It's a pretty common technique, Michael. The last application I developed using this idea was to control the speed of stepper motors in an electrical discharge machine depending on the pot setting. You need to keep your input resistances pretty low to avoid non-linearity problems with the comparators, though. Another approach is to vary the R in an R/C network, where one leg of the R goes to a D/O pin through a small fixed resistor (determines upper frequency limit and current limiting), the other leg goes to a D/I pin and to one leg of the C, and the other leg of the C goes to ground. By toggling the D/O pin when the D/I pin changes, you essentially do the delta/sigma routine - just count how long the C takes to charge/discharge. I've oversimplified this somewhat to show the concept - but actual implementation is really simple stuff! Good luck! If I can be of any help, just email me off-line. Dennis ----- Original Message ----- From: "michael brown" To: Sent: Saturday, February 01, 2003 8:58 AM Subject: Re: [PIC]:Success with 16f628 conversion On Saturday 01 February 2003 07:21 am, you wrote: Oops, that's what I get for typing in the dark. ;-D I accidentally sent the previous post before I was finished being long winded. I'm getting ready to implement the "very simple delta-sigma ADC" that Dave Tweed thoughtfully explained to me a few weeks ago. After explaining it to my wife last night, I now comfortably understand the theory. ;-) Does anyone else use that technique? I am attempting to read the value of a pot. using the 628's comparator and a TMR0 loop to sample the voltage at an R/C junction and compare that to the voltage at the wiper of the pot. The comparator output is then fed to the R/C time constant thru the R and also "added" to a counter. This, AIUI, PWM's the R/C creating a matching voltage accross the capacitor. Every 256 loops, the counter is copied and cleared. Hopefully, this all results in a feedback loop that works to give me an 8 bit value representing the wiper position of the pot. ;-) If all goes well, I should have that working today. Does that sound about right? Is there an easier/better way? michael brown -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads