Centroid Community CNC Support Forum

Investigating motor issues;
The motor is a Centroid p/n 3879 17 in/lb 2350 rpm @120 vdc
I took he X motor out, spun it by hand no problem. then I shorted the two wire and felt it dragging. I also ran it with 12 vdc and it spins freely.
I measured resistance; red to black 1.5 Ohm.
Red to gnd open
Black to gnd also open

I measured the Z axis motor which is fully operational
and the red to blk was 1.9 ohm
red to gnd 63 ohm - this surprises me...2x
blk to gnd 63 ohm

I measured the Z axis motor which is fully operational
and the red to blk was 1.9 ohm
red to gnd 63 ohm - this surprises me...2x
blk to gnd 63 ohm

That is very odd. I would have expected that to blow the Z axis of the drive as soon as you tried to put power to the Z motor.

There should be a 3-position power plug, under the plastic cap on the back of the motor.

If you disconnect the power leads from the motor, at the motor, then measure armature-to-ground resistance at the motor's power plug, do you still get low resistance (indicating that the low-resistance path is inside the motor)?

If not, if you then also disconnect the power leads from the Allin1DC and measure resistance between red and/or black and the machine chassis, do you get low resistance there (indicating a ground fault in the power leads)? If so, you could test again at the terminal strip in the box on the back of the machine, to see which of the two motor cables the problem is in.

Update to the motors;
I rechecked the Z axis motor, at the motor, and things seem to be more like you would expect; red to black 1.9 Ohm and for both blk to gnd and red to gnd the numbers are ~2 MOhm.
I also looked at the X axis motor, at the motor and the results are similar to what I had earlier 2 Ohm red to blk and essentially open on the red to gnd and blk to gnd.

Did you look at the Z motor power wiring, to see if you can find out where the 63 Ohm measurement came from?

cncsnw wrote: ↑Sun Apr 21, 2024 9:28 pm Did you look at the Z motor power wiring, to see if you can find out where the 63 Ohm measurement came from?

I did not find any resistance in the wires Red and black were open to ground and when connected together on one end there was about 1 Ohm across red/black

Hi Lavrgs, just curious, does it blow the fuse with every thing unhooked?

glbreil wrote: ↑Sun Apr 21, 2024 10:52 pm Hi Lavrgs, just curious, does it blow the fuse with every thing unhooked?

The short answer is No. I do have the servos disconnected and perhaps the contactor didn't close...
Several days ago I did a swap of X and Z and when I did that I got no motion from the X axis terminal, now driving the carriage. The problem is that the X axis would shake/jitter - I had no Idea the fuse was blown. I can't explain why on occasion I would get random motion. After I swapped X-Z the carriage was completely dysfunctional, I wanted to get things back to make sure that Z was OK and it was...I didn't check the fuse until a couple days later and I still haven't swapped Z onto X...to retest.

Is it possible to use external drives with an ALLIN1DC? I have a bunch of gecko drives that I could use to test my servo motor... For some reason I think it doesn't like step and direction. I am trying to do some test with a board that can't drive my servo motor.

The only external drives supported by ALLIN1DC are Centroid. I know the DC1 works, not sure about AC/DC.

You should be able to use the gecko drives to try and move the thing at least. I'm sure you could figure out some way of giving it some commands.

You could use the OpticDirect interface through the DriveBus connection on Allin1DC.

OpticDirect can run third-party drives in either analog velocity mode or in position mode. You are not guaranteed synchronized movement with the Allin1DC axes if you use position mode, but for basic functional testing -- or for an indexer application -- that should not matter.

However, since the OpticDirect is $550, you probably don't want to go that way just to test a motor.