Hot Backup - L33ER Switchover for Redundant PLC

[Krithik 0]

Dear Experts

I have Compact Logix L33ER processor for Hot Backup Redundancy Purpose in WTP application. Iam using Flexlogix 1794-OB16 DO outputs.

Flex adapter for IO communication.

Iam trying for Soft Redundancy from main processor to peer and peer to main processor .

During Switchover from Main to Peer and Peer to main Processor, the DOs are cut off.

While in the middle of the process if the Switchover of PLC happens due to failure of Main or Peer PLC, if the DOs are cut off, Should i Start the process sequence logic from beginning?

I tried configuring the DO properties of  Communication Fail Behavior in output modules properties as "Hold Last Output but still the DOS are cut off during switchover.

Then also Iam facing the problem of DO cutoff whle switchover. Iam having same program and IO configuration in main and peer plc generated through HotBackup tool.

Please let me know if there is any way to Prevent DO cutoff while switchover . Also in Panelview HMI iam using 2 screens for Main and Peer PLC. While switchover the screens in HMI are showing in boxes.

Please advise.

Regards

Krithik.K

[pturmel 157]

I don't think this platform can do this.  To keep the DOs alive, the backup processor must make a passive redundant connection to the output module.  Only the truly redundant processor types will do that.  (And the output module must support it, too.)

[Krithik 0]

Thanks for the reply @pturmel. Iam using 1794-ob16 module and flex adapter 1794-AENT. Does it support to hold the output during switchover? the module was tested with  Communication Fail Behavior in output modules properties as "Hold Last Output but still the DOS are cut off during switchover.

 

[pturmel 157]

8 hours ago, Krithik said:

Hold Last Output

Unrelated.

Look in the output device's EDS file's Connection Manager section for a redundant connection option.  But it will be moot for the L33ER.  It isn't a redundant processor.  You can't wave a magic wand to make it redundant.  The "R" suffix is for "Ring" support, not "Redundant".

Edited 19 Mar 2022 by pturmel

[Ken Roach 194]

The only Studio 5000 family controllers that support real "Redundancy" are the 1756 ControlLogix, when equipped, configured, and programmed properly with the appropriate firmware, network modules, network architecture, and Redundancy Manager modules.

There have been some attempts over the years to implement "hot backup" with ControlLogix and CompactLogix.   I am aware of a Application Technique document for High Availability CompactLogix that was last updated as version 4.0 about five years ago that used 1769-L30ER and 1794-AENTR products and architectures.

The document and the accompanying "hot backup tool" code generation software is not publicly available.   You can only get it from a Rockwell Automation sales office, and only if you are approved by them and their country manager and/or Commercial Engineering at RA.

Support for those systems is only available through the local field sales office that approved you to use it.   

You are correct to be looking at the Fault Action configuration for the 1794 FLEX Output modules;   they should be able to be set for Hold Last State during a Fault condition.   Remember that Program Mode and Fault Mode are separate settings for FLEX I/O.

Testing it is simple: set up a single-controller system with FLEX outputs configured to hold last state during a Fault, set some of them = ON, and unplug the CompactLogix.    If they work correctly and stay on when their connection is faulted, then the problem must be when they go back into RUN mode.

Also remember that you must use a direct Module connection to each Input and Output module;  "Rack Optimized" connections to the FLEX adapter are not supported.

You probably cannot easily solve the PanelView problem.    PanelView Plus terminals are specifically not supported in this kind of system because they cannot switch between IP address targets.   I've built systems like this using RSLinx Classic OPC Alias Topics with PC-based FactoryTalk View HMI stations.

Again, this is something that your local RA sales and support office should be involved in.