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Need help with PID


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Hi all,

I want to control a flow control valve using the PID function. After the autotune run is completed and the Status is 4, the CV control value goes to 0 instead of dynamically adjusting the value. May someone had the same problem when using an analog output? I would be very grateful for tips and advice..

BR, Joachim

 

 

PID_SCRSHT.png

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Hi Dave,

thank's a lot for your response. sorry the screenshot confuses a little bit. The PV max value is multiplied by factor 100 in the ladder later...so it's  actually 3000.  In attached another screenshot with all  values used by PID Config when Status is 4. (PID RUN) I'm not sure if all values are plausible because I don't have much experience with it..

 

Would be great to here from you again..

 

PID2.png

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Hi @Joa

attached a short video about the PID that I am using in the project that I am doing...the CV is used to manage a timer to ON/OFF a digital output...the PV is emulated increasing/decreasing a variable referred at the status of this DO.

The autotune BIT is "0" because I did it before...stored that vale in a DTI...save to a file..so every time that i energize the PLC it is uploaded and th ePID can run ok without a new autotune.

howevere I tried to immediately run the PID after the autotune and it works in the same ways as in the video.

also I tried to replicate what you show...I think...and it works...

so...one question is...how are the "control value derivative" and the "integral error" at the bottom of PID Config struct (missing in your picture)?

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