Raspberry Pi Tutorial: How to Use the DHT-22

The DHT-22 (also named as AM2302) is a digital-output relative humidity and temperature sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin. In this tutorial you will learn how to use the DHT-22 sensor with Raspberry Pi.

Tutorial updates and more Raspberry Pi tutorials can be found here:
http://www.ardumotive.com/how-to-use-the-dht-22-en...

Let's get started!

Step 1: About the DHT-22 Sensor

The DHT22 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed). Connections are simple, the first pin on the left to 3.3V power, the second pin to your data input pin and the right most pin to ground.

Technical details:

Power: 3-5V
Max Current: 2.5mA
Humidity: 0-100%, 2-5% accuracy
Temperature: -40 to 80°C, ±0.5°C accuracy

Step 2: What You Will Need - Hardware

For this tutorial you will need:

Step 3: The Circuit

The connections are pretty easy, see the image above with breadboard circuit schematic.

Step 4: Install Adafruit DHT Library

Before python code you need to download and install the DHT library in your Raspberry Pi. Open the terminal window and type:

git clone https://github.com/adafruit/Adafruit_Python_DHT.git
cd Adafruit_Python_DHT
sudo apt-get update
sudo apt-get install build-essential python-dev
sudo python setup.py install

Now you will have to reboot your Pi system to get the Adafruit driver.

Step 5: Python Code

#Libraries
import Adafruit_DHT as dht
from time import sleep
#Set DATA pin
DHT = 4
while True:
    #Read Temp and Hum from DHT22
    h,t = dht.read_retry(dht.DHT22, DHT)
    #Print Temperature and Humidity on Shell window
    print('Temp={0:0.1f}*C  Humidity={1:0.1f}%'.format(t,h))
    sleep(5) #Wait 5 seconds and read again

Download the code from here and open it with Thonny Python IDE or run it from terminal.