📖 Lesson 3.3.1 – Automatic Light Control with Brightness Control

🎯 Learning Objectives

After completing this lesson, students will be able to:

✅ Control LED brightness automatically

✅ Use PWM (Pulse Width Modulation)

✅ Convert LDR readings into brightness values

✅ Use the map() function

✅ Combine digitalWrite() and analogWrite()

✅ Create a smart dimming light system

1. Introduction

In Lesson 3.3, the LED was either:

ON
or
OFF

However, real smart lighting systems do not work this way.

Instead:

Very Bright Environment
        ↓
LED OFF

Moderate Light
        ↓
LED Dim

Dark Environment
        ↓
LED Bright

Complete Darkness
        ↓
LED Maximum Brightness

This creates a smooth and intelligent lighting system.

2. PWM (Pulse Width Modulation)

PWM allows Arduino to control brightness.

Arduino UNO PWM Pins:

3
5
6
9
10
11

We will connect the LED to:

Pin 11

because Pin 11 supports PWM.

3. Components Required

4. Circuit Connections

LDR Module

LED

5. Working Logic

Read LDR Value
      ↓
Convert to Brightness
      ↓
Brightness < 10 ?
      ↓
YES
      ↓
LED OFF using digitalWrite()

NO
      ↓
Control Brightness using analogWrite()

6. Arduino Program

int ldrPin = A0;
int ledPin = 11;

int ldrValue;
int brightness;

void setup()
{
pinMode(ledPin, OUTPUT);

Serial.begin(9600);
}

void loop()
{
ldrValue = analogRead(ldrPin);

// Convert LDR reading into PWM brightness
brightness = map(ldrValue, 0, 1023, 255, 0);

if(brightness < 10)
{
digitalWrite(ledPin, LOW);
}
else
{
analogWrite(ledPin, brightness);
}

Serial.print("LDR = ");
Serial.print(ldrValue);

Serial.print(" Brightness = ");
Serial.println(brightness);

delay(100);
}

7. Code Explanation

Read LDR

ldrValue = analogRead(A0);

Reads light intensity from the sensor.

Convert Reading

brightness = map(ldrValue, 0, 1023, 255, 0);

Example:

Turn OFF LED Completely

if(brightness < 10)
{
  digitalWrite(ledPin, LOW);
}

If brightness becomes very small, the LED is switched OFF completely.

PWM Brightness Control

analogWrite(ledPin, brightness);

Controls LED intensity smoothly from:

0 → OFF
255 → Maximum Brightness

8. Testing

Test 1 – Mobile Flashlight

Expected:

LDR = 950
Brightness = 5

LED OFF

Test 2 – Room Light

Expected:

LDR = 650
Brightness = 90

LED Dim

Test 3 – Cover Sensor

Expected:

LDR = 120
Brightness = 225

LED Bright

9. Real-World Applications

• Smart Street Lights
• Automatic Garden Lights
• Smart Home Lighting
• Solar Street Lamps
• Warehouse Lighting Systems
• Parking Area Automation

📊 Summary

In this lesson we learned:

✅ PWM Brightness Control

✅ analogWrite()

✅ map() Function

✅ Combining digitalWrite() and analogWrite()

✅ Smart Dimming System

✅ Advanced Automatic Light Control