On Wed, Dec 21, 2011 at 9:35 AM, Spehro Pefhany wrote: > At 08:49 AM 12/21/2011, you wrote: >>A simple question about transistor switches: > Using an inverted input drive (low =3D ON) and a PNP transistor (emitter = to > Vdd, base through resistor to input drive, collector through current limi= ting > resistor(s) to the LED(s)) will work, and the transistor will run much > cooler. This is also superior for high currents because the PIC can > sink the base current better than it can source it, and the current will > be better controlled for high Vf LEDs such as blue, assuming a 5V supply. Thank you to all of the responders for pointing out the more subtle limitations of my original solution, and for the suggestion of inverted drive and PNP. Since I have a box full of PNPs as well, I will go that route! -Eric --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .