July 19, 2019, 12:38:12 PM
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 Sticky DO

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May 24, 2019, 02:40:46 PM
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Silly sounding title, but serious issue. I have a simple BG logic program that goes as such:

If UO[6: Fault]=ON Then
DO[#:Light Tower(Red)] = ON
DO[#Light Tower(Red)] = OFF

Most days, it behaves. Then randomly, the DO stays on when the fault signal isn't present. I've checked the wiring to make sure it wasn't a short. The relay output card I'm using is sending the 24V out. The DO on the TP says its off also. To get it to turn off, I have to stop the BG logic program and manually turn the DO on, then off again.

I even added a counter with a 20 cycle delay before turning the light out to weed out any sort of cycle anomaly. Has anyone experienced faulty relay output cards sticking? 

Today at 12:38:12 PM
Reply #1



May 24, 2019, 02:46:57 PM
Reply #1


Not a solution, but could you simplify your code a bit to just

DO[#: Red Light] = UO[6: Fault]

Less code, less chance for weird errors. Not 100% sure if BG Logic will allow it though. It has some weird and convoluted rules sometimes.

More towards the issue, are all of your I/O unsimulated?

May 24, 2019, 03:05:56 PM
Reply #2


Thanks for the recommendation. I went to the DO's and turned it on a bunch of time until i got it to "hang". I couldn't get the other lights to do that. I swapped the light to a different channel and the problem went away. So, I concluded that its a faulty relay output.

May 24, 2019, 04:46:25 PM
Reply #3


If it's a relay output, it really could be sticking. I've seen AB relay outputs where i could smack the PLC and stuff would turn on. LOL.

Good luck!

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