Author Topic: Voltage problems with a PMDX 424. Motors not turning  (Read 289 times)

radio.dub

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Voltage problems with a PMDX 424. Motors not turning
« on: May 17, 2021, 05:21:48 PM »
Tried getting my PMDX 424 running with some small motors and motor drivers just to establish communication between Mach 4 and the motors.  I have established communication between Mach 4 and the 424. The enable LED on the 424 goes on when the enable button is clicked in Mach 4. The steps LED flashes on the 424 when Mach 4 is jogging an axis.  My motors don't turn when I jog them in Mach 4.  When I test the output voltage on j7, j8, and j9 I get the following conditions:

when STEP polarity is 'active high' voltage on the 424's motor driver output is 4.76V on step and 16.3 on dir.
when STEP polarity is 'active low' voltage on the 424's motor driver output is 15.9V on step and 15.9V on dir.

with the 424 unplugged from 110V and USB the output voltage on j7 is 3.1V on step and 4.2V on dir
                                                                                                j8 is 2.3V                   6.2V
                                                                                                j9    2.8V                   5.4V

I also get the following error when jogging in Mach 4:

PMDX: DEVICE ERROR 'SYSTEM ERROR(7): Motion Underrun'

I am running Windows 10 home 64bit

Mach 4 and plugin version:

Wed May 12 17:48:58 2021
Mach4 Version: 4612
Screen Set: wx4.set
Device: PMDX-424 [Rev D PCB] on COM3
Serial Number: SN39547 (D1 )
Plug-in Version: 0.53.263
Bootloader Version: 1.15.76
Firmware Version: 0.60.208

Any info you can provide would be much appreciated. Thanks

12strings

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Re: Voltage problems with a PMDX 424. Motors not turning
« Reply #1 on: May 18, 2021, 11:34:58 PM »
First question: where are you putting your ground lead of your meter when you are measuring those voltages?

So no 110VAC and no USB.  Presumably you still had your motor drivers connected when you measured that 2nd set of voltages on the PMX-424 connectors, right?  If that is not the case, exactly what did you have connected to the PMDX-424?  And what motor drivers are you using and how do you have them wired (both power and step & dir signals)?

If you really did have 15V on the step and dir pins, that might possibly have fried whatever output buffers the PMDX-424 has on it.  But first check the wiring.

radio.dub

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Re: Voltage problems with a PMDX 424. Motors not turning
« Reply #2 on: May 19, 2021, 04:59:06 PM »
I have the problem under control now. I was using a new DMM and I didn't realize it has an auto ranging function, so what I thought was 16 volts was actually 0.0016 volts. I realized the motors were probably turning before but I just couldn't see it because they were turning so slow. I adjusted the speed and got them turning. sorry for wasting your time!

12strings

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Re: Voltage problems with a PMDX 424. Motors not turning
« Reply #3 on: May 19, 2021, 11:54:18 PM »
Glad it was a "non-problem" :)