Page 175 - Advanced Course

KNX ADVANCED COURSE

4.6.6 Additional Notes

In general, the actuator is also addressed via central functions (see above) which switch
the lights on/off directly or also activate/deactivate the control for example via a time
switch. This must also be taken into account in the controller. A direct central switching
operation must also switch off the controller with positive drive. These addresses must
therefore also be linked to the disable objects of the controller; otherwise the controller will
always act against this external input and try to dim up the lights again.

4.7 Installation Notes

Many factors are decisive for the optimum installation of a brightness control system.
Some are listed here:

4.7.1 Alignment of the Measuring Sensor
The surface that is to be measured should be as undisturbed as possible i.e. should never
indicate different surface characteristics. External light should not directly penetrate the
receiving lens if possible, likewise artificial light.

Building ceiling
Correct Incorrect Suspended
Lamp ceiling
Receiver
Mounting height 2.5 - 6 m

Correct Incorrect
Light cone

4 4 0 w Calibration required
A n
A _ Measuring sensor +/-15%
9 5 Daylight

1
Figure 10: Optimum position of the measuring sensor (graphics do not resemble the sensor
exactly)

4.7.2 Several Light Strips with a Varying Proportion of External Light:
In this case, which rarely occurs, a single brightness sensor is only sufficient if it is
possible to generate different control values for the individual actuator channels. If you do
not have a controller that can do this, a separate sensor must be installed for each light
strip. As mutual influences (mostly unwanted) can arise, a partitioning of the sensors must
take place and the overlapping of the lighting surfaces underneath the individual strips
must be minimised. It can, however, invariably lead to oscillation processes or at least an
unexpected distribution of brightness (although the measured values of the sensors are
correct). The technically better solution nowadays is to only control one strip (whereby it is
not possible to simply select any strip but the strip which is installed at the window side,
which reacts the most sensitively to daylight changes). The other lighting strips are simply

Home and Building Management Systems KNX Association
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