The objective of this tutorial is to develop a program interacting with DHT22 Sensor.
Prerequisites
- Components < 70 EUR:
| Component | Site | Price |
|---|---|---|
| Raspberry PI 3 | Farnell | 37.69 EUR |
| Power supply Micro USB 5V 2500mA | Amazon | 8.99 EUR |
| Micro SD Card (16 Go class 10) | Amazon | 9.99 EUR |
| DHT22 Sensor | ebay | 5.60 EUR |
| Breadboard | ebay | 3.30 EUR |
| 10 x Cables male/female | ebay | 1.00 EUR |
| 10 x Cables male/male | ebay | 1.00 EUR |
| 10 x Resistors 10k | ebay | 1.10 EUR |
| Total: | 68.67 EUR |
Note: This is an example as a guide. You can buy all components in others sites and maybe with better prices.
Electronic wiring
Install Adafruit
Adafruit is a Python library to read the DHT series of humidity and temperature sensors on a Raspberry Pi.
Download the latest version
wget https://github.com/adafruit/Adafruit_Python_DHT/archive/master.zip
Unzip the package
unzip master.zip
Installation
cd Adafruit_Python_DHT-master/
sudo python setup.py install
See more here
or with a virtual env
virtualenv -p /usr/bin/python2.7 ~/workspace/venv2.7/
source ~/workspace/venv2.7/bin/activate
pip install adafruit_python_dht
See how to create a virtual environment here
Get Series of data
Get Series of Temperature and Humdity from DHT22
Create new script
touch getDHT22Series.py
Edit and add this code below
vim getDHT22Series.py
#!/usr/bin/python
import Adafruit_DHT
def getData_func():
humidity, temperature = Adafruit_DHT.read_retry(Adafruit_DHT.DHT22, 4)
if humidity is not None and temperature is not None:
print('Temperature={0:0.1f}*C Humidity={1:0.1f}%'.format(temperature, humidity))
return { '@type':'DHT22', 'temperature': temperature, 'humidity': humidity }
else:
print('Failed to get reading. Try again!')
return
if __name__ == "__main__": getData_func()
See source here
Execute the code
python getDHT22Series.py
Output:
Temperature=23.8*C Humidity=36.3%
