E-mailed question: writing a PID control program?

[Chris Elston 78]

Below is the result of your feedback form. It was submitted by YF Lin on Friday, June 27, 2003 at 00:55:41 --------------------------------------------------------------------------- question: Usage comments: Hello : I don't know how to use PLC to write a PID control program , would you send me a example to teach me ? TKS!(Mitsubishi PLC use "FXGPWIN")

[Guest Ian Johnston]

Hi, I've been writing for the new Q series using GX Developer (ver 5.0) and although it has some dedicated PID stuff I thought I'd write our own as an option to use once we get on site with the gear (we're controlling a large pulley disk brake based on the weight). Here is the main rung of the POU that takes the difference between the target weight and the measured weight and applies (adds or subtracts) brake as necessary. The the bigger the error then the harder it tries, and slowing down (steps) as it gets closer to it's target. Sorry I can't explain exactly how it works, we just got it working yesterday and right now all I know is it works! Ian.