Overview
The dht22 node reads temperature and relative humidity from DHT22 (AM2302) sensors.
This affordable sensor provides both measurements from a single digital pin, making it ideal for environmental
monitoring, smart home, and greenhouse applications.
±0.5°C
Temp Accuracy
±2% RH
Humidity Accuracy
-40 to +80°C
Temp Range
2 sec
Min Interval
DHT11 vs DHT22
| Spec | DHT11 | DHT22 |
|---|---|---|
| Temp Range | 0-50°C | -40 to 80°C |
| Temp Accuracy | ±2°C | ±0.5°C |
| Humidity Range | 20-80% RH | 0-100% RH |
| Price | ~$1 | ~$4 |
Wiring
4-Pin Module
VCC → 3.3V or 5V
DATA → GPIO 4
NC → Not Connected
GND → GND
3-Pin Module (Breakout)
VCC/+ → 3.3V
OUT/DATA → GPIO 4
GND/- → GND
Breakout modules have built-in pull-up resistor
Properties
| Property | Type | Default | Description |
|---|---|---|---|
| pin | number | 4 | GPIO pin (BCM numbering) |
| sensorType | string | "22" | Sensor type: "11" or "22" |
| interval | number | 5 | Reading interval in seconds (min 2) |
| tempUnit | string | "C" | Temperature unit: "C" or "F" |
Output
{
"payload": {
"temperature": 23.5,
"humidity": 45.2
},
"temperature": 23.5,
"humidity": 45.2,
"tempUnit": "°C",
"timestamp": 1640000000000
}Example: Room Climate Monitor
Display temperature and humidity on dashboard with comfort zone alerts.
// Function node: Comfort zone checker
var temp = msg.temperature;
var humidity = msg.humidity;
var status = "comfort";
var alert = null;
if (temp < 18) {
status = "cold";
alert = "Temperature too low!";
} else if (temp > 26) {
status = "hot";
alert = "Temperature too high!";
}
if (humidity < 30) {
status = "dry";
alert = "Humidity too low!";
} else if (humidity > 60) {
status = "humid";
alert = "Humidity too high!";
}
msg.payload = {
temperature: temp,
humidity: humidity,
status: status,
alert: alert
};
return msg;Troubleshooting
Checksum errors
- Add 10kΩ pull-up resistor if not using breakout board
- Keep wires short (<20cm preferred)
- Don't read faster than every 2 seconds
Timeout errors
- Check wiring connections
- Verify sensor is getting power
- Try different GPIO pin