Building an ESP32 Weather Station

The ESP32 is a versatile microcontroller that’s perfect for IoT applications. In this tutorial, we’ll use it to build a weather station that displays the current weather conditions for a specific city using data from an online weather API. Additionally, we’ll incorporate a DHT11 temperature sensor to measure the room temperature.

Features

1. Display real-time weather information for a chosen city.
2. Measure and display the room temperature using a DHT11 sensor.
3. Use an OLED screen to show the data.

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What You Need

Hardware

• ESP32 microcontroller
• DHT11 temperature and humidity sensor
• SSD1306 OLED display (I2C)
• Jumper wires and breadboard

Software

• Arduino IDE (with the ESP32 board library installed)
• Adafruit_GFX and Adafruit_SSD1306 libraries
• ArduinoJson library

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Circuit Setup

1. Connecting the OLED Display

   • VCC to 3.3V on the ESP32
   • GND to GND
   • SCL to GPIO 22 (default I2C clock)
   • SDA to GPIO 21 (default I2C data)

2. Connecting the DHT11 Sensor

   • VCC to 3.3V
   • GND to GND
   • DATA to GPIO 4

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Code Explanation

Here’s the full Arduino code to run the weather station. Copy and paste it into the Arduino IDE.

#include <Wire.h>
#include <WiFi.h>
#include <HTTPClient.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <ArduinoJson.h>
#include "DHT.h"

// Wi-Fi credentials
const char* ssid = "wifi name";
const char* password = "wifi password";

// OLED setup (I2C)
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Weather API URL (use HTTPS)
const char* weather_url = "https://wttr.in/Dresden?format=j1";

// DHT11 setup
#define DHTPIN 4        // Pin connected to the DHT11 data pin
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(115200);

  // Initialize OLED
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED initialization failed!");
    while (true);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  // Initialize DHT sensor
  dht.begin();

  // Connect to Wi-Fi
  WiFi.begin(ssid, password);
  display.println("Connecting to Wi-Fi...");
  display.display();
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to Wi-Fi...");
  }
  display.clearDisplay();
  display.println("Wi-Fi Connected!");
  display.display();
  delay(2000);
}

void loop() {
  display.clearDisplay();
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    http.begin(weather_url); // Use HTTPS URL
    int httpCode = http.GET();

    Serial.print("HTTP Response Code: ");
    Serial.println(httpCode);

    if (httpCode == 200) { // HTTP OK
      String payload = http.getString();
      Serial.println("HTTP Response:");
      Serial.println(payload);

      // Parse JSON
      DynamicJsonDocument doc(4096); // Increase buffer size for large payloads
      DeserializationError error = deserializeJson(doc, payload);

      if (error) {
        Serial.print("JSON Parsing failed: ");
        Serial.println(error.c_str());
        display.clearDisplay();
        display.setCursor(0, 0);
        display.println("Error parsing");
        display.println("weather data!");
        display.display();
      } else {
        // Extract weather data
        String weather = doc["current_condition"][0]["weatherDesc"][0]["value"].as<String>();
        String temp = doc["current_condition"][0]["temp_C"].as<String>();

        // Truncate long weather descriptions
        if (weather.length() > 20) {
          weather = weather.substring(0, 20) + "...";
        }

        // Read room temperature
        float roomTemp = dht.readTemperature();
        if (isnan(roomTemp)) {
          Serial.println("Failed to read from DHT sensor!");
          roomTemp = -999; // Placeholder for failed reading
        }

        // Display weather and room data on OLED
        display.clearDisplay();
        display.setCursor(0, 0);
        display.println("Dresden Weather:");
        display.print("Temp: ");
        display.print(temp);
        display.println(" C");
        display.print("Condition: ");
        display.println(weather);
        display.println();
        display.println("Room:");
        display.print("Temp: ");
        if (roomTemp != -999) {
          display.print(roomTemp);
          display.println(" C");
        } else {
          display.println("Error");
        }
        display.display();
      }
    } else {
      // Print error
      Serial.print("HTTP Error: ");
      Serial.println(http.errorToString(httpCode).c_str());

      // Display error on OLED
      display.clearDisplay();
      display.setCursor(0, 0);
      display.println("Failed to fetch");
      display.println("weather data.");
      display.println("Error:");
      display.println(http.errorToString(httpCode).c_str());
      display.display();
    }
    http.end();
  } else {
    Serial.println("Wi-Fi disconnected!");
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("Wi-Fi Disconnected!");
    display.display();
  }
  delay(60000); // Update every 60 seconds
}

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Explaining the Code

Connecting to Wi-Fi

The ESP32 connects to your Wi-Fi network using the WiFi.begin() function. Replace the ssid and password variables with your network credentials.

Fetching Weather Data

We use the weather API from wttr.in, which provides JSON-formatted weather data. Replace the city name in the weather_url (e.g., Dresden) with your desired city. The API response includes temperature, weather description, and more.

Parsing JSON Data

The ArduinoJson library extracts relevant data like temperature and weather conditions. Ensure you allocate enough memory to handle the API’s JSON response.

Reading Room Temperature

The DHT11 sensor measures room temperature, and its reading is displayed alongside the weather data.

Displaying Data

The Adafruit_SSD1306 library updates the OLED screen with weather and room temperature details.

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Customizing for Other Cities

To fetch weather for a different city, change the weather_url to include your desired city name:

const char* weather_url = "https://wttr.in/London?format=j1";

You can also customize the API format and include additional data by exploring the wttr.in documentation.

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Conclusion

This project demonstrates how to integrate an ESP32, an online weather API, and a DHT11 sensor to create a functional weather station. You can expand this project by adding humidity readings, a clock, or even storing data for analysis. Happy tinkering!