Mini Weather Station using Arduino, DHT11 and OLED

A simple mini weather station built with Arduino Uno, DHT11 temperature & humidity sensor, and a 128×64 I2C OLED display.
It measures room temperature and humidity and shows the values in real time on the OLED screen.

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Features

• Reads temperature (°C) and humidity (%) using DHT11
• Displays data on a 128×64 SSD1306 I2C OLED
• Prints readings to the Serial Monitor for debugging
• Built on a breadboard, easy to reproduce and modify

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Components

• Arduino Uno Rev3
• DHT11 sensor module (3‑pin: VCC, GND, DATA)
• 128×64 OLED display (I2C, 4‑pin: VCC, GND, SCL, SDA)
• Breadboard
• Jumper wires (male–male and male–female)
• USB A‑to‑B cable

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Circuit Connections

Power

• Arduino 5V → Breadboard + rail
• Arduino GND → Breadboard − rail

DHT11 (3‑pin module)

• DHT11 VCC → Breadboard + (5 V)
• DHT11 GND → Breadboard − (GND)
• DHT11 DATA → Arduino digital pin 2

OLED (SSD1306, I2C, 4‑pin)

• OLED VCC → Breadboard + (5 V)
• OLED GND → Breadboard − (GND)
• OLED SCL → Arduino A5 (SCL)
• OLED SDA → Arduino A4 (SDA)

The DHT11 and OLED share the same 5V and GND rails and use different signal pins.

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Libraries

Install via Arduino Library Manager:

• DHT sensor library (Adafruit)
• Adafruit Unified Sensor
• Adafruit SSD1306
• Adafruit GFX Library

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Finding the OLED I2C Address

To detect the OLED I2C address, upload an I2C scanner sketch.
In this project, the scanner reported:

I2C device found at address 0x3C

So the code uses 0x3C in display.begin().

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Arduino Code

Create weather_station.ino and paste:

#include "DHT.h"
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

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

#define DHTPIN 2
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  dht.begin();

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {  // I2C address
    Serial.println("OLED not found!");
    for(;;);
  }

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  display.println("Weather Station");
  display.display();
  delay(2000);
}

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

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %  Temp: ");
  Serial.print(t);
  Serial.println(" C");

  display.clearDisplay();

  display.setTextSize(2);
  display.setCursor(0,0);
  display.print("T:");
  display.print(t);
  display.println("C");

  display.setTextSize(2);
  display.setCursor(0,30);
  display.print("H:");
  display.print(h);
  display.println("%");

  display.display();
  delay(2000);
}

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How It Works

1. The Arduino powers the DHT11 and OLED from the 5 V and GND rails.
2. In setup(), the DHT11 sensor and OLED display are initialized.
3. A startup message “Weather Station” is shown on the OLED.
4. In loop(), the DHT11 readings (readTemperature() and readHumidity()) are taken every 2 seconds.
5. The values are printed to Serial Monitor and displayed on the OLED in large font.

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Usage

1. Build the circuit according to the connections above.
2. Install the required libraries.
3. Upload weather_station.ino to the Arduino Uno.
4. Open Serial Monitor (9600 baud) to see readings.
5. Check the OLED for live temperature and humidity.

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Future Improvements

• Track and display min/max temperature and humidity
• Add LED or buzzer alerts for threshold values
• Add a real-time clock (RTC) to show time/date
• Port to ESP8266/ESP32 and upload data to the cloud

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License

Add your preferred license here (e.g. MIT, or “All rights reserved”).