Micro 850 Issue

[eddicuss]

Hello. I have an issue with a Micro 850 PLC. Issue is when it is in RUN mode, and an output is energized, the whole PLC just turns off, then turns back on and reboots. As soon as it transitions to RUN when rebooting, it turns off again and just does this never ending cycle.

The only way to recover is setting the switch to PROG on the PLC then redownloading the firmware. When setting back to REM or RUN, it's fine, but then when one of the rungs are true to energize an output, that issue mentioned earlier happens.

Not sure if this is some kind of fault, I can't capture it since it loses connection when it does happen.

 

[ASF]

What's connected to that output?

 

[drbitboy]

What's connected to that output?

+1.


The most likely explanation is that the output pulls too much current, which current comes from the supply that is powering the Micro850, the PS (Power Supply) voltage drops, the Micro850 shuts down, which opens the output and reduces the load on the PS, the PS recovers, the Micro850 reboots to RUN mode.


Rinse, repeat, ...

 

[parky]

I have had this problem, assuming something is connected to the outputs & not just a test on the bench then it is probably a short on one of the outputs i.e. a solenoid or some other component.
I was stumped at first it appeared that when a particular input came on the psu would shut down, when the Safety relay was energised it would shut down, disconnecting the aux contact to the PLC input cured the problem.
Turned out to be a brake solenoid that was short so when the safety relay was energised the aux contact that fed the plc input would energise the brake output from the PLC.