ABB i-bus KNX Product Manual page 194

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ABB i-bus KNX
Planning and application
E
D
C
B
A
The table assumes ideal DALI equipment (DALI dimming range 0.1...100 %) and in the DLR/A a KNX
dimming range of 0.4...100 %.
Rows A and B are the brightness value that the DLR/A is receiving via the KNX as digital number values
(0...255) or in % (0...100) empfängt. The DLR/A transfers these to DALI (row C). Then(row D) there is the
DALI characteristic of the luminous flux from the luminaire. Finally the DLR/A sends the status of the bright
value (row E) back to the KNX again.
The dimmable range printed on the ballast relates to the luminous flux. Typical specifications are 3 % or
0.2 %, which due to the logarithmic nature of the DALI curve, are the KNX values of 49 % (126) or 10 %
(26).
The maximum possible dimming range can only be set with DALI equipment, which has a dimming range
up to 0.1 % (KNX value 1 or 100/255 % = 0.4 %). Other DALI equipment has a limited dimming range. This
value is a physical property of the ballast and cannot be changed. This dimming limit has nothing to do
with the minimum dimming value parameterized in the application.
As an example, in the following, DALI equipment with a minimum physical luminous flux of 3 % can be
observed. In the KNX, a dimming range of 126...254 is thus available. This means, the lowest brightness
value that can be set and fed back on the KNX is 126 or 50 %. KNX values, which are less than 126 or
50 %, are set by the DALI equipment to the threshold value and fed back by the DLR/A on the KNX.
E
D
C
B
A
The characteristic curve described in the following section is represented as the useable range for the
ballast with the control value range for the brightness value on the KNX. In this way, a higher resolution of
the brightness values on the KNX is possible. However, nothing changes in the physical threshold values
of the ballast and the light yield.
Note
Characteristic adjustment can only be carried out correctly if brightness value is calculated internally
with characteristic adjustment via the DALI Light Controller, simulated, and provided to the DALI
devices. This is the case e.g. when setting the brightness value.
When dimming, irrespective of whether this is via a group or a central command, differences can occur
between the set brightness value and the simulated status of the brightness value. To make it possible
to obtain equal dimming, the DALI commands DIM-UP and DIM-DOWN must be used on the DALI Light
Controller. These commands trigger a dimming step in the DALI device, which is then transformed into
the DALI characteristic on the DALI device. As the exact length of the dimming step is unknown,
deviations can arise between the calculated (simulated) value and the actual set brightness value.
This can become apparent if, after dimming, the brightness value status is fed back directly to the
dimmed lighting group as the brightness value. Where this is the case, it can result in a jump in
brightness.
192 2CDC507128D0202 | DLR/A 4.8.1.1
KNX status
brightness
0 1
value
Luminous flux
0 0.1
[%]
DALI value 0 1
KNX value 0 1
KNX value [%]
0 0.4
KNX status
brightness
0 126
value
Luminous flux
0 3
[%]
DALI value 0 1
KNX value 0 1
KNX value [%] 0 0.4
60 85 126 144 170
0.5 1 3 5 10
60 85 126 144 170
60 85 126 144 170
24 33 49 57 67
126 126 126 126
3 3 3 3
8 26 60 85
8 26 60 85
3 10 24 33
195 210 220 229 235
20 30 40 50 60
195 210 220 229 235
195 210 220 229 235
77 82 86 90 92
126 144 229 235 241
3 5 50 60 70
126 144 229 235 241
126 144 229 235 241
49 57 90 92 95
241 246 250 255
70 80 90 100
241 246 250 254
241 246 250 255
95 97 98 100
246 250 255
80 90 100
246 250 254
246 250 255
97 98 100