Greater intelligence is the major factor driving trends in PLCs and PACs. In recent years, control devices have gained complexity while actually becoming easier for the user to deploy. These devices are taking on increased network responsibility, including safety, which has migrated entirely into the control network, eliminating network redundancy. Meanwhile, HMI has advanced, allowing a deep view into plant metrics on visual-rich consumer-like screens. In fact, sometimes it is a consumer screen, as plant data becomes Smartphone-ized.
Even low-end PLCs are combining the controller and operator interface into one compact housing while the combination unit takes up less panel space than separate devices. The combined HMI-plus-PLC unit minimizes wiring because no connections need to be made between the HMI and the PLC. "A single power source powers both the HMI and PLC, and only one network connection needs to be made," said Don Pham, a product specialist at IDEC. "As compared to a separate PLC and HMI, the combined unit will always cost less up front, an important attribute."
No integration is required between the PLC and HMI when they're combined. "There's only one software programming package to purchase, master, and update," said Pham. "Programming time is less, since there's no need to integrate the HMI and the PLC because communication and configuration parameters are set up and usable right out of the box."
In recent years, PLCs and PACs have shifted away from being dedicated machine-logic devices. They are now an integrated machine platform. The size of commercial chipsets has decreased, while the capabilities are continually increasing. "We are now able to fit more functionality onto a single device. This can be as simple as the addition of a web server to allow users to display diagnostic and operational data to the local network through a VPN connection," said Derrick Stacey, solutions engineer at B&R Industrial Automation.
He noted you can use the VPN connection to view the data from anywhere in the world. "We can give a machine designer the platform to send SMS [short message service] and emails to necessary personnel in emergency or maintenance situations," said Stacy. This level of sophistication also means that PLCs and PACs can report directly to the ERP system, thus increasing the integration of ERP with the data from the manufacturing floor.
Another important trend Stacy points to is the end of specialized controllers. PLCs and PACs have become the do-it-all devices on machines and manufacturing lines. They are able to run HMIs, motion, I/O, even some safety functionality. "There is no longer a need for dedicated motion controllers or messy HMI software packages that require extensive configuration to report screen inputs back to the PLC or PAC," said Stacy.
All of this results in saved space in the operating system. Stacy notes that B&R's P3 drive is capable of running 3 axes of motion in the space normally reserved for a small single-axis servo drive. "As these components give more of their onboard capabilities to the machine controller, they can decrease in size and shrink electrical cabinets, which also shrinks the cost of those cabinets," he said. "This means the world to OEMs as they work to differentiate themselves in competitive marketplaces."
What's a PLC and What's a PAC Nowadays?
The lines between PLCs and PACs are beginning to blur, leading many to believe that a PLC-based PAC is probably a better name than PAC. PLC-based PACs are taking proven, rugged PLC hardware designs and incorporating low-cost technologies from both the PC and mobile device worlds. "Manufactures are combining these technology advancements to meet the ever-changing needs of their users, delivering PLC-based PACs in response," said Jeff Payne, automation product manager at AutomationDirect.
The shared characteristics between high-end PLCs and PACs are numerous. They include faster scan times, tag-name programming, significant onboard memory, documentation stored in the controller memory, task manager program organization, and multiple built-in Ethernet ports and protocols. "These characteristics enable both types of controllers to perform high-speed control, advanced control, data acquisition, and other tasks," said Payne.
He noted that although high-end PLCs and PLC-based PACs share many characteristics, PLC-based PACs have higher maximum I/O capability, ranging into the tens of thousands, whereas PLCs top out in the thousands. "They also have more program memory, and often feature a wider range of programming languages," said Payne. "On the downside, PLC-based PACs tend to be more expensive and take up more space."
He also noted that while a high-end PLC can handle most machine control applications, a PLC-based PAC would be a better fit in highly complex applications requiring integration of multi-axis coordinated motion, triggering of vision systems, and collection and storage of inspection results.
PLCs and PACs Are Getting Computer-Like
Developments in PLCs and PACs are beginning to parallel computers. The ever-increasing intelligence, the fast processing speeds, and the downward pressure on prices are a few of the similarities. "We use the same processors that computers are using, though they are a little more ruggedized because they have to handle vibration," said Stacy. The similarity to PCs takes some of the development work out of PLCs and PACs. "We don't have to come up with custom processors to run these guys," said Stacy. He noted that if you're trying to provide high usability, it makes sense to use high-performance PCs.
When manufacturers debate what forms of automation controllers to integrate into their systems, PLCs and PACs usually make the list of devices to implement. Yet choosing which controller is best for a particular application can be daunting, since each offers its own set of benefits. While traditional PLC and PAC systems have their merits, at Beckhoff Automation they're recommending PC-based control, since it offers advanced alternatives for integrators seeking higher levels of power and flexibility in the control system.
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According to Beckhoff engineers, a DIN-rail mountable embedded PC provides a solution in the familiar form of traditional PAC and PLC systems, while offering a significant power boost with multi-core processors "With the performance and connectivity demands on PLC and PAC hardware continuing to rise, systems are becoming inherently more complex," said Reid Beilke, IPC and embedded PC specialist at Beckhoff. "We address this by offering PC-based control hardware that does the work of multiple PLCs and PACs." He noted that the DIN- rail mountable PC controller now has the processing power once reserved for top-of-the-line, full-size industrial PCs.
The embedded PC can also make integration easier by leveraging standard PC- and Ethernet-based connections. You also get the ability to remotely control, set-up, and download to the embedded PC through a secure Internet network connection. "Tapping into the power of cloud-based databases through OPC UA has opened the door to much more expansive levels of secure connectivity and Big Data management in manufacturing," said Beilke.
Rob Spiegel has covered automation and control for 15 years, 12 of them for Design News. Other topics he has covered include supply chain technology, alternative energy, and cyber security. For 10 years he was owner and publisher of the food magazine, Chile Pepper.
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