AHT20 Temperature and Humidity Sensor

The AHT20 is a low-cost I2C temperature and humidity sensor, suitable as a more stable replacement for DHT11/DHT22 for indoor environment monitoring. The current driver is a lightweight implementation that does not depend on additional third-party libraries, making it available for slim ESP32 firmware.

Wiring

AHT20	ESP32
VCC	3.3V
GND	GND
SDA	GPIO21
SCL	GPIO22

Default address is 0x38.

Configuration

Method 1: Web Interface Configuration (Recommended)

Before saving AHT20 configuration, verify the I2C bus, address, and sampling interval.

Step 1: Navigate to Peripheral Management Page

1. Open a browser and navigate to the ESP32 IP address
2. After logging in, click Peripheral Configuration in the left menu

Step 2: Add AHT20 Peripheral

1. Click the Add Peripheral button

2. Fill in the configuration:

   Field	Value	Description
   Peripheral ID	aht20_i2c	Unique identifier
   Name	AHT20 Temp & Humidity	Display name
   Peripheral Type	Generic Sensor (type: 38)	I2C sensor
   SDA Pin	21	I2C data pin
   SCL Pin	22	I2C clock pin
   I2C Address	0x38	Default address
   Sampling Interval	5000	5 seconds

3. Click Save

Step 3: Verify Configuration

1. Find the newly added peripheral in the peripheral list
2. Click the Enable toggle
3. Wait 5 seconds and check temperature and humidity data

💡 Tip: AHT20 is a low-cost I2C alternative to DHT11/DHT22 with better accuracy

---

Method 2: JSON Configuration File Import

{
  "id": "aht20_i2c",
  "name": "AHT20 Temp & Humidity",
  "type": 2,
  "enabled": false,
  "pinCount": 2,
  "pins": [21, 22, 255, 255, 255, 255, 255, 255],
  "params": {
    "frequency": 100000,
    "address": 0,
    "isMaster": true
  }
}

Peripheral Execution Integration

Web Interface Configuration Steps

Create Humidity Collection and Control Rule

1. Switch to the Peripheral Execution Management tab
2. Click the Add Rule button
3. Configure a timer trigger:
   • Trigger Type: Timer Trigger
   • Execution Interval: 30 seconds
4. Add action:
   • Action 1: Read humidity
     • Action Type: Sensor Read
     • Target Peripheral: aht20_i2c
     • Data Field: humidity
5. Enable Report Data After Execution
6. Click Save

Create Low Humidity Humidifier Rule

1. Create a new rule
2. Configure an event trigger:
   • Trigger Type: Event Trigger
   • Event ID: ds:aht20_i2c_humidity
   • Comparison: Less Than
   • Comparison Value: 40 (%)
3. Add action:
   • Action Type: High Level
   • Target Peripheral: relay_humidifier (humidifier relay)
4. Click Save

💡 Tip: Event ID format is ds:{peripheralID}_{fieldName}

---

JSON Configuration Example

{
  "id": "exec_aht20_humidity_read",
  "name": "AHT20 Humidity Collection",
  "enabled": false,
  "triggers": [
    {
      "triggerType": 1,
      "timerMode": 0,
      "intervalSec": 30
    }
  ],
  "actions": [
    {
      "targetPeriphId": "aht20_i2c",
      "actionType": 19,
      "actionValue": "{\"periphId\":\"aht20_i2c\",\"sensorCategory\":\"AHT20\",\"dataField\":\"humidity\",\"sensorLabel\":\"Humidity\",\"unit\":\"%\",\"decimalPlaces\":1,\"driverParams\":{\"addr\":\"0x38\",\"sda\":21,\"scl\":22}}",
      "useReceivedValue": false,
      "syncDelayMs": 0,
      "execMode": 0
    }
  ],
  "reportAfterExec": true
}

Low Humidity Humidifier Relay

{
  "id": "exec_aht20_dry_relay",
  "name": "AHT20 Low Humidity Humidifier",
  "enabled": false,
  "triggers": [
    {
      "triggerType": 4,
      "eventId": "ds:aht20_i2c_humidity",
      "operatorType": 3,
      "compareValue": "40"
    }
  ],
  "actions": [
    {
      "targetPeriphId": "relay_humidifier",
      "actionType": 0,
      "actionValue": "",
      "useReceivedValue": false,
      "syncDelayMs": 0,
      "execMode": 0
    }
  ],
  "reportAfterExec": true
}

Available Data Fields

dataField	Meaning	Unit
temperature	Temperature	℃
humidity	Relative Humidity	%