Compactlogix Rung true but OTE does not energize

bornwild

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Join Date
May 2010
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Riyadh
Posts
429
Hey all,

I have a wierd problem. I have a compact logix processor the rung condition is true but one input of the rung fluctuates as it overwriiten by some other rung . The output doesnt come on sometimes what could be the reason. Some times it works and sometimes it doesnt . What should i do to solve the problem
I have the same program in the other processor which is also compact logix and runs fine
 
If you have an input condition on the rung that is rapidly changing state, the output may not function the way you expect.

Cross-reference the address of all the tags involved with that rung and figure out what is over-writing them.
 
It is seal in circuit .So atleast one scan the input is true it should seal the circuit right. I have the same program in the other machine and it works fine.
 
As ken says - check your cross reference. Check for word access to the output. Check the code is actually executing that part of the program. It is never a problem with the PLC.
 
"Anything downstream trumps actions that occur upstream". Use this rule and do not let the green true indicator deceive you. The BOOL may be set downstream to provide a true indication, but it is most likely set false upstream somewhere else.

Multiple OTEs of the same BOOL is sometimes not allowed in other programming platforms for good reasons. Rockwell does provide warnings in the program when the project is verified. Check your program if you see warnings such as "Duplicate Destructive Bit Reference Detected:"

BOOL control using OTLs and OTUs may prove to be better.
 
There is something unique to your program, as this is not a bug anyone else has seen.

As well as the other suggestions, have you used xio instead of xic for the seal in?
 

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