Problem with Ge Fanuc micro plc

Hi Members!

We have a machine which is controlled by Ge Fanuc IC693 UDD110 micro plc (not versa micro). It worked properly so far, now it is always freezing with watchdog fault. Yesterday I changed the plc but the new plc also freezed with software fault. I am sure that the new plc is good. The plc has an expansion unit, is it possible that the expansion unit freezes the plc?
Thanks your help.

Watchdog fault means that it is taking longer than 200 milliseconds to complete a full scan. The scan includes updatating the inputs and outputs as well as logic solution. It is possible that a bad expansion unit or noisy communications with the expansion unit could slow things down enough so that a scan takes longer that the watchdog time.

Do you know what the scan time was before it started acting up? Do you have programming software to communicate with it? Is there anything out of the ordinary in the ladder logic?

There isn't any out of the ordinary in the program, it was working correctly in the past. Unfortunately, I can't change the expansion unit because I don't have other. And the worst that I can't order one because its production is stopped. Only Versamax micro plc exists instead of it. By the way, I made an other attempt, the plc has a display and I connected it to the other port of the plc. Perhaps...

I feel your pain.

I remember having the exact same problem, probably about five years ago. We shipped a stainless steel bench, which had about 12 of these PLC's and 12 Maple operator interfaces. About 2 months after the initial installation the customer called, and said that two of the PLC's were no longer in run mode. I was sent up to Canada, to look at the problem, and it was a watchdog fault. We did just about everything to try and alleviate the situation, but I know it was never really fixed. The bench was shut down, when the company was sold, and I think it was sent over seas?
I have used the same PLC many times, without ever seeing this problem, I have even used it with an Optimate operator interface from Automation Direct, without seeing this problem. So I would have to conclude the the problem in my case stemmed from the Maple Systems interface.

I hope you get to the bottom of this,

Good Luck.

GE Fanuc Micro IC693xxxxxx Watch-Dog

The very earliest versions of these PLCs had a bug that would cause this. In most cases it can be fixed by updating the Flash OS.
Go here to get the last one. http://www.geindustrial.com/cwc/gefanuc/support/ControllersIO/s90micro-d.htm
Obviously if the problem is a bad expansion unit this will not help, but you should load it if your version is not the latest.