PIR Sensor Circuit And Module Working

A sensor is used to detect the changes in quantities or events and generate the respective output signals such as an electrical signal output or optical signal output. The sensors are classified into various types, but, primarily the sensors can be categorized into analog sensors and digital sensors.

The various types of sensors include temperature sensors, pressure sensors, gas sensors, fire sensors, pyroelectric sensors, piezoelectric sensors, IR sensors, PIR sensors, and so on. Here, in this article we specially discuss about PIR sensor – circuit – module and its working.

PIR Sensor

The electronic sensor used to detect the movement of human being within a certain range of the sensor is called as PIR sensor or passive infrared sensor (approximately have an average value of 10m, but 5m to 12m is the actual detection range of the sensor). Fundamentally, pyroelectric sensors that detect the levels of infrared radiation are used to make PIR sensors. There are different types of sensor and here let us discuss about PIR sensor with dome shaped Fresnel lens.

The PIR sensor circuit is used in numerous electronics projects which are used to discover a human being entering or leaving the particular area or room. These passive infrared sensors are flat control, consists of a wide range of lens, and PIR sensors can be easily interfaced with electronics circuits.

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.

PIR Sensor Circuit

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.

PIR Sensor Working

Whenever, human being (even a warm body or object with some temperature) passes through the field of view of PIR sensor, then it detects the infrared radiation emitted by a hot body motion. Thus, the infrared radiation detected by the sensor generates an electrical signal that can be used to activate an alert system or buzzer or alarm sound.

The PIR sensor internally is split into two halves, one half is positive and the other is considered as negative. Thus, one half generates one signal by detecting the motion of a hot body and other half generates another signal. The difference between these two signals is generated as output signal. Primarily, this sensor consists of Fresnel lens which are bifurcated to detect the infrared radiation produced by the motion of hot body over a wide range or specific area.

If once the sensor gets warmed up, then the output remains low until it detects motion. If once it detects the motion, then the output goes high for a couple of seconds and then returns to a normal state or low. This sensor requires settling time, which is characteristically in the range of 10 to 60 seconds.

Practical Applications of PIR Sensor

PIR sensors have numerous applications in different fields such as automatic switching operation of outdoor lights, lift lobby, common staircases, automatic switching operation of garden lights based on the presence of a human being, for covered parking area, automatic door operating system in shopping malls, and so on. Let us discuss about a few innovative electronics projects designed using a PIR sensor circuit.

PIR Sensor based Automatic Door Opening System

The automatic door opening system is an innovative electronic project that is designed using PIR sensor. If any human passes through the door, then the sensor generates output pulses. These pulses are sent to the microcontroller which is used to control the operation of motor driver. This motor driver is controlled by microcontroller by giving appropriate pulses to the input and enable pins.

Thus, the motor driver controls the motor interfaced to it and fixed to the door. Hence, if the circuit detects any human passing in its region will enable the motor to operate the door automatically.

PIR Sensor based Security Alarm System

This project is intended to use in the places such as banks and other security intended places. This circuit is interfaced with the alarm system that includes IC UM3561. The UM3561 is an integrated circuit that takes digital input and generates multi tones such as an ambulance or fire engine or police sirens. Thus, if a human being is detected by the PIR sensor circuit, then the digital output is generated by it. This digital output is fed to the IC UM3561 that generates the siren or alarm.

Do you know any other real time applications of PIR sensor? Then, post your answers in the comments section below and help the other readers to improve their knowledge.