DALI colour control

When it comes to colour control, vastly varying constellations are possible. Colour mixing is often based on one of the following three principles:

  •  RGB: the composition of the resulting colour is achieved using three light sources with the base colours red, green and blue.

  • RGBW: like RGB, only with an added white light source. Often used where luminaires, e.g. at different times of day, are used for decorative as well as functional lighting.

  • White-white (tunable white): control of white light colour temperature. Usually utilised to imitate the colour temperature progression of daylight (see also chapter “Human Centric Lighting”).

For all three cases, DALI control in broadcast or addressing mode can be realised. The following must be noted, however:

  • Broadcast mode requires every single colour in every luminaire to be generated by a light source with a separate, single-channel control gear unit. The control device must provide one separate broadcast output per colour. One control line pair must be installed per colour.

  • In addressing mode, it is also possible to control luminaires in which light sources of different colours are generated through a multi-channel control gear unit with several DALI addresses at one single DALI connection. One control line pair is sufficient. This allows the operation of a total maximum of 64 DALI participants (colour channels). For RGBW control, this means e.g. a maximum of 16 luminaires. A system expansion via repeaters is not possible (see footnote).

Colour control can also be implemented using special DT8 (Device Type 8) components. It is important to note the following:

  • In DT8 operation, control gear units as well as control device must support the special DT8 colour control functions. This allows for an operation of up to 64 control gear units, since each DT8 control gear unit only occupies one DALI address to execute colour mixing via the received DALI DT8 command. DT8 colour control functions can be executed in addressing mode as well as broadcast mode (see figure).

Commercially available repeaters only transmit broadcast commands to the connected luminaires on secondary side. Separate control via assignment of colours to group addresses, which is possible in theory, fails due to a lack of suitable repeaters.