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Arduino - Temperature Humidity Sensor - OLED Display
In this tutorial, we are going to learn:
- How to read the temperature and humidity from DHT11 sensor and display it on an OLED.
- How to read the temperature and humidity from DHT22 sensor and display it on an OLED.
Hardware Required
| 1 | × | Arduino UNO or Genuino UNO | |
| 1 | × | USB 2.0 cable type A/B | |
| 1 | × | SSD1306 I2C OLED Display 128x64 | |
| 1 | × | Temperature and Humidity Sensor DHT11 | |
| Or 1 | × | Temperature and Humidity Sensor DHT22 | |
| 4 | × | Jumper Wires |
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About OLED display, DHT11 and DHT22 Temperature Humidity Sensor
If you do not know about OLED display, DHT11 and DHT22 temperature humidity sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:
- Arduino - OLED tutorial
Wiring Diagram
Arduino - DHT11 Module LCD Wiring
Image is developed using Fritzing. Click to enlarge image
Arduino - DHT22 Module LCD Wiring
Image is developed using Fritzing. Click to enlarge image
Arduino Code - DHT11 Sensor - OLED
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/tutorials/arduino-temperature-humidity-sensor-oled-display
*/
#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 DHTPIN 2 // pin connected to DHT11 sensor
#define DHTTYPE DHT11
Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1); // create SSD1306 display object connected to I2C
DHT dht(DHTPIN, DHTTYPE);
String displayString;
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(2); // text size
oled.setTextColor(WHITE); // text color
oled.setCursor(0, 10); // position to display
dht.begin(); // initialize DHT11 the temperature and humidity sensor
displayString.reserve(10); // to avoid fragmenting memory when using String
}
void loop() {
float humi = dht.readHumidity(); // read humidity
float tempC = dht.readTemperature(); // read temperature
// check if any reads failed
if (isnan(humi) || isnan(tempC)) {
displayString = "Failed";
} else {
displayString = String(tempC, 1); // one decimal places
displayString += "°C";
displayString += String(humi, 1); // one decimal places
displayString += "%";
}
Serial.println(displayString); // print the temperature in Celsius to Serial Monitor
oledDisplayCenter(displayString); // display temperature and humidity on OLED
}
void oledDisplayCenter(String text) {
int16_t x1;
int16_t y1;
uint16_t width;
uint16_t height;
oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height);
// display on horizontal and vertical center
oled.clearDisplay(); // clear display
oled.setCursor((SCREEN_WIDTH - width) / 2, (SCREEN_HEIGHT - height) / 2);
oled.println(text); // text to display
oled.display();
}
Quick Steps
- Open Arduino IDE, Go to Tools Manage Libraries
- Search “SSD1306”, then find the SSD1306 library by Adafruit
- Click Install button to install the library.
- You will be asked for intalling some other library dependencies
- Click Install All button to install all library dependencies.
- Search “DHT”, then find the DHT sensor library by Adafruit
- Click Install button to install the library.
- You will be asked for intalling some other library dependencies
- Click Install All button all library dependencies.
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Put the sensor on hot and cold water, or grasp the sensor by your hand
- See the result on OLED and Serial Monitor
※ NOTE THAT:
The about code automatically horizontal and vertical center aligns the text on OLED display
Arduino Code - DHT22 Sensor - OLED
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/tutorials/arduino-temperature-humidity-sensor-oled-display
*/
#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 DHTPIN 2 // pin connected to DHT22 sensor
#define DHTTYPE DHT22
Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1); // create SSD1306 display object connected to I2C
DHT dht(DHTPIN, DHTTYPE);
String displayString;
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(2); // text size
oled.setTextColor(WHITE); // text color
oled.setCursor(0, 10); // position to display
dht.begin(); // initialize DHT22 the temperature and humidity sensor
displayString.reserve(10); // to avoid fragmenting memory when using String
}
void loop() {
float humi = dht.readHumidity(); // read humidity
float tempC = dht.readTemperature(); // read temperature
// check if any reads failed
if (isnan(humi) || isnan(tempC)) {
displayString = "Failed";
} else {
displayString = String(tempC, 1); // one decimal places
displayString += "°C";
displayString += String(humi, 1); // one decimal places
displayString += "%";
}
Serial.println(displayString); // print the temperature in Celsius to Serial Monitor
oledDisplayCenter(displayString); // display temperature and humidity on OLED
}
void oledDisplayCenter(String text) {
int16_t x1;
int16_t y1;
uint16_t width;
uint16_t height;
oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height);
// display on horizontal and vertical center
oled.clearDisplay(); // clear display
oled.setCursor((SCREEN_WIDTH - width) / 2, (SCREEN_HEIGHT - height) / 2);
oled.println(text); // text to display
oled.display();
}
※ NOTE THAT:
Code for DHT11 and DHT22 are identical except for one line of code. Library for DHT11 and DHT22 are the same.
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