Arduino UNO R4 - DHT22 Temperature Humidity Sensor - OLED
In this guide, we will learn how to check and show the temperature and humidity using the DHT22 module on an OLED screen.
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables STEM V4 IoT Starter Kit (Arduino included) | |
| 1 | × | DIYables STEM V4B IoT Starter Kit (Arduino included) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .
Additionally, some of these links are for products from our own brand, DIYables .
Buy Note: If you want a bigger OLED display, use the 2.42 inch OLED Display 128x64 .
Overview of OLED display, DHT22 Temperature Humidity Sensor
Learn about the OLED display and DHT22 temperature humidity sensor, including their pinouts, how they function, and programming methods, in the tutorials below.
- Arduino UNO R4 - OLED tutorial
- Arduino UNO R4 - DHT22 tutorial
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
If you plan to keep this circuit, think about screw terminals. Put a Screw Shield V2 or a Proto Screw Terminal Block Shield on top of the Arduino UNO R4, then tighten each wire under a screw. Here is the same circuit wired through the Screw Shield V2:
This image is created using Fritzing. Click to enlarge image
See The best way to supply power to the Arduino Uno R4 and other components.
Arduino UNO R4 Code - DHT22 Sensor - OLED
/*
* This Arduino UNO R4 code was developed by newbiely.com
*
* This Arduino UNO R4 code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-r4/arduino-uno-r4-dht22-temperature-humidity-sensor-oled
*/
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <DHT.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define DHT22_PIN 2 // The Arduino UNO R4 pin connected to DHT22 sensor
Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1); // create SSD1306 display object connected to I2C
DHT dht22(DHT22_PIN, DHT22);
String temperature;
String humidity;
void setup() {
Serial.begin(9600);
// initialize OLED display with address 0x3C for 128x64
if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
Serial.println(F("SSD1306 allocation failed"));
while (true);
}
delay(2000); // wait for initializing
oled.clearDisplay(); // clear display
oled.setTextSize(3); // text size
oled.setTextColor(WHITE); // text color
oled.setCursor(0, 10); // position to display
dht22.begin(); // initialize DHT22 the temperature and humidity sensor
temperature.reserve(10); // to avoid fragmenting memory when using String
humidity.reserve(10); // to avoid fragmenting memory when using String
}
void loop() {
float humi = dht22.readHumidity(); // read humidity
float tempC = dht22.readTemperature(); // read temperature
// check if any reads failed
if (isnan(humi) || isnan(tempC)) {
temperature = "Failed";
humidity = "Failed";
} else {
temperature = String(tempC, 1); // one decimal places
temperature += char (247); // degree character
temperature += "C";
humidity = String(humi, 1); // one decimal places
humidity += "%";
Serial.print(tempC); // print to Serial Monitor
Serial.print("°C | " ); // print to Serial Monitor
Serial.print(humi); // print to Serial Monitor
Serial.println("%"); // print to Serial Monitor
}
oledDisplayCenter(temperature, humidity); // display temperature and humidity on OLED
}
void oledDisplayCenter(String temperature, String humidity) {
int16_t x1;
int16_t y1;
uint16_t width_T;
uint16_t height_T;
uint16_t width_H;
uint16_t height_H;
oled.getTextBounds(temperature, 0, 0, &x1, &y1, &width_T, &height_T);
oled.getTextBounds(temperature, 0, 0, &x1, &y1, &width_H, &height_H);
// display on horizontal and vertical center
oled.clearDisplay(); // clear display
oled.setCursor((SCREEN_WIDTH - width_T) / 2, SCREEN_HEIGHT/2 - height_T - 5);
oled.println(temperature); // text to display
oled.setCursor((SCREEN_WIDTH - width_H) / 2, SCREEN_HEIGHT/2 + 5);
oled.println(humidity); // text to display
oled.display();
}
Detailed Instructions
Follow these instructions step by step:
- If this is your first time using the Arduino Uno R4 WiFi/Minima, refer to the tutorial on setting up the environment for Arduino Uno R4 WiFi/Minima in the Arduino IDE.
- Connect the Arduino Uno R4 board to the DHT22 module and OLED display according to the provided diagram.
- Connect the Arduino Uno R4 board to your computer using a USB cable.
- Launch the Arduino IDE on your computer.
- Select the appropriate Arduino Uno R4 board (e.g., Arduino Uno R4 WiFi) and COM port.
- Go to the Libraries icon on the left side of the Arduino IDE.
- Search for "SSD1306" and locate the SSD13011406 library by Adafruit.
- Press the Install button to install the library.
- You need to install additional library dependencies.
- Click the Install All button to install all the required libraries.
- Search for "DHT" and look for the DHT sensor library by Adafruit.
- Click the Install button to install the library.
- You will need to install additional library dependencies.
- Click the Install All button to install all the library dependencies.
- Copy the code and open it in the Arduino IDE.
- Press the Upload button in the Arduino IDE to transfer the code to your Arduino UNO R4.
- Place the sensor in hot and cold water, or hold it in your hand.
- Check the results on the OLED display and the Serial Monitor.
※ NOTE THAT:
The code automatically centers the text horizontally and vertically on the OLED display.