Lurk Mode: OFF If you check the voltage of the battery with the engine running, and with the engine off, you will find a 1 to 2 volt difference. I would think with a simple comparator circuit that you would be able to determine these two voltages as well as 0 volts....As long as you have backup power for the sensing circuit that is... Good luck! Hope it helps - D. >From: Bob Ammerman >Reply-To: pic microcontroller discussion list >To: PICLIST@MITVMA.MIT.EDU >Subject: Re: [EE:] Voltage measurement >Date: Wed, 3 Dec 2003 11:02:43 -0500 > >I got the assumption that the OP was trying to determine the three states: > >1: No battery >2: Engine off >3: Engine running > >By only looking at a +12v line in the car, without any other sensors. > >I would think that 2 vs. 3 could be distinguished easily by the amount/type >of noise on the line over a short period of time. > >Bob Ammerman >RAm Systems > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads _________________________________________________________________ Browse styles for all ages, from the latest looks to cozy weekend wear at MSN Shopping. And check out the beauty products! http://shopping.msn.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads