Temperature Input to PID time base output

2020-02-27T23:31:32.714000Z

you can find everything you need in source code on

Temperature Input to PID time base output

2020-02-27T23:31:31.038000Z

Originally created by: Nicolai_Hanssing

frankwim hat geschrieben:
Hello, We are using a wago 750-841 and CoDeSys for the first time and have a PID application in which we need help. We will use a 750-469 Type J T/C module and would like PID control to output an on/off pulse (750-530) based on percent output of the function block. In other words...no output at 0 percent and full on output at 100%. At 50% with a 1 second cycle time the pulse width would be .5 sec on and .5 sec off. Is the PID_Fixcycle function block the best choice? What is the output units of the function block; 0-100% or 0-32767 16 bit range? Has anyone ever done the math for converting the function block output demand to a time based pulse width? TIA

The PID-fixed cycle is just a PID-controlle wher eit has to be called with a fixed time-interval, nothing else. Its still an analog output.

Converting a analog signal to PWM when using fixed scanrate is very simple, and only takes few lines if code.

SAy fixed cycltime for the PLC-scan of 10ms, dutycycle of 1sec:

AO <-- Analog output to be converted [0..100%]

cnt <- cyclecounter

DO <-- Digital PWM-output for heating-coil

cnt:=cnt+1;

if count>=100 then; cnt:=0; end_if

DO := AO>cnt

Can be done with more finesse (among other things using residuals).

Regards

Nicolai Hanssing

Temperature Input to PID time base output

2020-02-27T23:31:29.372000Z

You probably should read about duty cycle.

http://en.wikipedia.org/wiki/Duty_cycle

Regards, Frank

Temperature Input to PID time base output

2020-02-27T23:31:24.737000Z

Hello, We are using a wago 750-841 and CoDeSys for the first time and have a PID application in which we need help. We will use a 750-469 Type J T/C module and would like PID control to output an on/off pulse (750-530) based on percent output of the function block. In other words...no output at 0 percent and full on output at 100%. At 50% with a 1 second cycle time the pulse width would be .5 sec on and .5 sec off. Is the PID_Fixcycle function block the best choice? What is the output units of the function block; 0-100% or 0-32767 16 bit range? Has anyone ever done the math for converting the function block output demand to a time based pulse width? TIA

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