occp sensor
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OCCUPANCY&
PHOTOSENSORS
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OCCUPANCY SENSORS
SWITCHING DEVICE
PRESENCE AND ABSENCE OF PEOPLE
IN THE SENSORS FIELD OF VIEW
MOTION DETECTOR + POWER SUPPLYUNIT + RELAY
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OPERATION
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Controller Functions
SENSITIVITY OF SENSOR TO MOTION
TIME DELAY
LUX CONTROL
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SENSOR SENSES MOTION
GIVES ELECTRONIC SIGNALS TO CONTROL UNIT
CONTROLLER DECIDES ABOUT OCCUPANCY STATUS
CONTROLLER ENERGISES / DE-ENERGISES RELAY
RELAY CONTACTS OPERATE LUMINAIRE
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TYPES OF SENSORS
ULTRASONIC
PASSIVE INFRA RED (PIR)
DUAL (ULTRASONIC + PIR)
ACOUSTIC
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PASSIVE INFRA RED (PIR)React to the infrared heat energy
emitted by people
Employ a Pyro-electric transducer
to detect infrared radiation whichconverts the IR energy into avoltage signal
They are called Passive devicesas they only detect radiation,they do not emit it
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A many faceted lens surrounds the transducer and focusesheat energy onto the detector.
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The lens views the area with a multitude of narrow and discrete beams or cones (does not
view the area in a continuous fashion)
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The detection pattern of PIR sensors isfan shaped, forming "fingers" of detection.
Each finger is a cone of heat detection"seen" by a segment of the detector'sfaceted lens.
There are gaps of coverage betweenadjacent fingers which widen with distance.
Since the sensor is most sensitive tomotion that moves from one sensing cone
to another, its sensitivity decreases withdistance as the gaps between sensing coneswiden
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DETECTION PATTERN
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They are strictly line-of-sight devices
They cannot "see" around corners and a
person will not be detected if there is anobstruction, such as a partition, betweenthe person and the detector
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PIR
PIR sensors are less susceptible to falseONs than ultrasonic sensors.
In addition they are better in
applications where it's desirable todetect occupancy in only a portion of aspace.
PIR detectors can be effective in spaceswith ceilings up to 20 ft or more
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Sensor coverage diagram
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ULTRASONIC
A quartz crystal emits ultrasonic wavesthroughout the space
The unit then senses the frequency of thereflected waves
If there is motion, the reflected wave'sfrequency will shift slightly
This change in the ultrasonic waves frequencyis detected as motion in the space
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A person, or any object in the room, reflectswaves emitted by the occupancy sensor.As a person moves in the space, the
frequency of the waves reflected off theperson changes. The occupancy sensordetects this change in frequency and reactsby switching on the lamps.
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ULTRASONIC
Operate at frequencies higher than thenormal human ear can detect to avoidpossible incompatibility with other devices(such as hearing aids)
Most modern ultrasonic sensors operate atfrequencies 32 kHz or higher
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ULTRASONIC
The ultrasonic sound waves cover theentire area in a continuous fashion.There areno blind spots or gaps in the coveragepattern. They can also detect movement
behind some barriers. For this reason,ultrasonic sensors may be more effectivein detecting occupancy than PIR-baseddetectors
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ULTRASONIC
Ultrasonic sensors are more sensitive to false ONsthan PIR detectors. A false ON occurs when anoccupancy detector switches on lighting when thespace is not occupied. False ONs are caused by
motion in adjacent spaces, by air turbulence nearair diffusers and open windows, and by hangingobjects in the space. Most ultrasonic sensors workbest in spaces with ceilings below 14 ft but there
are some that can detect a moving person from aheight of 30 ft or more.
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Special Features of
Occupancy SensorsManual ON mode
Automatic modeAuxiliary contacts
Annunciators and warning signals
Fail ON function
Masking labels
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Manual ON Mode
While most occupancy sensors are capable ofswitching lights on as well as off, it's oftendesirable to deactivate the automatic ONfeature so that the lights switch on only if theoccupant chooses it. This mode is also calledmanual ON/auto OFF.
Most modern sensors allow the occupant toturn lights off manually whether they remain inthe space or not
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Automatic Mode
Automatic mode turns lights on uponoccupancy and off upon vacancy.
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Auxiliary Contacts
An extra switch or set of contacts so
that more than one load can becontrolled by a single occupancy sensor.
An extra set of contacts can be used to
switch an HVAC load, an exhaust fan,or provide a contact closure to abuilding management system.
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Annunciators and Warning Signals
Detection status using an LED built into thesensor
Alarm shortly before extinguishing the lights.
{This reminds an occupant to move or wave
an arm to prevent the lights from beingswitched off }
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Annunciators and Warning Signals
This is useful for situations when theoccupant may remain unusually still for aperiod of time, or for applications where thesensor's sensitivity has been calibrated to
respond only to stronger movements.
This feature is particularly important forsensors that are operated in the manualON/automatic OFF mode if no grace period isincluded.
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Fail ON Function
Sensors with this feature keep the lights on ifthe sensor fails.
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Masking Labels
PIR occupancy sensors often have maskinglabels that allow the installer to fine-tune thecoverage range of the sensors in
applications where extraneous motioncauses a sensor to false trigger ON.
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Masking LabelsFor example, if an open door leads to a hallway
within the sensor's line of sight, a masking labelcould be used to deaden the sensor's response inthe direction of the doorway.
A preferable method is to accomplish this
electronically by reducing the sensitivity,automatically, when a room is vacated so thatmotion in the hallway will not be detected.
When a person steps across the threshold, thelights are turned on and the sensitivity isautomatically increased to its original setting.
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PHOTOSENSOR
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The photo-sensor automatically measures thelight level within or entering the controlled
building space.
The photo-sensor generates an electric signalbased on a sampling of the light in the space.The particular geometry of the photocell and itshousing determines the sensitivity of the cell to
light from different directions.
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Controller
The control unit translates the photo-sensor
signal into a command to the dimming orswitching control unit. The design of its controlalgorithm, dead bands and delays determineits responsiveness to varying lighting
conditions.
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Photo-sensor Types
Photodiode Type:
produces a voltage that is directly
proportional to the detected light
Photoconductive Type:
produces a voltage that is inverselyproportional to the detected light in a
roughly exponential relationship
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PhotoconductiveType:
Photoconductive sensors are lessexpensive than photodiodes, they arevery non-linear in response andtherefore much less accurate .
Because of their limitations,photoconductive sensors are usedprimarily in controlling nighttime outdoorlighting and indoor switching applicationsthat do not require precise light level
control
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Photodiode Type:Photodiode controls should be used inswitching and dimming applications wheremore precise light level control is important.
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Lighting When You Need
Presence Detected Insufficient
Daylight Lights ON
Presence detected sufficient
Daylight Light RegulatedAbsence Detected Lights Off
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THANK YOU
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