I’m looking for alternative suggestions of how to control an output with PID that does not operate on a 0-100 scale, ie bit level, (solenoid valve).



I currently take the PID CV OUT word and create a true condition if it is GRT a looped 1 sec (0.01 time base) TON timer ACC valve.



Is works but I don’t like the duty cycle I wind up getting on my valves, I know I could increase my time base, I didn’t know if anyone else had a better way.





TRW

The way you're doing it is the recommend method, your time base should be based upon the period of the system. If you are at steady state, and manually open the valves, how long does it take the system to respond? Then use the response time for you time values. Set your pid out put to 101, that way you don't get cycling when 100% is required.

Here is a tech note from the AB website that has an example using a micrologix 1500 processor, even though the ML uses a PD data type instead of an N file for the PID, the instruction operates the same on both processors.

http://domino.automation.rockwell.com/appl...63?OpenDocument