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Messages - Steve Stallings

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This sort of upgrade is usually possible, but it will require enough understanding to configure the new software to match your old machine. If you have never done this sort of thing, you are in for a learning experience including investigating how your old setup was wired and configured.

Box level controller products / Re: Pmdx-340 stalls stepper motors
« on: August 07, 2022, 09:01:40 PM »
If you feel the motor vibrating or making a squealing noise, then the PMDX-340 is still driving the motor.

Your symptoms sound like the motor's speed or torque capabilities are being exceeded.

Check to see that your DIP switch settings for motor current have not accidentally changed.

Check to see that your software's maximum speed settings have not changed.

Also check that your mechanical systems are clean, properly lubricated, and aligned.

If you are using a VFD, then normally the Run command for the VFD comes from the terminals of the PMDX-107 itself.

If you just need to use the small K2 relay independent of the Direction signal, then set JP2 to the Multimode position and then the relay will be controlled by Pin 14 of the second parallel port input on the PMDX-126.

The proper way to prevent drivers from being enable before Mach3 is running is to utilize a "charge pump" signal.

You can configure the K2 relay to monitor the "charge pump" to control the enable signal to your driver. You should set JP2 to the MultiMode position and have Dip Switch config 8 to the open position. See Table 4 on page 8 of the manual.

With an 80 foot long cable there is a risk of electrical noise pickup causing false E-Stops. I would suggest that you have a relay near the PMDX-126 to connect in your E-Stop loop and arrange a 12 or 24 volt circuit to control the relay from across the room.

Try checking the Digitize signal on the Diagnostic screen to see if the signal really is seen reliably by Mach3.

If not, make sure that the probing circuit has a reliable ground. If you are relying on your cutting tool as part of the probe signal path, try attaching a ground clip directly from the PMDX-126 input terminal block to the cutting tool itself instead of expecting ground to pass through the metal parts of the spindle.

Customer had a calibration problem. The VFD was limiting the maximum output frequency to 400 Hz and he had continued to increase the gain of the CAL pot beyond what was required to reach maximum speed. This resulted in the lower speeds being shifted upward.

Your motor drivers likely have an input called Enable or something similar. This input uses a confusing name due to industry convention. The driver will run normally if you leave this input disconnected. When you apply a signal to this input it will DISABLE the driver.

General Discussion / Re: Can we use both and ESS and SmartBob?
« on: August 07, 2022, 08:07:33 PM »
You could do this by swapping the input cable for the PMDX-126 from the PMDX-411 to the ESS. Yes you would need two profiles with matching machine configurations.

General Discussion / Re: Replacing PMDX122
« on: August 07, 2022, 08:05:05 PM »
In many cases it is possible to connect the master and slave axis to the same step and direction terminals on the PMDX-122. The PMDX-122 outputs will normally drive two stepper motor drivers without problem.

If the slave motor needs to turn the opposite direction, you can accomplish this by reversing the wires on ONE coil of the stepper motor.

If you are using gantry squaring with separate home switches for master and slave axis this approach cannot be used.


We have identified an incorrect resistor value that was installed in the output protection for the Aout signal on a couple of units and based on serial number yours is likely one of those. The output voltage would check out correctly using a high impedance meter during testing, but would droop under the lower impedance load of the VFD input.

Please return your unit for free warranty repair.

Our shipping address can be found here:

Sorry for the inconvenience.

Steve Stallings

The ISO+5 and ISO_GND on J5 are provided by an on board inverter and failure of this inverter or a short on its output could cause the symptoms you describe.

The +5OUT and GND on J7 are controlled by a power management switch that feeds USB power after the unit has completed its power on sequence. This power is not isolated and does not rely on the inverter. It is unusual that your board would be running if this power has failed.

When measuring power you cannot mix connections from the ISO power with the non-isolated power. Both probes must connect to the same power system.

You could check again with your wiring unplugged to make sure that power is not being shorted somewhere in the wiring.

If you still do not have power, you will need to return the board for warranty repair.

There are three reasons that I can think of that would cause problems running a parallel port for Mach3 on an XP computer.

1) The computer is running a 64 bit version of XP. Rare, but it does exist. All 64 bit versions of Windows prevent direct access from Mach3 to the parallel port hardware as needed for CNC pulse generation.

2) There are BIOS settings or other issues that cause problems with PCI port addressing. PCI cards with drivers to allow addressing them at the legacy 0x278 or 0x378 port addresses are problematic and we recommend using the 0xNNNN style PCI port addressing.

3) The parallel port card has a 5 volt only PCI interface, and the computer is running a 3.3 volt PCI bus.

The 32 bit version of Windows 7 will run Mach3 and allow direct access to the parallel port. Windows 8 is unpopular and poorly supported. Windows 10 will not work with a parallel port for Mach3.

To the best of our knowledge, the PMDX-1PARPCI will install and run on any 32 bit install of XP or Windows 7.

The default configuration of the PMDX-424 makes Common for the stepper drivers be ground, but the wiring you describe would require that Common be set to +5V for proper operation. You will find this in Config > Plugins > PMDX-SmartBOB and when the configuration panel opens, select the Motor Config tab and the setting will be in the top right corner of the panel.

You might also try looking in Windows Device Manager to see if the if the STMicro comm port driver is actually installed in Ports Comm and LPT.

Did Windows respond with a sound or system tray popup acknowledging that a USB device was inserted? Note: PMDX-424 must have power in order for Windows to find it.

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