Temperature & Humidity Monitor Using Arduino Nano, DHT11 & 0.9" OLED Display

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In this project, we will build a simple and accurate Temperature & Humidity Monitor using an Arduino Nano, a DHT11 temperature & humidity sensor, and a 0.9-inch GM009605v4.2 OLED display.

The DHT11 sensor will measure the ambient temperature and humidity, and the OLED will display the readings in real-time.

This project is perfect for beginners and can be used in weather stations, greenhouses, or home automation systems.

Supplies

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Materials Required

Arduino Nano

DHT11 Sensor

GM009605v4.2 OLED Display (0.9")

SSD1306-based I2C OLED

Breadboard

For easy connections Jumper Wires

Male-to-male

USB Cable

CIRCUIT DIAGRAM

CIRCUIT DIAGRAM

OLED Display Arduino Nano

VCC ---------- 5V

GND --------- GND

SCL ---------- A5

SDA --------- A4

DHT11 SensorArduino Nano

VCC --------- 5V

GND -------- GND

DATA -------- D2

Install Arduino IDE & Libraries

Download and install Arduino IDE from arduino.cc.
Open Arduino IDE, go to Sketch → Include Library → Manage Libraries.
Install these libraries:
Adafruit SSD1306
Adafruit GFX Library
DHT sensor library by Adafruit

Arduino Code

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

#include <DHT.h>

// --- Display setup ---

#define SCREEN_WIDTH 128

#define SCREEN_HEIGHT 32

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// --- DHT Sensor setup ---

#define DHTPIN 2

#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

void setup() {

Serial.begin(9600);

if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {

Serial.println(F("SSD1306 allocation failed"));

for (;;);

}

display.clearDisplay();

display.setTextSize(1);

display.setTextColor(SSD1306_WHITE);

display.setCursor(0, 0);

display.println(F("Initializing..."));

display.display();

dht.begin();

delay(2000);

}

void loop() {

float humidity = dht.readHumidity();

float temperature = dht.readTemperature();

if (isnan(humidity) || isnan(temperature)) {

Serial.println(F("Sensor error"));

display.clearDisplay();

display.setCursor(0, 0);

display.println(F("Sensor Error"));

display.display();

delay(2000);

return;

}

Serial.print(F("Humidity: "));

Serial.print(humidity, 1);

Serial.print(F("% Temp: "));

Serial.print(temperature, 1);

Serial.println(F("C"));

display.clearDisplay();

display.setTextSize(2);

display.setCursor(0, 0);

display.print(temperature, 1);

display.print((char)247);

display.println("C");

display.setCursor(0, 20);

display.print(humidity, 1);

display.println(" %");

display.display();

delay(2000);

}

Wiring & Upload, Test

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Wiring

Connect the DHT11 to Arduino Nano: VCC → 5V, GND → GND, DATA → D2.
Connect OLED: VCC → 5V, GND → GND, SCL → A5, SDA → A4.
Double-check wiring before powering up.

Upload & Test

Select Tools → Board → Arduino Nano.
Choose the correct COM port.
Click Upload.
After upload, the OLED should display Temperature in °C and Humidity in %.
Open Serial Monitor (9600 baud) to see live readings for debugging.

Troubleshooting

No display output: Check I2C address (0x3C is default for SSD1306).
Nan values: Ensure DHT11 is wired correctly and has a pull-up resistor (if using a bare sensor).
Flickering display: Increase delay in loop() to 2-3 seconds.