Commissioning of a motorised valve to plc

[hegde10122]

How do we interface a motorised valve to Micrologix 1200 PLC?

 

[Bitmore]

With care!
What motorized valve? Make & Model?
What M1200? Model number?
What do you expect? Mind reading too?

 

[Bitmore]

Ok, sorry,
Maybe not yet,
Posting two questions will confuse you and the real problem, from what I have gathered is you need some help with a motorized valve and what we call a "slide wire" feedback resistance. You really didn't have to post two seperate questions. Better yet,,,, hold on.
Just a bitmore majic!

I am supposed to program for the following data:
There are 4 motorised valves and the resistance mounted on motor shaft is used as percentage opening data to plc. The PLC module is Micrologix 1200 AB plc and 1762-IR4 RTD module. The value of the resistance lies between 0 to 600 ohms.
How do we interface a motorised valve to Micrologix 1200 PLC?

There we go, now nobody else will be as confused as me....
answers to follow... I need a beer first...

 

[Tom Jenkins]

It sounds like you are trying to emulate a typical valve postioiner in your PLC. No problem.

First, you need to establish a bandwidth setting - this is simply the error you will allow between the desired percent open and the actual position feedback before you move the valve. You add and subtract half the bandwidth from the nominal position target, and this gives you two values - a minimum threshold and a maximum threshold.

Then you need to convert the position feedback data to % open. This is a standard scaling problem, and in the ML-1200 you can use the SCP function.

Then you need two compares. If the feedback is greater than the max threshold you turn on the output for closing the valve. If the feedback is less than the min threshold you turn on the output for opening the valve. If the feedback is equal to or between the min and max threshold you do nothing.