a/b pto and hsc help

Hi all:
I am using an A/B Micrologix 1200 to control a stepper. The system is running fine, but I need to add a "stall" detect. I am using it a little different than intended, I think. My application is to rotate a product, sense a tab, and continue to rotate to a specific position from that tab. Short version of sequence as follows:
1) turn stepper output on, PTO:0.HIP set to 30000 pulses (generate error as process did not complete if the hi preset is reached)
2) On a signal from a sensor, enable and start the count HSC:0.CE(input from encoder)
3) When count (position) setpoint is reached, set the PTO:0.CS (controlled stop) bit. Product decels, stops, and the next process begins with the product in register.

I am having trouble figuring how to detect a stall. I know I have a pulse train going out, but my count may or may not be enabled yet, as the product may not have reached the reference sensor. If I didn't get to the sensor to start the count yet, the PTO:0.TOP <= PTO:0.OPP will go true and stop the process as an error (after 30K pulses and a noticeable racket). I don't think I can monitor the encoder input until I start the registration sequence and enable the counter. I tried comparing the PTO:0.OPP (output pulses generated) with the count HSC:0.ACC, but with hit and miss results. I would appreciate any suggestions.

-tommy23t

All you need to do is to check that the HSC.0.ACC count is incrementing.

Of course it would be better to do the comparison between the command and the feedback, but as you have found the Micro is not a full blown motion controller and isn't quite deterministic enough.

If you simply define that a "stall = no more counts for xxx msec", then all you need is a timer comparing counts now with counts xxx msec ago.

I would add also the OK contact of the driver (if you have it).
The counter might be done but the driver in fault or power off so you are not in stall.
The best way if you have encoder on your shaft you can detect if the shaft rotate when he supposed to be in stall, that real detection.

Arik

Phil: HSC:0.ACC is not incrementing yet, as I am still in my "search for reference" mode. The micro does strange things, different than I interpreted from reading the manuals. I guess ya get what ya pay for, and I didn't pay enough. thanks anyway, I'll try a few more things.

ArikBY: same problem. No contact to monitor, encoder is on the shaft, but I haven't told it to start counting yet. I really need two counters, one when the motor starts, one when the registration counting starts.

-tommy23t banghead

Tommy

If you have encoder its very easy, put counter on the encoder input.
If the cuonter count more then 5 pulses(for exampel) when the motor supposed to be in stall that mean you are not in stall.You dont need
HS counter.This circuit just for that purpose,I aware that might be problematic you may be need to add timer before you start to count.

Ok...I understand that you are not enabling the counter while still searching for the reference. This seems to be the core of your problem.

Why not just allow the counter to be enabled all the time and use the sensor pulse to reset the count to zero? This is how I would have assumed is the natural way to do it.