If there are plug-in cards or gold plated edge connectors anywhere, unplug, rub with an eraser, dust clean and re-insert. Might help remove stray capacitance. I've just had trouble with a set of plug-in cards on a machine here (not control cards, but the same principle applies).
Marcus On 2 Nov 2017, at 02:18, Peter C. Wallace wrote: > On Wed, 1 Nov 2017, Eric H. Johnson wrote: > >> Date: Wed, 1 Nov 2017 19:25:36 -0400 >> From: Eric H. Johnson <[email protected]> >> Reply-To: "Enhanced Machine Controller (EMC)" >> <[email protected]> >> To: "'Enhanced Machine Controller (EMC)'" <[email protected]> >> Subject: [Emc-users] Odd encoder problem >> All, >> >> >> >> A machine (table) that has been running for about three months has developed >> an odd problem in the last couple weeks. Not sure if it has been getting >> worse or if just the nature of the patterns being run has made the problem >> more pronounced. The machine is an XYYA configuration with a pneumatic Z, >> and using mainly Mesa boards. The problem is in the A axis. It seems to be >> losing encoder counts at very low speed, but not otherwise. It took a bit to >> track down because when I initially had it moving multiple rotations I could >> not get any errors running A by itself. Running with a feed rate in excess >> of 20000 (Degs per min), resulted in no errors. Slowing down to 10000 >> started to show a very small amount of error, and from 5000 on down the >> error was very pronounced. >> >> >> >> The hardware is a Mesa 7i43 FPGA, 7i33 quad analog servo card and YEnc line >> drivers. The table is 15' x 30', thus requiring line drivers on X and A, but >> for uniformity, were put on all four axes. The encoders are wired >> differentially. The error is always in the same direction regardless of the >> velocities used for the cw and ccw directions, thus would seem to be >> dropping counts. >> > > I would check that you get decent differential voltages across the 7I33 > inputs in both states of the inputs (no less than +-2.5 across the A,/A B,/B > or Z,/Z pairs in any state) > > >> >> >> I did not have a scope with me to check the encoder signals. While a low >> probablility, I do have spare YEnc modules, but ran out of time before >> trying to swap it out. I don't really see how this type of problem >> (electrical) can develop over time, but do not see how it can be anything >> else. >> >> >> >> Anyone seen anything like this when using that hardware? >> >> >> >> Thanks, >> >> Eric >> >> >> >> ------------------------------------------------------------------------------ >> Check out the vibrant tech community on one of the world's most >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > Peter Wallace > Mesa Electronics > > (\__/) > (='.'=) This is Bunny. Copy and paste bunny into your > (")_(") signature to help him gain world domination. > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
