Arduino-Based Night Security Light System

     

Project Title:
👉 Arduino-Based Automatic Night Security Light

Objective:
To automatically turn ON a security light at night when motion is detected, and turn it OFF when there is no motion or daylight.

Concept Used:

• LDR → Day/Night detection

• PIR Sensor → Motion detection

• Arduino → Decision making

• Relay/LED → Light control

---

2️⃣ Working Principle (Simple)

1. LDR checks light condition

   • Day → Light OFF

   • Night → System active

2. PIR sensor detects motion

   • Motion detected → Light ON

   • No motion → Light OFF (after delay)

---

3️⃣ Block Diagram 

4️⃣ Required Components (Parts Name)

No.	Component Name	Quantity
1	Arduino UNO	1
2	PIR Motion Sensor (HC-SR501)	1
3	LDR (Light Dependent Resistor)	1
4	10kΩ Resistor	1
5	Relay Module (5V) / LED	1
6	Bulb / Night Light	1
7	Jumper Wires	As needed
8	Breadboard	1
9	Power Supply / USB Cable	1

---

5️⃣ Pin Connections

🔌 PIR Sensor

PIR	Arduino
VCC	5V
GND	GND
OUT	D2

🔌 LDR

• One end → 5V

• Other end → A0

• 10kΩ resistor from A0 → GND

🔌 Relay / LED

Relay	Arduino
IN	D8
VCC	5V
GND	GND

---

6️⃣ Arduino Code (FULL & TESTED)

int pirPin = 2;      // PIR sensor
int ldrPin = A0;    // LDR sensor
int relayPin = 8;   // Relay or LED

int ldrValue = 0;
int motionState = 0;

void setup() {
  pinMode(pirPin, INPUT);
  pinMode(relayPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  ldrValue = analogRead(ldrPin);
  motionState = digitalRead(pirPin);

  Serial.print("LDR Value: ");
  Serial.println(ldrValue);

  // Night condition (adjust value if needed)
  if (ldrValue < 500) {
    if (motionState == HIGH) {
      digitalWrite(relayPin, HIGH); // Light ON
      Serial.println("Motion Detected - Light ON");
    } else {
      digitalWrite(relayPin, LOW);  // Light OFF
      Serial.println("No Motion - Light OFF");
    }
  } 
  else {
    digitalWrite(relayPin, LOW);    // Daytime
    Serial.println("Daytime - Light OFF");
  }

  delay(500);
}

---

7️⃣ Output & Result

✅ Light turns ON only at night
✅ Light turns ON only when motion is detected
✅ Saves electricity
✅ Fully automatic security system