Slc Redundancy - Ab

Hi,

There are 4 SLCs..,
SLC 1&2 are Primary and secondary at one end, and SLC 3&4 are
Primary and secondary at other end. All SLCs are communicating through Ethernet network. If SLC1 is Primary and SLC2 is secondary, and if SLC1 looses communication with SLC 3&4, then I would like to switch SLC 2 as primary and SLC1 to slave. How it is done through software ??

Thanks,

Guru

Assuming the hardware doesn't already support redundacy, you are implementing it in an ad-hoc fashion, and you've made the proper electrical connections, I would first consider watchdog timers.

Each PLC has a watchdog timer that would be assigned to the remaining PLCs in your communication networks. Each PLC sends a message to the other PLCs that clears its assigned watchdog timer in the receiving PLC. If a watchdog timer times out then each PLC will assume that the PLC assigned to that timer is no longer functioning.

The algorithm/schedule (whatever you want to call it) will have to be thought out by you. Create a decision matrix listing all of the possible scenarios and what each PLC should do for each condition. The decision matrix should also consider a break in the communications network but all PLCs still active. Then implement it in ladder logic.

Something to chew on and get started with.