Harold, As per your advice, I will take steps to ensure the ground plane is appropriately designed (no ground loops either). Thank you. Mario Harold M Hallikainen wrote: > > On Mon, 20 Sep 1999 03:45:32 -0400 Mario Thomaidis > writes: > > >Harold > >I am genuinely glad to hear that you have your project working (this > >gives me great hope in terms of not having to go to an off chip A/D). > >May I ask what values you use for your bypass capacitors and what type > >of voltage source you are using? > > > > I've got 10K with one end tied to +5V, the other to ground. The > wiper goes to one of the 8 inputs on a 4051. The 4051 drives the 16c74b > analog input directly. This whole thing is done three times to read a > total of 24 pots. The whole circuit is driven with a 7805 regulator. PS > bypass at the PIC and the 4051s is 220nF. There is no PS bypass at the > pots. The PIC is using +5V as its reference. This same process has been > used in several products that read various number of 10K slide pots. I > can look at the output of the A/D and it appears very stable. Any wobble > at the bit boundaries is minor if you can find it at all. > After troubleshooting other designs where the A/D is noisey, I > believe the biggest problem is a lack of a ground plane. EVERYONE has to > agree on where ground is. Otherwise, the input to the A/D will have > noise on it, and the noise will show up in the conversions. > > Harold > > Harold Hallikainen > harold@hallikainen.com > Hallikainen & Friends, Inc. > See the FCC Rules at http://hallikainen.com/FccRules and comments filed > in LPFM proceeding at http://hallikainen.com/lpfm > > ___________________________________________________________________ > Get the Internet just the way you want it. > Free software, free e-mail, and free Internet access for a month! > Try Juno Web: http://dl.www.juno.com/dynoget/tagj. -- If it wasn't for the last minute, nothing would get done.