Articles and whitepapers

The DALI Lighting Control Protocol (1/6/2006)

By Gary Brown, Helvar

DALI (Digital Addressable Lighting Interface), developed by a group of European ballast manufacturers, is now established worldwide as the standard communication protocol for digital lighting control. The purpose of establishing the new standard was to support the idea of 'open architecture' so that devices from any manufacturer could be interconnected in a digital lighting system. The precondition to this was for the manufacturers to commit themselves to the DALI standard.

DALI is meant only for communication in lighting systems, and is not designed to compete with BMS (Building Management Systems) which offer other functionality such as HVAC and alarm system control. In addition, a BMS system typically has unlimited expansion possibilities, whereas DALI is limited to 64 addresses. DALI does however, offer a number of design and installation benefits for the lighting designer and building services engineer and installer. It is cost-effective and versatile, whilst offering enhanced functionality over comparative systems.

The benefits of DALI

Individual control of each ballast is one of the most significant benefits provided by a DALI lighting system, giving building designers tremendous design flexibility. Multiple uses of rooms can be easily accommodated, as can the needs or preferences of individual occupants. Up to sixteen different light levels can be programmed and stored in the ballast memory. In addition, each ballast can belong to as many as sixteen discrete groups, allowing different lighting scenes for workspaces or room applications. Alongside this, dimming or switching in response to ambient light levels and occupancy are readily accomplished with the addition of devices such as PIR sensors.

DALI digital dimming electronic ballasts

Wiring can be carried out with a standard 5-core cable (no separate bus cable is required), and the system is polarity-free for ease of installation. In addition, there is no need to wire luminaires in groups as the system is programmed with a PC and software. This ensures complete flexibility throughout the life of the system as there is no costly rewiring required if there is a change in room use, just simple reprogramming. In addition, central monitoring of luminaire status makes fault-finding easier and less time-consuming.

DALI is specifically targeted at the needs of commercial and architectural lighting, although it is making inroads into the residential market in the UK - especially at the upper end. Because it is designed to be very easy to install and configure, it has achieved wide acceptance within the architectural lighting community. Recent DALI projects include the new RNIB headquarters, KPMG's Bristol offices, a large apartment complex at Lancaster gate in London and the Xscape theme park in Castleford. The diversity of these projects demonstrates both the wide application of DALI technology and its future potential.

DALI provides full lighting control in all parts of this villa in Norway. 20 Helvar DIGIDIM panels control 25 converters that dim transformers with 1-10V. There is a master panel at the main entrance, scene control in the living room, kitchen and staircase, and local control in the bedrooms and WCs

DALI versus 1-10V analogue control systems

Since each unit in the DALI network has its own individual address, it is possible to communicate directly to the components in the fittings for individual control. At the same time, through only one pair of control cables, several different groups of fittings can be controlled at the same time. DALI's bidirectional information flow means that instead of only giving commands about the light level to the fitting, the system supports information feedback on the condition of the fittings, such as whether the light is switched on or off, what the preset light level is, and what the condition of the ballast is.

DALI only requires simple wiring. Cabling consists of a simple two-wire cable, independent of any building topology between the units in the system, and lights can be switched off by commands directly from the DALI control system, eliminating the need for mains switching. Once the system is installed and configured, it is very easy to change how it functions. Scenes and lighting function changes are only involve re-programming and require no further hardware changes. It is also easy to add new components. For example, if the lighting system needs to be enlarged, new components can be added anywhere in the DALI system with no wiring restrictions on the configuration.

DALI in residence

A recent project that demonstrates the benefits of DALI in a residential environment is a new extension to a farmhouse in Hertfordshire, UK. Epitomising modern living, the ground-floor extension at this private family home has been designed as a luxurious yet functional space for working, relaxing and entertaining. The farmhouse's impressive new living area, study and home cinema feature the very latest in home automation technology, including Helvar DIGIDIM lighting control.

The farmhouse living area, study and home cinema with automated lighting using DALI

Custom installer Audio Visual Projects (AVP) developed a practical and cost-effective lighting control solution that is capable of delivering genuine 'touch-of-a-button' lighting control for the complete space. In addition, the scheme also incorporates unique elements such as custom-made Edwardian-style switch plates and an integrated audio/lighting switch module for the cinema room.

The extensive lighting scheme at the farmhouse is an 'illuminating' demonstration of the many features and benefits that DALI offers to residential end-users and installers alike. The three-room scheme features twelve separate lighting circuits featuring mainly recessed LV tungsten halogen downlights mixed with several 5-amp sockets - all wired back to the DIGIDIM rack. Multiroom lighting levels and ambience are set as desired with a hand-held infra-red remote control, or at the sleek seven- and five-button wall plates. In addition to the pre-set lighting scenes available, it is also simple to reconfigure the system for more individual tastes, or indeed, for maximum versatility, if room layouts are altered and lighting requirements change.

Conclusion

The DALI communication protocol is designed to operate on a two-wire cable, and the range includes a series of controllers, lamp interface units and special purpose-designed modules, featuring converters and other products to ensure maximum system versatility. The system is designed for both simple and complex installations, but in all cases, wiring and configuration is designed to be kept to a minimum.

Gary Brown is the UK Sales Manager at Helvar - one of the original developers of DALI. Helvar is a global leader in the development and manufacture of lighting control, exporting to over 50 countries worldwide.

www.helvar.co.uk
www.dali-ag.org