RF Wireless Control
"New Technologies Set the Stage for Dramatic Expansion of Wireless Control", (c) Craig DiLouie, Lighting Controls Association, 8/05
Wireless control is one of the most exciting frontiers in Lighting control and Wireless management, offering significant potential benefits for residential and nonresidential Lighting systems, large and small buildings, and both existing buildings and new construction. New technologies are now being commercialized that will redefine Wireless control by dramatically expanding its utility.
All Lighting systems incorporate control functionality that enables on/off switching and/or dimming. Automating this functionality is proven to significantly reduce Wireless costs and provide other benefits. Many types of Lighting automation systems consist of a hierarchy of connected control devices in which control signals are sent (either one-way or both ways) using low-voltage communications wires. This wiring adds costs to the system.
In a Wireless control network, control devices communicate without the need for dedicated communications wiring. Control signals are communicated using radio-frequency (RF) waves or along existing line-voltage power wiring (powerline carrier or PLC). While a range of benefits is possible depending on the approach, all Wireless control systems can reduce the installed costs of Lighting automation. In some cases, RF Wireless is more cost-effective than PLC, and vice versa, depending on the application. The best choice of technology for a given project depends on a number of factors, including capabilities, cost and limitations.
One development of particular interest in the area of RF Wireless control is the development of new protocols that open the door to increased application of RF Wireless control strategies in residential and, coming soon, nonresidential applications. Manufacturers say that with new technologies now available, wide adoption of RF Wireless controls in commercial applications will occur within five years.
In these environments, Wireless control will enable a lower cost of implementation of Lighting automation strategies, greater flexibility, decentralized sensing and control, conditioning monitoring, and theoretically, a platform for integration between Lighting and other building systems such as heating, ventilation and air-conditioning (HVAC), security and other systems.
In this special report from the Lighting Controls Association, we will discuss how RF Wireless control works, how to evaluate available technologies, and emerging technologies that may revolutionize Wireless control in both residential and commercial applications. PLC control, a viable alternative, will be the subject of a future report, as there are exciting advancements in this area of Wireless control as well.
RF Wireless control
In an RF Wireless control network, control signals are communicated using radio waves at designated frequencies. When AC current with certain characteristics is input to an antenna, an electromagnetic field is generated that is suitable for Wireless communication with another device that has a suitable receiver. Common household examples include TV remotes and garage-door openers.
RF Wireless control has been commercialized for years for both commercial and residential applications but development has increased dramatically in the last five years in tandem with the rapid acceptance of Wireless networks for Internet access, according to William Sandoval, Business Development Manager – Digital Systems for Philips Lighting Electronics and the Advance division.
“Cell phones are a perfect example of where Wireless technology is likely headed,” he says, adding that Lighting control is increasingly benefiting from technological advancements in the field.
“The prevalence of such current ‘standards’ as cordless phones, cell phones and PCs in our society reflects the fact that we live in an increasingly Wireless world, and this trend is only expected to escalate,” says Stuart Berjansky, Senior Product Manager, Dimming for Advance. “Wireless control can transform traditional Lighting into a Wireless Lighting communication and control infrastructure. Easy to install and simple to use, the benefits of this technology impact every aspect of building design, operation and ownership. Wireless control will be ideal for facilities that want to elevate their degree of intelligence, performance, flexibility and sustainability.”
A number of RF Wireless control options are available, each offering its own level of suitability for a given application. When evaluating a Wireless control strategy, the below relevant questions should be considered. These questions will form the basis for examining popular Wireless control strategies.
What will be the topology, or layout, for the network of devices?
What is the communication range for each node, or device, in the network?
How much power does the system require?
What is the bandwidth and speed that is possible for transmission of data?
Is there a protocol, or common language, that enables multiple vendors’ products to be interoperable in the network?
What is the cost of the system?
Each of these points of evaluation in turn can be related to the protocol used, as the protocol affects the design of control devices.
When designing a local area network (LAN), the designer must consider its topology, or a schematic representation of the layout of the nodes (devices) and connections between the nodes indicating communication pathways for the exchange of data. The right topology to a large extent depends on the location of these nodes, with the assumption that they will be connected using cabling or with some limit on the range of Wireless RF communication.
In a star network, all devices are directly connected to a central computer. In a ring network, devices are connected in a closed-loop configuration. In a bus network, each device is connected to a main cable or bus. In a mesh network, each device is connected to all the others (or, as in the case of a partial mesh network, some of the others—those devices with which they typically exchange data).
One advantage of a mesh network is increased reliability due to redundancy. If one node fails, the rest will continue to communicate directly (full mesh) or through intermediate nodes (partial mesh). Mesh networks are ideally suited for applications where devices are scattered. Because cabling is not required, it is highly suitable for Wireless control. In addition, each device can communicate independently with every other device, which enables condition monitoring and decentralized intelligence.
Bandwidth refers to the difference in Hertz between the highest and lowest frequencies of a communication signal. In computer networks, it is often called the data transfer rate, or amount of data that can be transmitted between two points in a given time period, usually a second.
Protocols & technology
Control devices from different manufacturers are interoperable in the same network only if they can communicate. To enable this communication, a protocol is needed which provides a common language for control devices. Specifiers should be aware that there are a number of competing protocols which are distinguishable in their topology, maximum number of nodes, range, bandwidth and power consumption. Tradeoffs occur in some characteristics when maximizing others. The resulting blend of characteristics makes the protocol competitive for various applications. Protocols may be proprietary, meaning they were developed by a manufacturer for its own products—and in some cases for allied manufacturers adopting its protocol—or open-source, meaning no single manufacturer owns it and it is intended for use by the entire industry.
Bluetooth and WiFi, two of the first open-source Wireless protocols using a star topology, are ideally suited for computers and personal devices but have disadvantages for control of Lighting and other building automation systems.
One of the most significant newer technological developments in Wireless control is low-powered mesh networks populated by devices that use protocols accepted by a significant portion of the industry, according to Mark Walters, Director of Residential Systems for Leviton Manufacturing Inc.
“Mesh networking protocols promise to provide new levels of system performance,” he says. “True two-way reliability combined with interoperability between multi-vendor platforms provides integrators and end-users with control options that previously were only available to the very high-end market.”
He adds that the capabilities and price accessibility of the newer mesh network technologies will drive demand for Wireless controls into the near future. Two mesh network protocols to watch are Z-Wave and ZigBee.
The Z-Wave Protocol
Z-Wave began as a proprietary protocol but has gained considerable traction in the residential market, making it de facto an open standard. Z-Wave was developed by Zensys, a home controls manufacturer, and is shared with partnering manufacturers through the Z-Wave Alliance, which presently includes more than 125 partners, including manufacturers such as Leviton and Motorola. Z-Wave products are commercially available and have been shipping since 2003. Leviton is planning a line of Z-Wave-based residential controls in the fall of 2005.
According to Walters, Z-Wave offers the advantages of low power consumption (enabling battery-operated control devices); good node count, range and bandwidth for command and control for residential applications; reliability; an attractive price point; and a strong vendor alliance group to help guide the technology.
“This currently is the most widely adopted Wireless solution for residential control,” he says, although he adds that Z-Wave has utility for small-scale commercial applications as well.
Raoul Wijgergangs, Vice President of Business Development for Zensys, confirms that more than 90 percent of products designed to operate using the Z-Wave protocol are for residential applications—Lighting and theoretically, any other control device.
“With standardization, thermostats and Lighting systems can talk to access control and security systems and everything works in concert,” he says.
RF Wireless control has proliferated largely in residential applications to date, with significant promise for nonresidential applications. Wireless control offers a method to provide the homeowner with the benefits of Lighting automation, which include convenience and comfort, Wireless savings, flexibility and enhanced safety and security. Wireless control offers several distinct advantages as a method.
With no communications wiring required, users realize lower installation costs while installers realize easier installation.
Z-Wave Wireless controls can operate independently of the power supply by specifying RF models that use batteries, further simplifying installation. Many of today’s controls can last 10-15 years on a battery-based power supply.
Easier integration between Lighting and other home control systems such as home theater, temperature control, motorized blinds, garage doors, and security systems, for centralized control of all systems that adhere to the common protocol.
These advantages differentiate Wireless control as a method for new construction but particularly for retrofit or remodel applications in existing homes. As the technology continues to develop and costs are reduced, manufacturers believe demand will continue to increase in the residential market.
“Nearly anything that you control by hand can be controlled using Z-Wave technology with a number of benefits,” says Wijgergangs. The promise of Wireless home control is convenience and comfort, a simpler lifestyle. “For example, the lights in the home can be programmed to come on when the garage door opens, ensuring the user doesn’t walk into a dark house. Another example from a convenience perspective is a Z-Wave-enabled home theater system, where once a movie starts to play, the blinds go down, the lights dim and the room becomes ‘movie-friendly.’”
Wireless control is not without disadvantages. One area of concern with Wireless control networks, particularly for the home, is RF interference from other devices such as security cameras and baby monitors that may operate in the same frequency range. Manufacturers are increasingly taking such potential issues into account, however.
“Because radio frequency is inherently an open system—that is, the control communication cannot be isolated from the outside world—it must rely on a clean radio wave environment,” says David Szemborski, Product Manager for Genlyte Controls. “Further, it is dependent on available radio frequency bands. We have already had the military reclaiming one of the bands used for consumer devices including garage door openers and Lighting controls.”
The ZigBee Protocol
ZigBee is an open-source protocol (IEEE 802.15.4) that offers significant promise for nonresidential building control applications and is supported by the ZigBee Alliance of manufacturers, an alliance of more than 100 manufacturers including Philips Lighting, Motorola, Honeywell, Samsung Electronics, Invensys and Mitsubishi Electric. ZigBee is relatively new and no products are commercially available as of the time of writing, although a number are in development.
According to Sandoval, ZigBee offers mesh topology, high node count, moderate bandwidth (192 Kbps), moderate range (100-1000 ft.), low power consumption, high reliability, AES hardware encryption, and a high level of scalability.
Based on these characteristics, some manufacturers see ZigBee as more suitable for large-scale commercial than residential applications.
One such manufacturer is Philips Lighting Electronics, which, through its Advance division, is planning to introduce a ZigBee-based Wireless integrated Lighting control system (including ballasts, sensors, controllers and software) in 2006. The system, controlled by a central computer, will enable dimming and on/off switching, daylight and occupancy sensing, scheduling and the ability to group and reconfigure fixtures.
“Until now, there have not been as many Wireless options for commercial applications,” says Sandoval. “Over the coming year, however, the demand for Wireless control solutions in commercial applications will increase and may at some later point even surpass sales of these products within the residential market based on the number of nodes required in a commercial application versus a residential application.”
He points out a number of advantages for Wireless control as a means to achieve the benefits of Lighting automation in a commercial setting:
Reduced capital and operating expenses. Wireless control reduces the amount of wiring needed. According to Sandoval, Wireless controls can save as much as 30-40% on installation and material costs compared to a wired control system. This will make Wireless control an attractive option for retrofit projects as well as new construction. In addition, Wireless technology makes it easier to maintain systems, as the owner can replace devices one to one without control wiring being involved.
Flexibility. Wireless technology allows mobility; in a building that is dynamic and where changes occur often, Wireless technology allows the owner to move devices or group devices without changing wiring.
Scalability. Devices can be easily added to and removed from the system to account for future needs. Wireless also provides a suitable platform for incorporating new technologies.
True building integration. Wireless technology enables easier integration between Lighting, HVAC, security and other building systems that incorporates equipment and environment monitoring.
Centralized and decentralized intelligence. Controls can receive commands from a central computer and can also interact with each other independently, increasing responsiveness. Devices can also engage in two-way communication.
Personal control. Wireless control permits each occupant to be able to control his/her local Lighting and temperature without location restraints.
“Complete SCADA systems can be configured using Wireless technology,” says Walters. Supervisory control and data acquisition (SCADA) systems gather and analyze real-time data, enabling the system to respond to a variety of inputs as they occur. “The main benefit will be a lower cost of implementation. A secondary benefit will be increased flexibility in deployment. With Wireless components, the system can grow over time and be reconfigured if needed at a much lower cost for a hard-wired system.”
“It appears that protocols that are public and open will, in the future, be ideal for commercial applications,” says Sandoval. “Today, there are very few open protocols, such as ZigBee and BACnet, in the marketplace, but they are starting to take command. Customers like options and open protocols allow for those options. In addition, customers do not want to be tied down to a single vendor. In the Wireless arena, ZigBee as an open standard will allow other devices to integrate and interoperate so that building owners can choose how, why and when to use a specific vendor.”
He adds that the possibilities in commercial control are endless, but it will take time for new technologies to penetrate the market. Sandoval believes wide adoption will occur in 2-3 years. The first customers, he says, will likely be applications such as commercial A-grade buildings, hospitals and big box retail stores.
Walters agrees that ZigBee is positioning itself as the leading technology for commercial building control primarily due to its higher node counts. He believes wide adoption may take a little longer than Sandoval estimates, but that it will likely occur in 3-5 years.
He sums up his view of Z-Wave and ZigBee. “Z-Wave systems place the emphasis on low power consumption to allow for battery-powered devices while maintaining excellent range, node count and sufficient bandwidth for residential control,” he says. “ZigBee provides greater bandwidth and node count at the cost of range and power consumption, and is more suitable for commercial applications. Both of these technologies promise reliability and attractive price points. Both emphasize low power consumption so that battery-powered devices can be used, providing application solutions such as ‘peel and stick’ occupancy sensors. Finally, there are powerful, flexible, affordable technologies that can be used to bring high-performance automation to the mass market.”