Arduino Temperature & Humidity Monitoring Project (DHT11)

1. Project Overview

This project measures ambient temperature (°C) and relative humidity (%) using a DHT11 sensor and displays the readings on the Arduino Serial Monitor.

Applications

• Weather monitoring
• Smart home automation
• Environment logging

IoT sensor nodes (entry-level)

3. Understanding the DHT11 Sensor

Key Specifications

• Temperature range: 0–50 °C
• Humidity range: 20–80 % RH
• Accuracy: ±2 °C, ±5 % RH
• Interface: Single-wire digital

DHT11 PiNS

• VCC → pin
• DATA → Digital I/O pin
• GND → Ground

If using a bare DHT11 (4 pins), a 10 kΩ pull-up resistor between VCC and DATA is required. Most modules already include it.

4. Circuit Connections

Arduino ↔ DHT11 Wiring

DHT11 Pin Arduino Pin

VCC 5V

DATA D2

GND GND

5. Installing Required Library

• Open Arduino IDE
• Go to Sketch → Include Library → Manage Libraries

Search and install:

• DHT sensor library by Adafruit
• Adafruit Unified Sensor

6. Arduino Code (Tested & Verified)

 #include <DHT.h>

#define DHTPIN 2        // Data pin connected to D2
#define DHTTYPE DHT11  // Sensor type

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  dht.begin();
  Serial.println("DHT11 Temperature & Humidity Test");
}

void loop() {
  delay(2000);  // DHT11 needs 2 seconds delay

  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature(); // Celsius

  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.print(" %  |  ");

  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");
}

7. Output (Serial Monitor)

Humidity: 56.00 %  |  Temperature: 28.00 °C
Humidity: 55.00 %  |  Temperature: 27.80 °C

Set baud rate to 9600 in the Serial Monitor.