Some lighting fixtures with DALI communication support color control according to the ČSN EN 62386-209 standard (Particular requirements for color control - Type 8 equipment). What is it about?
The original DALI standard does not address color, light is controlled "one-dimensionally": all commands only concern intensity, without specifying any color shade, color temperature, etc. However, with the advent of LED lights, there was a need to define color in the protocol, because it is set by a combination of the luminance of the individual components - red, blue, green and possibly also cool white and warm white.
We recommend studying the above standard in detail, especially chapter 4, where the color temperature (T) and its reciprocal value "Mirek" (micro-reciprocal-degree) are described:
Mirek = 1,000,000 / T [K-1]
The Mirek value in relation to color temperature looks like this:
Relationship between color temperature and Mirek units. Source: ČSN EN 62386-209
And it is in Mirek units that the desired color in the DALI standard is specified.
Example: for the short address of the ballast 0, we want to set the color "quite yellow" with a temperature of 16.3 K. First, we convert this to the Mirek format, i.e. 1,000,000 / 16.3 = 61070 Mirek, which is EE 8E in hexadecimal form. There are no direct commands for setting the color tone in the R091 converter, so we must proceed using block commands according to the example in the R091 catalog sheet, page 37. Understanding the principle of block commands is essential for further considerations!
In the example, we will use blocks 8 to 11 to send the relevant DALI telegrams (see the table on page 18 of the R091 catalog sheet). The registers must be filled as follows:
reg. 516 - A3 8E: write 8E to DTR0 - this is the LSB of the color tone in the "Mirek" format
reg. 520 - C3 EE: write EE to DTR1 - this is the MSB of the color tone in the "Mirek" format
reg. 524 - 08 C1: before setting the color temperature we must send the command Enable device type = 08 to the ballast, see the standard:
Command to enable DT8. Source: ČSN EN 62386-209
The content of the lower byte, C1, is the value 193, which means the above command 272, see also the standard.
reg. 528 - E7 01: E7 is the "1110 0111" as defined in command 231 below, 01 is the ballast address (short address 0, i.e. YAAA AAA1 = bin 0000 0001 = hex 01):
Command to enable DT8. Source: ČSN EN 62386-209
The color value is taken from the DTR0 and DTR1 registers, where we wrote it in the first two commands.
reg. 511 - write 15 (bin. 1111) executes four commands that are needed for the entire setup, i.e. sends pre-prepared blocks 8 to 11 to DALI. (For repeated - next write, it is necessary to write 0 and then 15 again to reg. 511, writing to DALI is performed when the relevant bit is raised from 0 to 1.)
If we were to use the ModComTool service program as a Modbus client for tests, the completed Modbus table looks like this:
Modbus table for the above example of setting the color temperature to 16.3 K
If everything is successful, in the diagnostic terminal (TCP terminal client connected to TCP port 23 interface R091) we can watch the communication output on the DALI bus:
MBBLOCK:a3 8e 00 00, Len:02, T:3723222 TR:3723252,00 00 00 00, Len:00, Flg:11 - write DTR0
MBBLOCK:c3 ee 00 00, Len:02, T:3723262 TR:3723292,00 00 00 00, Len:00, Flg:11 - write DTR1
MBBLOCK:c1 08 00 00, Len:02, T:3723302 TR:3723332,00 00 00 00, Len:00, Flg:11 - Enable device type 8
MBBLOCK:01 e7 00 00, Len:02, T:3723342 TR:3723372,00 00 00 00, Len:00, Flg:11 - set Tc
Please note that the color change (activation) will only occur when the brightness changes by at least one step - perhaps it is a specialty of the tested type or Osram in general.
This is much more complicated than direct intensity control, as we commonly practice, but it is possible to fully use all DALI functions with the Modbus TCP driver, which is clearly seen in the example of color control for Device Type 8.
