Codesys PID and PWM...?

[Jake in Toledo 0]

I'm new to the forum, and a cursory check did not yield the answer I was looking for, so here goes.... I am needing a PID control for a heating application. The PID function blocks provide an output value that is a REAL variable, and goes positive or negative. My two needs: Tuning this PID loop--are there good resources for taking the guesswork out of this? Applying the output value to a Pulse Width Modulator. Since the output value of the PID goes both positive and negative, I've been trying to logically work out in my head how that would apply to the pulse width modulation of a relay to my SSR that controls my heating element.

[Joan M 3]

Temperature PID have also the negative part just in case you would have a refrigeration system attached to your heating plant. If that is not the case you should be able to parameterize the PID to forget about the negative part. If the PID block you are working with doesn't have this parameter type, take a look at the OSCAT library (WWW.OSCAT.DE), wh¡ch should help you find the right one for you. Adjusting a PID is always the same: P at the beginning until it starts to oscillate, remove a little of P and then start with I and D to fine tune it. In a temperature case you could probably make it with P and I only or even with P only, it will all depend on the desired results. Hope this helps.