Controlling the colour temperature

Settable colour temperature range

When controlling DALI operating devices that support the device type "DT8 - Tunable White", the colour temperature of the connected lamps can be changed. The settable colour temperature range of a group or single device can be limited by defining a lower and upper colour temperature value. The "Minimum colour temperature" and "Maximum colour temperature" parameters in the parameter node "DALI system... -> Configuration groups -> [x] Group name -> Colour temperature" or "DALI system... -> Configuration single devices -> [x] Device name -> Colour temperature" define the colour temperature values that are not undercut or exceeded in any operating state of the gateway. In this way, the colour temperature of the controlled lamps of the DALI operating devices can be limited individually and adapted to the respective application.

In addition, the colour temperature value can be specified that is set when the device is switched on. The "Switch-on colour temperature" parameter defines this colour temperature value separately for each group and single device.

The switch-on colour temperature as a value specification can be configured basically within a range of 1,000...10,000 K. If the switch-on colour temperature is outside the range defined by the minimum or maximum colour temperature, the gateway limits the switch-on colour temperature to the defined limits.

Example of a configured colour temperature range with switch-on colour temperature

DALI luminaires that can change the colour temperature are usually fitted with two different lamps for warm white and cold white light. The luminous flux of both lamps can be varied independently and thus the colour temperature changed within the specified range by varying control by the upstream DALI operating device (e.g. DALI DT8 LED driver). In the lower colour temperature range, only the warm white lamp is usually switched on. In the upper colour temperature range, only the cold white is switched on. A DALI operating device according to DALI device type 8 essentially changes the proportional luminous flux of the lamp while maintaining the total luminous flux that is specified by the brightness of the DALI group or single device. During a dimming process of the colour temperature, the operating devices may switch the lamps on or off as required. This can lead to switching process within the transition ranges that cause the colour temperature dimming processes to briefly appear unsteady.

Setting minimum colour temperature

The minimum colour temperature can be set separately for each group and single device.

  1. Set the "Minimum colour temperature" parameter on the parameter page "DALI system... -> Configuration groups -> [x] Group name -> Colour temperature" or "DALI system... -> Configuration single devices -> [x] Device name -> Colour temperature" to the required colour temperature.
  • The set colour temperature is not undershot in any operating state.

The configured minimum colour temperature must be lower than the maximum colour temperature.

If an absolute colour temperature is received by the KNX that is less than the configured minimum colour temperature, the gateway will set the minimum colour temperature as the new colour temperature value for the group or single device concerned. In this case, the "colour temperature invalid" status can be generated optionally.

Setting the maximum colour temperature

The maximum colour temperature can be set separately for each group and single device.

  1. Set the "Maximum colour temperature" parameter on the parameter page "DALI system... -> Configuration groups -> [x] Group name -> Colour temperature" or "DALI system... -> Configuration single devices -> [x] Device name -> Colour temperature" to the required colour temperature.
  • The colour temperature set is not exceeded in any switched-on operating state.

The configured maximum colour temperature must be greater than the minimum colour temperature.

If an absolute colour temperature is received by the KNX that is higher than the configured maximum colour temperature, the gateway will set the maximum colour temperature as the new colour temperature value for the group or single device concerned. In this case, the "colour temperature invalid" status can be generated optionally.

Setting the switch-on colour temperature

The switch-on colour temperature can be set separately for each group and single device. The "Switch-on colour temperature" parameter on the parameter page "DALI system... -> Configuration groups -> [x] Group name -> Colour temperature" or "DALI system... -> Configuration single devices -> [x] Device name -> Colour temperature" defines the behaviour.

  1. Set the parameter to "Track".
  • When switching on, the internally tracked colour temperature most recently specified and in the "Brightness 0%" state is preset. The tracked colour temperature value is not influenced by an ETS programming operation or by a bus voltage failure ("no change"). When the bus/mains voltage returns, the colour temperature active most recently before the bus/mains voltage failure is restored. Hence, this colour temperature is taken into account as a colour temperature value to be tracked when switching on. As long as no colour temperature value could be tracked yet, the default value is "2.700 K", which is optionally limited by the minimum or maximum colour temperature.
  1. Set the parameter to "preset". Perimeter the desired colour temperature value in the "Colour temperature" parameter.
  • The set colour temperature is set when receiving an ON telegram via the communication object "Switching - Setting" or when receiving a central telegram with the polarity "activated".
  1. Set the parameter to "memory value (value before the last switch-off)".
  • When switching on, the colour temperature is set that was active and stored internally before switching off the last time. This memory value is stored in a non-volatile manner in the gateway so that the value is retained after the bus or mains voltage returns. After an ETS programming operation, the memory colour temperature value is predefined to "2.700 K". This value is optionally limited by the minimum or maximum colour temperature.

In the "preset" setting: The switch-on colour temperature can always be configured within a range of 1,000...10,000 K. If the switch-on colour temperature is outside the range defined by the minimum or maximum colour temperature, the gateway limits the switch-on colour temperature to the defined limits.

In the "memory value" setting: A memory value is stored internally by a switch-off telegram also if the bus-controlled switch-off is overridden, for example, by a disabling or forced position function or by a manual operation. In this case, the internally tracked colour temperature value is saved as memory value.

The colour temperature to be set by switching on is either dimmed in the configured dimming time or is jumped to directly depending on the configured dimming behaviour (absolute dimming). The dimming characteristic curve for colour temperature changes is always linear.

Dimming characteristic and dimming speeds

When activating DALI operating devices that support the device type "Tunable White" (DT8 - TW), the colour temperature can be changed by a relative or absolute dimming process. The limits of the colour temperature range adjustable by a dimming process is defined by the minimum and maximum colour temperature predefined in the ETS.

Example of a dimmable colour temperature range

A DALI group or single device can be dimmed by...

  • Relative dimming:
    Relative dimming of the colour temperature can be triggered either by the 4-bit communication object "Relative colour temperature - Setting" available for each group or single device or by the 3-byte combination object "Relative dimming (brightness and colour temperature) - Setting". As with relative dimming of the brightness, the data format of the 4-bit object complies with the KNX DPT 3.007, which means that the dimming direction and relative dimming increments can be specified in the dimming telegram or dimming processes can also be stopped. The data format of the 3-byte object corresponds to KNX DPT 250.600, which enables combined relative dimming of brightness and colour temperature by means of separate dimming increments and dimming directions. A relative dimming process allows a colour temperature value to be changed constantly and always starts from the colour temperature that is set at the time of the dimming command.
    In the ETS, the dimming speed for relative dimming of the colour temperature can be configured for a brightness change separately for each group or single device and independently of the dimming speed.
    A relative dimming telegram for controlling the colour temperature can also switch on a group or single device in the "OFF" state. In some applications, it may be necessary, however, for a switched off group or switched off device to still remain off until a relative dimming telegram of the colour temperature is received. This is interesting, for instance when using light scenes: Several DALI groups are set to a defined colour temperature by a light scene. Other groups are switched off by the scene. Only the colour temperature of channels not switched off by the scene recall should be changed by dimming up afterwards. Here, it is necessary for groups or single devices not to respond to relative dimming of the colour temperature and thus not to switch on. The parameter "Behaviour in switched off state when changing the colour temperature by relative dimming" defines whether a group or single device in the "OFF" state is switched by via a relative dimming telegram of the colour temperature or remains switched off and only tracks the dimming process internally.
  • Absolute dimming:
    Absolute dimming is triggered by specifying a colour temperature value. This value can be specified either by the 2-byte communication object "Absolute colour temperature - Setting" available in each group or single device according to KNX DPT 7.600 or by the 6-byte combination object "Absolute dimming (brightness and colour temperature) - Setting" according to KNX DPT 249.600 for the combined control of brightness and colour temperature. In addition, colour temperature values can also be set by the scene function.
    When specifying a colour temperature value by the objects or by a scene call-up, it can be configured in the ETS whether the value is jumped to directly or alternatively dimmed to over a dimming time or fading is carried out. When dimming by means of the 6-byte combination object, it is possible to specify an individual dimming time in the KNX telegram. If a valid time is specified there, the gateway executes the dimming time transmitted in the KNX telegram and not the one specified in the ETS. The colour temperature and brightness specified in the telegram value is then dimmed to within the transmitted dimming time (fading). If the time is defined as "invalid" in the telegram, the gateway always executes the dimming behaviour defined in the ETS parameters during absolute dimming.
    Just as with relative dimming, an absolute dimming telegram for controlling the colour temperature can also switch on a group or single device in the "OFF" state. Here too, it may be necessary in some applications for a switched off group or switched off device to still remain off if a new colour temperature value is specified absolutely. The parameter "Behaviour in switched off state when changing the colour temperature by absolute dimming" defines whether a group or single device in the "OFF" state is switched on by a new absolute dimming telegram of the colour temperature or remains switched off and only tracks the colour temperature value internally.

A dimming time for relative dimming or absolute dimming (with dimming to the colour temperature values) is set at the gateway within the range from the minimum colour temperature to maximum colour temperature. The dimming times are derived directly from the configured times between two dimming steps.

The dimming characteristic curve for colour temperature changes is always linear
.

Optionally, the 1-bit status object "Colour temperature invalid - Status" can be used to indicate whether an externally specified colour temperature is invalid. This is the case, if the specified colour temperature violates the set limits of the minimum and maximum colour temperature.

The dimming of the colour temperature cannot be triggered by manual operation directly on site on the device.

Even if colour temperature values are instantly jumped to, the dimming procedure on DALI operating devices always takes a very short time. This dimming procedure is dependent on the system. The colour temperature value jumped to will be dimmed to within 0.7 seconds (short fading). This time cannot be altered.

It is optionally possible to automatically change the colour temperature proportionally when dimming the brightness. This makes it possible with little project planning to simulate a thermal radiator using almost any colour temperature controllable lamp (perception of the light source such as an incandescent or halogen lamp).

Setting dimming behaviour for absolute dimming

In the ETS, the dimming behaviour for absolute dimming can be set separately for each group and single device. The parameter "When receiving a colour temperature value" on the parameter page "DALI system... -> Configuration groups -> [x] Group name -> Colour temperature" or "DALI system... -> Configuration single devices -> [x] Device name -> Colour temperature" defines the behaviour.

  1. Set the parameter to "jumping to".
  • As soon as a new colour temperature value is specified, it is instantly jumped to.
  1. Set the "dimming to" parameter.
  • Once a new colour temperature value is specified, it is set by means of the configured dimming step time for absolute dimming.
  1. Set the "fading" parameter. Configure the duration of the dimming process for the parameter "Time for colour temperature via fading".
  • As soon as a new colour temperature value is specified, it is set by means of the configured fading time for absolute dimming. The dimming process then always takes exactly the set time, regardless of the initial value of the dimming process.

During a scene recall, the dimming behaviour can be configured separately.

Setting dimming time for relative dimming

In the ETS, the dimming time for relative dimming of the colour temperature can be set separately for each group or each single device.

  1. Set the parameter "Time between two dimming steps for relative dimming" on the parameter page "DALI system... -> Configuration groups -> [x] Group name -> Colour temperature" or "DALI system... -> Configuration single devices -> [x] Device name -> Colour temperature" to set the required dimming step time.

The relative dimming of the colour temperature always takes place within the range limited by the configured minimum and maximum colour temperature. This range is divided into 255 dimming steps. The duration of a complete dimming process within this colour temperature range is calculated with to the formula: t = 255 x time between two dimming steps [ms].

Setting dimming time for absolute dimming

In the ETS, the dimming time for absolute dimming can be set separately for each group and single device.

  • The dimming behaviour must be configured as "dimming to".
  1. Set the "Time between two dimming steps for absolute dimming" parameter on the parameter page "DALI system... -> Configuration groups -> [x] Group name -> Colour temperature" or "DALI system... -> Configuration single devices -> [x] Device name -> Colour temperature" to set the required dimming time.

The absolute dimming of the colour temperature always takes place within the range limited by the configured minimum and maximum colour temperature. This range is divided into 255 dimming steps. The duration of a complete dimming process within this colour temperature range is calculated with to the formula: t = 255 x time between two dimming steps [ms].

Setting dimming behaviour in OFF state for absolute dimming

Absolute dimming of the colour temperature can also be switched on by a group or single device in the "OFF" state. In the ETS, the behaviour in the "OFF" state when receiving an absolute colour temperature telegram can be set separately for each group and single device by the parameter "Behaviour in switched-off state when changing the colour temperature by absolute dimming".

  1. Set the parameter to "Switch-on".
  • The group or single device in the "OFF" state is switched to the configured switch-on brightness by an absolute colour temperature telegram. The colour temperature is set to the colour temperature value received. If the dimming behaviour is configured to "jumping to", the intended colour temperature value is immediately preset.
  • If the dimming behaviour is configured to "dimming to", the dimming process starts at the colour temperature value most recently set by the gateway or which was tracked in the "OFF" state. The dimming process is executed according to the set dimming step time. The dimming process stops after reaching the specified colour temperature.
  • If the dimming behaviour is configured to "fading", the dimming process starts at the colour temperature value most recently set by the gateway or tracked in the "OFF" state. The dimming process is executed according to the set fading time. The dimming process then always takes exactly the set time, regardless of the initial value of the dimming process. The dimming process stops after reaching the specified colour temperature.
  1. Set the parameter to "No reaction".
  • The group or single device in the "OFF" state is not switched by the absolute colour temperature telegram. The group or single device remains switched off. The next time the device is switched on, the last colour temperature value received is tracked only if the "Switch-on colour temperature" parameter is configured to the "track" setting.

Setting dimming behaviour in OFF state for relative dimming

A relative dimming telegram for controlling the colour temperature can also switch on a group or single device in the "OFF" state. In the ETS, the behaviour in the "OFF" state when receiving a relative colour temperature telegram can be set separately for each group and each single device by the parameter "Behaviour in switched-off state when changing the colour temperature by relative dimming".

  1. Set the parameter to "Switch-on".
  • The group or single device is switched on in the "OFF" state by a relative dimming telegram of the colour temperature to the configured switch-on brightness. The colour temperature is set to the configured switch-on colour temperature. Based on this colour temperature state, the colour temperature to be dimmed is dimmed.Based on this colour temperature state, the colour temperature to be dimmed is dimmed.Based on this colour temperature state, the colour temperature to be dimmed is dimmed. The relative dimming telegram that leads to switching on, specifies the dimming direction and dimming increment. The dimming process stops after reaching the specified colour temperature.
  1. Set the parameter to "No reaction".
  • The group or single device in the "OFF" state is not switched on by the relative dimming telegram. The group or single device remains switched off. The next time the device is switched on, the colour temperature value dimmed last is tracked only if the "Switch-on colour temperature" parameter is configured to the "track" setting.

Setting the behaviour of the colour temperature when dimming the brightness

It is optionally possible to automatically change the colour temperature proportionally when dimming the brightness. This makes it possible with little project planning to simulate a thermal radiator using almost any colour temperature controllable lamp (perception of the light source such as an incandescent or halogen lamp). In the ETS, the behaviour of the colour temperature can be set separately by means of parameters for each group and single device for this application when dimming the brightness for relative or absolute dimming.

  1. Set the parameter "Behaviour of the colour temperature when changing the brightness by relative dimming" to "no change".
  • The relative dimming of the brightness by a 4-bit dimming telegram has no effect on the colour temperature of the group or single device. The colour temperature can be controlled only separately.
  1. Set the parameter "Behaviour of the colour temperature when changing the brightness by relative dimming" to "change proportional to brightness".
  • During relative dimming of the brightness with a 4-bit dimming telegram, the colour temperature of the group or single device is also changed proportionally. The colour temperature becomes warmer when dimming down. The colour temperature becomes colder when dimming up. The colour temperature can also be controlled separately.
  1. Set the parameter "Behaviour of the colour temperature when changing the brightness by absolute dimming" to "no change".
  • The absolute dimming of the brightness with a 1-byte brightness value has no effect on the colour temperature of the group or single device. The colour temperature can be controlled only separately.
  1. Set the parameter "Behaviour of the colour temperature when changing the brightness by absolute dimming" to "change proportional to brightness".
  • During absolute dimming of the brightness with a 1-byte brightness value, the colour temperature of the group or single device is also changed proportionally. The colour temperature becomes warmer when dimming down. The colour temperature becomes colder when dimming up. The colour temperature can also be controlled separately.

Example:
A DALI luminaire is fitted with colour temperature controllable LED lamps. The luminaire is switched and its brightness dimmed by KNX telegrams. When dimming, the colour temperature should adjust automatically to the brightness of the dimming setting without the colour temperature being specified separately via the KNX. At low brightness, the lamp should glow warm white, and at high brightness it should glow cold white. Thus, the colour temperature should change constantly in the same way as the brightness within the limits of the dimmable brightness range.

The maximum possible KNX brightness range (0...100 %) is mapped proportionally to the configured colour temperature range (minimum colour temperature [0%]...maximum colour temperature [100%]) during the automatic adjustment of the colour temperature. A configured minimum and maximum brightness limits the automatically adjustable colour temperature range. In the same way, a configured minimum colour temperature can never be undershot and a maximum colour temperature can never be exceeded even if the brightness range allows a greater adjustment range.

Automatic adjustment of the colour temperature to the set brightness
Example in the maximum brightness and colour temperature range
Automatic adjustment of the colour temperature to the set brightness
Example with limited brightness and colour temperature range
Automatic adjustment of the colour temperature to the set brightness
Example with limited colour temperature range

The colour temperature can be automatically adjusted to the brightness dimming setting of a DALI group or single device during relative dimming and absolute dimming. The parameters "Behaviour of the colour temperature when changing the brightness by relative dimming" and "Behaviour of the colour temperature when changing the brightness by absolute dimming" allow the described function for relative or absolute dimming to be activated separately.

The brightness of the lamp connected to the physical output of the controlled DALI operating device is dimmed by the DALI characteristic curve configured in the ETS for each group or single device. The colour temperature is constantly dimmed linearly.

Additional information