ABB i-bus KNX Product Manual page 198

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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/S, a KNX
dimming range of 0.4...100 %.
Row A and B are the brightness value of the DLR/S received via the KNX as a digital numeric value
(0...255) or in % (0...100). This value is implemented by the DLR/S on the DALI (row C). It results in the
luminous flux which is emitted by the lighting equipment via the DALI characteristic (row D). The DLR/S
then sends the status of the brightness value (row E) back on the KNX.
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, correspond to 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 section, DALI equipment with a minimum physical luminous flux of 3 % is
considered. In the KNX, a dimming range of 126...254 is thus available. This means that 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 this threshold value and fed back by the DLR/S 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 performed correctly when the brightness value is internally
calculated and simulated with the characteristic adjustment via the DALI Light Controller and transferred
to the DALI devices. This is the case when the brightness value is set, for example.
During dimming, irrespective of whether a group command or central command is concerned,
differences may occur between the set brightness value and the (simulated) status of the brightness
value. To allow even dimming, the DALI Light Controller must use the DALI commands DIM-UP and
DIM-DOWN. These commands trigger a dim step in the DALI device, which is transformed using the
DALI characteristic stored in the DALI device. As the exact length of the dim step is not known, there
may be deviations between the calculated (simulated) value and the brightness value actually set.
This can occur, for example, when, after dimming, the status of the brightness value is fed back to the
dimmed lighting group as a brightness value. In this case, there may be a brightness jump.
196 2CDC 507 100 D0202 | DLR/S 8.16.1M
KNX status
0 1
brightness
value
Luminous flux
0 0.1
[%]
DALI value 0 1
KNX value 0 1
KNX value [%]
0 0.4
KNX status
0 126
brightness 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