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Product Exclusive: Redundancy Finally Made Simple

ControlGlobal.com
03/09/2010

By Opto 22

Opto 22's new SNAP PAC Redundancy Option Kit (SNAP-PAC-ROK) can be used to design an Ethernet-based redundant control system with maximum reliability and distributed intelligence that can recover instantly from failure, uses standard off-the-shelf components and costs less than traditional redundant controllers.

Using standard Opto 22 S-series SNAP PACs and SNAP Ethernet I/O, combined with the SNAP PAC Redundancy Option Kit, customers can configure automation systems with dual programmable automation controllers (PACs) that essentially synchronize and run in parallel. In the event one controller fails or is knocked offline, the other controller will assume command and continue to execute the control program and the processes it runs with no interruption or restart necessary.

The SNAP-PAC-ROK has several features that distinguish it from other redundant systems. Two identically configured controllers (active and backup) are able to swap roles in the redundancy scheme at any time. This offers a unique flexibility and other benefits during system start-up and commissioning. Customers can keep their control system online and operating even as they make changes to or completely replace their control program. Once the new program is downloaded to one controller, it becomes active and the second controller is updated with the new instruction set. Customers can repeat this process as often as they like, as they test, fine-tune and configure their control program to their exact specifications. Similarly, customers seeking to make their existing system redundant need only to add the SNAP PAC Redundancy Option Kit and a second S-series controller, which, upon commissioning, is automatically populated with the most current firmware and control program. 

"The way the system is set up, it doesn't use the traditional architecture in which one controller is the primary and the other is the backup," explains Benson Hougland, vice president of marketing and product development for Opto 22.  "With the ROK, the two controllers can be configured in any way. This give a lot of flexibility as to which is running and which is back up. Changing is a simple software command."

This capability simplifies the lives of maintenance technicians as well, says Hougland.

"If an active controller fails, the other will take over. Then the technician can go out and replace the controller and power it up, and it will automatically check that it has right firmware and programming and take over. The system will take care of itself and bring itself up to redundancy. We have made replacing a controller as simple as putting it in and powering it up."

The SNAP-PAC-ROK is also economical. It uses Opto 22's standard controllers, not more expensive special redundant controllers. It also communicates over Ethernet using standard Cat 5 cabling. No proprietary communication protocols, interfaces or custom cables are required.

"The thing we're most proud of is the fact that you can use our standard product to put together redundant system," says Hougland. "Our research indicates that if you're looking at a redundancy system, you have to use redundant controllers, but you will have to pay a significant premium for that. Overall cost will be significantly increased because you have to buy special controllers. We also use standard components off the shelf. The redundancy option uses standard Ethernet and or serial cables. With competitors you may need to buy special link, which also costs more."

The SNAP PAC Redundancy Option Kit includes:

• SNAP PAC Redundancy Arbiter -- a stand-alone processor that connects serially to both controllers and monitors, regulates their status and maintains synchronization of the control program during system start-up. 
• SNAP Redundant Power Switch -- allows power restarts to controllers in the event of failure and during firmware upgrades.
• Redundancy Option Configuration Utility -- for configuring redundant systems, including IP addresses, program synchronization and firmware matching and for maintaining and monitoring a functioning system.

The SNAP-PAC-ROK will be available from the Opto 22 website and a worldwide network of authorized distributors March 22, 2010.

For more information, call 800/321-6786 or go to www.opto22.com.