DALI: Forerunner of Today’s Breakthrough Lighting Technology

By Ken Walma, Product Manager, Lutron, Coopersburg, Pa. February 20, 2007

The power of lighting has been obvious to architects for centuries, but now, because of the path blazed by digital addressable lighting interface (DALI) control systems, specifiers consider it part of their province as well.DALI is the forerunner of even more sophisticated lighting technologies. Its impact on buildings, owners, tenants, occupants and the environment has been far-reaching.

DALI became an accepted protocol of the lighting industry for networked ballasts in 2002. Each ballast with a DALI interface is addressable, meaning that it can be communicated with individually. DALI is standardized in accordance with International Electrotechnical Commission (IEC) Standard 60929 for fluorescent lamp ballasts.

But, while DALI was revolutionary just 15 years ago, it has made way for a much improved technology that integrates addressable based devices.

Despite the promise of DALI protocols, actually integrating a group of devices, daylighting, sensors and software was an unusually daunting task. Typical projects required 8 to 10 minutes per ballast to program—and new ballasts would require reprogramming when a previous one failed. Because DALI ballasts had no decision-making capability, they required a controller or processor and up-front programming. DALI uses a “last command wins” protocol. This means that if a ballast is simultaneously instructed to perform multiple functions, it will perform only the last instruction given. In other words, if, at the same time, a daylight sensor tells the ballast to dim the lights, a timeclock tells it to turn off and an occupancy sensor instructs it to turn on, the ballast by default would only obey the last instruction, which is not always the most desirable action. In order to fix this, a controller or logic controller must be added and programmed on a ballast-by-ballast basis.

But a different type of technology has been introduced, one that gives ballasts enough “smarts” to make their own decisions and send commands to other ballasts.

The system allows precise scalable control from one’s personal work space to building-wide control, to campus-wide or even enterprise-wide control.Lighting scheme changes within rooms, floors or an entire building can be accomplished without rewiring. The same is true for monitoring each piece of hardware, including individual ballasts and light fixtures. Only a PC is necessary and, with an internet connection, maintenance can be managed anywhere in the world.

The system incorporates dimming, daylighting and occupant sensing for energy savings. Only the required amount of fluorescent light is supplied at any given time and place. The system senses changes in lighting needs based on the amount of natural light entering each room and then adjusts the appropriate ballasts accordingly. Individual lighting adjustments for each workstation can be made with PCs, PDAs, hand-held remotes or wall controls. On a larger level, light levels for any combination of fixtures can be scheduled to dim or brighten to accommodate peak demand and energy rates.

The manufacturer also claims that its product redefines fluorescent lighting control as easy to design, install, maintain and reconfigure. Any combination of sensors or wall controls can be connected to the system’s specialized ballasts, depending on the building or room lighting requirements.Because there is no need for interfaces or power packs, sensors and wall stations can be removed or added with simple Class 2 connections at any fixture. Maintenance is also greatly simplified as replacement ballasts and bus supplies speedily “learn” their programming when they communicate with already installed devices.Every ballast is uniquely identified by a serial number, so replacing devices is as simple as entering two numbers into a handheld programmer—the visible serial number of the unit being replaced and the visible serial number of the new unit.Once entered, the new unit fully functions in the system.

The structure and versatility of the system remain intact as it grows from one ballast to several.The system allows users to connect up to 64 ballasts and a power supply with a simple 2-wire communication wire.Larger systems are constructed by connecting multiple 64-ballast loops.Within this lighting control network, any sensor or wallstation can speak to any or all of the other ballasts on the loop.

Installation is easily customized.The control wiring can be either Class 1, which runs in conduit with the power wiring, or Class 2, which is wired in a cable tray or with other communication wiring.Installers can select their preferred wiring format, such as daisy-chain, star method or T-tap, because the control wiring is topology-free.It’s also polarity-free.If the control wiring is reversed when connected, the ballast will still operate.Whether the control wiring is Class 1 or Class 2, the sensors and wallstations are easily added or removed with simple Class 2 connections at any fixture.Free from interfaces and power packs, there are fewer parts and pieces required when installing this system.As a result, the installation is less expensive than other systems.

As any facility manager knows, flexibility is a mandatory attribute of any office building because over 40 percent of office spaces change each year. In most existing office buildings, lighting is designed to provide equal amounts of light to all occupant spaces.Even large office buildings, where lights are turned on and off according to a time-of-day schedule, do not adequately address employee needs or optimize lighting demand reduction because they cannot adapt to continual changes in the office.EcoSystem allows for the lighting fixtures to be re-tasked without rewiring.As a larger room is split into two rooms, no conduit changes are required.Lighting levels can be changed to match the needs of a new client or department.

DALI was more than ten years in the making. It represents an important milestone in the history of fluorescent lighting, and its descendant technologies provide a vital tool for anyone designing, specifying or bankrolling a building.

For more about EcoSystem from Lutron, click here .