At 11:37 AM 5/31/99 -0500, you wrote: >You could add a diode across the batteries with a fuse >so that is the batteries are inserted the wrong way, the >fuse blows cutting off the power source. > - + > --------:|:|:|---------------------------------> To PIC >circuitry > | Battery | > | ^ > | ---- > | | > |-----------------------~--------------------> To PIC >circuitry > Fuse > >If the batteries are put in backwards, the diode turns on and >pops the fuse. Otherwise, the diode is reverse biased, and >doesn't even appear to be there. I've used this scheme >many times before. It works well. Hope it helps you out too. At a $1 plus per fuse, that can get very expensive when you have idiots replacing the batteries. How about replacing the fuse with one of the PTC thermal auto-resetting devices from Bourns or Littlefuse? Does anyone have any PRACTICAL experience doing this?? Are they fast enough with a big overload? Kelly **************************************************************************** ******** All legitimate attachments to this email will be clearly identified in the text. William K. Borsum, P.E. OEM Dataloggers and Instrumentation Systems &