PID subroutine


i’m doing something on old LCM4 and I need a PID loop. I know it is not a big deal to make, but if anybody has a subroutine or chart already made, i would be gratefull for it.

thanks and all best


Years and years (Ok… and years and years and years) ago Opto 22 had a chart that was a PID loop.
From my abused brain cells comes the faint memory that it was done by someone in Product Support… I also recall that they left Opto some time back…

All that said, it just so happens that I used the chart inside another of my charts.
Your request jogged my memory of this and so I opened up the old archives and extracted the PID part of the chart and have attached it to this post.
Just unzip it and import it using Factory Floor.

All the variable are prefixed with ‘fcu3’… I used it on Fan Coil Unit 3… hence the name.
You can of course rename then to be anything you like, but at least all the variables used in the chart will be grouped together in your strategy tree.

I cant really offer any support on this chart… its been a long long long time since I did any work with it. To my knowledge, its still in use to this day, so its been a chart based PID loop for over 16 years now.

Lets know how you get on.

Hi Ben,

sorry for my late response, i was bussy on another project.

I’m having trouble to open this chart. It is a .cht file and i can’t import it (you can only import .cxf file). I’ve try to create a dummy chart with the same name, and then replace that file with yours, but it still doesn’t work.
Is there a chance you export it in a cxf file?


Until about 2 months ago this was true. I finally replaced the old M4 with a PAC S1 and moved all of the I/O to an EB2. Now the PID is all brain based.

But having said that, the chart did serve its loop well right up until the end…



Sorry about that… try this one.


P.S Nick, thanks for letting us know. I think the thing to take away from this is that you swapped out the controller just to upgrade, not because the PID loop chart was ‘broken’ (after all, it had been running for some 15+ years).

Hey, thank you very much for this.

all best, Matej

Hi All,

In case anyone would like this chart in PAC Control Basic, this is a 9.0 version (which you can import into a strategy that’s 9.0 basic or better).
-OptoMary (2.71 KB)