher the energy of their color, the bigger the voltage drop). As long as you're in the low milliamp range, you can always try a current and see how bright your LED is (assuming it's visible and not IR, of course), then adjust the resistor accordingly if it seems too bright or dim.