
Art.-No.: 2095 LUX
4.2.4 Functional description
Control operating mode
The device can be used either for simple brightness on-off control (switching) or for convenient
constant light regulation (dimming).
In brightness on-off control the lighting is switched on as soon as the brightness drops below
the parameterised lower limiting value. Conversely, the lighting is switched off as soon as the
brightness exceeds the set upper limiting value. This means that the brightness controller can
also be used in systems that are equipped solely with switchable luminaires. As a special case
of the brightness on-off control, the operating mode "only automatic switch-on" can be set. In
this operating mode the lighting is only switched on depending on the brightness, and must be
switched off again manually or via a time program, for example. As an additional special case of
the brightness on-off control, the operating mode "only automatic switch-off" can be set. In this
operating mode the lighting is only switched off depending on the brightness, after it was
previously switched on manually or via automatic timing, for example.
In constant light regulation the lighting is regulated to the specified brightness setpoint via
dimming actuators or control units, depending on the lamp and the installation. In this type of
control the brightness setpoint can be preselected either as a parameter or alternatively via the
bus by means of a communication object. Furthermore, in "Master/Slave mode" up to four
additional luminaire groups can be dimmed as slaves either to the same value or each to a
different value differing from the master dimming value by a positive or negative offset.
Controlling one or more luminaire groups as a slave is advantageous, for example, when there
are several work stations in the room, but the device has been installed only over one work
station. Depending on whether the slave work stations are located closer to the window or
farther from the window than the master work station, the corresponding luminaire group must
be dimmed down or up accordingly.
Calibration
In the brightness measurement an average is always determined using the last measured value
and the new measured value, in order to damp out brightness jumps even during the
measurement. In the brightness controller the brightness measurement is pre-calibrated with a
rigid fibre-optic rod with a straight light incidence, mounted at a height of 2.50 m over a work
station at at height of 0.75 m with a work surface with approx. 30% degree of reflection. These
conditions vary, however, in practice, which means that it may be necessary to perform re-
calibration of the brightness measurement after installation. Thus for example recalibration is
necessary if the sloping fibre-optic cable has been used in the device in the course of
commissioning (see page 8).
A calibration of the brightness measurement can be performed via the bus and using the ETS.
In order to perform a calibration, communication via the bus must be possible. The installation
and commissioning of the device must thus be completed properly before this.
In the case of constant light regulation the lighting lighting must be switched on and dimmed in
such a way that the lux value shown on a calibrated light meter on the work surface directly
under the controller corresponds to the current setpoint for the constant light regulation.
Alternatively the setpoint for the constant light regulation can also be set in the ETS or using the
2-byte object "Setpoint..." to the displayed lux value.
After that a telegram must be sent on communication object 8 "Calibrate setpoint" to the
brightness controller (the contents of the telegram, a 0 or 1, is of no significance here). Only
after that is it possible - if set previously - to set the setpoint for the constant light regulation
back to the desired value.
In case of on-off brightness control or for the operating mode "only automatic switch-off" the
lighting should be set so that the lux value shown on the light meter corresponds to the current
setpoint for switch-off of the lighting. Here too it is possible as an alternative to first set the
switch-off setpoint to the displayed lux value. In case of the operating mode "only automatic
switch-off" the lighting should be dimmed so that the lux value shown on the light meter
corresponds to the current setpoint for switch-on of the lighting. Alternatively the switch-on
setpoint can first be set to the displayed lux value.
Page 18 of 27
Software "Brightness controller A01001"
Functional description