Generally regarded as a single technology, low-voltage LED lighting systems have nuances that users must sort through.
By Patrick McLaughlin
Over the past couple years the emergence of low-voltage lighting systems has bolstered the case that what traditionally has been recognized as a communications cabling infrastructure, might now be described as a building-systems infrastructure. Low-voltage lighting systems featuring light-emitting diode (LED) luminaires can be supported, in a number of ways, by twisted-pair cabling. This technological advancement has held promise to raise the proverbial tide for the cabling industry, because it could mean more business for organizations that manufacture, distribute, and install cabling products. At the same time, user organizations can realize a number of benefits from these lighting systems; driving some of these benefits is that low-voltage LED lighting systems often include sensor networks, which provide information that permits users to maximize energy efficiency associated with lighting in their facilities.
As such, low-voltage lighting systems often are characterized as a single technology. But the closer a system specifier, designer, installer or owner gets to implementation, the clearer it becomes that the low-voltage LED lighting systems available are different from each other in several respects. This article will look at a handful of systems available, discussing in broad terms how they accomplish similar objectives while also pointing out some of their differences.
Luminaires, sensors and more
CommScope's (www.commscope.com) Redwood intelligent lighting network solution by and large introduced the low-voltage LED lighting concept to the cabling industry in the early 2010s when then-standalone company Redwood Systems began marketing the system to the communications cabling industry. CommScope acquired Redwood in 2013.
The company has produced a 15-page Redwood Cabling Design Guide, which contains information on system architecture and cabling-design guidelines as well as suitable operating environments. The guide explains that a Redwood system contains a centralized power engine, sensors (of which there are multiple options), intelligent algorithms, a scalable management and monitoring software system, and several optional elements--specifically, dimmer switches, scene-controller switches, and a universal gateway are optional items in the Redwood system. CommScope explains the sensor options are as follows: 1) A Redwood sensor, located adjacent to each luminaire, that incorporates a gateway for communicating with the engine as well as a sensor pod for monitoring occupancy, light level and temperature; 2) A third-party fixture with an embedded Redwood sensor; 3) An LED gateway and separate sensor pod located adjacent to each luminaire; the gateway has one primary RJ45 jack for interfacing with structured cabling and two additional jacks that may be connected to separate engine ports for luminaires requiring certain wattages of power. The guide also details three physical-layer design options for the Category cabling used to support the sensor-and-lighting system.
NuLEDs (www.nuleds.com) offers the Lighting-over-IP system, which is driven by the NuSPICE protocol. NuLEDs explains the protocol "controls LED brightness through four channels, enabling ultra-smooth dimming, color-mixing and color-tuning." The system also includes: SPICEbox, a network device that connects directly to a Power over Ethernet switch; PowerTrim technology that allows for load shedding; NuLEDS software and NuBUS, which NuLEDs describes as "environment interface peripheral (EIP) technology [that] allows sensors of all types to be hosted and managed by SPICEbox." The company further explains, "Each SPICEbox is a network device with a unique MAC address and IP address." Each such device can serve as a sensor host for wall switches and various sensors.
Differing power technologies
So far the systems' functionalities, potential benefits and even components sound similar. Both systems use direct current (DC) rather than alternating current (AC) power, and laud DC as an enabler of efficiency gains (hence the term "low-voltage" lighting; these DC-powered systems require a lower voltage than AC-powered lighting). But the provision of that DC power is where the fundamental difference between NuLEDs and Redwood exists. NuLEDs is based on Power over Ethernet (PoE) technology, while Redwood has a centralized power and control system. CommScope explains, "The Redwood solution reinvents the way LED fixtures are powered and controlled by centralizing the AC/DC power conversion external to the LED fixtures and distributing the low-voltage DC by wiring to a large number of LED fixtures. This centralized approach for powering LED lights enables control signals to be applied at a central power source …"
NuLEDs' lighting power source is Cisco's (www.cisco.com) UPOE--Universal Power over Ethernet, which delivers up to 60 watts per port.
Both companies have publicized installations of their systems, emphasizing the installations' technological, business, and energy efficiency impacts. Most recently, Cisco outfitted its own customer briefing center (CBC) in Manhattan with NuLEDs. In January, NuLEDs announced, "This landmark installation at One Penn Plaza marks the beginning of a shift to low-voltage Ethernet-based lighting systems … Color-changing diamonds in the center of the fixtures can be used for visual communication in many applications."
Cisco's Internet of Things vertical business solutions leader, Prasanna Venkatesan, commented that the next generation of lighting will revolve around the so-called digital ceiling, and the industry will move toward PoE lighting. NuLEDs added, "The perfect storm for Lighting-over-IP is here. LEDs have reached the turning point where they are producing a very high quality of light for nearly half the power of traditional lighting; UPOE is now at 60 watts per port, and the building industry is about to begin the next cycle of growth as gas prices drop, the stock market reaches new highs, and new building energy-efficiency mandates sweep the nation. The time is now."
NuLEDs founder Lisa Isaacson added, "Working with Cisco has been an amazing experience. We have witnessed a new movement from the beginning. After being approached by Cisco, NuLEDs developed the first PoE-powered lights to be powered and controlled by the Ethernet network, and we have been watching the cogs turn in what will be the next generation of lighting."
CommScope has publicized several use cases of the Redwood system by organizations of several types, including public schools, healthcare, service provider data center spaces, and others. CommScope also recently published a document describing how three low-voltage contractors--Parallel Technologies in Minnesota, USA (ptnet.com); Direct Line in California, USA (dlcomm.com); and Data Techniques in the U.K. (datatechniques.co.uk)-- have expanded their portfolios by offering the Redwood system.
CommScope also published a document pointing out several differences between its own Redwood network and PoE-powered lighting control systems, including IEEE 802.3af and 802.3at, as well as Cisco's proprietary UPOE. The document examines the systems from the standpoints of efficiency, reliability, scalability, and cost. It slants toward the Redwood system's advantages.
Weighing the options
NuLEDs and Redwood are not the only options for sensor-based lighting systems. Acuity Brands (www.acuitybrands.com) offers a wide range of lighting devices and controls. Among its technology portfolio are luminaire brands for a variety of applications, as well as controls for indoor and outdoor environments. Within that broad portfolio is a set of LED "dimmable, controllable, low-voltage light fixtures," as the company describes them. These fixtures are manufactured according to standards created by the EMerge Alliance (www.emergealliance.org)--an association whose stated mission includes "developing standards leading to the rapid adoption of DC power distribution in commercial buildings."
Acuity explains that its EMerge Alliance-based low-voltage lighting portfolio is "designed and engineered to maximize the benefits of LED lighting," and the lighting "features options for dimming and integrating digital lighting control directly onto the fixture."
Mike Clemens, senior value stream manager with Acuity Controls, authored a white paper titled "Digital lighting in data centers," which is available for download from Graybar (www.graybar.com). In the paper, Clemens addresses multiple ways in which LED lighting can provide energy efficiency to data center environments. The comprehensive document also details several options, and the differences among those options, for control strategies in intelligent digital lighting systems. Specifically, Clemens outlines centralized versus distributed intelligence, and provides detailed information on sensor types (passive infrared, ultrasonic, and Acuity's own trademarked Microphonics).
The centralized-versus-distributed-intelligence examination is where Acuity's lighting system fundamentally differs from the Redwood and NuLEDs systems. Clemens explains that a centralized-intelligence system, like Redwood and NULEDs, "relies on a centralized controller that stores attributes and functions for the lighting control system. In this type of system, occupancy sensors, daylight sensors, and manual controls do not possess individual memory or intelligence. Instead all device information is stored in a central database and actions within the controlled space require constant communication with the central controller." In a distributed-intelligence system like Acuity's, by contrast, "all devices use an embedded microprocessor that can store information on how that device is to operate," Clemens explains. "The microprocessor is essentially the ‘brain' of the device and in many instances, not only stores information, but can actually learn from its environment."
Communications cabling remains the infrastructure that enables a distributed system's intelligence. Clemens explains, "A single Cat 5e cable is connected to each device to form a daisy-chain in the control zone. Each zone is configured to operate independently. The Cat 5e cable carries power to the low-voltage devices (sensors, wall switches, etc.) and provides system communication. If a network is desired, simply connect a single Cat 5e from the last control device to a port on a network access point, commonly called a bridge. The bridge is then connected to a network control device (gateway) that stores information about the system and maintains the system time clock."
In the document, Clemens also puts forth that higher-voltage AC power also can be recognized as a viable option for intelligent LED lighting systems. He makes the point, "The fact remains that a vast majority of lighting systems are and will remain 120-277 VAC powered. DC-powered lighting systems are interesting and appropriate for some applications, but options are limited …" In the data center, he notes, "AC power is most likely already present in the space … When digital fixtures are combined with an intelligent digital control system, the ability to deliver a highly flexible infrastructure that will support your needs well into the future is unparalleled."
As is the case with many technology investments, there are numerous considerations to make when exploring an LED-based lighting system in any environment. But few dispute the idea that lighting--once exclusively the domain of the electrical trade--has emerged as a building system applicable to professionals in the communications-infrastructure business.
Patrick McLaughlin is our chief editor.
Is LiFi lighting's next technological horizon?
As if this article didn't bring up enough to sort out concerning light-emitting diode (LED) lighting systems, a technology on the not-too-distant horizon could give user organizations even more to think about. The technology is dubbed LiFi, a takeoff on WiFi, because LiFi uses LED lights to provide wireless communication access in indoor environments.
Carrying the flag for LiFi is an organization called pureLiFi (www.purelifi.com), which spun out of the University of Edinburgh. The organization explains that its chief scientific officer, Professor Harald Haas, "first demonstrated LiFi technology live on stage at TED Global in July 2011." The company adds that research into visible-light communication began at U of Edinburgh in 2008.
pureLiFi published a paper titled "The siren call of LiFi: A brighter solution," in which it explains, "LiFi is well-defined as the networked, mobile, high-speed VLC [visible light communications] solution for wireless communications. To facilitate pervasive indoor wireless access, each LiFi system requires … high speed … bidirectionality … multiple access … [and] mobility/handover." The paper details each of those characteristics, and also warns of the dangers of what it calls quasi-LiFi. "The lure--the siren call if you will--is that ‘first mover advantage' harbors many pitfalls for all but a few well-defined applications in specific market segments. Rushing to products, i.e., missing more than one of the core features, potentially dead-ends those products in a technological niche." In other words, pureLiFi is saying, some technologies claiming to be LiFi don't meet all the criteria, as originally conceived, at the University of Edinburgh.
The organization points out that LiFi is intended to be complementary to, and non-interfering with, radio-frequency-based wireless communications. "Excess capacity demands of cellular networks can be offloaded to LiFi networks where available," pureLiFi says. "This is especially effective downlink where bottlenecks tend to occur." The company also lists mobile connectivity and smart lighting among the technology's applications. "Laptops, smartphones, tablets and other mobile devices can interconnect directly using LiFi," it says. "Short-range links give very high data rates and also provide security." Of smart lighting, it comments, "Any private or public lighting, including street lamps, can be used to provide LiFi hotspots and the same communications and sensor infrastructure can be used to monitor and control lighting and data."
Long before LED lighting became commonplace, LEDs' place in the communications and networking arena was within optical transceivers. In the days preceding gigabit speeds, LEDs were the light sources used in optical transceivers. So the concept that LEDs can produce communications signals is nothing new. The notion that they can simultaneously light a room and provide it with a communications stream--that is new.
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