Digital Addressable Lighting Interface (DALI)

What is lighting control and why is it used?  Lighting control is a network-based light controlling system this includes communication between many inputs and outputs of lighting controls with the help of one or more controlling device. Lighting controls are used to eliminate energy or power wastage in the building and give comfort by providing or balancing the amount of light needed by the people. Light will work on a pre-programmed way, when an occupant is detected. One of the commonly used lighting interfaces is “DALI (Digital Addressable Lighting Control)”.

DALI

DALI is a technical standard for the network-based lighting control system and is commonly used in Building Automation and it is the international standard for the network-based interface. This network consists of a controller and or more lighting devices like electrical dampers with lighting DALI interfaces. A controller can monitor and control each light device via bidirectional data exchange. The DALI protocol permits devices to be separately addressed and conjointly incorporates cluster and scene broadcast messages to at the same time address multiple devices at just once. DALI allows for unparalleled performance. It helps to save energy and offers comfort and flexibility. DALI is set up as the successor for 1-10v lighting controllers.

How do DALI works?

Hardware used in DALI is the same as that of typical lighting control the only difference is that with DALI LED driver and Ballast can be linked to the central computer, allowing each to control independently. About 64 LED drivers or ballasts can be connected in the loop. Every device connected in the DALI has an address and the loop is connected to the DALI control device. DALI systems are available for fluorescent lamps.

Each lighting device (e.g. Ballast or LED drivers) are assigned to a unique address in the numeric range from 0 to 63 i.e. Total of 64 devices in the standalone system. A system with multiple DALI gateways can address more than 64 devices. Communication is done by asynchronous, half-duplex serial communication. The DALI gives 254 levels of brightness from 0 to 100%, which is transmitted to a ballast power level through a logarithmic curve. Thus the brightness can be controlled. DA devices such as ballast can be controlled via its short address.

                  Fig: Block Diagram of DALI

Fig: Schematic Diagram of DALI

                                The DALI gateway controller controls the individual DALI devices like electric ballast. This ballast includes EMI filter, rectifier, power factor correction, and ballast output stage. The ballast contains a microcontroller for sending and receiving digital information. The function of the microcontroller is to store ballast address, receive user instruction, setting the dim reference for the ballast control, receiving Status from ballast control and sent that information to the user. By this technique, there will be a precise control for the entire lighting environment. Thus, by using the ballast and the DALI gateway controller, we can control the lighting of a building.

Advantages

• We can easily re-configure the without having to tear into the ceiling
• Installation is easy with DALI five wire system
• Because of the two way communication, LED drivers and ballast can be inspected individually for energy usage and failure of the device

Disadvantages

• The controls are Expensive
• DALI is not ideal for every situation
• Installation is a little tough