12
Logic controller 3 (brightness)
The brightness logic controller aims to maintain a uniform brightness in the sensor area at all times. Two brightness
targets can be defined, subject to a successful calibration (as detailed earlier). In similar fashion to the movement
controllers, a logic expression can be constructed to choose which brightness target the controller should try to achieve.
This would allow the lights to be turned off overnight, or for the lights to be made brighter when the room is occupied.
The controller sends an 8-bit absolute percentage value to the dimmer. The installer may choose suitable values for the
dimming increment and interval: these values should be chosen to minimise dimmer oscillation and response time. A
deadband setting prevents the controller from making unnecessary adjustments. It is also possible to set a brightness
target via a KNX group object, allowing the brightness target to be controlled from elsewhere. This might be useful in
combination with a room reservations system, or to make the lights dimmer at weekends.
Dimming telegrams are sent when required by the controller; the controller will not send dimming telegrams when the
measured light level is close to the target value, subject to the deadband setting.
Setting
Options
Description
Enable/disable logic controller 3
Disable
Enable
Enable or disable the logic controller function.
Logic conditions
Movement detected
Movement cleared
Group enable input set
Group enable input clear
Group slave input set
Group slave input clear
Switch 1 input closed
Switch 1 input opened
Switch 2 input closed
Switch 2 input opened
Logic conditions may be combined using logic terms
to form an expression, which is used to perform one
action when the expression is true, and another when
the expression is false.
Logic terms
AND
OR
THEN
Logic terms are used to define the function. The AND
term indicates that ALL inputs must be true for the
expression to be true, whereas the OR term will
return true if one of the inputs is true. The THEN term
is used to indicate that the expression is complete,
and that the next item is an action.
Logic actions
Set brightness target A
Set brightness target B
Set remote brightness target
Set 'on'
Set 'off'
When the logic expression is evaluated, an action
may be associated with both the if-then and else
portions of the expression, i.e. Set brightness target 1
if the expression is true, else Set brightness target 2.
Brightness target A
Floating point
Target value in lux for the brightness controller to aim
for.
Brightness target B
Floating point
Target value in lux for the brightness controller to aim
for.
Telegram interval
0 – 65,535 milliseconds
How often to send commands to the dimmer when
varying the brightness.
Dimming increment
100%
50%
25%
12.5%
6.25%
3.125%
1.5625%
The amount by which each subsequent dimming
telegram raises or lowers the light level. Typically a
small value will be used here, but will depend on the
environment. Large values may cause the dimmer to
oscillate between light and dark.
Dimming deadband
Floating point
Deadband value in lux within which the controller will
not attempt to vary the light output.
Group Object
Data Type
Description
Percentage output
5.4 DPT_Percent_U8
Brightness control for connected dimmer. The
constant brightness controller will increase or
decrease this value depending on the target selected.
Note that either the dimming or percentage group
objects can be used, but not both at the same time.
Enable input
1.1 DPT_Switch
Global enable/disable input for this channel, allowing
remote objects to potentially enable or disable this
detector. The input must be part of the logic function
to enable this functionality.
Slave trigger input
1.1 DPT_Switch
Slave input for this channel, allowing the state of other
detectors to be read as part of the logic function.
Target lux input
9.4 DPT_Value_Lux
Brightness target value set by an external device,
rather than an internal preset.
Target lux output
9.4 DPT_Value_Lux
Brightness target value selected by logic function, for
use by other devices.
