Thank you for the info, I do need a more reliable event.
I am executing a script as each carton passes by a photo cell eye (via a conveyor running at 200 ft/min). The gateway tag change script executes very rapidly (2-14ms start to finish) but the event completes 270ms to 520ms after my scanner returns a value (results from thousands of samples). The scanner is on a timeout read cycle so it delivers the bar code at very consistent times (about 300ms from the scanner eye being triggered and scanner eye is directly connected to the scanner). Hard to believe, but based on the numbers I collected, the tag change eye activation varies up to 250ms. The tolerance for this application is about 100ms (about 3.3 inches).
If the triggering of the tag change event has this much variance, my application won’t work properly. I am not familiar with how to setup a tag change event in a project instead of on the tag itself (via the gateway tag change option). Could you steer me in the right direction on how I set that up? Do I use a gateway timed event? How do I recognize when the tag changes?
Lastly, in this script triggered by the eye, I write three integer values to a an ethernet connected Allen Bradley Micrologix 1100 PLC (this eye is connected to this same PLC). Any idea on how long it takes before the PLC values are set? Would this have any variance in time like I seem to be experiencing from the eye?