PIR Sensor -Few details
What is a PIR Sensor?
sensor that measures infrared light radiating from objects. PIR sensors mostly used in PIR-based motion detectors. Also, it used in security alarms and automatic lighting applications. The below image shows a typical pin configuration of the PIR sensor, which is quite simple to understand the pinouts. The PIR sensor consist of 3 pins
·Pin1 corresponds to the drain terminal of the device, which connected to the positive supply 5V DC.
·Pin2 corresponds to the source terminal of the device, which connects to the ground terminal via a 100K or 47K resistor. The Pin2 is the output pin of the sensor. The pin 2 of the sensor carries the detected IR signal to an amplifier from the
·Pin3 of the sensor connected to the ground
What does a PIR Sensor detect?
Generally,PIR SENSOR can detect animal/human movement in a requirement range. PIR is made of a pyroelectric sensor, which can detect different levels of infrared radiation.The detector itself does not emit any energy but passively receives it.
It detects infrared radiation from the environment. Once there is infrared radiation from the human body particle with temperature, focusing on the optical system causes the pyroelectric device to generate a sudden electrical signal.
Simply, when a human body or any animal passes by, then it intercepts the first slot of the PIR sensor. This causes a positive differential change between the two bisects. When a human body leaves the sensing area, the sensor generates a negative differential change between the two bisects.
What is the Range of PIR Sensor?
·Indoor passive infrared: Detection distances range from 25 cm to 20 m.
·Indoor curtain type: The detection distance ranges from 25 cm to 20 m.
·Outdoor passive infrared: The detection distance ranges from 10 meters to 150 meters.
·Outdoor passive infrared curtain detector: distance from 10 meters to 150 meters.
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Benefits or advantages of PIR sensor
Following are the benefits oradvantages of PIR sensor:
➨Detects motion reliably in indoors as well as in day or dark.
➨It consumes less energy (0.8W to 1.0W) compare to microwave sensor.
➨They are cheaper compare to microwave sensors.
➨They are good for electrical applications used in smaller and compact premises.
Drawbacks or disadvantages of PIR sensor
vFollowing are the drawbacks ordisadvantages of PIR sensor:
➨They have lower sensitivity and less coverage compare to microwave sensors.
➨It does not operate greater than 35 degree C.
➨It works effectively in LOS (Line of Sight) and will have problems in the corner regions.
➨It is insensitive to very slow motion of the objects.
➨Since PIR sensors sense heat signatures in room, they are not very sensitive if the room itself is warm. Hence PIR sensors are not able to detect human beings in the summer in some countries like INDIA.
➨Snoozing is another problem with PIR sensors. PIR sensors may turn off even if there is very little movement in occupied floors.
➨Thieves may find it easy to fool PIR detection range as they have slotted detection zone and not continuous one like microwave sensor
