Power Loss Notification

[bushman 0]

I'm using the Compact Logix L43 processor. Is there any system variable, or status bit, that indicates a pending power loss? i.e. when the power supply knows there is a limited time after it's lost it's input power and before it can no longer hold up the processor. I would like to store some critical process information before the system goes dark. Thank you in advance.

[Shiner 2]

Have an input from a relay that is held by outside power source....run a timer off of that that will initiate your shutdown...

[PLCMentor.com 60]

Do you have some sort of UPS? If not, you may want to power the PLC with a UPS and take your system power to an input to let you know when you have lost power. The UPS would not have to be large, just big enough to hold everything up until you get through with the manipulations you want to complete.

[TConnolly 13]

Sola makes a smallish din rail mounted UPS that is ideal for that.

[Ken Roach 194]

I've been using the Phoenix QUINT UPS modules and have been very satisfied with them. In one of our systems we actually run the PLC for about 20 minutes after power loss because it's a high-value, high thermal mass workpiece and if they can get power recovered before it cools off too much we can save the part. Phoenix, Sola and A-B also have "buffer" modules that will give you a short hold-up time, probably long enough to write to nonvolatile memory. What you might experiment with on the CompactLogix is the fault routine; the controller will probably fault on power loss right before it shuts down, and the fault routine will execute. It can't hurt to try.