TempHumid Monitor

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes ESP32 board	PURCHASE LINK
ESP32 Ultimate Starter Kit	ESP32 WROOM 32E +	BUY
Universal Maker Sensor Kit		BUY

Course Introduction

This ESP32 project uses a DHT11 sensor and an OLED display to monitor and display real-time temperature and humidity.

The data is updated every 0.5 seconds and shown clearly on a 128x64 I2C OLED screen. If sensor readings fail, an error message is displayed.

This setup is ideal for simple environmental monitoring applications.

Note

If this is your first time working with an ESP32 project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	ESP-WROOM-32 ESP32 ESP-32S Development Board	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	DHT-11 Module	1	BUY
6	OLED Display Module	1	BUY

Wiring

Common Connections:

DHT-11 Module
- OUT: Connect to GPIO27 on the ESP32.
- -:** Connect to breadboard’s negative power bus.
- +: Connect to breadboard’s red power bus.
OLED Display Module
- SDA: Connect to GPIO21 on the ESP32.
- SCK: Connect to GPIO22 on the ESP32.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for DHT , Adafruit SSD1306 and Adafruit GFX and install it.
Don’t forget to select the board(ESP32 Dev module) and the correct port before clicking the Upload button.

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

// ======== Display config ========
#define SCREEN_WIDTH 128                 // OLED width in pixels
#define SCREEN_HEIGHT 64                 // OLED height in pixels
#define OLED_RESET    -1                 // No dedicated reset pin
#define SCREEN_ADDRESS 0x3C              // Most 128x64 modules use 0x3C

// ESP32 I2C pins (change if your board uses different ones)
#define I2C_SDA 21
#define I2C_SCL 22

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// ======== DHT sensor config ========
// Use a safe ESP32 GPIO for the DHT data pin (avoid input-only pins 34–39)
#define DHTPIN 27                        // DHT data pin on ESP32
#define DHTTYPE DHT11                    // Sensor type
DHT dht(DHTPIN, DHTTYPE);

// Suggested sampling interval for DHT11 is ~1s
const uint32_t SAMPLE_DELAY_MS = 1000;

void setup() {
  // Faster serial for ESP32
  Serial.begin(115200);
  Serial.println(F("DHT11 with OLED test (ESP32)"));

  // Initialize I2C on explicit ESP32 pins
  Wire.begin(I2C_SDA, I2C_SCL);

  // Initialize display
  if (!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;) { /* halt */ }
  }

  // Initialize DHT sensor
  dht.begin();

  // Prepare screen
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println(F("Init OK"));
  display.display();
}

void loop() {
  // Respect DHT11 recommended interval to reduce NaNs
  delay(SAMPLE_DELAY_MS);

  // Read humidity and temperature (blocking ~250ms for DHT11)
  float h = dht.readHumidity();
  float t = dht.readTemperature(); // Celsius

  // If reads failed, show an error message
  if (isnan(h) || isnan(t)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    display.clearDisplay();
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    display.setCursor(0, 0);
    display.println(F("Sensor error"));
    display.display();
    return;
  }

  // Clear and render fresh values
  display.clearDisplay();

  // Humidity label
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println(F("Humidity:"));

  // Humidity value (large)
  display.setTextSize(2);
  display.setCursor(0, 10);
  display.print(h, 1);  // 1 decimal place
  display.println(F("%"));

  // Temperature label
  display.setTextSize(1);
  display.setCursor(0, 35);
  display.println(F("Temperature:"));

  // Temperature value (large)
  display.setTextSize(2);
  display.setCursor(0, 45);
  display.print(t, 1);
  display.println(F(" C"));

  // Push buffer to OLED
  display.display();

  // Print to serial for debugging
  Serial.print(F("Humidity: "));
  Serial.print(h, 1);
  Serial.print(F("%  Temperature: "));
  Serial.print(t, 1);
  Serial.println(F(" C"));
}