19
ABB i-bus
®
KNX
Functional description
Scene dimming is possible with the DALI-Gateway DG/S 8.1 and the central
command “Relative dimming” are described as follows:
The set brightness values and the relative brightness differences of the indi-
vidual channels are maintained during the central dimming process (object
relative dimming, channels A…H). This information is also maintained when
the maximal or minimal brightness value is reached and when all of the
luminaries have reached the maximal or minimal dimming value. When the
minimal or maximal brightness values are dimmed up or down, the original
brightness conditions are restored.
The following illustrations explain the principles of scenic dimming.
To make it easier to understand, the minimal and maximal dimming values
of the channels were set to 0% and 100% respectively.
Fig. 8: Scene dimming with central command
In detail, scenic dimming via the central dimming object (relative dimming,
channels A…H) differs slightly from relative dimming in a channel. This is
necessary, since all channels are regarded as a group of luminaries. At the
beginning of scenic dimming, the current brightness values of each individu-
al channel are determined as the starting point for dimming. Every dimming
value can be dimmed up by + 50 % or down by – 50 %. This is mapped
onto the actual brightness range. This means that a brightness value of
20 % can be dimmed by + 50% (which corresponds to a range of
20 – 100 %) or by -50 % (which corresponds to a range of 0 – 20%).
Depending on the dimming intervals defined in the KNX, the ranges are split
up and dimmed.
With an initial brightness of 50 %, this leads exactly to the dimming behav-
iour used for relative dimming in the individual channels.
If at the beginning of scenic dimming all channels (A to H) are OFF
(0 % brightness) or ON (100 % brightness), the possible dimming range will
be set only unilaterally. This leads to a full utilisation of the dimming range
without allowing dimming into the OFF or ON direction.
3.5 Scene
dimming
Dimming up
A B C D E F G H
Channel
Starting point
100
80
50
10
A B C D E F G H
Channel
100
80
50
10
Dimming up
A B C D E F G H
Channel
100
80
50
10
Dimming down
Starting point
A B C D E F G H
100
80
50
10
Dimming down
A B C D E F G H
100
80
50
10
Dimming up
Starting point
A B C D E F G H
100
80
50
10
Brightness
Brightness
Brightness
Brightness
Brightness
Brightness
Channel
Channel
Channel
