aht20

Overview

The aht20 node reads temperature and humidity from the ASAIR AHT20 sensor via I2C. This affordable, factory-calibrated sensor provides good accuracy for its price point, making it ideal for indoor air quality projects, smart home automation, and basic environmental monitoring.

Wiring (I2C)

Properties

Output

{
  "payload": {
    "temperature": 24.1,
    "humidity": 48.5
  },
  "temperature": 24.1,
  "humidity": 48.5,
  "timestamp": 1640000000000
}

Example: Indoor Air Quality Monitor

Calculate comfort index and display on a dashboard with historical trends.

// Function node: Comfort index calculation
var temp = msg.temperature;
var humidity = msg.humidity;

// Heat index calculation (simplified)
var heatIndex = temp;
if (temp >= 27 && humidity >= 40) {
    heatIndex = -8.784 + 1.611 * temp + 2.338 * humidity
        - 0.1461 * temp * humidity;
}

// Comfort level assessment
var comfort = "comfortable";
if (temp < 18) comfort = "too cold";
else if (temp > 26) comfort = "too warm";
else if (humidity < 30) comfort = "too dry";
else if (humidity > 60) comfort = "too humid";

msg.payload = {
    temperature: temp,
    humidity: humidity,
    heatIndex: heatIndex.toFixed(1),
    comfort: comfort,
    score: comfort === "comfortable" ? 100 : 60
};

return msg;

Example: Multi-Room Monitoring

Use multiple AHT20 sensors on separate I2C buses for room-by-room tracking.

// Since AHT20 has a fixed address, use I2C multiplexer
// or separate buses for multiple sensors

// Function node: Aggregate room data
var rooms = flow.get('roomData') || {};
var room = msg.topic; // e.g., "living_room", "bedroom"

rooms[room] = {
    temperature: msg.temperature,
    humidity: msg.humidity,
    updated: Date.now()
};

flow.set('roomData', rooms);

// Find hottest and coldest rooms
var names = Object.keys(rooms);
var sorted = names.sort(function(a, b) {
    return rooms[a].temperature - rooms[b].temperature;
});

msg.payload = {
    rooms: rooms,
    coldest: sorted[0],
    warmest: sorted[sorted.length - 1]
};

return msg;

Use Cases