You could use the voltage drop across the resistor and feed it to the ADC. Then using some math, you can calculate the current (since you already know Ohm's law!) Thomas >From: Roman Black >Reply-To: pic microcontroller discussion list >To: PICLIST@MITVMA.MIT.EDU >Subject: Re: [EE]: Current monitor for battery controller >Date: Sun, 1 Apr 2001 01:50:59 +1000 > >Jacob M Hartman wrote: > > > > I'm working on a battery charger/discharger for some of my projects, and > > have a design problem with the current monitor. I want to be able to > > monitor both charging and discharging rates. Unfortunately, my >knowledge > > of analog electronics does not extend far beyond Ohm's law.... :-) > > > > My current (naive) design is as follows: > > (1) Battery's negative connector is separated from ground by a 0.2 ohm > > power resistor. So, if the battery is powering the circuit, its >negative > > connector will be at a negative voltage (relative to ground); if the > > battery is being changed, the connector will be at a positive voltage. > > >Hi Jacob, this sounds easy, but have you considered >using a toggle switch to change the polariy of the >resistor and/or sense circuit?? > >Also you did have a 2k or larger resistor between the >op-amp output and the PIC input pin?? :o) >-Roman > >-- >http://www.piclist.com#nomail Going offline? Don't AutoReply us! >email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body