Pid

I am controlling a heating system trough PWM. The problem is that I have too much overshoot and downshoot. Can anyone give a hint how to avoid this and how I need to do the PID in a correct way.

It sounds like you need to tune your PID loop.
Have a look at this thread.

http://www.plctalk.net/qanda/showthread.php?t=16769

Also be sure to read Ron's excellent trilogy starting HERE... :nodi:



-Eric

PID adjustment seems in place.

Some guide lines witch I use:
- Start with only the P factor. Leave I and D 0. With anly a P you will never get to the setpoint. If you set it correctly you won't get an over shoot. If you get an overshoot your P factor is to high.
- After setting the P factor you start plaing with the I factor.
- The D factor is almost never used. After setting the P and I factor you can try a bit of D-factor.

What kind of proces is the PID controlling. What is the reference point of the PID and what is the PID controlling ?

Regards,
Jurgen