Loss of PLC program after cycling the poweron micro 1500 1764-LRP

[kiran]

Hello everybody,

I want to findout the reason and solution for losing the PLC program every time the micrologix 1500 is powered down. I have never come accross this problem before. We recently replaced the processor but that did not help. Could anybody help?

Thanks.

 

[TConnolly]

Fix your system ground.

 

[Ken Roach]

Are you powere cycling it along with some other gigantic load ? I've never heard of this happening in any of the hundreds of these controllers I've seen installed.

The MicroLogix 1500 memory is actually battery-backed, but it has a hold-up capacitor that will retain memory for quite a while (several days). You actually have to manually go in and unjumper the battery and drain the capacitor to clear the memory of the MicroLogix 1500.

Do you maybe have an EEPROM module with a default program in it ?

 

[TConnolly]

We had a plant in NJ that was having the same problem with a SLC-500. I was being sent out there to have a look at the system. I asked around here before I left and a guy at the regional AB office said that he had seen the problem once before and that the system was not grounded. Sure enough, when I got to the plant and opened the cabinet there was no ground wire at all in the cabinet. We grounded it and viola, problem solved.

 

[zmanvortex]

Try putting a MOV or TVS device on the power terminals of the processor. Sounds like you are disconnecting a large load when you power down the processor.