PWM for PID

Koncarevac · Mar 4, 2006

Hi, I have a problem. I am supposed to control gas flow by an automatic motor driven valve. The valve receives 2 input signals, impulses for open and close respectively. I am using a PLC Function Blocks diagrams for the ABB RTU560. There is an analog PID FB, but I need to process its analog output control signal to get a three position control signal. The thing I need is a PWM block, which I don’t have implemented in the PLC.

Does some one have an answer to my problems? A hint how to make my own PWM block?

CroCop · Mar 4, 2006

PWM is farily straightforward.
Run a base timer that resets itself for a time period, say 1 second.
Scale the PID output to 0-1 seconds, so if it's 12 bit output, 0-4095, then divide the PID OUTPUT by 409.5
Move the result into the preset value of a second timer.
Reset the second timer with the first timer done bit.
Now the output of the 2nd timer will be a % of the first based on the PID output.

burnerman · Mar 7, 2006

I did exactly this on a GE Fanuc last month. I'll post the ladder diag. later if you wish (it's on my other PC)

manikandan · Mar 7, 2006

I am also working on the same. but for oil flow.

Dear Burnerman, can u please send ur diagram to me also?

Manikandan
[email protected]

burnerman · Mar 7, 2006

Burner valve control attached here (rungs 7 - 40)

percy_nk · Jul 9, 2021

PID Control for Gas Burner

I have Motorized valve Gas Burner (open and close) i want to control with PLC PID Control with RTD input and close and open relay, motor full open to close time is 30sec please suggest the logic to control.

Steve Bailey · Jul 9, 2021

Percy_nk, I suggest you start a new thread instead of reviving a pair of fifteen year old ones.

PWM for PID

Koncarevac

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CroCop

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burnerman

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manikandan

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burnerman

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percy_nk

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Steve Bailey

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