PID Control, Any idear how to make a three point stepping controller?

  • Thread starter Thomas Christiansen
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Thread Starter

Thomas Christiansen

I have made a small PID controller on a Siemens S7-200. Making the Analog part was no problem. But I have to Control a valve. With step up, neutral, or step down signals. I made a test where i used the controllers output to control a timer and a fixed "step" lenght, but the "hardware" I have seen, used a varible step lenght and i varible pause. Is there somebody who can tell me how to convert Analog output signals to stepping signal the "right" way.
The easiest way to do an (digital) control of ex. Heating / cooling. is to do your own controller. read the set temp ( ex 90 ) and a window setpoint. This prog. execute with an timer interrupt. Ex. +1 degree ( 91 ) = cooling output - 1 ( 89 ) = heating out put no cooling + no heating = neutral I tryed this several times and it works ok. ( easy to use but not "perfekt" or by the book )