I found the encoder pulse killer! Each input of that SainSmart board has a noise filter, which starts with a 100 nf capacitor to ground. In the form of a very tiny chip capacitor.
Lifting one for effect, fixed that channel, so I excised the 3 that were on the encoder input channels. Now, at the pin driving the db25, headed for the 5i25, I have quite clean square waves with a duty cycle thats +- 3% max of a perfect 50% on my digital scope. With rise and fall times in the 10ns area. And quadrature error is the above timing wobble. So, I believe this particular problem has been properly terminated/solved. Too bad we don't have a halscope button to AC couple a channel. Looking at the velocity output of the encoder, at 300 revs, its so close to a flat line that at maximum gain and offset which still puts the active trace on screen, its one pixel from a flat line, so low its not possible to see an encoder quadrature cyclic error. This is going to work a heck of a lot better. Now all I have to is re-edit my hal file for the simpler method Les suggested, and install a fresh servo amp when it arrives. Taking advantage of a steady revs at either 300 or 150, I took a few more readings of the scale factor needed, and came up with a quite repeatable 7161.61 for high gear, and 14095.34 in low gear. That, using Les's idea, means a scale of 0.508083522639397134 for low gear. I'd have to assume that is accurate enough for rigid tapping. :) Progress. A VBG even. ;-) I checked the inputs of some of the other bob's I had laying around, but none were high enough resistively to measure any capacitance, just an OL that took 10 seconds to appear. But this is certainly something to keep in mind if a new encoder is giving flaky answers. This Chinese rs485 board works well, might even work with the 120 ohm termination present, but they will need /RE and OE jumpered to ground, enabling the receiver, and disabling the transmitter. But for under a buck apiece, and the size of it, are both huge plusses. Cheers everybody, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
