FMD1616-10 step stop issue

[cch1955]

I have a program that uses stepmove command. Stepspeed is set before stepmove. I need to stepstop the move at any time in the move. I have done this many times before with other Triangle boards.

The step move will start and if I issue stepstop while step move is still ramping the step move will stop when step stop triggered.

If the stepmove reaches full speed (not in ramp) stepstop will not stop the move. In addition if I am watching program from my PC, the PC is kicked off (looses communication link) until the stepmove completes the 5000 step move, then it starts up again.

I have tried many versions and removed all from program to just have bare minimums with same result. I think the ladder scan is stopping during the maximum speed portion of the move and resuming when the move terminates - why?

Any ideas?

[support]

We ran a test on a FMD1616-10 and did not observe what you reported. A STEPSTOP executed in a CF triggered by an input stop the stepper motor anytime whether it is ramping up or down or during constant speed.

Did you trigger the STEPSTOP control input from online monitoring via serial port? Did you try it by activating the physical input?  Since you reported losing communication when the stepper is moving you may think that STEPSTOP did not work but actually could it be due to the communication did not work? You may want to check if the electrical noise generated by the stepper driver is affecting your serial communication. Can you try with an Ethernet connection to see if it makes a difference.

[cch1955]

I have been using physical input.

I am using RS 232 link for communication no Ethernet.

If I have electrical noise problem, why can I trigger stepstop with physical input during ramp to stop ok but not during maximum speed portion of same stepmove?

I will send program this AM for your comments. Very simple program.
 

[cch1955]

Are the inputs and outputs on the FMD1616-10 opto-isolated?

[cch1955]

I determined the problem was being caused from a quadrature encoder input to pins 3&4 from a ULN2003A driver. I set it up as shown on page 7-1 of FMD1616-10 manual.

I added 2.2K ohm current limiting resistors on the lines comming from the driver outputs to inputs 3&4 and the problem was solved.

[support]

Sorry for the late reply. Having a busy day but looks like you have found a solution to the problem although we are not exactly sure the cause of your problem.

The FMD PLC digital inputs and outputs are not opto-isolated. So it is important that the ground (0V) of the PLC power supply and the stepper motor driver and the encoder must be in common.

It sounds like the encoder is generating very high frequency pulses that it might have overwhelmed the CPU?  The PLC's digital inputs already have 5.6K pull  up resistor to 24V DC so normally it is not required to add the 2.2K resistor that you mentioned.

Was there a grounding issue? The encoder inputs can handle 10KHz incoming pulses and it is unlikely that the noise that is overwhelming the CPU is the actual signal from your encoder. If the encoder and the PLC have no common ground then it could be high frequency resonant pulses that is causing havoc. Your addition of a 2.2K resistor might have dampened the oscillation that was the trouble maker.

[cch1955]

I agree grounds can be a problem. I checked them all and made sure no ground loops. No matter what I did with grounds did not help. On a scope the encoder signal comming in were very clean, no signs of noise riding on them. The drive is a AC servo with line filter on power and shielded cables grounded at one end. Thanks for the help.