Cannot Change PID setup while online?

[amcraw16]

Usually I just read other posts on here but I simply cannot find the answer to my problem this time.

I have a PLC-5 40E. There is a PID that controls a burner and we need to adjust the P and I in the setup.
When I change the values in the PID setup screen, they never actually change in the data file. Same for editing them right in the PD data file.

Then we tried changing the PID settings offline and downloading to the controller. Even then, the old PID settings remain. What gives? How can I adjust the PID settings, preferably online if possible?

 

[Frost999]

Sounds like they may be being written from a MSG (in another PLC) or some form of HMI that is persistent, or even a local recipe that is moving data.

 

[Engineerj22]

Cross reference the control file used for the PID loop and make sure that it's not being written to from any other source.

 

[amcraw16]

You are both right. Thanks for the simple pointers.
Every scan cycle the PD data file was being written to by floating point values. Doesn't seem to be any particular reason, the PID is not controllable by HMI.

 

[geniusintraining]

WAG... not sure if this is the case but a lot of the time I will put things like this in registers so when tuning its easier and faster to change a register than it is to pull up a PID and modify the parameters, same thing with steppers when you have several its a LOT easier to have a spread sheet that you can make changes to and not have to search the program for parts when commissioning

 

[mylespetro]

WAG... not sure if this is the case but a lot of the time I will put things like this in registers so when tuning its easier and faster to change a register than it is to pull up a PID and modify the parameters, same thing with steppers when you have several its a LOT easier to have a spread sheet that you can make changes to and not have to search the program for parts when commissioning

This would be my guess too, HMI (or other source) writing to NX:X which is getting written to the actual word containing the PID parameters.

 

[saultgeorge]

WAG... not sure if this is the case but a lot of the time I will put things like this in registers so when tuning its easier and faster to change a register than it is to pull up a PID and modify the parameters, same thing with steppers when you have several its a LOT easier to have a spread sheet that you can make changes to and not have to search the program for parts when commissioning

I had a few projects that used a LOT of PID's and I put tags in MOV blocks to send parameter changes to P, I and D. Worked well; when I was online and needed to modify a setting I just wrote in what I needed without having to go off line or open the PID as you mentioned. If the PID was named "PID_GasValve" then I made a tag "Gas_Valve_kp" for moving changes to "PID_GasValve.KP". That worked and I see no reason it couldn't be written from an HMI, however that might be quite risky.