Typical automatic lighting control applications involve an input device, such as a photosensor, interacting with a power controller, such as a switch. In some cases, these components may be integrated into the same device, as in the case of a wall-box occupancy sensor. In other cases, the components are installed separately, as in the case of a ceiling-mount occupancy sensor and a wall switch.
For these separately installed components to interact, the input device must send a control signal to the controller, which then controls the load. The predominant traditional approach is to send a control signal along dedicated low-voltage wiring. A more recent approach, which is emerging as a popular option particularly for lighting upgrades in existing buildings, is to communicate using radio waves—radio-frequency (RF) wireless control.
The value proposition is short and sweet—using radio waves instead of wiring eliminates wiring, with multiple potential benefits.
“The primary benefit of wireless RF lighting controls is that they can be retrofitted into a space at any time and can be easily scaled as needs change,” says Eric Lind, Vice President-Global Specifications, Lutron Electronics Co., Inc. “Existing buildings can now take advantage of energy savings and occupant benefits associated with wireless lighting controls without the need for a total building makeover.”
The result is a potentially lower cost for introducing automatic lighting control strategies into existing buildings without changing existing wiring or adding new dedicated control wiring. This is particularly advantageous in outdoor lighting and in indoor spaces featuring hard ceilings. The latest commercial building energy codes require automatic shutoff for retrofits in which 10+ percent of the connected lighting load is replaced. Wireless offers an option that is potentially less costly, simpler and less disruptive.
It can also simplify installation in new construction, promoted by the added benefit of being able to more easily move sensors and thereby fine-tune control performance during both commissioning and ongoing building operations.
RF wireless controls consist of actuators and input devices. The actuator is the power controller, a relay-based device that provides ON/OFF switching and 0-10VDC full-range dimming. The actuator features an embedded wireless receiver that accepts radio signals within range from transmitters in wireless input devices, which may be occupancy/vacancy sensors, photosensors and switch stations. It then acts upon those signals within its set rules.
The input device may be powered by an internal battery or by harvesting energy (based on EnOcean’s technology) from ambient light, temperature differential or mechanical energy produced by flipping a switch. If the device is battery-operated, it should feature a high-quality battery that provides reliability and long service life. It should also be matched to the most efficient devices to maximize the amount of time before a battery charge is required.
The actuator is typically installed in or on a luminaire or in a junction box. The input devices are installed wherever they’re needed. During setup, all devices are discovered and added to a programmable network, where they’re grouped and given assignments. Setup methods vary by manufacturer and include pushbutton programming, bar code scanning, mobile app setup, database generation and others.
“Wireless RF lighting control primarily got its start in the residential market,” says Mike Crane, Senior Product Manager, Hubbell Building Automation, Inc. “With the creation of robust and reliable radio-based technologies like ZigBee, EnOcean and SNAP, developing and providing commercial solutions is now possible. Although the technology has been around for a while and the demand is increasing, we are still at the very early stages of adoption within the commercial market.”
Some manufacturers have developed niche solutions around specific applications such as parking garages, outdoor lighting, hotel card switches, plug-load controls and others. Some specialize in indoor versus outdoor lighting. As the technology continues to develop and gain acceptance, manufacturers are expected to begin to increasingly offer one-stop shopping covering a wide range of indoor and outdoor applications. Leading this trend are LED luminaire manufacturers that have begun to offer complete systems featuring luminaires with integral wireless control and push-button setup for simplified commissioning. This provides intelligent individual luminaire control, streamlines the amount of equipment required, and offers confidence that all elements of the wireless LED lighting system are compatible and will work together properly.
“LED luminaires with integrated RF lighting controls and sensors are helping specifiers and installers eliminate extra design work and redundant equipment, while maximizing energy savings,” says Tom Hinds, Product Portfolio Manager, Lighting, Cree, Inc. “Integrated solutions attack not only the wasted electrical energy in buildings but the costs typically associated with designing and installing lighting controls. Advances in automating commissioning and simplifying the process help systems get set up correctly and quicker.”
Devices can be tied together to form a network for control of lighting in large rooms and even buildings. Each control device is individually addressable in the network, allowing group and potentially individual luminaire control. Solutions can be scaled from single rooms to entire buildings, with building-level control achieved by connecting rooms to a building network via wireless access points with a software interface. Because communication is two-way, the potential exists for energy measurement and power monitoring. In fact, many systems now include actuators and/or control modules that feature a Hall Effect sensor, which senses current and allows generation of current, voltage, energy, kVAh, lamp burn time and other parameters for retrieval and analysis.
RF wireless lighting control networks typically use a self-healing mesh or star topology. In a self-healing mesh network, data flows between devices to communicate between a gateway and a given control point. If a device fails, the signal flow automatically reroutes through other devices (“self healing”), which increases reliability. In a star topology, signals from all wireless devices are transmitted directly to and from a series of gateways that form the backbone of the network. The relatively low signal traffic volume may increase reliability and speed.
For devices to communicate, they require design in accordance with a common protocol. Popular protocols include ZigBee, Xbee, EnOcean, Bluetooth, Bluetooth LE and the Synapse Network Appliance Protocol (SNAP). A number of systems are also offered that use proprietary protocols, many of which are similar to ZigBee. The wireless controls can be integrated with wired lighting and building automation systems using either gateways (for translating from one protocol to another) or by sharing a common protocol.
Crane says security is not a significant issue, as multiple security measures are taken to prevent hacker intrusion and interference from other wireless signals. He does advise that a sufficient number of devices be installed within range to ensure good communication. “One of the challenges with wireless lighting controls is making sure that devices are within radio range of the other devices in the wireless network,” he says. “If a device is out of range then there exists the possibility that the device will never be able to communicate with other devices. This is typically addressed in applications by having the wireless devices act as message repeaters and by adding additional wireless device/repeaters to the network. This ensures that a message sent within a network can reach all the devices within network.” A related concern is the characteristics of the application; spaces with many reflective materials, such as machine rooms, can be challenging for wireless communication because these materials can block or inhibit radio signals.
Crane further advises that addresses for devices placed in a network (typically printed on a sticker attached to the product or on a set of stickers included with the product) be saved, as these facilitate commissioning and, as needed, later re-commissioning.
“RF wireless lighting controls will change the way you view lighting and will increase your bottom line,” says Hinds. “Energy efficiency will continue to be a top priority for cutting costs, and with energy representing 30 percent of the typical office building’s costs, LED lighting with RF lighting controls will get you there.”
Craig DiLouie, LC wrote this article for the April 2015 issue of tED Magazine. Reprinted with permission.