Aim:
To create a digital smart room in Tinkercad that can automatically turn ON/OFF lights and fan using sensors.

Requirements:

• Computer with Internet access

• Tinkercad Circuits

• Arduino Uno

• LED (represents room light)

• DC Fan

• LDR (Light Dependent Resistor) – senses brightness

• Temperature sensor (LM35 or TMP36) – senses heat

• Resistors and wires

Steps:

Step 1: Build the circuit

1. Open Tinkercad → Circuits → Create New Circuit.

2. Drag Arduino Uno and a breadboard.

3. Place an LDR on the breadboard. Connect:
   • One side to 5V with a resistor going to GND.

   • The junction point → A0 (Analog pin on Arduino).

4. Place the temperature sensor (LM35). Connect:
   • VCC → 5V

   • GND → GND

   • Output → A1.

5. Add an LED (room light) to pin 9 (with resistor).

6. Add a DC Fan to pin 10 using a transistor as a switch (just like in Lesson 4).

Step 2: Write the code

int ldr = A0;          // LDR sensor pin

int tempSensor = A1;   // Temperature sensor pin

int led = 9;           // LED pin

int fan = 10;          // Fan pin

void setup() {

  pinMode(led, OUTPUT);

  pinMode(fan, OUTPUT);

  Serial.begin(9600);

}

void loop() {

  // Read LDR value

  int lightValue = analogRead(ldr);

  // Read temperature

  int tempValue = analogRead(tempSensor);

  float voltage = tempValue * (5.0 / 1023.0);

  float temperature = voltage * 100;  // Convert to Celsius

  // Print values

  Serial.print(“Light: “);

  Serial.print(lightValue);

  Serial.print(” | Temp: “);

  Serial.println(temperature);

  // Smart Light Control

  if (lightValue < 500) {     // Dark condition

    digitalWrite(led, HIGH);  // Light ON

  } else {

    digitalWrite(led, LOW);   // Light OFF

  }

  // Smart Fan Control

  if (temperature > 30) {     // If hot

    digitalWrite(fan, HIGH);  // Fan ON

  } else {

    digitalWrite(fan, LOW);   // Fan OFF

  }

  delay(500);

}

Step 3: Run Simulation

• Start simulation and open Serial Monitor.

• Adjust the light slider to make the room dark or bright → the LED will turn ON/OFF.
  
• Adjust the temperature slider → the fan will automatically turn ON above 30°C.