PIC Controller on GE 90-30

[denman_100]

Hi,

I have a GE 90-30 CPU 374 PLUS. The program currently has a PID controller that controls a mixing valve. I would like to add a second PID controller to control fans. However I am having a problem implementing the 2nd PID controller. When I upload the program and run it, all the parameters are constantly changing. The P,I and D gains fluctuate, upper/lower clamps, etc are changing. The original controller still functions properly. Moreover, if I remove the old controller (mixing valve) and run it, the new fan controller now runs fine. I ensured that the controllers each have enough reserved memory, (40 words). Has anyone had any similar problems? I couldn't find any documentation that stated the 90-30's could only handle 1 PID controller.
Any help would be appreciated.

 

[cjd1965]

Hi,

are you sure the new PID addresses are not used elswhere? Have you done an implicit search?

For the start of the new PID, try assigning it to start at %R which will automatically give you the next free address.

Cheers

 

[denman_100]

Thanks for the reply. it appears the address was used elsewhere after the implicit search. I will try the program again and update this thread.