**RESOLVED** Help with runaway motors

[Lee Lemon]

With DC power removed from the contactor I have verified the limit switch functionality as well as that of the encoders by turning the shafts by hand. When I shut down the system and restart with DC power applied through the contactor, after hitting the "Reset" button in Mach3, the contactor clicks and either immediately or within a few seconds, one of the motors starts turning, have seen both X and Y jump, until Mach faults out with a position error warning. After clearing the warning and resetting, it happens again. The shaft couplings are loose so the motors are just spinning free. This is on an MPU11 and DC3IOb. Any suggestions?

Thanks.

[diycncscott]

Lee,

It sounds as though you may have the polarity reversed on your motors. Try switching the Red & Black wires on one of your motor cables at the DC3IOB drive.

One more thing to be clear on - when powering up or powering off, power needs to be removed and applied simultaneously to the MPU11 and DC3IOB.

[rppman]

Lee, I was wandering if you corrected this problem? And what did you have to do? I have the same condition now. My z axis is doing exactly how you described. I am almost 100% sure I have the power wires correct. Also. My y axis (when under power) makes a little clicking noise and the shaft is locked but that is a different problem. Thanks for any input. Scott

[diycncscott]

RPMAN,

Just try reversing the leads - it just changes the direction the motor goes.

What happens is this:

The drive commands motion in one direction -let's say it CW. The encoder signals that come back tell the motion control that the motor is actually going in the opposite direction - uh-oh. The control tries to correct by applying even MORE more power in what it "thinks" is the opposite direction - the motor jumps -Position error

This can happen either because the encoder is wired backwards (A & B channels) OR the power leads are reversed.

[rppman]

Ok I will try to switch the leads (red and black) on that axis. This is the first axis that is doing this, but if others follow I will try the same thing. Thanks Scott, I am getting so close to getting this thing. Just working on getting the bugs out...

[Lee Lemon]

Swtiching the wires solved my problem. I am currently up and running and very appreciative of the support I have received from this forum.

Cheers.

[rppman]

I switched the wires and that worked for me also. My x axis motor has a slight hum when power is applied but hopefully after I tune them it will go away. Thanks for everyones help. Scott