To ZigBee or Not to ZigBee?

“Compared to past years, this is almost turning into a wireless show,” remarked Tim Cutler, vice president, sales and marketing, for Cirronet Inc.

ZigBee products launched at Sensors Expo included Cirronet?EUR™s ZigBee sensor modem and ZigBee gateway.
ZigBee products launched at Sensors Expo included Cirronet?EUR™s ZigBee sensor modem and ZigBee gateway.

(www.cirronet.com), a Norcross, Ga.-based wireless products vendor that was one of some 185 exhibitors at the Sensors Expo & Conference June 6-9 in Chicago.

That’s a bit of an exaggeration, given the broad range of sensor technologies on display at the show. But there’s no doubt that wireless mesh sensor networking and the recently approved ZigBee wireless networking specification were grabbing plenty of attention at the event.

ZigBee enthusiasm

“There’s just an awful lot of interest in ZigBee, and lots of people wanting to try it,” said Cutler, whose company was demonstrating ZigBee sensor modems and ZigBee gateways designed to accommodate that desire. Cirronet’s ZigBee sensor modems connect to any existing 4-20 milliAmp sensor or actuator, and its ZigBee gateways will connect to existing programmable logic controllers (PLCs), enabling design engineers a quick and easy way to try out ZigBee-based wireless sensor networking without tearing out existing installations, Cutler said.

Cutler is enthusiastic about the prospects for ZigBee, which is designed to provide a low-cost approach for wireless networking based on an open, global standard. ZigBee is built on top of the Institute of Electrical and Electronic Engineers IEEE 802.15.4 wireless standard, and supports mesh networking—an ad hoc or decentralized scheme by which nodes communicate through a series of redundant pathways that is designed to be more resilient than traditional hierarchical network topologies. Potential applications include home control, building automation and automated meter reading, as well as industrial monitoring and control.

But while a number of companies at the Sensors exhibition were enthusiastically touting new ZigBee offerings, at least a few vendors plan to continue to focus on their own proprietary wireless networking systems. The Millennial Net (www.millennial.net) booth, for example, displayed a placard stating its membership in the ZigBee Alliance (www.zigbee.org)—the association of more than 150 companies that developed the ZigBee specification. The Alliance ratified the ZigBee specification last December. But Mark Pacelle, Millennial Net vice president of marketing, said that the Burlington, Mass.-based company has no current plans to develop a ZigBee product. Instead, he said, Millennial Net intends to continue marketing its own proprietary, low-cost, industrial-grade wireless sensor networking system, known as MeshScape.

Boiling the ocean?

MeshScape has been available for several years and is already installed in a number of large-scale commercial and industrial applications. MeshScape’s lightweight, scalable protocol “fits in about half the memory footprint that ZigBee does,” Pacelle said, adding that the ZigBee specification doesn’t currently meet Millennial Net customer needs. “ZigBee has tried to address such a broad spectrum that it compromises in almost every application area,” Pacelle declared. “It’s so deep and wide that it’s like trying to boil the ocean.”

At the show, Millennial Net introduced MeshScape 4.0, which features a new ultra-low-power mesh, and turnkey support for Modbus and other serial protocols. The company also announced a strategic partnership with Austin, Texas-based Freescale Semiconductor Inc. (www.freescale.com)—the former Motorola semiconductor unit—by which Freescale will support MeshScape on its MC1319x wireless hardware platform.

Mark R. Williams, a technical staff member at Freescale, said that porting the proprietary MeshScape solution for use with its wireless chip sets will offer an additional alternative to Freescale customers, in addition to ZigBee or other wireless networking solutions. The Millennial Net technology provides a more “turnkey” solution than ZigBee, and it is also more mature and was “engineered specifically for sensor data collection,” Williams observed.

But Williams noted too that a major advantage of ZigBee will be its status as a standardized approach to wireless mesh networking —ensuring that products supplied by multiple vendors will be interoperable. Interest in ZigBee is running high among Freescale customers, said Williams. The company has already sold about 2,000 Freescale ZigBee evaluation kits, he noted.

Peter Stein, vice president of business development and marketing for Sensicast Systems (www.sensicast.com), Needham, Mass., said that his company is encountering some customers who insist that any wireless networking system they use must be standards based. For this group, he said, Sensicast will introduce a ZigBee-compliant 2.4 GHz radio module before yearend that can be used with Sensicast’s Modular Interchangeable Networking Device (MIND) platform.

The MIND was unveiled at the Sensors show, designed as a flexible platform to enable original equipment manufacturers to develop a single sensor interface module, which can then be equipped with any of several Sensicast radio modules. And while Sensicast is developing a ZigBee module, said Stein, he believes that many industrial users may ultimately choose 900 MHz or 2.4GHz modules based on the company’s proprietary SensiNet wireless networking protocol. The SensiNet protocol uses a method known as distributed frequency spread spectrum (DFSS), which Stein said will perform better than ZigBee in harsh industrial environments.

Single-chip ZigBee

One company that is squarely in the ZigBee camp is Ember Corp. (www.ember.com), a Boston-based supplier of ZigBee chips and software. Since the company was founded in 2001, “our vision was always to be a standards-based company,” said Ember Marketing Manager Ravi Sharma, and the company is focused exclusively on ZigBee development.

Ember rolled out several new products at the Sensors show, including the Ember EM250, billed as “the world’s first ZigBee system-on-a-chip.” The EM250, according to Ember, is the first 802.15.4-based semiconductor device built to be ZigBee compliant that integrates a microprocessor, Radio Frequency (RF) radio, ZigBee network protocol stack and memory into a tiny, single-chip solution.

Among the EM250’s primary advantages, compared to earlier multi-chip ZigBee solutions, will be lower cost and smaller package size, said Sharma. The package housing the EM250 device measures just 7 millimeters square. And according to Sharma, its cost will come in at about 40 percent less than Ember’s previous generation EM2420 multi-chip ZigBee product. Samples of the EM250 are scheduled for July availability, with production expected by late third quarter or early fourth quarter this year, said Sharma. The EM250 will be priced at less than $4 per unit in high volumes, according to the company.

Wes Iversen

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