Arduino UNO R4 - DHT22 - LCD

We'll learn programming an Arduino UNO R4 to read temperature and humidity from a DHT22 sensor and show these on an I2C LCD display.

Arduino UNO R4 DHT22 LCD I2C

Hardware Preparation

1×Arduino UNO R4 WiFi
1×Arduino UNO R4 Minima (Alternatively)
1×USB Cable Type-C
1×DHT22 module
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino UNO R4
1×(Recommended) Screw Terminal Block Shield for Arduino Uno
1×(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
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Overview of DHT22 and LCD

Learn about the DHT22 sensor and LCD, including their pinout, functions, and programming, in the tutorials below:

Wiring Diagram

The wiring diagram between Arduino UNO R4 DHT22 LCD

This image is created using Fritzing. Click to enlarge image

Arduino UNO R4 Code - DHT22 Sensor - LCD I2C

/* * This Arduino UNO R4 code was developed by * * This Arduino UNO R4 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * */ #include <LiquidCrystal_I2C.h> #include <DHT.h> #define DHT22_PIN 2 // The Arduino Uno R4 pin connected to DHT22 module LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27 (from DIYables LCD), 16 column and 2 rows DHT dht22(DHT22_PIN, DHT22); void setup() { dht22.begin(); // initialize the sensor lcd.init(); // initialize the lcd lcd.backlight(); // open the backlight } void loop() { delay(2000); // wait a few seconds between measurements float humi = dht22.readHumidity(); // read humidity float tempC = dht22.readTemperature(); // read temperature lcd.clear(); // check if any reads failed if (isnan(humi) || isnan(tempC)) { lcd.setCursor(0, 0); lcd.print("Failed"); } else { lcd.setCursor(0, 0); // start to print at the first row lcd.print("Temp: "); lcd.print(tempC); // print the temperature lcd.print((char)223); // print ° character lcd.print("C"); lcd.setCursor(0, 1); // start to print at the second row lcd.print("Humi: "); lcd.print(humi); // print the humidity lcd.print("%"); } }


The LCD I2C address can differ based on the manufacturer. In our code, we used the address 0x27 as provided by the manufacturer DIYables.

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 to the DHT22 module and LCD I2C 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.
  • Click on the Libraries icon on the left side of the Arduino IDE.
  • Type "DHT" in the search box and look for the DHT sensor library by Adafruit.
  • Click the Install button to add the library.
Arduino UNO R4 DHT sensor library
  • You will need to install additional library dependencies.
  • Click the Install All button to install all library dependencies.
Arduino UNO R4 Adafruit Unified sensor library
  • Search for "LiquidCrystal I2C" and choose the LiquidCrystal_I2C library by Frank de Brabander. Click the Install button to install the library.
Arduino UNO R4 LiquidCrystal I2C library
  • Copy the code above and open it in Arduino IDE.
  • Click the Upload button in Arduino IDE to upload the code to Arduino UNO R4.
  • Change the temperature around the sensor to either hotter or colder.
  • Observe the result on the LCD.

If the LCD screen shows no information, please check here: Troubleshooting on LCD I2C

Video Tutorial


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