PIR SENSOR

A PIR (Passive Infrared) sensor is a type of electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most commonly used in security alarms and automatic lighting systems.

**How PIR Sensors Work:**

1. **Detection Mechanism**: PIR sensors detect changes in the amount of infrared radiation hitting the sensor, which varies as warm bodies move in and out of the sensor’s range. Human bodies generate infrared heat, which is picked up by the sensor when there is movement.

2. **Components**: The main parts of a PIR sensor include two halves of a special material that is sensitive to IR. The sensor is designed so that the two halves are in a differential mode; this means that when one half sees more or less IR radiation than the other, the sensor is triggered.

3. **Field of View**: The sensor’s lens focuses the infrared rays from the environment onto the sensor elements. This lens also determines the sensor’s field of view, which is typically divided into zones and sectors. When a warm body passes from one sector to another, the sensor detects the change.

4. **Output**: When motion is detected, the PIR sensor typically outputs a digital signal (high/low) to a microcontroller or relay module, which can then trigger an alarm, activate lighting, or initiate other appropriate responses.

5. **Applications**: PIR sensors are widely used in various applications such as:
– **Security Systems**: For detecting movement in a protected area.
– **Automated Lighting**: Lights that turn on when someone enters a room and turn off when they leave.
– **Energy Conservation**: In devices that need to activate only in the presence of a person, thereby saving power when no one is present.

PIR sensors are popular due to their low cost, low power consumption, ease of use, and reliable detection of human presence. They are considered passive because they do not emit energy for detection purposes but merely detect infrared radiation emitted from objects in their field of view.