🔹 Step 1: Components Needed

• Arduino Uno (or Nano) – 1x
• DHT11 Temperature & Humidity Sensor – 1x
• 16×2 LCD with I2C module – 1x
• Jumper wires – some
• Breadboard – optional

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🔹 Step 2: Wiring Diagram (Connections)

DHT11 → Arduino

• VCC → 5V
• GND → GND
• Data → D2

I2C LCD → Arduino

• VCC → 5V
• GND → GND
• SDA → A4
• SCL → A5

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🔹 Step 3: Arduino Code

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <DHT.h>

#define DHTPIN 2       // DHT11 data pin connected to D2
#define DHTTYPE DHT11  // Using DHT11 sensor

DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 16, 2);  // LCD at I2C address 0x27

void setup() {
  lcd.init();        // Initialize LCD
  lcd.backlight();   // Turn on backlight
  dht.begin();       // Start DHT11 sensor
  lcd.setCursor(0,0);
  lcd.print("Temp & Humidity");
  delay(2000);
  lcd.clear();
}

void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  // Check if any reading failed
  if (isnan(h) || isnan(t)) {
    lcd.setCursor(0,0);
    lcd.print("Sensor Error!");
    return;
  }

  lcd.setCursor(0,0);
  lcd.print("Temp: ");
  lcd.print(t);
  lcd.print(" C");

  lcd.setCursor(0,1);
  lcd.print("Hum: ");
  lcd.print(h);
  lcd.print(" %");

  delay(2000); // Update every 2 seconds
}

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🔹 Step 4: How It Works

1. The DHT11 sensor reads temperature and humidity.
2. Data is sent to the Arduino UNO.
3. Arduino sends values to the LCD via I2C.
4. The display refreshes every 2 seconds, showing Temp (°C) and Humidity (%).

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🔹 Step 5: Next Upgrades (Optional)

• Add a buzzer if temperature exceeds a limit.
• Add an SD card module to log data.
• Send readings to a mobile app or cloud via ESP8266 WiFi module.