trivial. When plants or lines are being redesigned, it’s common to add sensors to existing equipment and install new machines. When all these nodes must be wired, costs can rise quickly.

“If IT (information technology) departments drop an Ethernet line on the shop floor, it can cost $300 to $700. For simple implementations, that’s not cost-effective. A lot of companies are looking at wireless,” says Lantronix’s Blyther.

For many communications companies, wireless is a double-edged sword. For example, Opto 22 is rolling out a link to wireless sensors, but it also sees wireless as a threat. The company’s wireless strategy was planned during a fluid stage for wireless standards, but the company decided the technology is now settling down. The success of IEEE 802.11n provides enough speed and market acceptance to let the company settle on this version of the wireless fidelity, or Wi-Fi, specification. Generally, speed rises as the alphabetic notation progresses.

While wireless technologies can complement Ethernet, they will also provide some competition. “Technologies like ZigBee provide a true alternative for systems with relatively small numbers of parts that are widely distributed,” Opto’s Edwards says. Beyond ZigBee, he adds that “there’s room for a lot of wireless technologies.”

Though wireless technologies are seeing rapid growth, they aren’t yet applicable in all areas. In motion control, for example, there’s little interest at this point. “Wireless is eventually going to give us the capability to extend distance and reduce cost, but it’s not something we’re pursuing yet,” says Bosch Rexroth’s Thayer.

Wires forever

Though there’s a lot of interest in wireless technologies, there’s also a fair amount of caution. Skeptics note that speeds aren’t high and that bits can be lost when they’re sent through the air in noisy factory environments. “Wireless has some reliability problems. Some manufacturers are going with dual wireless to eliminate them,” B&R’s Sandhoefner says.

There are also applications within the I/O world that have demanding requirements that still can’t be addressed with wireless communications. “If you need high speed or synchronization, you probably need to use a medium. Wireless doesn’t have high speed or great predictability,” says Stubbs, at the EtherCat Technology Group.

Others note that wireless is an emerging area where several technologies are vying for success. As can be expected in a rising application, some wireless approaches have higher reliability levels than others. “I prefer 802.11a because there’s more noise immunity, particularly at the I/O level where 10 to 50 millisecond response times are usually fine,” Blyther says.

Most observers feel that the concerns over trustworthiness will dissipate as successful wireless protocols undergo more real-world testing and technology advances. That has already occurred with other networks. “The fears people have with wireless today are basically the same concerns they had with Ethernet a few years ago,” Black says.

Some product developers note that wireless is often discussed as a single technology, but in reality, there are many different flavors of wireless. The standards and proprietary communication schemes each have their own positives and negatives.

Some groups are working to provide suggested good practice for implementing wireless. For example, the PTO, Hart Foundation and the Fieldbus Foundation are working together to provide consistency for wireless sensor networks.

Although wireless is treated as a new technology, some groups have longstanding efforts that work without wires. “There’s been a lot of fuss lately about wireless sensor networks. We’ve done wireless Ethernet for a long time, picking up 802.11,” Henning says.

To view the accompanying article, "Software Tools Manage Data Flow", go to www.automationworld.com/view-4204.