How to Use AHT20: Examples, Pinouts, and Specs

The AHT20 is a digital temperature and humidity sensor designed for precise environmental monitoring. It integrates a capacitive humidity sensor and a high-performance temperature sensor, providing accurate and reliable measurements. The AHT20 features a built-in I2C interface, making it easy to connect to microcontrollers and other digital systems. Its compact size, low power consumption, and high precision make it ideal for a wide range of applications.

• Weather monitoring systems
• HVAC (Heating, Ventilation, and Air Conditioning) control
• IoT (Internet of Things) devices
• Industrial automation
• Home appliances (e.g., dehumidifiers, air purifiers)
• Environmental data logging

1. Power Supply: Connect the VDD 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 both SDA and SCL lines if not already present on your board.
3. Initialization: The AHT20 requires initialization commands to start measurements. Ensure your microcontroller sends the correct I2C commands to configure the sensor.
4. Data Reading: Read temperature and humidity data from the sensor via the I2C interface. The data is provided in a 6-byte format, which needs to be processed to extract meaningful values.

• Power Stability: Ensure a stable power supply to avoid measurement errors.
• I2C Pull-Up Resistors: Verify that pull-up resistors are present on the SDA and SCL lines to ensure proper I2C communication.
• Environmental Factors: Avoid exposing the sensor to extreme conditions (e.g., condensation, dust) that could affect its accuracy or damage it.
• Calibration: The AHT20 is factory-calibrated, so no additional calibration is required.

Below is an example of how to use the AHT20 with an Arduino UNO:

#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); // Wait for the sensor to initialize
}

void loop() {
  // Trigger measurement
  Wire.beginTransmission(AHT20_ADDRESS);
  Wire.write(0xAC); // Command to start measurement
  Wire.write(0x33); // Fixed data byte
  Wire.write(0x00); // Fixed data byte
  Wire.endTransmission();
  delay(80); // Wait for measurement to complete

  // Read data from the sensor
  Wire.requestFrom(AHT20_ADDRESS, 6);
  if (Wire.available() == 6) {
    uint8_t data[6];
    for (int i = 0; i < 6; i++) {
      data[i] = Wire.read();
    }

    // Process humidity data
    uint32_t humidityRaw = ((uint32_t)data[1] << 12) |
                           ((uint32_t)data[2] << 4) |
                           ((data[3] & 0xF0) >> 4);
    float humidity = (humidityRaw * 100.0) / 1048576.0;

    // Process temperature data
    uint32_t temperatureRaw = (((uint32_t)data[3] & 0x0F) << 16) |
                              ((uint32_t)data[4] << 8) |
                              (uint32_t)data[5];
    float temperature = ((temperatureRaw * 200.0) / 1048576.0) - 50.0;

    // Print results
    Serial.print("Humidity: ");
    Serial.print(humidity);
    Serial.println(" %");
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.println(" °C");
  }

  delay(2000); // Wait before the next measurement
}

1. No Data from the Sensor:

   • Ensure the sensor is powered correctly (check VDD and GND connections).
   • Verify that the I2C address (0x38) matches the one used in your code.
   • Check for proper pull-up resistors on the SDA and SCL lines.

2. Inaccurate Measurements:

   • Ensure the sensor is not exposed to condensation or contaminants.
   • Verify that the sensor is operating within its specified temperature and humidity range.

3. I2C Communication Errors:

   • Check the wiring and ensure SDA and SCL are connected to the correct pins.
   • Confirm that the I2C clock speed is compatible with the AHT20 (typically up to 400kHz).

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

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 5V systems.

Q: What is the typical response time of the AHT20?
A: The typical response time is ≤8 seconds for humidity and temperature measurements.

Q: How do I protect the sensor from environmental damage?
A: Use a protective enclosure or filter to shield the sensor from dust, condensation, and other contaminants.