How to Use Adafruit HTU21D-F Temperature & Humidity Sensor: Examples, Pinouts, and Specs

The Adafruit HTU21D-F is a high-quality, digital temperature and humidity sensor that communicates over an I2C interface. It offers excellent measurement accuracy and is ideal for a wide range of applications, including environmental monitoring, HVAC control, and weather stations. Its small form factor and low power consumption make it suitable for portable and battery-powered devices.

• Measurement Range:
  • Temperature: -40°C to +125°C
  • Humidity: 0 to 100% RH
• Accuracy:
  • Temperature: ±0.3°C
  • Humidity: ±2% RH
• Resolution:
  • Temperature: 0.01°C
  • Humidity: 0.04% RH
• Operating Voltage: 3.3V to 5V
• Current Consumption: 500µA during measurement, 1.5µA in standby
• Communication Interface: I2C
• I2C Address: 0x40 (fixed)

1. Power Connections:

   • Connect the VDD pin to a 3.3V or 5V power supply.
   • Connect the GND pin to the ground of the power supply.

2. I2C Connections:

   • Connect the SDA pin to the I2C data line of your microcontroller.
   • Connect the SCL pin to the I2C clock line of your microcontroller.
   • If necessary, use pull-up resistors on the SDA and SCL lines.

3. Microcontroller Configuration:

   • Set up the I2C interface on your microcontroller.
   • Use the I2C address 0x40 to communicate with the sensor.

• Place the sensor in a location with good air circulation to ensure accurate measurements.
• Avoid exposing the sensor to direct sunlight or moisture.
• Use proper ESD precautions when handling the sensor to prevent damage.

#include <Wire.h>
#include "Adafruit_HTU21DF.h"

// Create an instance of the Adafruit_HTU21DF class
Adafruit_HTU21DF htu = Adafruit_HTU21DF();

void setup() {
  Serial.begin(9600);
  Serial.println("HTU21D-F test");

  if (!htu.begin()) {
    Serial.println("Couldn't find sensor!");
    while (1);
  }
}

void loop() {
  float temp = htu.readTemperature();
  float humidity = htu.readHumidity();

  // Check if any reads failed and exit early (to try again).
  if (isnan(temp) || isnan(humidity)) {
    Serial.println("Failed to read from HTU21D-F sensor!");
    return;
  }

  Serial.print("Temperature: "); Serial.print(temp); Serial.println(" C");
  Serial.print("Humidity: "); Serial.print(humidity); Serial.println(" %");

  delay(2000); // Wait a few seconds between measurements
}

• Sensor Not Detected: Ensure that the wiring is correct and that the sensor is properly powered.
• Inaccurate Readings: Verify that the sensor is not placed near heat sources or in direct sunlight.
• I2C Communication Errors: Check for proper pull-up resistors on the SDA and SCL lines.

Q: Can the sensor be used with a 5V microcontroller? A: Yes, the HTU21D-F can be interfaced with both 3.3V and 5V systems.

Q: How long should I wait between measurements? A: The sensor can provide a new measurement every 2 seconds. It's recommended to wait at least this long for the most accurate readings.

Q: Is the sensor waterproof? A: No, the HTU21D-F is not waterproof and should be protected from moisture and condensation.

For further assistance, consult the Adafruit HTU21D-F datasheet and the Adafruit support forums.