DALI - Digital Addressable Lighting Interface

DALI is a trademark for network-based systems that control lighting in building automation. The underlying technology was established by a consortium of lighting equipment manufacturers as a successor for 0-10 V lighting control systems and as an open standard alternative to Digital Signal Interface (DSI), on which it is based.

DALI is specified by technical standards IEC 62386 and IEC 60929. Standards conformance ensures that equipment from different manufacturers will interoperate. The DALI trademark is allowed on devices that comply with the current standards when manufactured.

The DALI system uses two wires which can connect to a device regardless of polarity. Connecting cables have to be mains-rated, with 600V isolation and at least 1mm thickness. The cables can be 300 meters long at most, with a maximum voltage drop of 2 volts. Signal wires need to be galvanically separated and do not require termination resistors.

A DALI bus requires a 24V DC 250mA power supply unit to function. Some of this current can be used by devices to power them to a limited extent, such as for wall switches and PIR motion sensors.

The operating voltages for the signal are defined as 0V ±4.5V for a 0 and 16V ±6.5V for a 1. The bus is not differential, as with RS485, but the DATA+ wire is being shorted against DATA-, thus indicating the 0.

The communication protocol is an asynchronous, half-duplex, serial protocol over a two-wire bus. The data is exchanged in packets of 30bit size. The speed of the bus is 1200bps. DALI allows addressing of individual devices on the bus, groups of devices or all devices at once. The address of the device is between 0-63, therefore there cannot be more than 64 devices on one channel (+ master).

The 4 channel DALI bus is available on the Axon S605 controller.