6
KNX function and configuration
Introduction
A presence detector monitors the detection zone for occupancy, and causes one or more actions to be executed when a
person enters the detection area. In their simplest form, presence detectors could be used to turn on a light when a
person enters a room, and to turn it off again after the person leaves.
This range of presence detectors use the same basic infra-red or microwave detection technology, but make use of the
KNX system to communicate with other devices. The KNX standard defines how devices should communicate with each
other, allowing systems to be constructed using components from many different manufacturers. The standard also
guarantees that a presence detector from one manufacturer will effectively control a lighting dimmer or HVAC system
from another.
Central to the KNX system is the ETS configuration tool. This Windows application allows an installer to configure all
functions of each individual device in the system, and also how triggers and data are passed between different devices.
For instance, the tool can be used to set the sensitivity of the presence detector, and can be associated with a particular
lighting on-off channel. When someone walks into the room, the light will be turned on, and turned off after a
configurable delay. The tool maintains a configuration database for the entire system, and downloads this configuration
to each system element.
Functional Description
The presence detector consists of a infra-red detector element, reflected light sensor and two volt-free switch inputs. The
KNX application has been designed to offer the installer a variety of useful functions such as movement detection,
constant brightness control, lighting scene recall via infra-red handset and simple transmission of input states. Three
ETS-configurable logic controllers allow the installer to fine-tune the behaviour of the detector in response to sensor
state, switch inputs and KNX group objects offering a level of control that would normally require an external logic block.
The various functions are grouped in ETS as follows:
General settings
Basic settings such as walk test LED enable/disable, sensor sensitivity, movement timeout and light sensor
calibration.
Basic movement detection
Raw switch output from the movement detector, suitable for signalling security systems etc.
Switch inputs
Defines the behaviour when each of the switch inputs change state, e.g. dimming, switching or scene recall.
Switch inputs may also be used as inputs to the three logic controllers.
Infra-red scene control
Defines which KNX scenes are mapped to the scene recall button on the UHS7 remote control, and how the on/
off buttons should behave.
Logic controller 1/2 (switch/scene)
Defines a custom logic function using simple drop-down boxes to send either switch or scene recall telegrams in
response to the state of various inputs, sensor state and KNX group objects.
Logic controller 3 (brightness)
Defines a custom logic function using simple drop-down boxes to determine a brightness target value that should
be maintained. The logic function may use various inputs, sensor state and KNX group objects to determine which
brightness target should be active.
For larger rooms, several Presence Detectors can be used to increase the coverage area. In this configuration, one presence
detector acts as the master, and all other detectors act as slaves. When movement is detected by any of the slave detectors, a
telegram is sent to the master via the KNX bus. The master detector uses this information as part of a logic expression to send
dimming, scene recall or brightness commands to the controlled device. The movement timeout period is defined on the
master device; slave devices simply need to send a telegram whenever movement is sensed.
