Is it possible to have a 'virtual' limit switch? Can't get motors to stop after a set number of steps.

[th12]

Motors - 2 NI NEMA 23 stepper motors (780073-01 and 780077-01)

Motor Power Drive - NI MID-7604 

Motion Controller - NI PCI-7334

Using NI MAX, I was able to find my motion controller and play around with it (get the motors to move forward and backwards). The last drop down menu under my motion controller is something about interface which allows me to set the velocity, acceleration, steps, etc. Under the first axis (axis 1), I set the forward limit to be 1000 steps and the reverse limit to be -1000 steps. The issue I'm having is the limit never actually kicks on when I run a test using the interface. For instance, once I set the 'home' position by resetting the step value I'd tell it to do 10,000 steps in a direction and it won't stop after 1,000. Is it possible to set a limit without a physical limit switch? Is it possible to have this limit enabled without creating a LabVIEW program?

[MarcoMauri]

Hi,

with Max you should be able to enable and configure software limits.

(http://digital.ni.com/public.nsf/allkb/C6227B9AC9C69B25862579A6006C51B8)

Regards,

Marco

[th12]

I really appreciate your reply. I actually did just that and it seems to work, but not really. If I set the limit on an axis to be +/- 1000 steps and do a move using the interface it'll stop at 1030 steps. If I click start again the motors will run completely ignoring the limit that I set. The reason I'm doing this is to prevent the motors from running into a wall and I want this to be as dummy proof as possible. 

[MarcoMauri]

Hi!

What happened looks strange. Did you enable and apply the software limits(http://digital.ni.com/public.nsf/allkb/2B9BAB838E4D681486256B4B0069CD6D)?

As for the most dummy proof solution, you could consider placing limit switches for emergency stop cutting the power line of the motor or cutting the interlock line...

The switches I'm suggesting should be closer to the wall with respect to the standard limit switches.

Regards,

Marco