Application cycle time is greater than 2000 ms

[otrotabi]

I get this alarm when trying to use a PID Advance FB.

What does application cycle time mean ? And what may I try to reduce it ?

[otrotabi]

Although I am curious to know why the PID advance function block checks cycle time (is it maybe a FB which uses too many resources ?) I think the error in my project comes from a while loop not working correctly. 

[Bastian_Schmitz]

Please check if you use the PID Advance in the timed task. Normaly I would not expect that you have such a large cycle time in a timed task. You could check the real cycle time via the target variable. 

[otrotabi]

Thanks for your feedback.  Yes, the PIDAdvanced is used inside a POU running as a timed task.  It is related to this topic on how to handle a variable speed fan working alongside a fixed speed fan.

https://community.se.com/t5/HVAC-and-Pumping-Forum/Fan-management-variable-speed-and-fixed-speed-fan...

The PIDadvanced FB is used as input to a CompMgmtVS FB which does the actual handling to the fans.

I checked the variable, it´s about  7600 msec. I never checked before so it means nothing to me. Is it too high ?

[otrotabi]

According to this article: https://kwoco-plc.com/plc-cycle-time/#:~:text=PLC%20cycle%20time%20is%20the,act%20before%20starting%....

An acceptable PLC cycle time depends on your application’s needs. For most processes, cycle times from a few milliseconds (ms) up to 100 ms are common. Determine what your process requires and set your acceptable threshold accordingly.

So it looks like to either my program is doing something completely unacceptable or I am not understanding the result of the variable correctly.

How does HMI programming in a TM172 affect PLC load itself ? Do they have separate CPUs inside the hood?

[FedericoM · Accepted solution]

Hello,

Timed task has a fixed period of execution of 100ms, so the code running on this task should be executed in less than 100ms to give space to all the other tasks.

I think you have to review what you have in the timed task, 7.6s is not normal for TM17x PLCs.

[otrotabi]

Thanks. I will asap.