Is PLC a Dirty Word Now?

March 5, 2012
Controllers Now Are Called PACs, Industrial PCs, or Just About Anything Else Except What They Really Are
About the Author
Dan Hebert is senior technical editor for Control, Control Design and Industrial Networking. Email him at [email protected] or check out his Google+ profile.Just a few years ago, every controller vendor touted its PLCs, and machine and robot builder OEMs echoed the theme when discussing automation features with their customers. But past affection for PLCs is now the love that dares not speak its name — as controllers now are called programmable automation controllers (PACs), industrial PCs, or just about anything else except PLCs.


Changing names sometimes is just about marketing hype, but not in this instance. Virtually every modern machine, robot or motion controller employs multiple technologies directly borrowed from the commercial PC world. This makes the modern controllers more like PCs, and a lot less like PLCs.

For a variety of reasons, chief among them installed base, major U.S.-based vendors were among the last to relinquish proprietary PLC technology and move to the PC world. On the other hand, vendors based in Europe, particularly in Germany, were among the first to jump on the PC bandwagon.

"Beckhoff follows the technology migration set by Intel and adopts the latest processors for industrial use. We offer industrial PCs that use second-generation Intel Core i3, Core i5 and Core i7 processors in a rugged plant floor-worthy housing," says Graham Harris, president of Beckhoff Automation. "For machine builders and robot builders, this adds functional layers in software rather than via separate hardware boxes."

When Wago describes its current controller offering, it does so using PC and IT terminology. "Our Ethernet 2.0 platform provides modularity, scalability and high performance," notes Charlie Norz, product manager of I/O systems for Wago. "Gen II of our Wago-I/O-System Ethernet 2.0 packages those attributes with higher-performance processors into three distinct and compact programmable fieldbus controllers (PFCs). For networking/control flexibility, OEMs can choose features like SD card capability and network redundancy, and all our PFCs have a dual-port Ethernet switch to support daisy-chaining."


Like Wago, Phoenix Contact uses PC technology to greatly reduce form factors, providing DIN-rail mounting capability. "Our ILC 100 class controllers feature an integrated web server and function block libraries for IT-friendly functionality," notes Dan Fenton, control and software product marketing specialist at Phoenix Contact. Technologies borrowed from the PC world such as SNMP and web-based HMIs further enhance connectivity and communications.

Rockwell Automation didn't invent the PLC, but it certainly was a leader in promoting its use in machine automation. But when it comes to making the term PLC verboten, it's et tu Rockwell. "Our ControlLogix PAC enables a manufacturer to integrate motion, safety, sequential, drive and process control to provide a high-performance control solution," says Mike Burrows, a director at Rockwell. "One common Ethernet layer allows the integration of plant information with enterprise systems, using standard Cisco technology for security. The CompactLogix controller gives machine builders integrated motion on EtherNet/IP."

Although larger U.S.-based PLC vendors were relatively slow to jump on the PC train, smaller suppliers were onboard early. "Our SoftPLCs are open-architecture PACs, running ladder logic as their primary language, but also supporting C++," explains Cindy Hollenbeck, vice president of SoftPLC. "SoftPLCs have advanced PAC features such as data logging, database interface, advanced math calculations, email/texting and other communications, and more. The SoftPLC runtime engine is a Linux-based kernel that runs on an embedded computer such as an x86-, ARM- or PowerPC-based system."

Opto 22 has long championed Ethernet-based I/O, along with other technologies from the PC world such as task scheduling and distributed processing. "Unlike with a PLC, individual tasks can be scheduled and executed more logically with our Snap PAC and its flowchart-based control programs," says Selam Shimelash, application engineer with Opto 22. "If some of the machine I/O is less critical and doesn't need to be scanned as often, the control program can be designed and written that way. The PAC won't communicate with the I/O unless it needs to because the scanning of I/O points is a task performed by the remote brains."


About the Author

Dan Hebert | PE

Dan Hebert is a contributing editor for Control and Control Design.