Temperature and Humidity Readings on OLED Display

Components Required

• Dev Board
• 0.96 inch OLED Display
• DHT22 temperature and humidity sensor
• Breadboard
• Resistors
• Wires

Required Libraries

• OLED Display Libraries - Adafruit SSD1306 library is a commonly used library to interface the dev board to the OLED display conveniently. To install this type 'SSD1306' in the search bar of Manage Libraries. Install the Adafruit version of it. You also need to install the GFX library for graphics. Just search 'GFX' in the search bar and install it.
• DHT22 Library - Search 'DHT' in the search bar and install the Adafruit DHT Library. Also install the 'Adafruit Unified Sensor' Library.

Schematic

Code Explanation

Importing Libraries

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

Create a Display Object

Here, you need to define the OLED dimensions.

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

Now, we need to initialize the display object.

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

Create a DHT Object

Here, you need to define the type of DHT sensor you are using.

#define DHTTYPE    DHT22

Next, we need to initialize the DHT object

DHT dht(DHTPIN, DHTTYPE);

Setup

void setup() {
  Serial.begin(115200);

  dht.begin();

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  delay(2000);
  display.clearDisplay();
  display.setTextColor(WHITE);
}

Getting readings from the DHT Sensor

We use the readTemperature() and readHumidity() functions and store these values in variables t and h respectively.

float t = dht.readTemperature();
float h = dht.readHumidity();

Display the readings on the OLED Display

// clear display
  display.clearDisplay();

  // display temperature
  display.setTextSize(1);
  display.setCursor(0,0);
  display.print("Temperature: ");
  display.setTextSize(2);
  display.setCursor(0,10);
  display.print(t);
  display.print(" ");
  display.setTextSize(1);
  display.cp437(true);
  display.write(167);
  display.setTextSize(2);
  display.print("C");

  // display humidity
  display.setTextSize(1);
  display.setCursor(0, 35);
  display.print("Humidity: ");
  display.setTextSize(2);
  display.setCursor(0, 45);
  display.print(h);
  display.print(" %"); 

  display.display(); 
}

Full Code

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

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

#define DHTPIN 14     // Digital pin connected to the DHT sensor

// Uncomment the type of sensor in use:
//#define DHTTYPE    DHT11     // DHT 11
#define DHTTYPE    DHT22     // DHT 22 (AM2302)
//#define DHTTYPE    DHT21     // DHT 21 (AM2301)

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(115200);

  dht.begin();

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  delay(2000);
  display.clearDisplay();
  display.setTextColor(WHITE);
}

void loop() {
  delay(5000);

  //read temperature and humidity
  float t = dht.readTemperature();
  float h = dht.readHumidity();
  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
  }
  // clear display
  display.clearDisplay();

  // display temperature
  display.setTextSize(1);
  display.setCursor(0,0);
  display.print("Temperature: ");
  display.setTextSize(2);
  display.setCursor(0,10);
  display.print(t);
  display.print(" ");
  display.setTextSize(1);
  display.cp437(true);
  display.write(167);
  display.setTextSize(2);
  display.print("C");

  // display humidity
  display.setTextSize(1);
  display.setCursor(0, 35);
  display.print("Humidity: ");
  display.setTextSize(2);
  display.setCursor(0, 45);
  display.print(h);
  display.print(" %"); 

  display.display(); 
}

References

Random Nerd Tutorials