Ordering some of the partsPosted: 2005-March-19
I noted that the full-spectrum LED's I'm looking at from LSDiodes.com have the following voltages: 2.05 volts for red, 3.2 volts for green, and 3.6 volts for blue; all at 35 mA. Thus, to be driven at full brightness from 5 volts, I'll need an 84 ohm resistor (the closest standard value is 82 ohms) a 51 ohm resistor, and a 40 ohm resistor (closest being 39 ohms.) The 84 ohm resistor will drop the most amount of power at 0.1 watts, so pretty much any size is safe. While I'm at it, driving one of these LED's with all elements on at full brightness is 310 mW, so if I'm to limit the lighting to 6 watts or so, I can only use about 20 LED's at a time … of course, I can just program it so it's not trying to turn on all the LED's white at once.
I put in an order at Mouser.com for the resistors (I had to swap the 82-ohm resistors for 75-ohm since they were out of stock) a bunch of 10 µF capacitors (I already have 48 so I bought 50 more, expecting to wire in no more than 32 LED's) and a bunch of 2N3906 PNP general purpose transistors that I'll use with 74LS138 3-8 multiplexer chips to drive the cathodes of the LED's.