Created Date: October 26,2011

Created by: talotam

PID with PAC3000

I 've got my time proportioning control set up for the loops(I'm using 64 loops right now, but will expand to 100 temperature loops in the future).

I have a process variable below my setpoint. For example, my process variable is a thermocouple picking up ambient temperature at this time (71 deg F) and my setpoint is at 90 deg F.

My input max range is 65535, and min range is 0

My output max range is 65535, and min range is 0

PID tuning is:

Gain = 8

Reset = 2

Rate = 1

When I set the PID loop up for manual operation, I can set my process output at any value and it remains, this powers my output.

When I set the PID loop up for automatic operation, the process output goes to zero. I force a value to the process output and that value remains for one scan, then reverts to zero.

What should I try next??

Thanks,

Created Date: October 27,2011

Created by: talotam

process upper limit did it

Thanks, AAA. That was where my problem was. I had set up a variable to contain the process output upper limit, as well as a variable for the lower limit. I mis-understood these functions, thinking they would be a limit I could place on the maximum temperature selectable.

The PID loop is working fine now. I just have to finish constructing the next 99.

Thanks again.

Created Date: November 10,2011

Created by: talotam

I altered the output to include an interuppt by on/off control boolean. Without this, the output would still toggle even with the PID loop disabled.

I set up a bench test with a heater and thermocouple feedback, and allowed my niece (16 year old H.S. junior) to play with the PID tuning after a quick lecture on the basics. She got pretty good at narrowing in the bandwidth on the process variable, and then learned about autotuning. Very enjoyable 4 hours of her time.