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Arduino - Temperature Humidity Sensor

In this tutorial, we are going to learn how to read temperature and humidity value from DHT11 or DHT22 sensors

DHT11 and DHT22 are sensors that we can use to measure temperature and humidity. They are similar to each other. You can choose one of them, depending on your needs

If you only want to get temperature, we recommend using a waterproof DS18B20 temperature sensor instead. It is an inexpensive and neat sensor. You can put it in hot or cold water.

Hardware Required

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B
1	×	Temperature and Humidity Sensor DHT11
1	×	Temperature and Humidity Sensor DHT22
1	×	10 kΩ resistor
1	×	Breadboard
n	×	Jumper Wires

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About DHT11 and DHT22 Temperature and Humidity Sensor

The commons between DHT11 and DHT22

Pinouts are the same
Wiring to Arduino is the same
Programming (with a library) is similar (only one line of code is different)

The differences between DHT11 and DHT22

	DHT11	DHT22
Price	ultra low cost	low cost
Temperature Range	0°C to 50°C	-40°C to 80°C
Temperature Accuracy	± 2°C	± 0.5°C
Humidity Range	20% to 80%	0% to 100%
Humidity Accuracy	5%	± 2 to 5%
Reading Rate	1Hz (once every second)	0.5Hz (once every 2 seconds)
Body size	15.5mm x 12mm x 5.5mm	15.1mm x 25mm x 7.7mm

As you can see, the DHT22 is a little more accurate, larger range but more expensive than DHT11.

Pinout

DHT11 and DHT22 sensor in original form have four pins:

GND pin needs to be connected to GND (0V)
VCC pin needs to be connected to VCC (5V)
DATA pin the pin is used to communicate between the sensor and Arduino
NC pin Not connected, we can ignore this pin

DHT11 and DHT22 temperature and humidity sensor Pinout

Some manufacturers provide DHT11 and DHT22 sensor in module form with three pins: GND, VCC and DATA pins.

※ NOTE THAT:

In module form, the order of the module's pins can vary between manufacturers. ALWAYS use the labels printed on the module. Look closely!

DHT11 and DHT22 temperature and humidity module Pinout

Wiring Diagram

Wiring to Arduino is the same for both sensors. In orginal form, A resistor from 5K to 10K Ohms is required to keep the data line high and in order to enable the communication between the sensor and the Arduino

Arduino - DHT11 Sensor Wiring

Arduino DHT11 Temperature and humidity Sensor Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

Arduino - DHT22 Sensor Wiring

Arduino DHT22 Temperature and humidity Sensor Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

Arduino - DHT11 Module Wiring

Most of DHT22 sensor modules have a built-in resistor, so you don't need to add it. it saves us some wiring or soldering works.

Arduino DHT11 Temperature and humidity Module Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

Arduino - DHT22 Module Wiring

Most of DHT22 sensor modules have a built-in resistor, so you don't need to add it. it saves us some wiring or soldering works.

Arduino DHT22 Temperature and humidity Module Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

How To Program For DHTxx Temperature Sensor

Programming for both sensors is similar. There is only one line of code different.

Include the library:

#include "DHT.h"

Define the Arduino pin connected to DHT sensor:

#define DHTPIN 2

Define the sensor type: DHT11 or DHT22 (This is the different line of code)

#define DHTTYPE DHT11

#define DHTTYPE DHT22

Declare DHT object

DHT dht(DHTPIN, DHTTYPE);

Initialize the sensor:

dht.begin();

Read humidity:

float humi = dht.readHumidity();

Read temperature in Celsius:

float tempC = dht.readTemperature();

Read temperature in Fahrenheit:

float tempF = dht.readTemperature(true);

Arduino Code - DHT11

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-temperature-humidity-sensor */ #include "DHT.h" #define DHTPIN 2 #define DHTTYPE DHT11 DHT dht(DHTPIN, DHTTYPE); void setup() { Serial.begin(9600); dht.begin(); // initialize the sensor } void loop() { // wait a few seconds between measurements. delay(2000); // read humidity float humi = dht.readHumidity(); // read temperature as Celsius float tempC = dht.readTemperature(); // read temperature as Fahrenheit float tempF = dht.readTemperature(true); // check if any reads failed if (isnan(humi) || isnan(tempC) || isnan(tempF)) { Serial.println("Failed to read from DHT sensor!"); } else { Serial.print("Humidity: "); Serial.print(humi); Serial.print("%"); Serial.print(" | "); Serial.print("Temperature: "); Serial.print(tempC); Serial.print("°C ~ "); Serial.print(tempF); Serial.println("°F"); } }

Arduino Code - DHT22

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-temperature-humidity-sensor */ #include "DHT.h" #define DHTPIN 2 #define DHTTYPE DHT22 DHT dht(DHTPIN, DHTTYPE); void setup() { Serial.begin(9600); dht.begin(); // initialize the sensor } void loop() { // wait a few seconds between measurements. delay(2000); // read humidity float humi = dht.readHumidity(); // read temperature as Celsius float tempC = dht.readTemperature(); // read temperature as Fahrenheit float tempF = dht.readTemperature(true); // check if any reads failed if (isnan(humi) || isnan(tempC) || isnan(tempF)) { Serial.println("Failed to read from DHT sensor!"); } else { Serial.print("Humidity: "); Serial.print(humi); Serial.print("%"); Serial.print(" | "); Serial.print("Temperature: "); Serial.print(tempC); Serial.print("°C ~ "); Serial.print(tempF); Serial.println("°F"); } }

If you compare two above code, you realize that there is one line different (line 11)

Quick Steps

Connect Arduino to PC via USB cable
Open Arduino IDE, select the right board and port
On Arduino IDE, Go to Tools Manage Libraries

Search “DHT”, then find the DHT sensor library by Adafruit
Click Install button to install the library.

You will be asked for intalling some other library dependencies
Click Install All button to install all library dependencies.

Copy the above code corresponding to the sensor you have and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to Arduino
Make enviroment around sensor hotter or colder
See the result on Serial Monitor.

COM6

Send

Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 27.00°C ~ 80.60°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 32.00% | Temperature: 28.00°C ~ 82.40°F Humidity: 31.00% | Temperature: 29.00°C ~ 84.20°F Humidity: 32.00% | Temperature: 29.00°C ~ 84.20°F Humidity: 31.00% | Temperature: 29.00°C ~ 84.20°F

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9600 baud

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Video Tutorial

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Alternative DHT11 and DHT22 sensors

The Best Arduino Starter Kit

See the best Arduino kit for beginner

Arduino - Temperature Humidity Sensor

Hardware Required

About DHT11 and DHT22 Temperature and Humidity Sensor

The commons between DHT11 and DHT22

The differences between DHT11 and DHT22

Pinout

Wiring Diagram

Arduino - DHT11 Sensor Wiring

Arduino - DHT22 Sensor Wiring

Arduino - DHT11 Module Wiring

Arduino - DHT22 Module Wiring

How To Program For DHTxx Temperature Sensor

Arduino Code - DHT11

Arduino Code - DHT22

Quick Steps

Video Tutorial

Alternative DHT11 and DHT22 sensors

The Best Arduino Starter Kit

See Also