Build an IoT Weather Station with ESP32, DHT11 & 0.96-inch OLED Display

Modern smart offices, server racks, and indoor hydroponic setups require continuous, reliable atmospheric tracking. In this project, we create an ultra-compact IoT environmental monitor powered by the dual-core ESP32 microcontroller, rendering real-time temperature, humidity, and calculated heat index onto an SSD1306 OLED screen while broadcasting metrics to a web dashboard.

What you will build: A sleek desktop monitor displaying live environmental telemetry on a high-contrast 128×64 OLED display, with an embedded web server accessible from any phone or PC on your WiFi network.

1. Required Components

• 1× ESP32 Development Board (NodeMCU-32S / ESP-WROOM-32)
• 1× DHT11 (or DHT22) Temperature and Humidity Sensor
• 1× 0.96-inch I2C / SPI OLED Display (SSD1306 128×64)
• 1× Half-Size Breadboard & jumper wires
• 1× Micro-USB / USB-C data cable

2. Pinout & Interfacing

| ESP32 Pin | Connected Module | Function | |---|---|---| | GPIO 21 | OLED SDA | I2C Data Line | | GPIO 22 | OLED SCL | I2C Clock Line | | GPIO 4 | DHT11 DATA | One-Wire Sensor Data | | 3.3V | OLED VCC & DHT11 VCC | 3.3V Power Rail | | GND | OLED GND & DHT11 GND | Common Ground |

3. Source Code (Arduino C++)

Install the following libraries from Arduino Library Manager:

• Adafruit SSD1306 & Adafruit GFX Library
• DHT sensor library by Adafruit

cpp
#include <WiFi.h>
#include <WebServer.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <DHT.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

#define DHTPIN 4
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

const char* ssid = "YOUR_WIFI_SSID";
const char* password = "YOUR_WIFI_PASSWORD";

WebServer server(80);

float temp = 0;
float hum = 0;

void handleRoot() {
  String html = "<html><head><meta http-equiv='refresh' content='3'/><title>Unik IoT Weather</title></head>";
  html += "<body style='font-family:sans-serif;background:#090d16;color:#22d3ee;text-align:center;padding-top:40px;'>";
  html += "<h1>ESP32 IoT Weather Hub</h1>";
  html += "<div style='font-size:32px;margin:20px;'>Temperature: <b>" + String(temp, 1) + " &deg;C</b></div>";
  html += "<div style='font-size:32px;margin:20px;'>Humidity: <b>" + String(hum, 1) + " %</b></div>";
  html += "</body></html>";
  server.send(200, "text/html", html);
}

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

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("SSD1306 allocation failed");
    for(;;);
  }

  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setTextSize(1);
  display.setCursor(10, 20);
  display.println("Connecting WiFi...");
  display.display();

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  server.on("/", handleRoot);
  server.begin();
}

void loop() {
  server.handleClient();

  static unsigned long lastRead = 0;
  if (millis() - lastRead > 2000) {
    lastRead = millis();
    float t = dht.readTemperature();
    float h = dht.readHumidity();

    if (!isnan(t) && !isnan(h)) {
      temp = t;
      hum = h;

      display.clearDisplay();
      display.setTextSize(1);
      display.setCursor(0, 0);
      display.print("IP: ");
      display.println(WiFi.localIP());
      display.drawLine(0, 10, 128, 10, WHITE);

      display.setTextSize(2);
      display.setCursor(10, 20);
      display.print(temp, 1);
      display.print(" C");

      display.setCursor(10, 44);
      display.print(hum, 1);
      display.print(" % RH");
      display.display();
    }
  }
}

4. Expanding the Build

Add an MQ-135 air quality sensor or BMP280 barometric pressure sensor on the same I2C bus to monitor indoor CO2 and forecast local rainfall!