PID deadband?

[rupeje]

Has anyone had any luck implementing a deadband for their PIDs?  I don't see a built-in option for that, and I'm wondering how to go about it.  Can you do it by disabling the PID net when the process variable is within the deadband (after zero-crossing or other scheme), and then re-enable the net when the process variable goes outside of the deadband, or would that cause issues with the integral calculation?

[Walkerok]

There is nothing pre-built into the PID function block to give you this ability but you can write it for yourself easy enough. You decide when you want to run a PID loop in your ladder.  You can suspend a PID whenever your current value is within a dead band you hardcode in the ladder around a set point, or make it settable on a screen. (there is a pause I and D calculations block that will stop calculations for as long as you say.  You can stop the entire PID loop when you are within the dead band for a period of time.

 

Your choices as a programmer.

 

Good Luck

Keith

[rupeje]

Thanks for the help!  I've written some code for zero crossing, I'll give it a test when I get a chance.