Control of Contrologix Remote I/Os via two separate contrologix redundant Processors

[asim_rana]

Dear Experts

Is it possible two have following functionality using conrologix processors & I/Os at remote

1. We have two separate redundant contrologix systems SYS1 & SYS2 (suppose) at two different location
2. we have one remote chassis REM1 (suppose) having I/O cards
3. Our requirement is that normally this remote chassis REM1 should be controlled by SYS1 over control net but in case if this controlnet link goes down only then REM1 should be controlled by SYS2
4. Is it possible?
5. if possible do we need to to put two CNBRs at REM1 one for SYS1 & other for SYS2.Then through programing when we feel that link of REM1 with SYS1 is not ok we will change control of REM1 to SYS2.

Thanks

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Best Regards

Muhammad Asim Khan

 

[shades]

ControlLogix redundancy requires a 1757SCM module in each of the processor racks to determine the status of each CPU. They are linked with a 1757SRC1 cable. This an optical cable supplied at 1m but I'm not sure if you could use a long cable.
You require one CNBR in each of the cpu racks and io rack. The CNBR is a redundant media and has networks A & B.

If system 1 CNBR channel A faults then the remote IO continues to communicate by channel B. if there is a problem with a system 1's channel A&B then the cpu's switch automatically to retain communications to the remote rack.
I would also suggest that you install redundant psu units on the remote rack (1756-PAR2) to ensure power.

Firmware is always an issue and there is a special firmware pack available from AB to ensure that the CPU's & CNBR's are at a compatible level.

I've just finished a project with 1756-L61 cpu's loaded with FW 15.6.

 

[Ken Roach]

It sounds like you are trying to approximate the normal ControlLogix redundancy function without actually using ControlLogix redundancy.

This is not how the ControlLogix platform is designed to work. While there are some of the functions (connection enable/disable in the program) that could make this possible, they don't come up to the level of co-ordination provided by the 1757-SRM redundancy modules.

These redundancy modules synchronize the programs between two CPUs, synchronize data between two CPUs, and check for the status of the controller and network cards in each chassis.

I strongly recommend against attempting to "soft switch" I/O between two separate and different controllers as an attempt to provide controller or network redundancy. Use the tools that are already available.