The lighting industry has been talking about the benefits of digital addressable lighting interface (DALI) control technology for several years, but Dr. Martin Moeck is one of the first to actually do something with it. Moeck, who's an assistant professor of architectural engineering at Penn State University, placed his department at the forefront of the advanced technology by creating the first DALI instructional laboratory in the United States.
Located in Engineering Unit A, the lab is used in two architectural engineering courses. The hands-on teaching lab is a 1,200-square-foot facility with over 70 lighting fixtures, including typical commercial lighting fixtures, along with TV lights and accent lighting. All fixtures can be readily attached to any of the 16 different junction boxes. Each junction box has 10 five-prong outlets/multi-heads, which allow installation of luminaires anywhere in the ceiling.
Strangely enough, DALI wasn't at the top of Moeck's list three years ago when he was deciding what system to base the lab on. His biggest concern was controlling and dimming 90 fluorescent fixtures, which he planned to do on an individual basis because it seemed reasonable for a modern office setting. He changed his mind when he saw the price tag for such a setup, though. “I was surprised to find out the cost of a conventional (proprietary) 0-10V DC analog fluorescent dimming ballast system was $45,500,” Moeck says. “The DALI system cost $29,100 to install. After that, I cared about DALI.”
Price may have been the deciding factor for Moeck, but the industry is slowly awakening to the fact that DALI's benefits extend far beyond that and include advanced control options that were never available before the advent of digital control systems.
The dawn of DALI. Lighting controls offer convenience and versatility, allowing lighting systems to accommodate changes in a work area and shifts in activities. In addition, many states now have lighting power budget and control requirements that define the maximum watts-per-square-foot allowed in certain spaces and mandate where control systems must be used. Until recently, those requirements focused most discussions of lighting controls on the three main computer-based digital protocols: EIBus, BACnet, and LonWorks.
Unlike those options, though, DALI offers both dimming and switching functions via digital signals over a two-conductor control circuit. The technology started with European lighting equipment manufacturers, and the protocol is now part of Europe's IEC standard 60929. U.S. ballast and fixture manufacturers have “seen the light,” so to speak, and have also begun to offer DALI-based products.
The DALI protocol allows individual ballasts to be controlled or addressed, which provides a degree of flexibility previously unavailable to building and system designers. It also allows you to integrate with a building automation system and monitor ballast power, dimming levels, and failed lamps and ballasts from a central location. Standard low-voltage wiring connects the ballasts to the lighting controls, simplifying layout and providing a high degree of flexibility in the design stage and later when modifications are required.
In general, you connect all the fixtures in a room to the nearest un-switched power supply and to a single two-wire control cable from the lighting controller. Each DALI interface line, or loop, can control as many as 64 addresses (ballasts) and each of the addresses individually communicates with the controller.
Since DALI operates as a two-way communications system, it can accept error feedback and lamp and ballast operating information. A central computer or controller periodically polls each fixture for a status report on its lamp and ballast operation. If a problem is detected, then a facility manager can schedule a maintenance crew to specific locations. Furthermore, DALI commands can be sent at three communication control levels — broadcast, group, and address — and programmability includes groups, scenes, maximum and minimum light levels, fade times and emergency light levels.
Any fixture can belong to more than one control group. The system can also be set up so that, in the case of dimming, all of the units can reach the dimming setpoint simultaneously — even if they started from different lighting levels. Currently, DALI ballasts are available for the T8, T5, and T5 HO linear fluorescent, compact fluorescent, and biax lamps.
Industry experts see two parallel paths of acceptance for the DALI technology. The first would be a full-scale installation in a large building — a “test bed” type of demonstration. The second would be the use of stand-alone “wall box-type” DALI controls with push-button programming. This type of control allows for a tryout on a much smaller scale, while still providing scalability.
All of which isn't to say that DALI doesn't does have its drawbacks. First, it doesn't reduce the number of hours needed for programming and commissioning the control system. And it requires the use of a backbone network running a high level protocol if installed in a large building.
Many industry members also argue that DALI has significant limitations to gaining a large share of market. Installing wiring within the ceiling of an existing facility is always expensive and upsetting to tenants, and the project is naturally susceptible to wiring errors. Consequently, the market for a DALI-based system is seen as either new construction or major renovations, where the additional cost of adding low-voltage conductors to the lighting system installation is inconsequential.
Most agree that to significantly penetrate the existing building market, wireless transmission for DALI is the answer. And that possibility may not be far off. Within the last year, three wireless protocols useful for this application have emerged. And a few other organizations are doing their part to improve the adoption rate of this technology.
The National Electrical Manufactures Association (NEMA) is taking the lead in developing a DALI control standard to ensure compatible controls and ballasts, and to gain agreement on wiring practices, electrical characteristics, and expanded command sets. Recently, the NEMA Joint Sections Committee on DALI started working on extending the DALI protocol to a limited range of sensors. This is important because any complete control system has three types of devices: controllers, actuators, and sensors. Initially, sensors weren't a major consideration in the development of DALI.
The California Energy Commission (CEC) is also playing an important role in promoting the DALI protocol through a project under the auspices of its Public Interest Energy Research (PIER) program, which is aimed at increasing fluorescent dimming applications in offices and schools.
Not surprisingly, U.S. manufacturers are hoping to do what they can to buoy the protocol as well, and Moeck's project at Penn State has given them a prime candidate to demonstrate its capabilities. Currently, more than 25 manufacturers sponsor Moeck's lab at Penn State. They have donated more than $186,000 in equipment and resources that can be used to test human reaction to slowly changing lighting conditions during written tests and regular note taking.
And as far as Moeck is concerned, as long as those companies are willing to help keep the lab alive, he's willing to run it. “It has totally changed my teaching style,” Moeck says. “Anyone can write control software to dim these lights, and control can be extended to the Web. Digital addressable ballast capabilities are changing the way the industry will design and control lighting in spaces.”
Sidebar: Three More Reasons to Dig DALI
A DALI controller can be connected to a building management system network via a gateway, allowing a lighting system to be monitored from a central control desk.
A lighting designer, or engineer, no longer needs to plan how to wire the fixtures. Instead, the designer can focus on how to group, zone, or control the fixtures after the wiring is installed.
Building owners are attracted by the reduced costs, considering that the average office space is leased for only seven years. Tenants and users can value the ability to accommodate lighting to their specific needs.