727 L K - The Science of LightSensor technology for lighting systems

Jose A. Fonseca

1. Automatic control 2. Systems on/off

3. Flow regulating systems.

4. Lighting Management Systems.

5. Planning the Layout

6. Specifying Occupancy Sensors

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 fluxmore expensive;more efficient;security.

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

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 in combination with light-sensor.

ARGUS light-sensitive switch timer. Combines a light-sensitive switch and a timer.

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: •PassiveInfraRed(PIR). •Ultrasonic. •Dual-technology. •Radar-based. •Daylightsensors.

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.

Passive Infrared Motion Detector

PIRrespondtotheinfraredheatenergyemittedbypeople.Passivemeanstheydetectradiation,donotemitit.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

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 orceiling switch and are most suit-able for small environments.

Issues that might complicatetheir 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.

Single PIR Sensor Coverage Area

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 ofthereflectedsignal(Dopplereffect)andanydifferenceis interpreted as the presence of someone within coverage.

Ultrasonic sensors, meanwhile, are highly suitable forspaces 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.

Dual-Technology Sensors

Sensor that uses both technologies, infrared and ultrasound. Inthiscase,thelightingsystemisactivatedonlywhenboth 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.

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. Thisis because they are highly sensitive, and are very reliable over longer distances. Suitable for industrial environments.

Radar based

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 illumination levels.

Adjustment to 100% of arti-ficial illumination levels.

5. Lighting Management Systems

Systems such as DALI (Digital Addressable Lighting Interface)andEIB(EuropeanInstallationBus)

Allow combination of technologies: •Adjustingthelightingfortheamountofnaturallight

•Controlsensorsandschedulingofmovementwith 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.

Advantages: •Flexiblesolutionssystem; •Rapidamortizationofinvestment; •VarietyofSettings; •Energymanagement,maintenanceoflightsources; • integrationofthelightingsystem; •Expandability; •Attractivedesign;

Disadvantages: •Highinitialinvestment; •Separationofthepowercircuitandcommand,more connections, more cabling.

5. Planning the Layout

Propersensorlocationminimizesthepossibilityofnuisanceswitching 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.

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

6. Specifying Occupancy Sensors

• line-voltageoperationwithoutapowerpack,inenclosedspaces or where junction boxes are of difficult access.• self-calibratingsensorsadapttospace-usepatterns•manual-onoperationforgreaterenergysavings•powerpackswithtworelaysforbi-levelswitching•an integral photosensor to keep lights off if it detects sufficient daylight•acombinationdimmer-occupancy sensor• isolatedrelayforinter-facing with other loads, suchasHVAC•digital-networkconnec-tivity• smallsensorsavailableas part of the light fixture.