How does tunable white work technically?

The LED modules contains a mixture of diodes providing warm or cold light. By mixing the light from these we can get colour temperatures between 2700-6500 Kelvin out of a single luminaire. Everything is controlled via DALI Device Type 8 and can be managed with different types of control units depending on what you want. The simpler panels have buttons or levers where the colour temperature is controlled with a slider and the intensity with another.

For an automatic dynamic control of colour and intensity a router system that dictates the levels over time is used. The colour temperature and intensity is controlled by the clock and doesn’t reflect the actual lighting conditions outdoors as it would be very dark in the room during the winter months.

DALI Device Type 8

DALI ballasts that are compatible with DALI Device Type 8 provide functionality for controlling colour temperature.

DALI ballasts that are compatible with DALI Device Type 8 are controlled with only one DALI address that controls both the cold and the hot diodes.

The function with different colour temperatures requires no programming with respect to the mixture of cold and warm light since the logic is built into the devices. The desired colour temperatures for different scenes are set directly in programming.

Conversely, when using DALI ballast which do not communicate according to DALI extension 209 (as opposed to the Type 8 described above), two ballasts are required: one for the warm and one for the cold diodes. To achieve the varying colour temperatures, each level (i.e. 3000k, 4000k, 5000k) has to be both measured with a spectrometer and individually programmed. 

Read more about lighting control with DALI