How Does Brightness Detection Function; Function Of The Constant Lighting Control - ABB i-bus KNX Product Manual

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ABB i-bus KNX
4.7.5 How does brightness
detection function
4.7.6 Function of the constant
lighting control
© 2008 ABB STOTZ-KONTAKT GmbH
Planning and application
The Light Sensor LF/U 2.1 of the LR/S x.16.1 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 which are 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 environmentally-friendly 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.
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.
In principle, simplified light control can appear as follows. In the following
example, the setpoint brightness is achieved starting from an actual
brightness level to a setpoint brightness level in three steps:
Brightness
Setpoint
brightness
Actual
brightness
Y = increment
(brightness change)
T = step time
T
T
3 x step time
T
Y = increment
Time
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