AVR-Chat

At 08:26 PM 5/14/2005, wbounce wrote:
>You resistor value seems high.
>I use a 300 - 330 ohm resistor because a led needs 15 mAmps.  Ie 5V/330
>= .015 amps

You're off, but in a safe direction,.

The actual formula is (Vin - Vled) / R so you end up with about (5 - 
2) / 330 or 9mA, assuming a common red LED with approx 2V forward drop.
As the wavelength gets shorter, the voltage gets higher, an 
unavoidable consequence of quantum mechanics.