by Steve Mesh, LC and Craig DiLouie, LC, CLCPTypical automatic lighting control applications involve an input device, such as a photosensor, interacting with a power controller, such as a switch. Though these components may be integrated into the same device (e.g., wall-box occupancy sensor), often they are installed separately. To interact, the input device must send a control signal to a controller, which then controls the load. The predominant traditional approach is to send a control signal along dedicated low-voltage wiring (typically called “hardwired”). A more recent approach rapidly gaining in popularity is to communicate using radio waves that travel through the air, eliminating the need for dedicated control wiring.
The resulting advantages enable advanced lighting control with greater installation flexibility, good scalability, and lower labor installation cost, suitable for many applications but particularly hard-to-wire applications, exterior area lighting, non-accessible ceilings, hard ceilings, asbestos abasement issues, spaces requiring reconfiguration, and brick-and-mortar existing buildings.
This article, adapted from the new Education Express course EE301: Networked Wireless Lighting Controls, provides a basic understanding of wireless control, including functionality, benefits, protocols and topologies.
Wireless lighting controls have the basic functionality as hardwired advanced control systems, providing benefits such as energy cost savings and flexibility. Otherwise, the elimination of hardwiring control devices provides distinct benefits:
• Flexibility: The first is flexibility. Wireless control devices can be placed where they’re needed without limitation imposed by wiring, including areas that are difficult to wire. More flexibility is provided in unique applications. Electrical planning may be shortened. After installation, devices can be moved and the system expanded with relative ease.
• Labor and material cost savings: Wireless control eliminates the need for dedicated control wiring and associated switch legs, traveler wires, conduit in many cases, and other raw materials, speeding and simplifying installation. With no damage to walls or ceilings, and little to no disruption to business operations, wireless control lends itself well to installing even sophisticated control systems in existing buildings and applications like streetlighting.
• Scalability: Wireless lighting control systems can be easily scaled as space needs change.
The advantages of wireless control make these solutions particularly suitable for applications where the cost of running control wires is too costly or simply not possible, such as outdoor lighting, parking garages, warehouses and retrofits.
THE WIRELESS SYSTEM
Wireless lighting control systems consist of luminaire controllers (also called relay modules, power packs or dimming modules), typically installed in or on a luminaire or in a junction box; input devices (e.g., sensors and switches); and management devices including gateways (which function similarly to wireless routers) and servers.
Sensors feature a wireless transmitter that sends signals through the air to receivers embedded in gateways or repeater modules, which sends signals to a server, which then communicates back to the controller to adjust the status of the luminaire. Switches typically send signals directly to the luminaire controller.
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, graphical database generation and others.
For devices to communicate, they must be in range of each other to ensure reliable signal transmission. The devices are configured within a topology to ensure reliable signal pathways. And they must be designed to interoperate using the same protocol (communication method).
Otherwise, the system may be sized to two devices communicating within range up to autonomous pre-programmed room-based systems all the way up to building-wide networks programmable to controlled lighting via gateways and sending operating data back to a central server.
LUMINAIRE CONTROLLERSThe power controller is a relay-based device that provides ON/OFF switching and (in the majority of LED systems) circuitry enabling 0-10VDC (and/or potentially DALI) full-range dimming. In a wireless system, the controller features an embedded wireless receiver that accepts radio control signals within range. It then acts upon those signals within its set rules.
Some current lighting control systems offer controllers designed to be integrated into single luminaires. For example, a luminaire controller rated to handle up to 1A of load can only control up to 120W (on 120V) or 277W (on 277V) of lighting.
Many systems also offer controllers able to handle a much greater load, typically used to control multiple luminaires. In a warehouse aisle, for example, it may not be necessary to separately control every luminaire if they are all to respond to the same control sequence of operations. Note this requires line-voltage power and low-voltage dimming control wiring to be run from the controller to each luminaire.
It can be simpler and more economical to specify luminaire-integrated luminaire controllers. This maximizes control zone granularity, allowing for any desired zoning using luminaires as single units or groups, and eliminates the need to run additional wiring between luminaires and the controller.
Occupancy sensors and light sensors (photosensors) are input devices required in most interior and some exterior spaces by the majority of commercial building energy codes. The only difference in a wireless system is they contain a wireless transmitter to communicate with the system using radio waves.
Sensors may be specified as part of an integrated luminaire or a separately installed component. Some separately installed (standalone) sensors combine the functionality of occupancy and light sensing in a single device to minimize installation. Some sensors provide additional functionality such as temperature sensing.
Standalone sensors may be battery-powered or, if using EnOcean technology, powered by harvesting energy from the local space, such as ambient light. 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.
SWITCHES AND OTHER DEVICES
As with sensors, switches are required in the large majority of spaces to provide manual override of scheduling or occupancy sensing. They may also provide dimming. And as with sensors, they may be battery-powered or harvest local energy, such as the mechanical energy produced flipping a switch.
Some switches also offer additional functionality such as a button enabling selection of a preset lighting scene. Additional buttons allow more preset scenes.
Many control systems provide touchscreen manual control stations as an option. These screens provide manual control functions, programmable preset scenes, potential for networking, and potentially integrated non-lighting functions such as temperature control and scheduling occupancy for a space.
Lastly, some systems allow third-party devices to be incorporated into the network. For example, some systems communicate with wireless plug-load controllers to meet current codes, while others communicate with HVAC controllers to control temperature.
SERVERS AND GATEWAYS
If the wireless control system is networked for single-point day-to-day operation and data collection, it will feature a central server and/or gateways.
Typically residing in an IT or electrical closet, the server stores the information about what lighting and control points are on the network. It also stores commissioning/programming information and may also store energy use data.Most networked lighting control systems also use gateways to distribute the network connections from the server out to the devices (controllers, sensors and switches). This is true in most wireless systems as well as in most wired systems. In a wireless system, a gateway is essentially a wireless router and is typically installed in the finished space.
If the connection between the server/gateway and control devices is interrupted, the control devices will continue operating as last configured. The loss of connection to the server may result in energy data and other functionality being lost, however.
In some systems, the server function (central brain) has been incorporated into the gateway. By combining this server function with the gateway function, one device located in the controlled space suffices to do both jobs.
However, in most systems, the server is a separate device from the gateway(s). This is universally true for centralized control systems and typically true as well for most room-based systems. In that case, the gateway(s) must be connected to the server via some form of cable. This is typically accomplished by using Ethernet cable (i.e., Cat 5e). In a large space, such as a large open office floor, the server is usually located in an IT room or electrical closet in the core. The gateways are located throughout the controlled space. Therefore, the cable must be routed from the gateway(s) in the controlled space to the IT room or electrical closet.
If the owner allows it, it may be possible to connect the gateway(s) to the server by using the owner’s existing IT network. If you can physically connect the gateway(s) as well as the server to existing network ports, then you only have to determine the IP address of the gateways in order for the server’s software to find them and pull them onto the lighting control system. In that case, no addition cable needs to be run from the controlled space to the building’s core to make this connection.
Some manufacturers allow the owner to use a server in the Cloud, which means there is no server on-site. The wireless lighting control system connects with a virtual server located in the Cloud. Some lighting control system vendors actually offer this as a service (similar to when you utilize and pay for “software as a service,” where a website or remote query is utilized to complete a task or analysis).
Some systems have a dedicated method of making this connection—e.g., using a dedicated 3G cellular modem. In that case, it’s important to check with the manufacturer to know where you can locate this device to ensure that its signal reaches the nearest cell tower. If that signal is temporarily lost, the system’s components should still operate normally, except that certain functions (e.g., energy usage recording) won’t work until the connection to the server is restored.
When you use a wireless lighting control system that has a server in the Cloud, typically the manufacturer will deal with some/all of the commissioning and/or maintenance functions. This may include zoning, rezoning, updating software, updating firmware, etc. The owner typically pays for this with an on-going contract for a certain duration of time.
A protocol is a set of rules for the design of a device so that it interoperates with other devices designed according to the same protocol. Note that 0-10V is a control method, not a protocol, though DALI or another protocol may be used for dimming.Popular protocols include ZigBee, DALI’s wireless extension, Xbee, EnOcean, Bluetooth, Bluetooth LE and the Synapse Network Appliance Protocol (SNAP). In July 2017, Bluetooth announced Bluetooth Mesh. 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 or by sharing a common protocol.
PROTOCOLS: OPEN VERSUS PROPRIETARY
Protocols may be open standards, de facto standards or proprietary. Open-source protocols such as ZigBee (IEEE 802.15.4) provide frameworks for interoperability between devices manufactured by any vendor using that particular protocol. It also allows communication with additional devices from other manufacturers such as wireless plug-load controllers and thermostats. However, if something goes wrong with the system as a whole, one must determine the responsible party among multiple vendors.
De facto standards such as EnOcean are based on a proprietary technology that is licensed to other manufacturers, who offer devices based on that protocol.
Proprietary protocols are designed so that all devices in the system are pre-tested as interoperable, but all devices must be acquired from a single manufacturer. This provides assurance the system will operate as intended and designate a single responsible party. However, the owner is tied to a single manufacturer and its product line.
Wireless controls communicate on open short-wave radio-frequency bands on the electromagnetic spectrum. ZigBee and Bluetooth both operate on a frequency of 2.4 GHz. Because many other devices also operate on the 2.4 GHz, proprietary manufacturer protocols often operate at a different frequencies such as 315, 434 and 900 MHz.
Networks are configured in topologies. Radio-frequency wireless lighting control networks typically use a self-healing mesh or star topology.
In a self-healing mesh network, data flows between devices (D1, D6, D11 shown here) to communicate between a gateway and a given control point. If a device fails, the signal flow automatically reroutes through other devices (“self-healing”) (D1, D6, D9, D10, D11), which increases reliability through multiple nodes and redundancy of nodes.
In a star topology, signals from all wireless devices are transmitted directly to and from a series of gateways that form the backbone of a fixed network. In some systems, one or more luminaire controllers may be designated as repeaters to boost range. The relatively low signal traffic volume may increase reliability and speed, making control effects more responsive.
Manufacturers offer other topologies such as clusters. Since wireless lighting technology is relatively new, there isn’t a significant body of research supporting one technique over another. The specifier and owner should ask manufacturers for concrete examples of how their solutions will benefit a project.
ROOM-BASED VERSUS CENTRALIZED SYSTEMS
Wireless lighting control systems are available with varying levels of functionality and attendant cost and commissioning so as to enable specifiers to precisely match solutions to project needs.
The majority of installed lighting control systems are room-based, in which the system in each room operates autonomously. The system must be programmed, zoned and calibrated in the field, though some manufacturers offer connected lighting packages with onboard sensors and controllers with preprogrammed sequences of operation based on energy code compliance.
Although future reprogramming, rezoning and recalibration is possible, room-based systems are largely designed to be left alone after installation. Some manufacturers have made their systems more commissioning-friendly, enabling a technician with less training to set up and adjust system operation using a mobile device app.
Many systems offer controllers with integral power metering chips, eliminating the need to install current transducers on branch circuits for metering. This enables energy measuring, with data graphically displayed on a user interface, and monitoring, with the potential for automatic notifications/alarms. (Accuracy varies, so ask the manufacturer how they measure energy consumption.) This type of system may offer standalone sensors in addition to luminaire-integrated sensors, and allow a hybrid wired/wireless design, providing design flexibility.
Wireless lighting control systems also typically have recommended limits on the number of nodes connected to a particular gateway. In a wireless control system, a node is any device that transmits and receives instructions and data wirelessly, with its own unique address (i.e., luminaire controllers, sensors, switches, etc.). For example, one manufacturer’s system has a hard limit of 700 nodes per gateway. Another has a recommended limit of 100 nodes per gateway. (Some protocols may define nodes instead as a feature/characteristic such as occupancy sensing, daylight, dimming, etc.).
Make sure that you understand whether it is a recommended limit or a hard limit. Even if it’s only a recommended limit, it’s preferable not to exceed it. In some systems, the operating software may be hard-coded so that gateways can handle only up to a specific number of nodes. In other systems, the limit is merely a recommendation. This is usually governed by the anticipated data traffic over the (wireless) network. Remember that some devices may transmit and receive substantially more data than others. If it turns out that your installation has a much greater percentage of those devices than others, there may be an impact on how the gateway handles that traffic.
An important factor affecting the location of wireless control devices is signal range. These signals are typically low power, which limits their reach. Wireless control systems are typically designed for low power, low data rate, and close proximity range.
Manufacturers often publish recommendations for coverage area and/or maximum range between devices and gateways. While the owner wants to minimize the number of devices installed to minimize cost, keeping wireless devices within these boundaries provides greater confidence of reliability.
When designing a wireless control system, pay special attention to manufacturer recommendations for limitations when the signal must travel through obstacles such as interior partitions and dense construction materials such as cinderblock walls. The manufacturer may offer other recommendations to help locate devices, such as keeping them a certain distance from metal objects that may impact the accurate transmission of network information.
TYPICAL OPEN OFFICE LAYOUT
In an open office floor, wireless signals usually have an obstructed pathway between luminaires and from luminaires, sensors and switches to gateways. Hence, open offices are great candidates for the use of wireless lighting control systems.
In systems that use luminaire-integrated controls, every luminaire has its own integral controller and sensors. Other systems have options for controllers that can handle a larger load. As a result, a group of luminaires may be connected to one controller upstream of the luminaires. In open office spaces—as well as many other types of spaces—current codes require luminaires in daylight zones to be automatically controlled in response to available daylight. Therefore, careful planning is required when using systems with high-amperage controllers upstream of a group of luminaires to ensure that they can be controlled as a distinct zone corresponding to primary and secondary daylight zones as defined in the applicable energy code. However, keep in mind that future changes to the space may require some rewiring when using such a system.
TYPICAL CLASSROOM LAYOUT
Just as in open office spaces, luminaires in classrooms that are in the primary and secondary daylight zones also have to be automatically controlled in response to available daylight to comply with most current energy codes. In a classroom with three rows of luminaires parallel to the window wall, one row is typically in the primary daylight zone, and the next row is in the secondary daylight zone.
As a result, it’s easy to comply with the code requirements for zoning luminaires in primary and secondary daylight zones whether luminaire-level lighting controls are used or high-amperage controllers are used to control each row.
TYPICAL WAREHOUSE LAYOUT
Luminaires in warehouses are typically installed in rows, centered in each aisle. Energy codes typically require automatic shutoff (or at least automatic dimming) of luminaires in each aisle during vacancy. This shutoff (or dimming) of luminaires is triggered by occupancy sensors. Since codes typically require that all luminaires within a specific row turn on or off automatically based on occupancy vs. vacancy, sensors at the ends of the rows—as opposed to being integrated into every luminaire—may be sufficient to comply with applicable codes.
In the system shown below, each luminaire has an integral controller (for turning the luminaire on and off and dimming it). Standalone occupancy sensors are installed at the north end of each row, mounted separately from the luminaires. In this system, a sensor interface is tethered by low-voltage wire to the nearest luminaire controller. Therefore, the signal for the sensor information passes through the wireless controller in the luminaire and back to the gateway/server.
If a system with luminaire-level lighting controls is used—where each luminaire not only has a controller but also integral sensors—then no additional wiring/tethering is required. The electrical contractor simply installs each luminaire and connects the power wires (hot, neutral and ground). Even if each luminaire doesn’t require its own sensor based on this application, using luminaire-level lighting controls may reduce the installation cost and complexity.
In certain locations (such as in California), luminaires in spaces with toplighted daylighting (i.e., skylights) must be automatically dimmed based on available daylight. Therefore, photosensors will be required as well as occupancy sensors. Don’t forget that local area switches are typically required by codes as well.