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> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
