Automatic or semi-automatic operation
The presence sensors can be configured for automatic or semi-automatic operation:
• in automatic operation the lighting is switched on and off according to the presence or
absence of movement in the detection fi eld and/or according to the level of daylight
measured in the room;
• in semi-automatic operation, the lighting is automatically switched off in the absence
of movement and/or in the event of suffi cient daylight; it is always switched on
manually by means of a bus button, an App on a smartphone or a voice command.
With this mode of operation it is possible to achieve greater energy savings than with
automatic operation.
In some applications the stand-by function is useful; when no movement is detected for a
fixed period of time (corresponding to the stand-by time), the lighting can be adjusted to
a lower intensity level; if no further movement is detected, the lighting is automatically
switched off, once the stand-by time has expired.
Detection field
The shape of the detection field of presence sensors is typically 180° (semi-circular)
or 360° (circular); the former is characteristic of wall-mounted sensors, the latter of
ceiling-mounted sensors. The detection capability and accuracy of a presence sensor is
influenced by several factors:
• the amplitude and speed of movement;
• the temperature difference between the person and the environment;
• the direction of movement (tangential or radial to the detection area);
• the distance of the sensor from the moving person.
The size of the detection area is determined by two values in the technical documentation
of the devices: the smaller value refers to the central area where even small movements
are sufficient for detection, the larger value refers to the larger area where larger
movements are necessary. The detection area of a presence sensor can however be
extended by configuring a presence sensor as a ‘master’ device and one or more sensors
of the same type as ‘slave’ devices.
Master
Slave
Slave
Slave
Extended zone:
motion
detection
360°
Central zone:
presence
detection
Tangential direction:
high sensitivity due
to the crossing of several
detection sectors
Large movements
Little movements
Mounting height
Radial direction:
lower sensitivity
for crossing fewer
detection sectors
Constant brightness control
A brightness sensor integrated in the luminaires enables constant brightness control in
combination with luminaires equipped with dimmable sources.
Switch-off delay
The switch-off delay is set during the sensor configuration phase and is the time interval
between the last movement detected (or the achievement of a pre-set daylight threshold)
and the actual switch-off of the lighting. Values between 10 seconds and 20 minutes
are quite frequent; however, this parameter depends not only on the application to be
implemented and the intended use of the environment, but also on the available light
sources. Just think of the case of those corridors of office buildings crossed with such a
frequency that presence sensors configured with a delay of 15 minutes never turn off the
lights throughout the day; in the case of fluorescent sources a delay time of less than 15
minutes is generally not used because of both the long on time and the shortening of the
useful life, while in the case of LED sources a delay of a couple of minutes can be achieved
without problems.
As an example of how:
• passages with low crossing frequency, such as corridors in basements or cloakrooms:
5 to 15 minutes;
• passages with a high frequency of crossings, such as main corridors, stairwells or lift
landings: 1 to 2 minutes. Here the light source is decisive: delay times of 1 minute only
make sense in combination with LED technology;
• main rooms, such as offi ces or classrooms: 5 minutes (with LED lamps) to 15 minutes
(with fluorescent lamps)
Automatic control in standards
Appendix K of UNI CEN/TR 15193-2 defines automatic lighting controls activated by
sensors that react to occupancy (presence and movement) and light level. With regard
to occupancy, a distinction is made between absence detection and presence detection
which correspond to different ways of configuring presence sensors, as shown in the table
below.
Daylight harvesting and constant illuminance control
A distinction is made between two requirements for light level control: daylight harvesting
and constant illuminance. A prerequisite for both is adjustable luminaires. In the first
case, the required illumination is provided totally or partially by daylight during most of
the occupancy period and artificial lighting has a simple daylight supplementing role. The
estimated energy saving compared to purely manual control is around 60%. In the second
case, the artificial lighting adjusts the luminous flux to maintain the required illuminance
in order to compensate for performance degradation over time. This type of control offers
energy savings of around 15% compared to purely manual control.
Ekinex combined sensors, capable of detecting both presence and light level, can combine
the different control conditions required by the standard and provide savings of up to 75%
compared to purely manual control.
Multifunctional use of sensors
The availability of several independent lighting control channels is particularly useful for
rooms with multiple luminaires with different functions, e.g. basic/orientation lighting and
main/accent lighting.
In building automation, however, it is frequently necessary to control several technical
systems - in addition to lighting alone - in the same rooms or areas. A typical example
is heating, cooling and ventilation functions: to take into account the particularities of
controlling these systems, which differ from lighting, presence sensors usually offer one
or more channels specifically dedicated to the automatic control of HVAC functions. In
addition, an alarm channel can activate or deactivate a load or a group of loads according
to the number of movements (trigger events) detected in a certain time interval.
In this way, a single presence sensor can be used multifunctionally for lighting, HVAC
and alarm signalling with advantages in terms of convenience, ease of connection and
aesthetics, thanks to the installation of just one device in the room.
Normative references
UNI EN 15193-1 Energy performance of buildings - Energy requirements for lighting -
Part 1: Specifications, module M9
UNI CEN/TR 15193-2 Energy performance of buildings - Energy requirements for
lighting - Part 2: Explanation and justification of EN 15193-1, module M9
Automatic control according to occupancy
(source: UNI CEN/TR 15193-2)
Sensors of
Ekinex presence
Technique of
detection
Switching
On
Switching
Off
Estimated savings
(compared to
manual control)
Mode of
Absence
detection
Manual
Automatic
approx. 35%
Semi-automatic
Presence
detection
Automatic
Automatic
approx. 30%
Automatic
SMART LIGHTING
SMART LIGHTING
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