I've just hooked up some NPN Proximty Sensors as limit switches and when the moving (Y) axis trips the sensor Mach3 (latest version) responds as expected with "limit triggered" message and Mach3 state change to Reset mode.

The bad thing that happens is that the (Y) axis stepper motor driver (Gecko G203V) goes into "fault" mode which takes it offline as far as Mach3 is concerned.

Any ideas on how to keep Mach3 from faulting the driver?

Thanks!

Would imagine the reason it is going into fault is because when the Limit is hit Mach puts a stop immediately to the pulses but the axis travels slightly further and the drives sees the difference between the command and the actual position so trips on a following error.
Best thing for you to do is set up soft limits and that will stop you hitting the real limits unless something goes wrong and that is exactly where the hard limits come into play
Hood

Yes, soft limits are a good idea, I will try that too. Thanks!  I did learn of something new to add... I have a SmoothStepper in the mix and I noticed that when the limit switch is triggered I hear a short Z-I-N-G from the stepper as though it is stalling.  Since these are big neam 42 steppers it's a pretty scary sound    I am familiar with stalling on the way up (in RPM) but not on deceleration.  Could this be the SmoothStepper issue?

Oh sorry was presuming it was a servo system when you said the drive was tripping. Not familiar with the G203's, do they  have an error trip on them?
They wont stall as such when you E-Stop but with them being big motors the inertia, when the step pulse is removed without any decel, is likely to make them move on a bit and thats likely the sound you hear.

Hood

Sounds right!  Thanks for the help on this!!  Yes, the Gecko G203 stepper driver has a terminal named "Disable", there is also a drive fault/error mode.  It may be that the 'back EMF' from the stepper causes the driver to fault.  The G203 Disable terminal also serves as the fault reset, the other way to reset is powering down for a few seconds.

Case closed  and thanks again!