A sensor is used to identify changes in events or quantities and produce the appropriate output signals, such as an optical or electrical signal. Although there are many different kinds of sensors, two main categories exist: analog sensors and digital sensors. The different kinds of sensors include those that measure pressure, temperature, gas, fire, pyroelectric, piezoelectric, infrared, and PIR, among others. This article focuses specifically on the operation of the PIR sensor circuit module.
PIR Sensors(What is a PIR sensor?)
Passive infrared (PIR) sensors are electronic sensors that are used to detect human or any physical movement within a specific range. They have an average value of around 10 meters, but their real detection range is between 5 and 12 meters. PIR sensors function as pyroelectric sensors that measure infrared radiation levels. There are various kinds of sensors; here we'll talk about PIR sensors that have dome-shaped Fresnel lenses.
For many electronics applications, the PIR sensor circuit is utilized to detect whenever any person enters or exits a certain space. These passive infrared sensors have a broad range of lens options, have flat control, and are simple to integrate with electronic circuits.
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| Fig: Pin Configuration |
The figure displays the PIR sensor's pin layout. Three pins make up a PIR sensor: power, signal, and ground at the bottom or side. PIR sensors typically have a 5V maximum power output; however, large-sized PIR modules use a relay instead of a direct output. Connecting a sensor to a microcontroller is a pretty straightforward process. The PIR's output can be either high or low, and it is often digital.
Key Components of a PIR Sensor
Pyroelectric Sensor: The core component that detects infrared radiation.
Fresnel Lens: Focuses the infrared radiation onto the pyroelectric sensor.
Signal Processing Circuit: Amplifies and interprets the signal from the sensor.
Housing: Protects the internal components and sometimes includes an adjustable mounting arrangement.
PIR Sensor circuit
The power supply pin, the output signal pin, and the ground pin make up the three pins that make up the PIR sensor circuit. In addition to the filter window and ceramic substrate depicted in the picture, the PIR sensor circuit also features a dome-shaped component known as a Fresnel lens.
PIR Sensor Working Principle (pir sensor work?)
PIR sensors pick up infrared radiation from moving hot bodies whenever a human, or even a warm body or anything with some warmth, passes through their range of vision. Thus, the sensor's detection of infrared radiation produces an electrical signal that can be utilized to turn on an alarm, buzzer, or alert system.
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| Photo Courtesy: gl-e.uk |
How Does a PIR Sensor Work?
PIR sensors operate based on the principle of detecting changes in infrared radiation levels in their field of view. Here is a step-by-step breakdown:
Infrared Radiation Detection
Every object with a temperature above absolute zero emits infrared radiation. Human bodies, for example, emit IR radiation in the range of 8–14 micrometers.
The pyroelectric sensor within the PIR device is sensitive to this IR radiation.
Fresnel Lens Focus
The Fresnel lens segments the field of view into multiple zones, focusing the infrared radiation onto specific areas of the pyroelectric sensor.
This segmentation allows the sensor to detect changes in IR radiation as objects move between zones.
Signal Generation
When a warm object, like a human, moves through the sensor's detection area, the level of infrared radiation changes.
These changes create small voltage signals in the pyroelectric sensor.
Signal Processing
The signal processing circuit amplifies the voltage signals and filters out noise.
It then interprets the changes as motion if they match predefined patterns.
Output Trigger
Upon detecting motion, the PIR sensor outputs a signal, which can activate an external system, such as turning on a light or triggering an alarm.
PIR Motion sensor wiring diagram
Most PIR modules have a three-pin connection on the side or bottom. One pin will be ground, another will be signal, and the last will be power. Power is typically 3-5VDC input, but can be as high as 12V. Larger modules do not always have direct output and rather operate a relay, in which case there are ground, power, and two switch connections.
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| Motion sensor light/alarm circuit |
Advantages of PIR Sensors
Energy Efficiency: PIR sensors consume very little power, making them ideal for battery-operated devices.
Affordability: They are cost-effective and widely available.
Reliability: PIR sensors are highly reliable for detecting motion in a defined area.
Ease of Use: Simple to install and integrate into various systems.
PIR Sensor Applications
PIR sensors are widely used in many different fields, including covered parking areas, automatic door operating systems in shopping malls, automatic lighting control of outdoor lights, lift lobbies, common staircases, and garden lights based on human presence.
Security Systems: Motion detection for alarms and surveillance.
Lighting Automation: Automatic lights in homes, offices, and public spaces.
Consumer Electronics: Used in devices like automatic doors and smart home systems.
Industrial Automation: Detecting human presence in factories and warehouses.
Limitations of PIR Sensors
Limited Range: Typically effective within 10-20 feet.
Temperature Sensitivity: Performance can be affected by extreme temperatures.
Static Detection: Cannot detect stationary objects, only motion.
Conclusion
PIR sensors are an essential part of modern automation and security systems. Their ability to detect motion based on infrared radiation changes makes them versatile and effective for various applications. By understanding their working principle, you can make better decisions when choosing or deploying these sensors in your projects.
