It is hard to even guess the cause of this from your description. You are just going to have to go down the line and test each part independently.
I remember reading here in this forum someone posting about "redundant" onto isolators being on both the breakout board and the motor drivers. Maybe this shows that even using two of them in series is not good enough unless you take other precautions in the design. I Think the #1 thing most amateur and many professional engineers forget is that all ground wires and ground traces have some finite amount if resistance and Ohm's Law applies to them A good why to demonstrate this is to place an AC voltmeter into an AC socket in a large building. Measure between Ground and Neutral and you might see as much as 1.5 volts. Yes the ground and neutral are tried together at the service entrance but the neutral is currying some current, the ground wire in the normal case is not. I'm guessing the root cause here is mixing up the types of grounds. Logic level returns (called "ground" in many circuits) are not the same as protective ground or AC mains return paths but many times "it is all just "GND" and gets connected haphazardly by those metal shells and screws on cables and inside power supplies and other places. This is almost impossible to get "right" when you are assembling a system from little boxes made by others. On Thu, Sep 8, 2016 at 2:59 PM, Gene Heskett <ghesk...@shentel.net> wrote: > Greetings Peter; > > Someone made the remark a while back that it was indeed possible to look > at the output of a function, in this case the first pwmgen of a 5i25 > with the prob-rfx2 firmware in it. > > I've had a blowup, the ultimate cause of which I have not found yet, but > from the damages done to the cnc4pc C1G BoB that I have found so far, I > am inclined to think the spindle motor psu, or possibly something line > powered failed. The C1G damages so far found are 1 blown 74ACT245N, and > an almost invisible use of a ground trace on the pcb as a fuse. All the > opto's in my spindle encoder would appear to have failed. Those I have > a bag of, but that pcb makes the tinfoil of a pack of smokes look like > boiler plate, so I'll have something I won't call fun replaceing them. > > I can run the x/z motors just fine, but the limit switches would appear > to be closed as those leds are at full britness when its several inches > from the switches. > > What happened is that I had started a short program that called for a 400 > rpm spindle but had neglected to engage the headstocks back gear, so the > motor took off and wound out to max speed before I could hit the big red > button. And about 1/2 second before my hand hit the button, there was a > pop that came from the box over the spindle motor and everything coasted > to a stop. The pop sounded like it could have been the top of one of > the hexfets on the Pico Systems PWM-servo amp I am driving the motor > with. But they look pristine, and all the other components in that box > look good and a DVM says they are properly powered. Thinking the motor > may have thrown a winding, I've looked it over and checked for shorts > and come up empty so far. > > Back to the 5i25 question. So I fire up the halscope and send it to > gpio1.in or in_not. And try to start the spindle from axis with the > cable to the bob unplugged. > > I am seeing a short pulse of 1 volt p-p, which becomes inverted if I look > at the in_not, and trying to increase its speed has no effect. So its > beginning to look as if I may have blown this 5i25. And I've still no > clue what did it. > > Do you concur, Peter? In that event, I'll need three more, with low > profile brackets as I believe the one I was going to run either my toy > mill, or this Sheldon lathe, has a bad pin that I was using for the > probe, G38.2, and it got flaky. That was because the big dummy I can > see in the mirror here forgot to run a decent ground to the frame of my > G0704. And it was pretty darned noisy when I put a scope on it. Fixed, > but too late for that 5i25. So now I need one for the little monster, > one for the Sheldon, and one for my toy mill that I've not found a round > tuit to do yet. > > Thanks Peter, or John T. > > 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> > > ------------------------------------------------------------ > ------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
