How to Use Temperature and Humidity (DHT) Sensors

Components and supplies

Arduino UNO & Genuino UNO

Jumper wires (generic)

Resistor 10k ohm

DHT11 Temperature & Humidity Sensor (4 pins)

Without driver

DHT22 Temperature Sensor

Without driver

Breadboard (generic)

Apps and online services

Arduino IDE

About this project

The DHT22 sensor (also known as the AM2302 reference) and his little brother the DHT11 are temperature and humidity sensors.

DHT22

The DHT22/AM2302 sensor is able to measure temperatures from -40 to + 125 °c with an accuracy of +/-0.5 °c and relative humidity levels from 0 to 100% with an accuracy of +/-2% ( +/-5% at extremes, to 10% and 90% ).

A measurement can be performed every 500 milliseconds ( twice per second ).

DHT11

The DHT11 sensor is able to measure temperatures from 0 to + 50 °c with an accuracy of +/-2 °c and relative humidity levels of 20 to 80% with an accuracy of +/-5%. A measurement can be done every second.

Then, the DHT22 will be better to use.

But … in this project I will show you how to use DHT11 and DHT22.

However, the DHT11 has a lower cost.

Connections

First pin ( DHT ) --> 5V

Second pin ( DHT ) --> Pin D2

A resistance must be connected between the wire of the second pin and the wire of the first pin.

Third Pin --> Nothing

Fourth Pin --> GND

The Code

You must download a library before used the code:

Go on Arduino IDE, go on file/example/DHT sensor Library/DHTtester (the code on DHT tester is the same as the code above and in attachments) of and observe:

Code

Code for DHT22Arduino

#include "DHT.h"
#define DHTPIN 2     
#define DHTTYPE DHT22   

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println("DHTxx test!");

  dht.begin();
}

void loop() {
  
  delay(2000);
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  float f = dht.readTemperature(true);

  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  float hif = dht.computeHeatIndex(f, h);
  float hic = dht.computeHeatIndex(t, h, false);

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hic);
  Serial.print(" *C ");
  Serial.print(hif);
  Serial.println(" *F");
}

Code for DHT11Arduino

#include "DHT.h"
#define DHTPIN 2     
#define DHTTYPE DHT11   

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println("DHTxx test!");

  dht.begin();
}

void loop() {
  
  delay(2000);
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  float f = dht.readTemperature(true);

  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  float hif = dht.computeHeatIndex(f, h);
  float hic = dht.computeHeatIndex(t, h, false);

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hic);
  Serial.print(" *C ");
  Serial.print(hif);
  Serial.println(" *F");
}