Virtual IoT Lab DEI

Instructions

Objective:

Learn how a photoresistor (LDR) detects light intensity and controls LED brightness automatically.

Steps to Perform:

Click "Start Simulation" to power up the Arduino circuit.
Click on the photoresistor (circular sensor) to activate it.
Use the slider to simulate different light levels (0-100).
Observe how the LED brightness changes based on light intensity.
Higher light values → Brighter LED glow.
Lower light values → Dimmer LED glow.

Key Concepts:

LDR: Light Dependent Resistor - resistance decreases with more light
Analog Read: Arduino reads voltage (0-1023) from the voltage divider
PWM: Pulse Width Modulation controls LED brightness (0-255)
Mapping: Converts sensor range (0-1023) to LED range (0-255)

Arduino Code - main.ino

            int sensorValue = 0;  // To store analog value from LDR

const int ldrPin = A0;   // LDR output to analog pin A0
const int ledPin = 9;    // LED connected to PWM pin 9

void setup() {
  pinMode(ldrPin, INPUT);   // LDR analog input
  pinMode(ledPin, OUTPUT);  // LED output
  Serial.begin(9600);       // Initialize serial monitor
}

void loop() {
  sensorValue = analogRead(ldrPin);  // Read LDR value (0–1023)
  Serial.println(sensorValue);       // Display light intensity

  int ledValue = map(sensorValue, 0, 1023, 0, 255);  // Map to brightness
  analogWrite(ledPin, ledValue);                     // Set LED brightness

  delay(100);  // Delay for stability
}
          