On Thu, Jan 29, 2015 at 2:52 PM, Dwayne Reid wrote= : > I've had problems with cheap rotary pots (both carbon and > conductive-plastic) getting noisy when they have any amount of DC > voltage across them for an extended time period. That said: we've > shipped many, many hundreds of our light sequencers which use a Phier > PC-mount carbon pot with 5Vdc across them and they seem to be holding > up quite well. We use a 10k pot which gives us a max source > impedance of 2.5k and we usually always have a 100n capacitor from > the ADC pin to ground. Where are you sourcing those pots? Are you going through their US rep? > One technique that works extremely well for us is the classic RC Time > measurement. We use the same 10k pot with a good-quality film 100n > capacitor as well as a pair of 220R resistors (one in series with the > pot, the other in series with the cap). We get 9 bit resolution that > seems to be stable with both time and temperature. The real > advantage of the RC Time measurement is that there is voltage across > the pot only while the measurement is being made. You know, I've never done this. I wonder if it's time I give it a try! Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .