I am getting a strange defect after recently adding the UC-100 to my build. The build worked fine with a parallel port in windows 7, but I was tired of dealing with the lack of support with win7 and upgraded to win10 and added the UC-100.

After reconfiguring, setting ports/pins, motor tuning etc - the machine is running fine, the estop works, spindle under full remote control through Mach3, and the motors all operate correctly.

However, the limit switches do not function correctly. In both the UC-100 and the Mach diagnostics page, the input pins do not activate at all, even though the hardware side of the limit switch does show activation signals. When I jog the machine over to a limit switch, the machine does stop as if the limit switch was triggered, but Mach does not indicate a triggered limit, and limit override doesn't work. I have to disconnect the limit switch wire, restart Mach, and then jog the machine off the limit.

The limit switches are pepperl Fuchs proximity sensors, and as I said, they worked fine on the previous build.

I'm using pin 10 for X lim and X home, 11 for y, and 12 for A home.

I know there are some other topics related to this error, but I was not able to find any information that helped.

If anyone has some suggestions, I'm all ears, thanks.

First question is in mach are the limits set to active high or low?

Are your switches NO( normally open
Or NC( normally closed?

I have the same setup as you with uc100 and g540,but I use manual limit switches with no issues.

I've also gone through the Win 10 / UC100 upgrade process.  Actually virtually all my config just transferred across and the limit switches on my mill work exactly as they used to.  (Though I'm still using discrete 2M542 drivers.  I can't see whu using the G540 should change things.  I suggest that you double check all the port/pin assignments and the active low/high settings.

Thanks for the replies. I should have closed/updated this thread.

I did resolve the issue finally. It was a grounding issue. I am using a separate 12v power supply for the limit switches, and what the G540 wanted to see was a common ground, so a simple jumper between the -12V DC block and the common ground terminal for the rest of the system was all I was missing. Inputs on the UC100 are working fine now, and the limits are being triggered appropriately.

Not sure why adding the UC100 caused this to surface, maybe the additional hardware between the pc and g540 made it more sensitive to grounding, but glad it is working now.