In the lighting industry, protocols are sets of product design rules that regulate interoperability between control devices. As such, they are a critical aspect of a lighting control system’s operation performance and reliability.
For the electrical contractor, understanding protocols to one degree or another is important, whether one is specifying, starting up, troubleshooting or integrating a control system with other building systems. As the world of lighting control increasingly meshes with the internet of things (IoT), protocols will continue to grow in importance until, ideally, interoperability is solved at an industry level, and protocols cease to be problematic.
The first thing to know is that protocols may be proprietary, open or a mix of the two. The majority are proprietary to a single manufacturer, such as Lutron’s Vive, or licensed to an alliance of manufacturers such as EnOcean. Manufacturers take this approach to differentiate their products. ECs are more likely to select this type of system than build one from different manufacturers, even if it ties the owner to one vendor, because it’s simple and a single company takes responsibility for reliability.
Open protocols are industry standards that nominally permit interoperability between off-the-shelf devices from different manufacturers. In some cases, manufacturers may adopt an open protocol but tweak it in the physical implementation to “tune it up” for product differentiation and a competitive advantage. Protocols are also periodically updated, which may result in products designed to different versions. An open protocol, therefore, does not necessarily guarantee compatibility.
Examples of industrywide protocols include Bluetooth LE, EnOcean, Wi-Fi and Zigbee for wireless control systems. Each provides varying degrees of capability, speed, power draw, networking, specialized equipment and cost in a series of trade-offs.
DALI enables the construction of lighting networks with addressable luminaires and bidirectional communication that allows measuring and monitoring. However, communication may be relatively slow, and each device must be commissioned.
With its high speed and addressability, DMX also requires special cabling and is often relatively costly, which results in it commonly implemented for color-tuning applications.
BACnet, while well-defined, flexible and allowing a high degree of compatibility between devices, is also often relatively costly, requires special equipment and can be comparably slow in control response.
Among wireless, let’s look at two major players, Zigbee and Bluetooth LE. Zigbee (IEEE 802.15.4) operates at 2.4 gigahertz (GHz), and for very low power it offers self-healing mesh networking and a large number of network nodes. Bluetooth LE (IEEE 802.15.1) operates at 2.4 GHz and for very low power, offers star or mesh networking, higher data rate and compatibility with numerous computing devices, though fewer nodes are typically available. When it was launched in July 2017, Bluetooth mesh was hailed as a potential solution for the IoT, though it is still young and proving itself.
David Buerer, director of product management at Leviton, Melville, N.Y., said the implementation of these protocols is most commonly expressed through physical connection, topology, addressing, speed and messaging. The physical connection covers whether communication is wired or wireless, connector type (RJ-45, USB, etc.), frequency and cable/antenna type. Topology is how devices within a system interact and involves issues such as whether more than one device can be on the same cable. Addressing means devices on a network can be identified, including whether devices can identify each other. Speed is how fast data can move through the network, and messaging is the encoding and decoding of messages crossing the system.
If the control system must integrate with other systems such as building automation, both systems must be designed to the same protocol such as BACnet or use a gateway, which is a device or built-in software that nominally ensures the different systems will understand each other and work together.
Kendell Clark, product manager for Quantum at Lutron Electronics, Coopersburg, Pa., said it is not uncommon to find a mix of proprietary and open protocols in a fully implemented control system. The proprietary protocol provides differentiation in ground performance, while the open protocol facilitates connections between different building systems. He said this is a model for how the industry might move forward in an IoT world with its demand for open interoperability. It is not “one protocol to rule them all,” but the proliferation of robust connectors that allow manufacturers to differentiate their products while ensuring integration between systems.
Buerer predicted the market will evolve toward fully digital control systems with specialized coordinators and a high degree of device interoperability. Until then, for ECs tasked with integrating devices or systems from different manufacturers, it can pay to test a sampling of devices in a mock-up prior to commitment. For contractors selecting any control system that may lock its owner to a particular manufacturer, ensure the manufacturer is reputable and has both longevity in the marketplace and a strong commitment to its customers.