Arduino and DHT22 example

In this example we use the DHT22 (or AM2302) humidity/temperature sensor and the Arduino UNO board to read data and print it out to the serial monitor.

The DHT22 is better than the DHT11 because it has a wider range of measurement, 0 to 100% for humidity and -40°C to +125°C for temperature. Also it has a digital output that provides greater data accuracy.

DHT22 output calibrated digital signal. It utilizes exclusive digital-signal-collecting-technique and humidity sensing technology, assuring its reliability and stability.Its sensing elements is connected with 8-bit single-chip computer.

Every sensor of this model is temperature compensated and calibrated in accurate calibration chamber and the calibration-coefficient is saved in type of programme in OTP memory, when the sensor is detecting, it will cite
coefficient from memory.

Small size & low consumption & long transmission distance(20m) enable DHT22 to be suited in all kinds of application conditions.

Schematic/layout

I used a breakout but here is how to wire the device to your Arduino Uno

uno and dht22

Code

I used an older version of the adafruit library prior to them introducing the Unified sensor library – https://github.com/adafruit/DHT-sensor-library/tree/1.2.0

[codesyntax lang=”cpp”]

#include "DHT.h"
 
#define DHTPIN 6     // what pin we're connected to
#define DHTTYPE DHT22   // DHT 22  (AM2302)

 
DHT dht(DHTPIN, DHTTYPE);
 
void setup() 
{
  Serial.begin(9600); 
  dht.begin();
}
 
void loop() 
{
  // Wait a few seconds between measurements.
  delay(2000);
 
  float hum = dht.readHumidity();
  // Read temperature as Celsius
  float tempC = dht.readTemperature();
  
  // Check if readings have failed
  if (isnan(hum) || isnan(tempC)) 
  {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }     
  
  Serial.print("Humidity: "); 
  Serial.print(hum);
  Serial.print(" %\t");
  Serial.print("Temperature: "); 
  Serial.print(tempC);
  Serial.println(" *C ");
 
}

[/codesyntax]

Links

DHT22 Digital Humidity AM2302 and Temperature Sensor Module