I've resorted to using the NUDxxxx series of relay drivers from ON semi. It has the built in diode protection, logic level drivers, and its designed to be used for solenoid or relay drive. Albiet its a little more expensive than using a NPN, resistor and diode, it takes up less room and its the correct part for the job. I've retrofitted several designs that were having problems with the other Q/R/D method and never had a problem since. "William \"Chops\" Westfield" wrote: On May 18, 2008, at 8:50 PM, James Newton wrote: > "High side driver" means.... > Emitter to +Vcc and Collector to the coil with the other side to > ground? Yep. BillW -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist