weather-client

This application monitors the temperature and humidity of a DHT20 sensor connected to a Raspberry Pi, and regularly relays the data to an instance of the weather-server

This client HTTP POSTs data to the weather server for storage and display.

Prerequisites

Weather server

First set up an instance of weather-server to serve as the receiver and database for the collected temperature information. See https://github.com/sd-hi/weather-server for more information.

Weather clients

For each instance of the client you want to set up, you will need:

• Raspberry Pi with Raspberry Pi OS installed (this documentation uses a Raspberry Pi 3B v1.2)
• DHT20 Temperature sensor)
• 4x female-female jumper wires

Wiring

Connect the DHT20 temperature sensor to the relevant Raspberry Pi pins:

1. Pi 2 - 5V
2. Pi 3 - GPIO2
3. Pi 9 - GND
4. Pi 5 - GPIO3

For guidance on the pin numbering on your device, use command

pinout

To see a diagram (more info can be seen in the GPIO Zero documentation)

Setup

Set correct timezone

For data consistency between sensors, set the timezone on the Raspberry Pi consistent with its location. For reference, the temperatures are sent to the server in UTC. The following command will set the device to the New York timezone.

sudo timedatectl set-timezone America/New_York

To see a full list of timezones, use command timedatectl list-timezones. This can be filtered with grep, for example timedatectl list-timezones | grep "America"

Enable I2C on Pi

For the Raspberry Pi to read data via the pins, it is necessary to enable I2C interface on the device, this can be by altering the /boot/config.txt file:

sudo nano /boot/config.txt

Uncomment the following line by removing the preceding #

dtparam=i2c_arm=on

A reboot is required for this setting to take effect

sudo reboot

Install Python prerequisites

For Python to interact and read data from the DHT20 sensor, install the supporting Adafruit packages for AHTx0 sensors:

python3 -m pip install Adafruit_Blinka adafruit-circuitpython-ahtx0

Clone repository

Download the weather-client script into the device's home directory:

cd ~
git clone https://github.com/sd-hi/weather-client.git

This creates a ~/weather-client directory

Set environment variables

Create the .env file by copying the .env.example file:

cd weather-client
cp .env.example .env
nano .env

Set the appropriate environment variables: -CLIENT_DEVICEID - A unique ID for this device, for instance sensor1

• CLIENT_LOCATIONID - A unique ID to signify this device's location e.g. bedroom1
• SERVER_URL - The URL for the weather-server instance
• SERVER_PORT - Port the weather-server is exposed on
• SERVER_APIKEY - API key for the weather-server instance (consistent with its API_KEY environment variable)
• POLL_INTERVAL - How often (in seconds) a temperature reading should be taken
• SENSOR_TYPE - Sensor type
  • Leave as AHTx0 to read from DHT20 sensor
  • Setting to TEST will avoid reading from the sensor and will feed temperature and humidity values for testing purposes
• SUBMIT_INTERVAL - How often (in seconds) the server should submit collected readings

Caching of readings

If the device loses network connectivity, it will continue to collect readings every POLL_INTERVAL seconds. When connection is restored all cached readings will be submitted in a single payload. Loss of power to the device will lose any cached readings not yet submitted to the weather-server.

Add weather client to boot

Creating a service ensures that temperatures will continue to be collected and submitted following device reboot, without intervention from the user.

Create service

Create a weather-client.service service to be run by systemd

sudo nano /etc/systemd/system/weather-client.service

Use the following, assuming weather client is in /home/pi/weather-client/ folder

[Unit]
Description=weather-client Service
After=network.target

[Service]
Type=simple
User=pi
WorkingDirectory=/home/pi/weather-client
ExecStartPre=/bin/sleep 10
ExecStart=/usr/bin/python3 /home/pi/weather-client/weather-client.py
Restart=on-failure

[Install]
WantedBy=multi-user.target

Refresh systemd and enable the service

sudo systemctl enable weather-client.service
sudo systemctl daemon-reload
sudo systemctl start weather-client.service

Upon start of the service, the device should begin to submit readings to the weather-server!

Controlling the service

If you need to stop service, use

sudo systemctl stop weather-client.service

To check status of service run

sudo systemctl status weather-client.service

To get log of service run

sudo journalctl -u weather-client.service