Regarding Mr. Wade's LED question:

Calculating for LED's (or other diodes) is a bit different than with most
components.  There is a voltage ("forward voltage") that is the threshold of
the LED lighting up.  With an LED, you have to model your circuit as if this
forward voltage is a battery connected _backwards_ in your circuit.

Say the forward voltage is around 2V (a safe guess).  Say you have a series
circuit with a 5V source, the LED, a resistor, and then back to ground.  The
circuit voltage to calculate with is 3V, since the LED "removes" 2V from the
circuit (as a backwards 2V battery would).  If you want about 15mA current
(another safe guess), the Ohm's law equation would be:

R = V / I
R = 3 / 0.015 = 200 Ohms

If you have spec sheets for the LED's, use the actual values.  If not, the
example should be close enough.  You may want to increase the resistance a
bit (thus decreasing the current and brightness), to keep away from the 20mA
limit that the PIC's can handle.

BTW, this is my first posting to the PIClist, so I'm a bit gun-shy.  Don't
hesitate to correct me, anyone :)

Jon

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