We have conditions that lock machines then require a supervisor to scan their ID to unlock the machine.
The problem is when the same supervisor needs to scan a second time the Tag Change event never fires seemingly because it knows the same value received is the same if that makes sense.
It’s an OPC tag. A Tag Change gateway script. I’ve been trying different (Change Triggers) Enabling only Timestamp or Value etc but it still doesn’t fire when the value is the same.
Meh, it doesn’t matter. I don’t think you can make this work the way you want.
I was thinking to use the Include Timestamp-Only Changes OPC UA tag group property introduced in 8.1.10, but if that works it’s going to end up triggering every time the driver polls.
Yeah, you’re going to have to reset it. The driver is just going to see barcode “foo” each time it polls. It couldn’t possibly know that’s really a 2nd scan because it didn’t change.
I’ll have to play around with this a bit. See if I can (wipe content) or (reset it) or something similar. Talking to people here, theoretically, there will be scans of other barcodes between supervisor scans.
You really should not wipe it from Ignition. Echo it or use some other signal so the PLC wipes. Otherwise you will eventually lose more scans to the race condition.
They are telling me (the problem I describe in this post) won’t exist here because the logic-flow of this scanning process dictates that another barcode will always be scanned in between the supervisor scans.
I’ll stop trying to get a resolution for this issue for now.