Hi,
I need to impliment PID control with binary outputof 3 states: NULL, UP,DOWN (controlling of drive speed by two digital outputs: speed up, speed down).

Am I right that it's impossible to do with S7-200. As I see PID loop in S7-200 possible only with analog output or binary 2-state output (PWM). And for 3 state PID controlis needed S7-300.

Is it right? Help me please!

dchartier

Hello Rem2;
I thought I remembered a solution for this problem provided by Siemens; I had to look it up for a project where the client hadn't decided whether to use S7-200 or S7-300 CPUs.

I think this will provide you with all you need:

http://support.automation.siemens.com/WW/view/en/18748232

Hope this helps,
Daniel Chartier