Tony, I just finished a project that uses 4 AA batteries. At over 6 volts, I applied the voltage backwards for maybe 2 minutes or more. I wondered why my start-up beeps did not sound and just what went wrong. I checked my circuitry and found nothing.......I placed my finger on the F84 and it was very HOT. I said to myself...hey what's going on here........the battery pack was backwards (alligator clips). Bottom line.....what you say has merit. I never did put in any reverse polarity protection. The project is supose to run until the batteries are depleted and it is a low cost device. I could not afford a voltage drop. 3 volts would probably have minimal effect, except killing the batteries :) David ----- Original Message ----- From: Tony Nixon To: Sent: Monday, May 31, 1999 6:31 PM Subject: Re: Reverse Polarity Protection for 3V PIC Circuit. > Peter Homann wrote: > > > > 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. > > Just a thought, > > I wonder if the PIC will be damaged at all with a 3V reversed battery. > > Every protection diode on the IO pins will be conducting between VCC and > GND rails in the chip, thus trying to drop the battery voltage to around > 1.2V. > > Maybe no damaging current is available to flow into the chips' 'guts'. > > Perhaps a simple resistor in series with VCC will suffice to limit this > current. > > Maybe this is why I have not damaged 16F84's by inserting them into a > socket the wrong way around. > > -- > Best regards > > Tony > > PicNPoke - Multimedia 16F84 Beginners PIC Tools. > > http://www.picnpoke.com > Email picnpoke@cdi.com.au >