PLC battery backup memory loss

[jfry67]

I currently have several plc units that have the program settings stored in ram memory that is backed up by a 3v lithium cr2430 battery whenever the power is lost. These units are starting to loose the settings or have the settings stored in memery change intermittently. There is no apparent cause for these changes, has anyone else ever seen this problem on any other industrial control?

 

[Skogsgurra]

Yes,

That's a common problem in many controls. It may be a badly designed power down/power up sequence in the unit as such, but a more common reason is EMI interfering with the R/W or data/address lines of the memory.

Is there a lot of EMI? Do you have filters installed? Are there bown-out situations? In the latter case, it may be that your reset circuits are working erratically. Many possibilities. Talk to the manufacturer.

Gunnar Englund

http://www.gke.org

 

[denison]

I fyour PLC's are S5 units from Seimens, and the battery is marginal, it will reload the eprom module data wich may be different from you present.

 

[jfry67]

They are the M-11 series from SKH. My company has over 300 units installed, using these boards, but it seams like the troublesome units are located in the New England/New York area.

We are thinking that it may be EMI or RF causing it, but we have been unable to simulate the failure in the lab.