Brightness Detection - ABB i-bus KNX Product Manual

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ABB i-bus KNX
Planning and application
4.9.6

Brightness detection

The Light Sensor LF/U 2.1 of the DALI Light Controller DLR/A 4.8.1.1 detects the light intensity of the
surfaces in its detection range and converts it to a current. Before the light reaches the photodiode, it
passes through a light filter, whose maximum pass band attributes are in the visible wavelength range of
the human eye. The light intensity is on the one hand dependent on the lighting intensity, i.e. the intensity
of the daylight or artificial lighting, and on the other hand on the characteristics of the surfaces (reflections),
which are to be illuminated. If the surfaces in the detection range of the light sensor are completely
covered with white paper, the light sensor measures a different light intensity with the lighting intensity as
when the surface is covered with grey recycled paper. When setting the setpoint, the light density is
measured by the light sensor and stored as a setpoint value. Subsequently, the light control will control the
artificial lighting level in the room, so that it more and more accurately achieves this setpoint value, i.e. the
lighting control attempts to keep the lighting density and not the lighting intensity at a constant level.
4.9.7 Function of the constant lighting control
The task of a constant lighting control is to control the setpoint brightness, which results at a reference
point in the room as accurately as possible. Starting from the actual brightness, the setpoint brightness is
approached in steps (brightness change over time).
A control step is defined by the increment (brightness change) and the step time (time duration), in which
the brightness change is performed.
A simplified lighting control can in principle look as follows. The setpoint brightness is achieved starting
from an actual brightness level in three steps:
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