Hello,

I use TIA Professional v13 SP1 Update 9 and I have a problem with scheduled tasks.

So I have a scheduled task triggered when the value of an internal tag changes ('On Change'). In this scheduled task I execute some global functions and things like that.

Everything works fine, but the problem is that whenever I download my project to the device, the task is also executed. It looks as if during download the value in Internal Tags change for a moment or are re-initialized, which causes the scheduled task to trigger. Mentioned internal tag (trigger) can ONLY be changed by manual actions of someone who operates on the Runtime.

What can I do to stop this 'initial execution'? Is it even possible?

Thanks for help,
Nattana

Try to initialize your internal tag to zero.

good luck.

rdoliveira

Try to initialize your internal tag to zero.

good luck.

It doesn't work.

But anyway, my trigger tag is a string. So I set the initial value to "-" and then checked in my scheduled task if the Len(triggertag) < 2. If it was, the function should just return nothing. But it didn't work. The scheduled task was still executed. It looks like it happened before the value was re-initialized to "-"

Place a print of the scheduling properties and your tag, here.

What device are you using? MP, TP, PC?

Nattana

Hello,

I use TIA Professional v13 SP1 Update 9 and I have a problem with scheduled tasks.

So I have a scheduled task triggered when the value of an internal tag changes ('On Change'). In this scheduled task I execute some global functions and things like that.

Everything works fine, but the problem is that whenever I download my project to the device, the task is also executed. It looks as if during download the value in Internal Tags change for a moment or are re-initialized, which causes the scheduled task to trigger. Mentioned internal tag (trigger) can ONLY be changed by manual actions of someone who operates on the Runtime.

What can I do to stop this 'initial execution'? Is it even possible?

Thanks for help,
Nattana

Dear Nattana,

can you post a screenshot of you sheduled task?

With best regards

rh1990

I think I found a solution. It's not exactly what I would like it to be, because I had to create an additional internal tag (which is something I wanted to avoid), but hey, it works.

I don't really want to post screens, because the whole thing is scattered across the whole project, but the main description would be something like this:

1) I have an internal string tag, let's say "StringTag".
2) I have a TIA WinCC Faceplate with internal script, that indirectly writes some string to "StringTag" on an On-Click event.
3) Then I have a scheduled task that is executed when "StringTag" changes (so basically whenever I click on the faceplate)
4) Inside of the scheduled task I read the value of "StringTag" and then use this value as a parameter for some additional Global VBS function, which is also called in this scheduled task.

The problem was that whenever I restarted the Runtime OR simply downloaded the changes, the scheduled task would trigger and execute that function. And that should only happen when you click on the faceplate.

So basically there are 2 options: either the values of internal tags are reinitialized (and TIA reads it as 'changed') during download to the device, or it's the faceplates that indirectly write something to my "StringTag" during download. But even if that was the case, it doesn't make any sense because I checked that overwriting a string with the same string does not trigger 'on change' actions

But anyway, what I did was that I created an additional internal tag, let's call it "Initialization" and set its start value to 0. Then, in my scheduled task I created an If Statement and checked for the "Initialization Value". If it's '0', I would simply change it to 1 and leave the scheduled task. In any other case, I make it execute the code I want.

But the problem is still there. I don't know what causes it, especially since these are Internal Tags and have nothing to do with PLC. Also, the only way to change "StringTag" value is by manually clicking on the faceplate.

So even though I found some solution to my problem, I would still appreciate some input on why this happens and how to do something to overcome this issue completely. Cause frankly, I don't really see the point of using on--tag-change scheduled tasks if they are executed when you don't want them to

Sorry for this wall of text and thanks for help,
Nattana

New question published by kosmous is split to a separate thread with the subject How can prevent schedule task to execute without trggering event?.

Best regards
Jen_Moderator