Multiple events with Controllogix

pauly · Aug 15, 2012

If I want to create a number of event based tasks triggered from a local d.c. input card, how can this be achieved? The event trigger only allows slot level configuration and not bit level. If I wanted two events triggered by two seperate inputs on the same card, how can this be achieved? The local Rockwell tech support suggested that only one event per slot can be achieved! Surely this can't be right?
Any advice appreciated

MichaelG · Aug 15, 2012

I think that he is correct - the card sends one event trigger for the whole card
You have to process the event before the next input needs to be processed - high probability that you will miss one event

On one job they used one special input per card - the other inputs were used for general inputs (normal update rate)

Have a look at the 1756-IB16ISOE

Sequence of events card - tells you the CST time when inputs change state

Ron Beaufort · Aug 15, 2012

I got this to verify in Version 16 - but I won't be able to actually test its operation until I get to the lab later today ...

basic idea:

create a separate BOOL alias for each input - then use the trick below to be able to select the alias that you want to use for the event trigger ... (the "filter" check box must be cleared in order to see the BOOL alias) ...

I give it a 50-50 chance of working - but I'll let you know more this afternoon if you don't get to try it out first ...

.

pauly · Aug 15, 2012

Thanks for the info

Thanks for the reply Ron, great stuff. I find it odd though that an event can't be tied to an individual bool.

Ron Beaufort · Aug 15, 2012

I was afraid of this ...

sorry - but it won't work ... I just tried it out on an L55 processor using Version 16 software ... the system let me verify and download the program OK - and it ran without any Warnings or Errors - but I couldn't get the event task to trigger ...

looks like something for the "to do list" if the Rockwell guys ever have a slow day ...

sorry for the false hopes (but it sure did look promising) ...

daba · Aug 15, 2012

Great idea Ron....had to try it.

Strange that both Inputs trigger Event_2 task !! Event task 1 never gets executed....

Ken Roach · Aug 15, 2012

The way I learned it was that the triggering Tag was the Input.Data tag from the 1756 Input module. Any Change-Of-State event on the module (which is configurable point-by-point) would trigger the Event Task.

I never even considered trying to use a BOOL type Alias as the triggering tag.

I'm not sure what would happen if you had another Event before the Task was complete. My guess is that you'd get a Task Overlap; RA Commercial Engineering would have to answer that question.

daba · Aug 15, 2012

Still find it odd that one of the event tasks never gets executed, even if it is looking at the module tag, you'd think that both event tasks would execute for both pushbuttons.

As for task overlap, wouldn't it be handled by priority, just like periodic tasks - if both event tasks had the same priority surely it would time-slice them.

The fact that it is completely ignoring one of the tasks is not right.

daba · Aug 15, 2012

Here's another oddity....

I tried to change Event Task 1's trigger to that used for Event task 2, and the software complained that it was already in use by another Event Task...

OK, so I changed it to the module tag Local:2:I, and it let me.

Now Event Task 1 executes for either of the pushbuttons, (as expected), but Event Task 2 doesn't execute at all, even though it did before for either pushbutton.

It appears as though the system will only execute one event task per module, regardless of how the tag is specified.

RA probably omitted to check for two alias tags pointing to the same module tag.

Ron Beaufort · Aug 15, 2012

in my system I'm noticing that ANY input (switch) on the referenced module will trigger the "active" task ...

specifically, even though I've got the alias set to just ONE particular switch - ANY switch connected to the module seems to trigger the ONE task that will actually work ...

weirder and weirder ...

personally I'm prepared to say "you can't get there from here" and just let it go at that ...

daba · Aug 15, 2012

me too

Multiple events with Controllogix

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