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. Regards, Jim -----Original Message----- From: Peter Homann To: PICLIST@MITVMA.MIT.EDU Date: Sunday, May 30, 1999 7:01 PM Subject: Reverse Polarity Protection for 3V PIC Circuit. >Hi, > >I need to protect my PIC16LF84 against reverse polarity. Currently I'm >running the circuit of 2 x 1.5 N cells (2/3 AAA). I want to protect the >circuitry from the batteries being inserted the wrong way. > >I'm not keen to put a diode in series with the batteries as I'll loose 0.6V. > >Thanks, > >Peter. >--- >Peter Homann Email: peterh@adacel.com.au >Adacel Technologies Ltd _/_/_/ _/_/_/ _/ Phone: +61 3 9596 2991 >250 Bay St, Brighton _/ _/ _/ _/ Fax: +61 3 9596 2960 >Victoria 3186 _/_/_/ _/ _/ Home: +61 3 9555 5603 >AUSTRALIA _/ _/ _/ _/_/_/Mobile: 0414-494578 >------------------------------------------------------------------------