PIR sensors detect infrared radiation emitted from warm objects like humans and animals. They contain a pyroelectric detector and lenses that focus infrared radiation onto the detector. When infrared radiation changes due to an object moving in its field of view, the detector outputs a signal. PIR sensors have three pins - power, ground, and an output pin that connects to a microcontroller. They are used to detect motion for applications like security lights, alarms, and more.

1. PIR SENSOR
(PASSIVE INFRARED SENSOR)

2.  PIR (passive infrared) sensors utilize the
detection of infrared that is radiated from all
objects that emit heat.
 This type of emission is not visible to the
human eye, but sensors that operate using
infrared wavelengths can detect such activity.
 They are sometimes referred to as ‘motion-
based detectors’, as they sense the presence
of people, animals and objects through the
movement of their infrared wavelengths.

3.  They are referred to as “passive” due to the
fact that no heat or energy is emitted by the
sensor itself.
 It is also important to remember that PIR
sensors detect the emission of infrared
radiation, and not heat.

4.  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.

6. PIN CONFIGURATION

7.  The pin configuration of the PIR sensor is shown in the
figure.
 PIR sensor consists of three pins, ground, signal, and
power at the side or bottom.
 Generally, the PIR sensor power is up to 5V, but, the large
size PIR modules operate a relay instead of direct output.
 It is very simple and easy to interface the sensor with a
microcontroller.
 The output of the PIR is (usually digital output) either low
or high.

8. CIRCUIT DIAGRAM

9.  The PIR sensor circuit consists of three pins, power
supply pin, output signal pin, and ground pin.
 The PIR sensor circuit is having ceramic substrate
and filter window as shown in the figure and also
having dome like structure called as Fresnel lens.

11. TYPICAL CONFIGURATIUON

12. • Typically , the FET source terminal pin 2 connects through a pulldown
resistor of about 100k to ground and feeds into a two stage amplifier having
signal conditioning circuits.
• The amplifier is typically BW limited below 10H to reject high frequency noise
and is followed by a window comparator that responds to both +VE & -VE
transitions of the sensor output signal.
• A well filtered power source of from 3 to 15 volts should be connected to the
FET drain terminal pin 1.

13. PYROELECTRIC

14.  A Pyroelectric sensor is very sensitive to rapid
temperature changes.
 A rapid change in air temperature due to a
breeze from an open window or from an air
conditioner or heater can cause false triggering.
 The shadow and pin hole lenses described above
do not offer protection against such air
movement because they are actually open lenses
 For outdoor use we need protection against rain.

15. WHAT PIR DOES

16.  PIR sensor can detect animal/human movement in a requirement range.
 PIR is made of a pyroelectric sensor, which is able to 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.

17.  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.

18.  The passive infrared sensor does not radiate energy to space.
 It receives the infrared radiation from the human body to make an
alarm.
 Any object with temperature is constantly radiating infrared rays to
the outside world.
 The surface temperature of the human body is between 36° C - 27 °
C (96 F - 80.6F)and most of its radiant energy concentrated in the
wavelength range of 8 μm-12 μm.

19.  Passive infrared alarms classified into infrared
detectors(infrared probes) and alarm control sections.
 The most widely used infrared detector is a pyroelectric
detector.
 It uses as a sensor for converting human infrared
radiation into electricity.
 If the human infrared radiation is directly irradiated on
the detector, it will, of course, cause a temperature
change to output a signal.

20.  But in doing all this, the detection distance will not
be more.
 In order to lengthen the detection distance of the
detector, an optical system must be added to
collect the infrared radiation.
 Usually, plastic optical reflection system or
plastic Fresnel lens used as a focusing system for
infrared radiation.

21.  In the detection area, the lens of the detector
receives the infrared radiation energy of the human
body through the clothing and focused on the
pyroelectric sensor.
 When the human body moves in this surveillance
mode, it enters a certain field of view in sequence
and then walks out of the field of view.
 The pyroelectric sensor sees the moving human
body for a while and then does not see it, so the
infrared radiation of human body constantly
changes the temperature of the pyroelectric
material.
 So that it outputs a corresponding signal, which is
the alarm signal.

22. PIR CONNECTED TO
ARDUINO

23.  A PIR sensor module has only 3 pins – one is Vcc which
is a +5 volts input, a ground pin and finally the digital
output pin.
 Connect +5V from Arduino to Vcc of PIR sensor module,
connect a GND from Arduino to ground of PIR sensor .
 finally connect the output pin (marked as 'out') to any
digital pin of Arduino.

24.  As like we can connect PIR sensor to
Raspberry Pi
Pic micro controller
AVR
8051

25.  Indoor passive infrared : 25 cm to 20 m.
 Indoor PI curtain type : 25 cm to 20 m.
 Outdoor PI : 10 m to 150 m.
 Outdoor PI curtain detector: 10 m to 150 m.

27.  All outdoor Lights
 Lift Lobby
 Multi Apartment Complexes
 Common staircases
 For Basement or Covered Parking Area
 Shopping Malls
 For garden lights