On Friday 06 January 2017 15:03:16 Gene Heskett wrote: > On Friday 06 January 2017 14:13:07 andy pugh wrote: > > On 6 January 2017 at 18:55, Gene Heskett <ghesk...@shentel.net> wrote: > > > Switching back to the bare hook tip on the probe, I found about a > > > 15 volt square, with tons of ringing at about half the square > > > parts amplitude, > > > > Have you tried simply turning things off one at a time? > > Thats some of what I was doing today. Conclusion? Monitor, pi and > 7i90 can run although there is some noise from the vfd. I didn't get > up on my high stool and disconnect the vfd, but lcnc seemed to run > without any spastics from the encoder-velocity on a halmeter. I'll try > that when I locate some more giddy up. If that cleans it up well, > thats the first place I'll put one of these filters, and while doing > that, will see if that ground terminal is connected to anything on the > power input strip. This teeny little booklet is less than explicit on > that point. The power drawings it has show a hookup for a braking > resistor, but thats not the only thing not found in the unit. It also > shows something resembling an rs-232 plugin socket. That does not > exist either. No provision for either anyplace on its pcb's. Not even > empty solder pads. > > Thanks Andy. > > Cheers, Gene Heskett
Todays update: I think I am a little schmartder. As I said, the computer and 7i90, running by themselves seem to dead stable. I'd un-nutted the 127 to the two toroid transformers feeding the steppers so that I could turn the vfd on and off with the power switch on the stalk behind the spindle pan. The first thing obvious was that the relatively long power and ground strapping of the 5 volt supply needed to be a heck of a lot closer to the single point ground stud, so I squeezed it into a corner of the main box, shortening that ground strap to about 5" from its former 15"+. Then extended the DC cable to reach the former terminal strip on the lid that powers everything on the lid. That cut the noise on the ground plane and all the even numbered ground pins on the 7i90 from about 900mv to about 240 mv. So I reached around and powered up the vfd. That brought up the noise from the vfd's control inverter to about 4.5 volts at around 44 kilohertz. With a ringing frequency of 45 Megahertz. Obviously that tore up the encoder. I re-arranged some grounds, but to no avail, but the trend seems to indicate that I should cut that cable as it goes by that ground bolt, extract the drain wire and ground it to the ground bolt. Possibly by cutting the jacket and working it to expose the drain wire far enough from the rest of the wires and solder a wrap of the braid around it, and put a ring lug on the other end of about 2" of braid. Disconnect the current connection from the braid to a 7i90 grounded pin entirely so as to block the noise coming back from the encoder, and putting a much lower inductance ground as that cables shielding goes by the ground stud. That is also the -0 rail of the encoder, so to maintain symetry, drag the 5 volt conductor off the 7i90 and feed it from the + rail directly. Thats the plan anyway. Starting the spindle of course makes the noise worse. I setup the halscope to read, pulseA, pulseB, velocity and index. Triggered on the index, I had to reduce the velocity gain to about 10,000volts per vertical division to get the velocity peaks caused by the noise on screen with the motor running at 15Hz! But I'm out of #10 crimp-on ring lugs and almost out of bolt. Tomorrow starts with a trip to advance auto and TSC, which are right next door in the same shopping center at the far end of town. I _will_ whip this SOB if its the last thing I do. 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) 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
