The science of light about sensors

1. 727 L K - The Science of Light
Sensor technology for lighting systems
Jose A. Fonseca

2. 1. Automatic control
2. Systems on/off
3. Flow regulating systems.
4. Lighting Management
Systems.
5. Planning the Layout
6. Specifying Occupancy Sensors

3. 1. Automatic control
To eliminate energy waste, most energy codes require
some way to automatically shut off lights when not in
use, either based on a schedule or occupancy.
Many buildings require both strategies to achieve code
compliance economically and to achieve the best results
with automatic shutoff.
These allow the optimization of lighting installations, re-
sulting in significant energy savings, subject to the levels
of visual comfort needed at each location.
Control systems for regulating the luminous flux
more expensive;
more efficient;
security.

4. 2. Systems on/off
Timers.
Control of lighting circuits in a predetermined schedule.
Analog or digital time switch (more expensive but allow
saving the program in memory, with one or more chan-
nels, allowing more than one control circuit).
analog timer digital timer

5. Twilight Switch
Allow control of lighting circuits from a given level of
illuminance measured with a photodetector.
Allow you to make use of natural light and should be used
in conjunction with timers in situations where the work
schedule does not coincide with the hours that the lighting
is sufficient. This application is indicated for exteriors.
BBS universal twilight switch ARGUS light-sensitive switch timer. Combines
in combination with light-sensor. a light-sensitive switch and a timer.

6. 3. Flow regulating systems. Occupancy sensors
Examples of appropriate applications include offices, class-
rooms, copy rooms, restrooms, storage areas, conference
rooms, warehouses, break rooms, corridors.
Occupancy sensors are motion detectors.
A motion detector is an electronic device that detects the
physical movement in a given area and transforms mo-
tion into an electric signal.
These sensors turn on lighting in environments
occupied and after a pre-set duration turn off lighting in
unoccupied environments.
Technologies:
• Passive InfraRed (PIR).
• Ultrasonic.
• Dual-technology.
• Radar-based.
• Daylight sensors.

7. Passive Infrared Motion Detector
PIR respond to the infrared heat energy emitted by people.
Passive means they detect radiation, do not emit it.
The sensor is able to recognize a thermal infrared image
(created by infrared technology combined with a heat
sensor).
Sensitive to objects that emit 10
micrometers radiation wave-
length around the same value as
the wavelength of heat emitted
by the human body.
Dual PIR Sensor Coverage Area

8. Single PIR Sensor Coverage Area
Sensitivity decreases with re-
moteness; movement of hands is
sensed at 3.5 meters, the move-
ment of the arm and torso to 7
meters and movement of the
body up to 14 meters.
Directly replaces the wall or
ceiling switch and are most suit-
able for small environments.
Issues that might complicate
their application:
low levels of motion by
occupants, obstacles blocking
the sensor’s view;
sensors mounted on sources of
vibration or within 6-8 feet of
air diffusers.

9. Ultrasonic Sensor
Activates a quartz crystal which emits utltra-sonic waves
at frequencies above the limits of human perception (25
to 45kHz), by means of space, to detect the presence of
occupants.
This high frequency signal is compared with the frequency
of the reflected signal (Doppler effect) and any difference
is interpreted as the presence of someone within coverage.

10. Ultrasonic sensors, meanwhile, are highly suitable for
spaces in which a line of sight is not possible, such as par-
titioned spaces, restrooms, open offices, enclosed hallways
and stairways.
Issues that might complicate their application include:
ceilings higher than 14 feet; high levels of vibration or air
flow, open spaces that require selective coverage, such as
control of individual warehouse aisles.
Experts in the field of optics have developed different
designs or patterns, each of which is protected by
its own patent, to provide different coverage capabilities.

11. Dual-Technology Sensors
Sensor that uses both technologies, infrared and ultrasound.
In this case, the lighting system is activated only when
both detect the presence of people, which increases system
reliability by preventing the lighting system to light up
unnecessarily.
Because of higher cost, applications are indicated for
environments where you need a high degree of detection,
such as in classrooms and conference rooms.

12. Radar based
Continuous Wave (CW) motion detectors use microwave
signals to emit frequencies to bounce off of the surround-
ing area (which is why they are sometimes referred to as
“microwave motion detectors”)
.
Microwave sensors, which work much like ultrasound
with detection of noise, they emit receive and compare
frequency changes (when intruder passes field of sensor).
CW motion detectors are gen-
erally more expensive than
PIR motion detectors. This
is because they are highly
sensitive, and are very
reliable over longer distances.
Suitable for industrial
environments.

13. Daylight sensors and flow regulators “dimming”
Levels from natural lighting luminance are detected by
a photocell that adjusts and controls the flow of artificial
light depending on this level so as to have luminance lev-
el desired.
The artificial lighting is switched off continuously as nat-
ural light levels increase. This procedure avoids the prob-
lems of the system on/off.
Adjustment to 1% of artificial Adjustment to 100% of arti-
illumination levels. ficial illumination levels.

14. 5. Lighting Management Systems
Systems such as DALI (Digital Addressable Lighting
Interface) and EIB (European Installation Bus)
Allow combination of technologies:
• Adjusting the lighting for the amount of natural light
• Control sensors and scheduling of movement with
advantage of the user choosing the control method.
• Possibility of creating and memorizing scenarios,
ie, possibility to adapt the lighting to local conduct.
This technology can be used in large office buildings such
as schools, hospitals, commercial buildings but also in in-
dustrial and residential buildings.

15. Advantages:
• Flexible solutions system;
• Rapid amortization of investment;
• Variety of Settings;
• Energy management, maintenance of light sources;
• integration of the lighting system;
• Expandability;
• Attractive design;
Disadvantages:
• High initial investment;
• Separation of the power circuit and command, more
connections, more cabling.

16. 5. Planning the Layout
Proper sensor location minimizes the possibility of nuisance
switching and ensures lights will turn on when a person
enters the space and the sensor will maintain an unob-
structed line of sight to task areas at all times.
Specify the orientation of the sensor. Sensors should
point toward the area of greatest activity in the space.
Must also determine whether to install the sensor at the
wall switch, wall, corner, ceiling or task.

17. Ceiling-mounted sensors are appropriate for large areas
featuring obstacles, such as partitions, as well as narrow
spaces, such as corridors and warehouse aisles. Sensors
mounted high on a wall and at corners are appropriate
for covering large areas that feature obstacles.
Wall-switch or wall-box sensors are relatively inexpensive
and easy to install, and they are appropriate for smaller,
enclosed spaces, such as private offices with clear lines of
sight between the sensor and the task area. Workstation
sensors are appropriate for individual cubicles.
Multi Lens for coverage of up to360º

18. 6. Specifying Occupancy Sensors
• line-voltage operation without a power pack, in enclosed
spaces or where junction boxes are of difficult access.
• self-calibrating sensors adapt to space-use patterns
• manual-on operation for greater energy savings
• power packs with two relays for bi-level switching
• an integral photosensor to keep lights off if it detects
sufficient daylight
• a combination dimmer-
occupancy sensor
• isolated relay for inter-
facing with other loads,
such as HVAC
• digital-network connec-
tivity
• small sensors available
as part of the light fixture.