On Sun, Apr 10, 2011 at 12:49 AM, IVP wrote: >> Do I have to be concerned about connecting the output of the >> op-amp directly to the PIC ? > > Not really, but I'd pass the signal through a resistor (few hundred > ohms) and limit the PIC pin with a 5V1 zener, just in case. Add a > reverse-biased Schottky too, anode to 0V, cathode to PIC pin, to > catch any negative excursions. Analogue inputs are wont to frizz Fair enough. > Microchip do have recommended impedances for the signal. I > think there are two, 2k5 and 5k. It is possible to exceed that > with a greater or less effect on the result. An opamp would be > pretty low impedance. The resistors you choose for the divider > depend on the value of the pot. If the linearity of it is affected > you might buffer the pot and have the didvider after that Ah, interesting idea. I will try it without and see how it looks. I could also fix some of that with a lookup table in the firmware. The chip I'm currently looking at is the PIC18f25K22, a real beast in 28 pins. I chose it for the dual UARTs, but man does it have a lot of stuff crammed in there. I know I won't even come close to needing all of the SFR and program space. Wow! Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. =A0 =A0 =A0 =A0 -Douglas Adams --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .