HC-SR501 auto-senses light for various applications (in house, basement, outdoor, warehouse, garage, etc,) for ventilator control, alarm, etc.

Features

• Automatic infrared detection (LHI778 probe design)
  Output goes high when objects enter the sensing range, and automatically returns to low when object leaves
• Optional photosensitive control
• Optional temperature compensation
• Trigger mode jumper
• L: Non-repeatable / delay mode: sensor goes low after the delay, regardless of the presence of the object.
• H: Repeatable: sensor stays high as long as any object is detected during the delay time.
• Wide operating voltage range
• Micro-amp power
• Output high signal: easy to achieve docking with the various types of circuit.

• Infrared technology (LHI778 probe design)
• High sensitivity | high reliability
• Widely used especially for battery-powered products 

Specifications

• Voltage 4.8 V – 20 V
• Current (idle)  <50 µA
• Logic output    3.3 V / 0 V
• Delay time  0.3 s – 200 s, custom up to 10 min
• Lock time   2.5 s (default)
• Trigger repeat : L = disable , H = enable
• Sensing range   <120 °, within 7 m

How to interface with an Arduino?

The HC-SR501 PIR (Passive Infrared) motion sensor is a popular, low-cost sensor used for motion detection. It is widely used in various security systems and motion-activated lighting. This tutorial will guide you through interfacing the HC-SR501 with an Arduino Uno to detect motion.

Components Required

• Arduino Uno

• HC-SR501 PIR Motion Sensor Module

• Jumper wires

• Breadboard

• LED (optional for visual feedback)

• Resistor (220 ohms, optional for LED)

Understanding the HC-SR501 PIR Motion Sensor

The HC-SR501 sensor detects motion by measuring changes in infrared radiation levels caused by the movement of objects. It has three pins:

1. VCC: Power supply (5V)

2. OUT: Output pin, which gives a HIGH signal when motion is detected

3. GND: Ground connection

Connecting the HC-SR501 to Arduino

Follow these steps to connect the PIR sensor to your Arduino:

1. Connect the VCC pin of the HC-SR501 to the 5V pin of the Arduino.
2. Connect the GND pin of the sensor to the GND pin of the Arduino.
3. Connect the OUT pin of the sensor to digital pin 2 on the Arduino.

Optionally, you can also connect an LED to pin 13 of the Arduino with a 220-ohm resistor for visual feedback when motion is detected.

Arduino Code

Below is the Arduino code to interface the HC-SR501 PIR Motion Sensor with the Arduino Uno. When motion is detected, the output pin will go HIGH, and the onboard LED connected to pin 13 will light up.

#define PIRPin 2 // PIR sensor connected to digital pin 2
int LEDPin = 13; // LED connected to digital pin 13

void setup() {
  pinMode(PIRPin, INPUT); // Set the PIR pin as input
  pinMode(LEDPin, OUTPUT); // Set the LED pin as output
  Serial.begin(9600); // Begin serial communication for debugging
}

void loop() {
  int motionState = digitalRead(PIRPin); // Read the state of the PIR sensor
  if (motionState == HIGH) { // If motion is detected
    digitalWrite(LEDPin, HIGH); // Turn on the LED
    Serial.println("Motion detected!");
  } else {
    digitalWrite(LEDPin, LOW); // Turn off the LED if no motion
  }
  delay(100); // Small delay for sensor stability
}

Conclusion

By following this guide, you have successfully interfaced the HC-SR501 PIR motion sensor with an Arduino Uno. This setup can be expanded to create more complex projects, such as alarms, automated lighting systems, or security systems. The sensor's sensitivity and delay time can also be adjusted using the two potentiometers on the module.