Raspberry Pi Plant Monitor

This is a relatively simple system for monitoring and watering multiple (up to 4) pots.

Hardware

For the bill of components and assembly instructions see the blog post.

Installation

IMPOIRTANT: in order to use the ADC, you need to enable I2C interface via raspi-config.

The system is operated by running watering_station periodically (i.e. hourly), which will keep track of the state of each pot and initiate watering when needed.

As user pi run crontab -e and add the invocation of watering_station to your crontab. In my case, it looks like:

25  *  *  *  *  $HOME/bin/watering_station >> $HOME/log/watering_station.log 2>&1

By default the script runs mostly quietly. Run watering_station -h to see the available options.

Configuration

Copy the example .watering_station.config to your home directory and edit it. Configuration mostly deals with hardware setup (i.e. which GPIO pins and channels correspond to each pot) and pot- and sensor-specific cut-off levels for dry soil (which should be calibrated experimentally).

Stats processing

The system implements a simple but relatively flexible framework for collecting the sensor and watering stats. Once stats are gathered, they can be passed to a stats processor object, which can perform custom processing of such stats. Such custom stats processor class is implemented as a subclass of StatsProcessor. Two example processors are provided:

• StatsPrinter simply prints the stats on stdout.
• StatsCSVLogger appends the stats to a CSV file. It also demonstrates how such processor can be configured via a special section in the configuration file.

It should be easy to implement a class to do more elaborate stats processing, e.g. uploading them to Google BigQuery, saving in a database etc.

Stats processor is specified via stats_processor directive in the [general] section of the configuration file.

Shutdown button

Raspberry Pi doesn't have any hardware based method to shut down. One can either turn the power off which is a terrible idea for any OS or to log into the machine and shut it down via the command line. Neither is super convenient.

To make it slightly easier, I've added a hardware button connected to GPIO and a script to power the device off when the button was pressed for 5 seconds (to avoid accidental presses). The script is called shutdown_button (shocking, I know). To install and activate, do the following:

• Copy (or symlink) shutdown_button into ~/bin directory of user pi.

• By default the script assumes the button is connected to GPIO pin 25. If it is not, change the shutdown_button.service file to pass an appropriate value via --pin option to the script.

• Set up systemd configuration for the script and start it:

sudo cp shutdown_button.service /etc/systemd/system/
sudo systemctl start shutdown_button.service

Now you can check the status to verify that the script is running:

sudo systemctl start shutdown_button.service