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Building Better Connection Boxes

Nov. 1, 2013
How Suppliers Are Thinking Inside and Outside the Box About Connection Advances
About the Author

After working as a semiconductor process engineer, Hank Hogan hung up his cleanroom suit and now writes about process control and other technologies from Austin.

For machine builders and end users, better connections are on the way, thanks to thinking both inside and outside the box. As a result, cable runs can be cut and control improved, while adding little to cost.

Many of these connection advances rest on Ethernet technology. The chips that implement the networking standard are rapidly dropping in price. In the past, the use of Ethernet would bump up the cost of a connection box by a fifth or so, says Jason Haldeman, product marketing lead specialist at Phoenix Contact.

That differential wasn't too substantial for junction boxes found inside cabinets, as these were IP20-rated. The situation was different for IP67 boxes, which resist water and dust, and so are suitable for use outside of cabinets.

"On machine-mount products, because they're more expensive to begin with, a 20% increase was quite a bit. But that price has dropped down to almost equal now, so there's very minimal difference in cost," Haldeman says.

In response, Phoenix Contact created a new product family that takes the junction box to the next level, he says. Its products use industry-standard M12 cable connections throughout, but connectivity is actually via Ethernet, with box addresses settable by software or a rotary switch. The boxes can be daisy-chained, and have a simple web page for diagnostics.

Meanwhile, Omron Automation and Safety released a processor and products that support EtherCAT, which it picked because it offers the fastest performance, says Johnston Hall, Omron's commercial engineer in PLC, networks and distributed I/O.

Importantly, the master is a normal Ethernet port, while the slaves have dedicated hardware, he says. "The advantage of that dedicated piece of hardware is it allows you to daisy-chain the I/O, which Ethernet normally does not do. That gets rid of the need for a high-performance switch and the need to pull all the cables back to a central point."

Another benefit shows up in motion control. Connecting the slave junctions together with synchronizing clocks allows time-stamping events to the microsecond. That's well below the millisecond or so possible with earlier systems and a benefit for high-speed processing.

Beckhoff Automation also embraces EtherCAT, having rolled out a line of multi-function junction boxes that are IP67-rated. These include products that distribute power, handle multiple input and outputs, measure pressure and acceleration, and drive small steppers and motors.

Of course, to be fully taken advantage of, these advances outside the cabinet have to be accompanied by ones inside. One such advance comes from Rockwell Automation. About a year ago, the company unveiled its CIP Sync technology, which regional product manager of distributed I/O Scot Wlodarczak says solves a common problem: how to synchronize nodes for high-speed operations.

Synchronization depends on controller scan time and network latency. The ability to get clocks aligned to one another also has an impact. Consider a part moving past an inspection station. As it does so, a generated time stamp enables a controller to calculate when the part will be at a rejection point located further down the production line. Less clock jitter yields a more accurate calculation and, therefore, raises maximum allowable production speed.

At regular intervals, the Rockwell Automation solution synchronizes the local clocks in the input and output block of any connected distributed I/O junction with the controller master clock producing a tight time connection.

Siemens Industry's IP20-rated boxes fit inside automation control cabinets, but advances here are important, says Kevin Wu, distributed I/O product manager. He points to reduced response time and improved resistance to electromagnetic interference. Siemens redesigned the I/O backplane of its products, encasing pins with gold plating, and improving the fit. Another change was a bump up in the number of pins from seven to 26, meaning that some can be used for shielding.

Such beefed-up protection is increasingly necessary because of the growing use of wireless technology, Wu notes. Without the right precautions, wireless can lead to signal loss, throughput hits and engineering headaches.

Of the impact of those wireless gremlins, he says, "For critical processes, it can really be detrimental. You spend days trying to figure it out."

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