Craig DiLouie, LC, CLCP recently had the opportunity to interview David Buerer, Director of Product Management, Leviton, for an article for tED Magazine on the topic of nonresidential lighting control protocols. Below is the transcript.
DiLouie: What is a lighting control protocol and what is its purpose in a control system applied to a nonresidential building? Why should electrical distributors care about protocols?
Buerer: Tracing the etymology of the word protocol takes you to its Greek and Latin roots (prōtos kola) which in effect means to “glue together.” I like to think about this because the term protocol really describes how the digital 1’s and 0’s on the network cable are glued together to make meaningful messages. It’s that careful connecting of bits following a prescribed format that connects bits into bytes and bytes into words and words into messages…and messages have meaning. It’s a lot like a language. When all the components of our systems speak the same language, they can do useful and amazing things.
Since lighting control protocols define the language by which components of a lighting control system communicate or transmit information to each other, it would follow then that different protocols will not communicate with each other unless there is some type of translator like a gateway or network protocol converter.
DiLouie: What are the basic characteristics of a protocol that differentiate one from the next?
Buerer: Basic characteristics to take into account when examining protocols include the following:
• Protocol Name
• Wired vs. Wireless
• Open vs. Proprietary
As a general rule, the industry names protocols in a way that differentiates them from each other. The presumption is that anything with the same name can communicate together. But is that really true? In reality, any unexpected difference in protocol by either the transmitter or receiver will yield devices which cannot communicate with each other and ultimately an unsatisfactory installation. This means we often have to dive a little bit deeper. Some characteristics about lighting control protocols we should be aware of are as follows:
• Physical – How things connect together, ex. Wired vs. Wireless, Cable/Antenna Type, Frequency, connection methods (RJ-45, USB Type A, B, C, etc.)
• Topology – When you have more than two devices, how does communication move between them and how do you connect them together? Do you need hubs/switches/repeaters? Can multiple devices be on the same cable?
• Addressing – How devices are identified on the network – or do they even have a way to identify each other?
• Speed – Supported rates at which things move through the network
• Messaging – Encoding/decoding messages on the cable
DiLouie: What rules of thumb should a distributor use when recommend controls to their customer?
Buerer: Lighting controls range from simple switches and dimmers to advanced integrated systems that include multiple components. Once customers have identified an application, distributors should work with their customers to consider the following questions to help choose the right solutions and truly understand the needs of their customers:
• Is it a retrofit or new construction project? Size of the project? Are there windows or skylights? What types of lighting will be used?
• What goals do you want to achieve with your lighting control system? Must haves vs. nice to haves.
• How often do business needs change?
• What kind of budget do you have?
Based on the answers to these questions, the distributor should then be able to help choose a reputable manufacturer for the entire project as well as help customers evaluate total installation costs, integration with other building systems, and ongoing maintenance.
Of course, since we’re talking about lighting control protocols, the system should be first selected based on its merit to the application…and any specific protocol used is often secondary.
DiLouie: What are the most common protocols used for nonresidential lighting control, and what are their relative pros, cons, and most common applications?
DiLouie: The most popular dimming method is 0-10V, though this is implemented as a method rather than a standardized protocol. What is the difference, and what effect does this have on dimming performance?
Buerer: It is a method yes, but, it’s also a very simple protocol. In a basic 0-10V system, all controls send a dedicated output signal to the driver in the form of 0-10V analog voltage. The driver’s purpose is to provide the appropriate LED drive current in response to that signal. It is an analog signal that can only address a single device on its cable. As such it is very reliable and very easy to implement. That said, you still can see different responses by different devices on the network as each device will sometimes implement a different dimming curve. It is recommended to avoid mixing drivers from different manufacturers in the same lighting control zone. There are two types of 0-10V controls, sourcing and sinking, and the two are not compatible with each other.
Sourcing: A driver requiring a 0-10V sourcing control operates using a more traditional 0-10V analog controller. The controller provides all voltage and current and adjusts the voltage to set the dimming level. For example, when the controller sends 0V, the light will be OFF and when the controller sends 10V, the light will be full ON.
Sinking: Controllers supporting this type of signal “sink” absorb different amounts of voltage to indicate the dimming level. Each driver acts like its own power supply, allowing even a small controller to support a large number of devices.
DiLouie: For control devices to communicate, they must be able to recognize and understand each other. What are typical scenarios where lighting control systems, and lighting control and other building systems, must be integrated, and how are protocol conflicts eliminated?
Buerer: The simplest way to eliminate conflict is to test before implementation. Of course, this isn’t always the case. However, if and when given the opportunity it’s best to simulate as much of the system as you can to avoid surprises in the end. This is especially true when mixing products from different manufacturers. For example, not all manufactures implement ZigBee networks the same way and as such it’s best to test compatibility before rolling the trucks.
Usually, lighting control systems are from the same manufacturer with a single entity taking responsibility for the lighting control side so conflicts are naturally less of an issue. When integrating between systems, especially at the building wide level, BACnet is often used which is both very flexible and very well defined so field conflicts are minimized.
The second part of the article will describe what’s new in the world of protocols.
DiLouie: Looking at both supply and demand, how has the marketplace for lighting control protocols changed in the last 3-5 years?
Buerer: We see a plethora of protocols in the marketplace. The preference is often for interoperability which often drivers towards open protocols over proprietary as well as the increased need for connectivity between devices. Wired protocols offer reliable performance and greater control. However, the cost of wiring and installation can be high. Wireless protocols offer flexible and scalable solutions with lower wiring and installation costs and we anticipate that wireless solutions will become more widely adopted. We also see an increased use of smart devices to program, commission, control, and monitor lighting control systems.
DiLouie: Bluetooth Mesh promised very strong potential for advanced integration, particularly for centralized intelligent lighting control and integration with Internet of Things strategies. Where does the market stand on acceptance of Bluetooth Mesh? Is it a savior or just another protocol?
Buerer: Bluetooth mesh is a strong contender in the market offering a host of benefits. Combine its low power consumption and low cost to implement with extended range, faster data transfer, self-healing capabilities, and the benefit of having Bluetooth incorporated in every smart device, laptop, and computer.
That said, it is very new to the market and hasn’t really reached a point of maturity yet. Protocols, even if the best of situations, take years to mature, adapt, and gain acceptance. So whereas there is a lot of excitement, it’s going to take some time for it to cement its place in our market.
DiLouie: Proprietary protocols are argued to provide stronger assurances of interoperability, while open protocols promise the economic benefits of competition, broader adoption, and a stronger role for lighting in the Internet of Things. Where is the market now in terms of acceptance of proprietary versus open, and where is the market headed in the coming years?
Buerer: It initially seems logical that open protocols would spur better application and economic benefits. However, in practice, open protocols drive both high certification costs and high development costs as compatibility needs to be ensured across manufacturers. Both of these results in higher costs passed along to the consumer. That said, as the industry matures, especially in the wireless arena, we will see it settling down and one protocol (or the other) gaining broader acceptance and as such the widest application and highest degree of interoperability.
DiLouie: Staying with the Internet of Things, are protocols a roadblock to lighting play a strong role in its implementation? What is required moving forward for that to happen?
Buerer: Certainly barriers can be reduced by choosing devices with the same protocol which are designed to operate together. That said, we also are seeing a trend towards having coordinating devices which acknowledge the fact that different devices from different manufacturers operate differently and require slightly different means of interface. As such the coordinators inherently are more flexible and designed to work through these issues.
Going forward, manufacturers should continue to work together to define the required interactions between devices and ensure their interoperability and our customers should drive the appropriate level of specification and cooperation when necessary.
DiLouie: Where do you see the world of controls headed in terms of protocol development and adoption? What should distributors be looking for?
Buerer: Ultimately, the market is going to drive towards a fully digital solution with specialized coordinators and a high degree of compatibility between end-point devices. It’s going to take awhile to get there yet but it is where we will end up. In the meantime, choose reputable manufacturers that can offer proven solutions that are flexible, simple, and scalable. Choose partners and manufacturers who have been in the business a long time with enough depth and resources to support you when support is needed.
DiLouie: If you could tell the entire electrical industry just one thing about lighting control protocols, what would it be?
Buerer: Define your application well and select products that are designed to work well in that application.