PIR Sensor SR501

# Features

* Wide operating voltage range: 4.5–20V
* Digital output compatible with 3.3V and 5V systems
* Adjustable sensitivity and delay time via onboard potentiometers
* Low power consumption and high reliability for indoor use

# Technical Specifications

* Operating voltage: 4.5V – 20V (5V recommended for stable operation)
* Output: Digital HIGH/LOW (≈3.3V HIGH)
* Detection angle: \~120° horizontal
* Detection distance: \~3 to 7 meters (adjustable)
* Delay time: Adjustable from 3s to \~300s
* Initialization time: 30–60 seconds after power-up
* Operating temperature: \~ -15°C to +70°C

# Pinout

* **VCC** → 5V supply
* **GND** → Ground
* **OUT** → Digital input pin of microcontroller (HIGH when motion is detected, LOW when idle)

> Some versions include a jumper to set trigger mode:
>
> * **H (retriggerable):** Output stays HIGH as long as motion continues
> * **L (non-retriggerable):** Output remains HIGH only for the set delay, even if motion continues

# Adjustments

* **TIME** knob: Controls how long the output stays HIGH after detection
* **SENS** knob: Adjusts detection range (distance)
* Best placed at human eye level and away from direct heat sources for accurate detection

# Common Applications

Security alarms, automatic lighting, people counters, smart homes, and DIY projects with Arduino, ESP32, or Raspberry Pi.

# Usage Tips

* Allow about 1 minute after powering on for stabilization
* Use a stable 5V power supply with a common ground between the sensor and the controller
* In software, apply filtering or debounce logic to reduce false triggers