Thanks Gene, I hope you’re well also. I disconnected that grounding wire, no difference observed in the ppmc.0.encoder.03.index behavior. The noise seems the same both when spindle is running and stopped, with a tendency strongly toward "true" than "false." Pulses seem to be both long and short, but I’d guess they’re about 80-90% true. Not at all what I’d expect, even with noise.
Matt > On Aug 1, 2020, at 1:19 PM, Gene Heskett <ghesk...@shentel.net> wrote: > > On Saturday 01 August 2020 12:10:55 Matthew Herd wrote: > >> I'm still having issues with the rigid tapping. It works sometimes >> and fails other times. After scoping the motion.spindle-revs, it >> appears to be consistent with what we would expect aside from one >> possible issue. The spindle revs reset to zero upon G33.1 being >> called, then count up until they stop, reverse, go negative past zero, >> then return to clockwise motion. However, on the second zero crossing >> (going positive) the revs go positive, only to be reset to zero >> momentarily thereafter. I'm not sure if this is normal behavior or >> not. >> >> However, what isn't normal behavior is that the >> ppmc.0.encoder.03.index value is loaded with noise. Not occasional >> noise, but constantly triggering in irregular intervals regardless of >> whether the spindle is turning. I'm baffled as to how this could be >> so noisy and was wondering where you might look next. Grounds look >> fine aside from the fact that the control cabinet and the power >> cabinet have a ground wire connecting them in addition to being >> grounded through the machine. > > That quite likely is the problem. Thats a ground loop. Ground things > only at a single bolt in the control cabinet, and remove any machine > grounds at the encoder end of the wiring. Ground loops are only good > for acting as antennas to pick up noise. And in a machine full of motors > which are regulating motor currants by switching on and off to hold the > average you or the driver has set, there is 50 to 175 volts of noise > free for the asking. To ground the machine, connect the third, static > ground wire in its AC power cord to this bolt. If more than one power > supply, arrange the cordage to come thru a single power strip, with only > one of the individual cord grounds completed to that bolt. Ground the > switcher supplies earth terminals to that bolt, and if needed, the - > terminals of all those supplies to this bolt. You may need a long bolt, > thats ok. > >> When removed from the USC board, the >> index can be measured with a multimeter as the spindle is rotated. > > If reading to machine ground, thats bad, If reading to logic ground, > thats good. Logic ground can be connected to that single grounded bolt > but the distribution of that ground should resemble a star, and any > ground wire lifted off that bolt should not have continuity to ground > anyplace else. > > This is also good to protect the electronics in that machine from nearby > lightning strikes. That way, the lightning strike may bounce the machine > a hundred thousand volts, but its all in unison and the 3.3 volt logic > doesn't see it or get damaged by it unless there is a large capacitance > to earth ground to unbalance that bounce. Thats generally unavoidable > when several ton of iron is sitting on a concrete floor. But although > the pole that serves this house gets tapped occasionally, I have not > lost any electronics to those strikes in several years since I brought > the grandfathered in since the early 70's, pre NEC service up to code in > 2008 as I was building the garage. The power folks haven't been so > lucky, they lost a 25kw can once. It might have been an askerol filled > can which is a time bomb after 20 years or less anyway, but I think they > hung a 50kw full of Crisco in place of it. Outdoors, Crisco is legal, > but the PCB's are fireproof. > >> I >> forgot to bring my scope to the shop today (I didn't think I'd need >> it) so I can't scope anything until tomorrow. Is it possible there's >> a pull-up resistor missing? > > There might be. I am not using any except the normal pullups in the logic > that give a true on the halmeter when no input is connected. Mesa cards > generally have adequate pullups without external helpers. Sainsmart > bob's don't generally need them either. > >> Thanks, >> Matt >> > I hope this helps Matt, stay safe and well now. > > > Cheers, 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) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene > <http://geneslinuxbox.net:6309/gene>> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net <mailto:Emc-users@lists.sourceforge.net> > https://lists.sourceforge.net/lists/listinfo/emc-users > <https://lists.sourceforge.net/lists/listinfo/emc-users> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
