how to detect controllogix fault

Hi All,

There are three Controllogixs control seperate units and communicate together, how can one PLC know another two plcs are in fault status? Thanks.

wilsonzhu said:

Hi All,

There are three Controllogixs control seperate units and communicate together, how can one PLC know another two plcs are in fault status? Thanks.

Click to expand...

The easiest way would ne to set up a "heart beat" for each PLC and look for it from the other 2.
If you lose it, that means the PLC is faulted or at least stopped running its program.

but this way will also include the communication failure, it can not tell it's caused by PLC fault or communication network failure. Can I make a fault handler rountine and send a bit to another plc before this PLC go to fault mode?

bkottaras said:

The easiest way would ne to set up a "heart beat" for each PLC and look for it from the other 2.
If you lose it, that means the PLC is faulted or at least stopped running its program.

Click to expand...

wilsonzhu said:

but this way will also include the communication failure, it can not tell it's caused by PLC fault or communication network failure. Can I make a fault handler rountine and send a bit to another plc before this PLC go to fault mode?

Click to expand...

I'd use a GSV to monitor Comms failure for each PLC, remote adapter, etc..
I have no acess to my PC but in case no one jumps in (Ken Roach)I can dig up a setup for comms monitoring.

My question is if major fault happen, the PLC go to controller fault handler Task, Does the communication still works(major fault is not caused by Comm)? If the communication still works for some time, I can configure a routine in the fault handler to send a bit to other PLC via controlnet. Otherwise, I have a hard way to use a DO(Fault mode off, Program mode ON) and in this plc's program also energize this Do during plc running. The Other PLC us this DO as DI to know if this PLC is in Fault mode. How is that?

bkottaras said:

I'd use a GSV to monitor Comms failure for each PLC, remote adapter, etc..
I have no acess to my PC but in case no one jumps in (Ken Roach)I can dig up a setup for comms monitoring.

Click to expand...

Don't try to use the fault handler to initiate a message. That's not the purpose of the fault handler.

Use a repeating timer to fire a MSG instruction from the "monitoring" controller to the "monitored" controller, as described in RA Knowledgebase article ID # 21989. This uses the "Get Attribute List" service to read values from the Device Identity object.

This will allow you to read the Run/Prog/Fault controller state and Rem/Remote/Prog keyswitch position from the remote controller.

If the Message instruction fails with a communication error, you know that there is a communications path problem between the controllers.