Simpitemp

A simple web application to interface with a AM2302 (DHT22) temperature and humidity sensor.

Items Needed

• DHT22/AM2302 temperature and humidity sensor
• Raspberry Pi 3
• Jumper cables if your sensor did not include jumpers

Wiring Your Sensor

There are a few varieties of the DHT22/AM2302 (and you could technically use the DHT11 if you swap out some libraries), but the one we're using from the link above has the pull up resistor already incorporated so wiring is very straightforward.

There are three pins on the chip, VCC, ground and data.

• VCC -> Pin 2 (5V)
• Ground -> Pin 6 (GND)
• Data -> Pin 7 (GPIO4)

A la:

[ V * G * * * * * * * * * * ]
[ * * * D * * * * * * * * * ]

There are a lot of good guides online for how to wire up the chip if you'd like more visuals! You can use a different GPIO pin as well, just make sure to update stats_collector.py and change board.D4 to board.DX.

Let's get started

Note: Raspbian Buster or later is required

Install Git and Python Utils (and vim if you're tinkering)

sudo apt-get install git-core python3 build-essential python-dev python3-pip libatlas-base-dev libgpiod2 npm vim

Clone repo

git clone https://github.com/kyleflan/simpitemp && cd ./simpitemp

Install Docker

curl -fsSL https://get.docker.com -o get-docker.sh
sh get-docker.sh
sudo usermod -aG docker $USER

Log out and back in to register the group (usermod) change.

Install pm2

sudo npm install pm2 -g

Enable SPI and I2C

sudo raspi-config

Navigate to interfaces and enable SPI and I2C, reboot

Start Redis

mkdir ./redis_data
docker run --name redis-01 --restart always -p 6379:6379 -v /home/pi/simpitemp/redis_data:/data -d redis redis-server --appendonly yes

If simpitemp is installed somehwere other than the pi user's home directory, update the path to the -v arg

Install

cd ./simpitemp
pip3 install .

Start the app

pm2 start ./pm2/process.json

Note: PM2 is a process manager, originally built for node.js apps, but it's very user-friendly and works for generic apps as well

Browse to the app

By default, the flask app is set to be available outside of localhost (i.e from other devices on your network). To lock down the app to where it's only accessible via the pi, edit webapp.py and remove host=0.0.0.0 on the last line.

Go to this URL: http://<Pi IP Address>:8080 you should see something like this:

Startup Across Reboots

To have the app persist across reboots, do the following:

pm2 startup

Copy and paste the generated command to create a startup script, then run:

pm2 save

...to save the current set of pm2 apps.