PID Control on Q Series

[GerryB55]

I am using a Q02 PLC part of which needs to control a Heat / Cool system. Can anyone help with advice on setting up and controlling the outputs. Specifically do I use seperate PID loops for Heat & Cool? Thanks in advance.

[waynes]

Hi GerryB55, The setup of PID block in the Q cpu is far diffferent than that of say, the FX2N. The Q CPU handles up to 32 PID loops. I have attached the manual from mits on the q cpu pid control. you will find all that you need there. One major difference between heating and cooling applications, is the control action of the PID, Normal and Reverse. Normal implies that an output has to be applied for the process value to decrease, whereas reverse action means that an increase in output value would see an increase in process value. Ie, Normal mode for cooling applications, and reverse mode for heating applications. Any hassles, i will send you a program in which i used 23 pid loops to control temperatures in a plant. Check the examples first. QCPU_Prog_Man__PID_Control_Instr__SH_080040_C.pdf

[Guest Guest]

Waynes Thanks for help. I will try the examples in the manual.

[GerryB55]

Waynes Hi, i've tried the examples but seem to be having problems. PLC reports a conflict of some sort in the data types. I would appreciate any known working examples you may have. Gerry

[waynes]

I have working programs, Maybe post your program so i may have a look.

[GerryB55]

Problem solved: I had inadvertantly overlapped the data registers for the PID initialisation and the PID loop data. Moving the start registers cured the problem and all are up and running now. Thanks for all help.