ElectronParade

Project 8: Build Your Own Desktop Weather Station

Is it hot in here, or is it just the soldering iron? Today, we’re building a highly practical project: a real-time digital desktop weather station. By combining an Arduino, a DHT11 temperature/humidity sensor, and a classic 16x2 LCD, you’ll have your own climate monitor.

Arduino Weather Station

How It Works

This project is a fantastic introduction to combining different modules:

Recommended Gear & Components

Here are the specific parts you need to bring this weather station to life. (Using these links supports the site!)

Wiring Guide

Wiring I2C and the DHT11 is delightfully simple. Make sure your Arduino is unplugged before you start wiring.

1. Wiring the 16x2 I2C LCD

The I2C backpack reduces the LCD wiring down to just four pins:

2. Wiring the DHT11 Sensor Module

Note: If you have a bare 4-pin DHT11 instead of a 3-pin module, you will need a 10k pull-up resistor between VCC and the Data pin. Most modules include this built-in.

The Code

To run this code, you’ll need to install two libraries in the Arduino IDE. Go to Sketch > Include Library > Manage Libraries… and search for:

  1. “DHT sensor library” by Adafruit (also install the Adafruit Unified Sensor library if prompted).
  2. “LiquidCrystal I2C” by Frank de Brabander.

Once installed, copy and paste this code into your Arduino IDE, hit verify, and upload!

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

// Define the pin the DHT11 data line is connected to
#define DHTPIN 2

// Define the type of DHT sensor
#define DHTTYPE DHT11

// Initialize the DHT sensor
DHT dht(DHTPIN, DHTTYPE);

// Initialize the LCD. 
// The I2C address is usually 0x27 for these 16x2 modules.
LiquidCrystal_I2C lcd(0x27, 16, 2); 

void setup() {
  // Start the serial monitor for debugging
  Serial.begin(9600);
  
  // Initialize the LCD and turn on the backlight
  lcd.init();
  lcd.backlight();
  
  // Initialize the DHT sensor
  dht.begin();
  
  // Print a welcome message
  lcd.setCursor(0, 0);
  lcd.print("Weather Station");
  lcd.setCursor(0, 1);
  lcd.print("Initializing...");
  delay(2000);
  lcd.clear();
}

void loop() {
  // Wait a few seconds between measurements.
  // The DHT11 is a slow sensor, so 2 seconds is perfect.
  delay(2000);

  // Read humidity as a percentage
  float h = dht.readHumidity();
  // Read temperature as Fahrenheit (isFahrenheit = true)
  float t = dht.readTemperature(true);

  // Check if any reads failed and exit early (to try again)
  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    lcd.setCursor(0, 0);
    lcd.print("Sensor Error!  ");
    return;
  }

  // Print the Temperature to the first row of the LCD
  lcd.setCursor(0, 0);
  lcd.print("Temp: ");
  lcd.print(t);
  lcd.print(" F   "); // Extra spaces to clear old artifacts

  // Print the Humidity to the second row of the LCD
  lcd.setCursor(0, 1);
  lcd.print("Hum:  ");
  lcd.print(h);
  lcd.print(" %   "); // Extra spaces to clear old artifacts
  
  // Optional: Print to Serial Monitor
  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print("%  Temperature: ");
  Serial.print(t);
  Serial.println("°F");
}

Troubleshooting

Enjoy your new desktop weather station! Try modifying the code to display Celsius instead, or add a buzzer that triggers an alarm if the room gets too hot.