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Lesson 36: Using the HTU21D Temperature Sensor with an LCD Arduino Step-by-Step Course

Hardware Explained

Datasheet Details

• Use a pull-up resistor for SDA and SCL lines if not integrated.
• Ensure correct power supply voltage to avoid damaging the sensor.
• Maintain proper wiring to prevent communication errors.
• Check the I2C address if the sensor does not respond.
• Use a delay between readings to prevent sensor overload.
• Ensure the LCD is compatible with I2C communication.

Wiring Instructions

Code Examples & Walkthrough

void setup() {
  lcd.begin();
  lcd.backlight();
  if (!htu.begin()) {
      lcd.print("Robojax HTUD1DF");
      lcd.setCursor(0,1);
      lcd.print("sensor missing"); 
      while (1);
  } else {
      lcd.print("Robojax HTUD1DF");
      lcd.setCursor(0,1);
      lcd.print("Demo"); 
  }
  delay(2000);   
}

void loop() {
   lcd.clear(); // clear previous values from screen
   lcdDisplay(0, 0, "Celsius: ", 10, 0, getHTU('C'), 'd');  
   lcdDisplay(0, 1, "Fahrenheit: ", 10, 1, getHTU('F'), 'd');     
   delay(5000);
}

float getHTU(char type) {
   float temp = htu.readTemperature();
   float rel_hum = htu.readHumidity();
   if(type =='F') {
       return temp * 9/5 + 32; // convert to Fahrenheit 
   } else if(type =='K') {
       return temp + 273.15; // convert to Kelvin
   } else if(type =='H') {
       return rel_hum; // return relative humidity
   } else {
       return temp; // return Celsius
   }
}

Demonstration / What to Expect

Video Timestamps

• 00:00 - Introduction to the project
• 01:15 - Wiring instructions
• 03:30 - Code walkthrough
• 10:00 - Demonstration of the setup