20. Thermometer

Whether you're new to electronics or a seasoned maker, this project is a great way to dive into the world of Arduino and sensor interfacing. By the end of this tutorial, you will have a fully functional digital thermometer that displays real-time temperature and humidity readings on an LCD screen.

Materials

Component	Image
Breadboard
Jumper wires
Arduino Uno R4 Minima
LCD 1602 Module
DHT11 Temperature and Humidity Sensor

Instructions

1. Make the following connections using the breadboard and jumper wires.

Connections

LCD1602 to Arduino R4 Minima

• RS (Register Select) pin to Arduino digital pin 7
• E (Enable) pin to Arduino digital pin 8
• D4 pin to Arduino digital pin 9
• D5 pin to Arduino digital pin 10
• D6 pin to Arduino digital pin 11
• D7 pin to Arduino digital pin 12
• GND to GND
• VDD to 5V
• VO to the middle pin of a 10k potentiometer (the other two pins of the potentiometer to 5V and GND)
• BLA to 5V
• BLK to GND

DHT11 Sensor

• Signal to pin 2
• Vcc to 5V
• Gnd to GND

2. Download the "LiquidCrystal" and "DHT" libraries from the Library Manager on the Arduino IDE.

3. Paste the following code into your main Arduino sketch:

Code

#include <LiquidCrystal.h>
#include <DHT.h>

// Initialize the LCD library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

// Define the pin for the DHT11 sensor
#define DHTPIN 2

// Define the type of DHT sensor
#define DHTTYPE DHT11

// Initialize the DHT sensor
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  // Start the LCD
  lcd.begin(16, 2);
  lcd.print("DHT11 Sensor");
  
  // Start the serial communication
  Serial.begin(9600);
  
  // Start the DHT sensor
  dht.begin();
  
  delay(2000); // Wait 2 seconds before starting loop
}

void loop() {
  // Read humidity and temperature
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  float f = dht.readTemperature(true);

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    lcd.setCursor(0, 0);
    lcd.print("Sensor Error   ");
    return;
  }

  // Compute heat index in Fahrenheit (the default)
  float hif = dht.computeHeatIndex(f, h);
  // Compute heat index in Celsius
  float hic = dht.computeHeatIndex(t, h, false);

  // Print values to serial monitor
  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hic);
  Serial.print(" *C ");
  Serial.print(hif);
  Serial.println(" *F");

  // Print values to LCD
  lcd.setCursor(0, 0);
  lcd.print("Temp: ");
  lcd.print(t);
  lcd.print(" C");

  lcd.setCursor(0, 1);
  lcd.print("Humidity: ");
  lcd.print(h);
  lcd.print(" %");

  delay(2000); // Delay 2 seconds before the next reading
}

4. Connect your Arduino to your laptop using a USB-C cable and upload the code to the arduino.

5. Run! Observe the temperature and humidity on the display.

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19. LCD 1602 Module	21. Shift Registers and LED