Micrologix 1200

Hi to all,
we have a micrologix 1200 that changes mode by itself form run to program mode, don't know what may be causing that!, any idea?.

Can't change mode not even when cycling power, laptop is needed to change mode, then everything works fine for days,,,, then again.

Thanks in advance for any tips.

Does this happen on a power cycle?

Maybe..

http://www.plctalk.net/qanda/showpost.php?p=287169&postcount=3

1) Is it also faulting?


2) If you cycle the power when it is in Run mode, does it go back into Run mode after the power comes back? If not, is it possible there is an infrequent power loss causing this issue (loose wire, etc.)?

I had a 1200 behave the same, cause was dirty power to the PLC.
Put in a power conditioner and never happened again.

Yes it does shows fault, faults goes off at powerup but goes to program mode.
Will double check that next time that happens, maintenance tech powered system down before I was able to connect.

Seems interesting to try the power conditioner

Thanks much

FYI, I did set the bit to run on powerup for the next time and definitely will try a power conditioner, the thing is that this machine has been working with no issues for 2 years and suddenly this situation came up.

Thanks all.

Double check grounding.

Surge protection on inductive loads?

The fault probably means there is a problem in the program. I am guessing, but I suspect the 1400 "remembers" there was a fault and so "declines" to go into Run mode until the program is fixed. The next time this happens, connect to the 1400 with RSLogix and "Go Online," then "Goto Error."


Then the fun starts. Since this only happens every few days, perhaps there is an accumulating value that eventually overflows; look for +/- 32767 in Integer files, or +/-2G in Long files. Another likely issue is an indirect address that is out of range. However, these are all guesses; without having the program no one here can help much, and there is no guarantee that it is even a software issue. Was the program changed recently?