Smart Corridor Light System: Arduino & PIR Sensor

 1. Introduction

Energy conservation is a key part of modern smart homes. In this project, we build a Smart Corridor Light System that automatically turns on when it detects human motion and turns off after a set delay. This is perfect for hallways, staircases, or bathrooms, ensuring lights are never left on accidentally.

2. Components

• Arduino Uno or Nano

• PIR Motion Sensor (HC-SR501)

• 5V Relay Module (to control AC lights)

• LDR (Photoresistor) – Optional, to ensure lights only turn on at night

• LED (Status Indicator)

• 10kΩ Resistor

• Jumper Wires and Breadboard

3. Circuit and Connections

Pinout Diagram of Arduino Uno R3

Pinout Diagram of PIR Motion Sensor

Pinout Diagram of Single Channel Relay Module

LDR Diagram

• PIR Sensor: VCC → 5V, GND → GND, OUT → Digital Pin 2

• Relay Module: VCC → 5V, GND → GND, IN → Digital Pin 8

• LDR (Optional): One side → 5V, Other side → Analog Pin A0 (with 10k resistor to GND)

• Status LED: Anode → 220Ω Resistor → Digital Pin 13, Cathode → GND

4. Detailed Step-by-Step Circuit Working

1. Motion Detection: The PIR sensor detects infrared radiation from human body heat. When someone walks by, the OUT pin goes HIGH.

2. Light Sensing (Logic): If you include the LDR, the Arduino checks the light level. If it's already bright (daytime), it ignores the PIR signal to save even more power.

3. Switching: The Arduino sends a signal to the Relay (Pin 8).

4. AC Control: The Relay acts as a heavy-duty switch, connecting the live wire of your home bulb to the power source.

5. Timer: The Arduino keeps the relay active for a specific duration (e.g., 30 seconds) before turning it off.

5. Libraries to be included

This project uses standard Digital and Analog I/O. No external libraries are required, making the system extremely reliable.

6. Code

C++

const int pirPin = 2;
const int relayPin = 8;
const int ldrPin = A0;
const int lightThreshold = 400; // Adjust for your room's darkness

void setup() {
  pinMode(pirPin, INPUT);
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, HIGH); // Relay Off (Active Low)
  Serial.begin(9600);
}

void loop() {
  int motion = digitalRead(pirPin);
  int lightLevel = analogRead(ldrPin);

  if (motion == HIGH && lightLevel < lightThreshold) {
    Serial.println("Motion Detected at Night! Turning on Light.");
    digitalWrite(relayPin, LOW); // Turn Light ON
    delay(30000);                // Keep on for 30 seconds
    digitalWrite(relayPin, HIGH); // Turn Light OFF
  }
}

7. Detailed Step-by-Step Code Working

1. digitalRead(pirPin): Constantly monitors for high signals from the motion sensor.

2. Dual Condition (&&): The code only triggers the relay if both motion is detected AND the room is dark.

3. Active Low Relay: Most 5V relays turn ON when the pin is LOW, so we set it to HIGH in the setup to keep the light off initially.

4. Non-Blocking Delay: While delay(30000) works for a simple setup, you can mention "Millis()" in your tips for more advanced users.

8. Tips

• Sensitivity Adjustment: Use the orange potentiometers on the PIR sensor to adjust the "Delay Time" and "Distance."

• Safety First: Always remind readers to be extremely careful when working with AC High Voltage (230V). Suggest using a DC lamp for testing first.

• LDR Placement: Ensure the LDR is not directly under the bulb it controls, or it will create a "flicker loop."

9. Uses

• Smart Homes: Automatic lighting for corridors and porches.

• Security: Use it as a motion-activated floodlight for your garage.

• Energy Saving: Ideal for office cabins or public restrooms.

10. Conclusion

The Smart Corridor Light System is a perfect entry-point into home automation. It combines environmental sensing with power electronics to create a project that is both useful and environmentally friendly.

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