Result of SQL query into a Contrologix PLC tag

Ignition
1

I have a query tag that returns the result I am looking for. I don't need an array or anything, it is a single value. I want to write this into a global tag in my contrologix. Watching inductive university topics about query tags, at the bottom of the interface it looks like this used to be built in, because there was a checkbox with some drop downs where you could select the device and tag. This no longer exists. How do I accomplish this?

2

Just use a Tag valueChange Gateway Tag Change event, on the query tag, in combination with system.opc.writeValue() to write the value to the PLC anytime the value changes.

3

Here is what I just tried and it didn't like it:

Select top 1 [NumericAnswer]
From [Horizon].[dbo].[SpecimenResult]
where [DefinitionID] = 55 and [NumericAnswer] is not NULL
order by [BatchID] Desc;
system.opc.writeValue([default]Inverter_Room/StartingStress)

Just that last line is what I changed. It worked fine without it.

4

That is because, what you did is not what I suggested.

Instead you tried to use a scripting function in your SQL, and that doesn't work.

Instead, you need to add the function to the valueChanged Gateway Tag Change Scripting event triggered by the tag.

5

script
script1920×1032 150 KB

I tried this and it didn't work. Am I doing something wrong with the syntax?

6

Not safe in a tag valueChange event. That system call blocks, possibly for long time.

Use a gateway tag change event for such a script.

(Or, perhaps, use my Integration Toolkit's "Republish" tag actor, which works basically just like the old v7.9 functionality.)

7

Yeah, I'm not sure why I thought that was an Async function.

I have edited previous posts for a more appropriate solution.

8

Yes, you are using three variables in that script which have not been defined.

I handed out some poor advice, which has been corrected now. Sorry about that.

One way to approach this is to use a Gateway Tag Event Script:

You assign the query tag as a trigger tag, and then in the script you would use a script like this:

if not initialChange:
    server = "Ignition OPC UA Server"
    path = "OPC Path to the PLC Tag"

    # newValue is pre-defined by the event. It will hold
    # the new value of the tag which triggered the event.  In this case
    # the value of the query tag.
    system.opc.writeValue(server,path,newValue.value)