How to Use aht20: Examples, Pinouts, and Specs

The AHT20, manufactured by DFRobot (Part ID: AHT20), is a digital temperature and humidity sensor designed for precise environmental monitoring. It features a compact design, low power consumption, and I2C communication, making it ideal for integration into a wide range of microcontroller-based projects. The AHT20 is widely used in applications such as weather stations, HVAC systems, IoT devices, and industrial automation.

The AHT20 offers reliable performance with the following key specifications:

The AHT20 sensor has four pins, as described in the table below:

1. Power Supply: Connect the VCC pin to a 3.3V or 5V power source and the GND pin to ground.
2. I2C Communication: Connect the SDA and SCL pins to the corresponding I2C pins on your microcontroller. Use pull-up resistors (typically 4.7kΩ) on the SDA and SCL lines if not already present.
3. Address: The AHT20 has a fixed I2C address of 0x38.

• Ensure the sensor is not exposed to direct sunlight or water to maintain accuracy.
• Avoid placing the sensor near heat sources or in areas with high airflow, as this may affect readings.
• Allow the sensor to stabilize for a few seconds after power-up before taking measurements.

Below is an example of how to interface the AHT20 with an Arduino UNO using the I2C protocol:

#include <Wire.h>

// AHT20 I2C address
#define AHT20_ADDRESS 0x38

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Start serial communication for debugging

  // Initialize the AHT20 sensor
  Wire.beginTransmission(AHT20_ADDRESS);
  Wire.write(0xBE); // Send initialization command
  Wire.endTransmission();
  delay(10); // Allow time for initialization
}

void loop() {
  // Trigger measurement
  Wire.beginTransmission(AHT20_ADDRESS);
  Wire.write(0xAC); // Trigger measurement command
  Wire.write(0x33); // Data byte 1
  Wire.write(0x00); // Data byte 2
  Wire.endTransmission();
  delay(80); // Wait for measurement to complete

  // Read measurement data
  Wire.requestFrom(AHT20_ADDRESS, 6); // Request 6 bytes of data
  if (Wire.available() == 6) {
    uint8_t data[6];
    for (int i = 0; i < 6; i++) {
      data[i] = Wire.read(); // Read each byte
    }

    // Process temperature and humidity data
    uint32_t humidity = ((uint32_t)data[1] << 12) | ((uint32_t)data[2] << 4) |
                        (data[3] >> 4);
    uint32_t temperature = ((uint32_t)(data[3] & 0x0F) << 16) |
                           ((uint32_t)data[4] << 8) | data[5];

    float humidityPercent = (humidity * 100.0) / 1048576.0;
    float temperatureCelsius = (temperature * 200.0 / 1048576.0) - 50.0;

    // Print results to the serial monitor
    Serial.print("Humidity: ");
    Serial.print(humidityPercent);
    Serial.println(" %");
    Serial.print("Temperature: ");
    Serial.print(temperatureCelsius);
    Serial.println(" °C");
  }

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

1. No Data from the Sensor:

   • Ensure the sensor is properly connected to the I2C pins of the microcontroller.
   • Verify that the pull-up resistors are in place on the SDA and SCL lines.
   • Check the power supply voltage (2.0V to 5.5V).

2. Inaccurate Readings:

   • Ensure the sensor is not exposed to extreme environmental conditions.
   • Allow the sensor to stabilize after power-up before taking measurements.

3. I2C Communication Errors:

   • Confirm the I2C address (0x38) matches the one used in your code.
   • Check for loose or incorrect wiring.

Q: Can the AHT20 operate at 5V?
A: Yes, the AHT20 supports a supply voltage range of 2.0V to 5.5V, making it compatible with both 3.3V and 5V systems.

Q: How often can I take measurements?
A: The AHT20 has a response time of ≤8 seconds, but it is recommended to wait at least 2 seconds between measurements for optimal performance.

Q: Do I need to calibrate the AHT20?
A: No, the AHT20 is factory-calibrated and does not require additional calibration.