Micro820 Fault Loop Help!

Hello all!
I come asking if anyone has had this situation. I have a Micro820 controller that sits idle for some long periods (I use it to count and log machine cycles during the work day)
I check it every few days and lately it has not been executing code when I check on it. The status lights look like they are doing a startup flash, but they just loop forever. Here’s a video I took of it: https://youtube.com/shorts/wpV3sO7m47A?feature=share

It looks like a normal startup that keeps getting power interrupted. The 24VDC to it is fine though!

The only way I’ve been able to correct this is to cycle power, once I do that, no issues, and it goes back to performing correctly for (I assume) a couple days. More info: I cannot see the controller in Linx or CCW during this loop state, and there have been no code changes since it was commissioned. It has been fine for just about a year until now. Also, no fault exists in the controller once it is rebooted.

Any help would be great! Even if it is just a suggestion. I would hate to have to replace this guy already. Thank you in advance.

It's a bit of a remote shot, but I have had something like this happen with a different brand (Mitsubishi) of PLC. There was a short on an output that would cause this problem.


I figured out that the cycle was - the PLC would boot up, the affected output would turn on, the power supply would 'crow bar' down (shut down), the PLC would also shut down and the process would start all over again. It took me a while to figure this one out, as the power supply shutdown, in this instance, was so quick i didn't see it until I watched the 'cycle' very closely.

MikeVT said:

It's a bit of a remote shot, but I have had something like this happen with a different brand (Mitsubishi) of PLC. There was a short on an output that would cause this problem.

Click to expand...

Thank you Mike,
Luckily my outputs aren’t critical and I can remove them for testing for the time being. I will check it out.

As Mike says, I had the same on a Mitsi ironically, it was a solenoid coil short circuit, it took a little time to find it, I noticed when input X1 came on the fault occured, disconnected X1 & it cleared, but that was because X1 was the E-stop reset, so when the E-stop reset the solenoid operated, it is definitely something to check.

I have seen that many times in a SLC but not a 800, since it works on the reboot I think its an issue with the memory boot cycle

Since its a 820 do you have a SD card? another long shot I would try loading the program to a SD and have it boot from the SD on power up OR install a UPS on the CPU so the CPU will not power down

geniusintraining said:

I have seen that many times in a SLC but not a 800, since it works on the reboot I think its an issue with the memory boot cycle

Since its a 820 do you have a SD card? another long shot I would try loading the program to a SD and have it boot from the SD on power up OR install a UPS on the CPU so the CPU will not power down

Click to expand...

I can try both to see. Probably will do the UPS first since I am suspicious of power problems. I am not currently running an SD card program. UPS is a good idea just to ensure this thing isn’t messing up from blips. Thanks!