Synopsis

Code to go along with the Raspberry Pi Controlled Irrigation System Instructable by Ben Finio.

This code contains the script "run_sprinkler.py" which automatically runs an outside sprinkler on a fixed schedule using a crontab. The sprinkler will only run if there has been little to no rain in the past 24 hours. The script uses the Weather Underground API to estimate recent rainfall

Requirements

This project requires a free developer API key to the Open Weather API. Go here to register for one: https://openweathermap.org/api

Specifically, this uses the one call api which is available for free https://openweathermap.org/api/one-call-api#history

You'll also need the requests python module. These commands will get everything you'll need:

sudo apt-get update && sudo apt-get upgrade
sudo apt-get install git
sudo apt-get install python-pip
pip install requests
pip install configparser

Setup

Download or clone this repo onto your Raspberry pi. These commands will put a rpi_sprinkler directory containing code under your home directory:

cd $HOME
git clone https://github.com/markveillette/rpi_sprinkler.git
cd rpi_sprinkler

If you install the code somewhere else keep track of the location for the crontab file.

If you look in this directory, you'll see two files with a .sample extension. Start by copying or renaming these files to remove the .sample extension:

cp config.sample config
cp run.crontab.sample run.crontab

Open config with your favorite text editor (nano, vim, emacs, etc..) and fill in your information to the right of each equal sign. This is where you will paste the API key you obtained from Weather Underground above.

Testing

Before installing the crontab, it's probably a good idea to test the APi is working. To do so, run

python run_sprinkler.py test

If you see a message like

API seems to be working with today's rainfall=0.000000 and past 24 hour rainfall=0.020000

everything is going okay. If you see some other message, check the internet connection, the API key, and the info you entered in the config file.

To run the sprinkler (assuming it's hooked up), run

sudo python run_sprinkler.py force

This should run the sprinkler without checking if it rained. It will also make a note in the log file (specified in the config file). If this doesn't work, check the GPIO pin in config is correct.

Installing the crontab

Now that the script is working, the final step is to install a crontab so that run_sprinkler.py runs on a fixed schedule. A crontab (or cron for short) is a simple text file that is used by Linux to run tasks at specified times. We'll be setting a cron to execute the script run_sprinkler.py.

To setup the crontab, open run.crontab with your favorite text editor. The basic format of the crontab file is as follows (lines begining with "#" are comments):

# minute   hour    day of month   month    weekday      Command    
# (0-59)  (0-23)    (1-31)       (1-12)     (0-6)                
    *        *        *           *           *         command

Decide what schedule you'd like to set and replace the approprite asteriks * with the weekdays,hours,minutes, etc you'd like. For example, to execute run_sprinkler.py every day at 6am and 6pm, run.crontab should look like this:

# minute   hour    day of month   month    weekday      Command    
# (0-59)  (0-23)    (1-31)       (1-12)     (0-6)                
    0      6,18        *             *         *        /usr/bin/python3 /home/pi/rpi_sprinkler/run_sprinkler.py

Where the "6,18" in the hour column and *'s everywhere else means to run at 6:00 and 18:00 local time every day. Notice that we included the full paths to both python3 and the run_sprinkler.py script (if you have the script in a different location make sure to modify the path). The Linux environment in which a crontab runs is typically very minimal, so it's safe not to assume anything about your $PATH or other environment variables.

This example will run at 12pm every Monday, Wednesday and Friday:

# minute   hour    day of month   month    weekday      Command    
# (0-59)  (0-23)    (1-31)       (1-12)     (0-6)                
    0      12         *             *       1,3,5       /usr/bin/python3 /home/pi/rpi_sprinkler/run_sprinkler.py

This will run at 6pm every second day:

# minute   hour    day of month   month    weekday      Command    
# (0-59)  (0-23)    (1-31)       (1-12)     (0-6)                
    0      18        */2           *         *       /usr/bin/python3 /home/pi/rpi_sprinkler/run_sprinkler.py

Google "crontab examples" for more.

Once you're set up the run.crontab file, install the crontab by entering

sudo crontab run.crontab

and you should be all set. Check the log file every now and then to monitor how things are going.

UPDATE (5/14/16): I added a @reboot command on the last line of the crontab file that sets all GPIO pins used to GPIO.LOW when the pi restarts. This was done to make sure the sprinkler doesn't run spontaneously if the pi accidentally reboots. If you installed rpi_sprinker in a different spot, make sure the path to run_sprinkler.py matches on this line as well.

If you restart the raspberry pi, the crontab should restart with it. To check if it's running, enter

sudo crontab -l

and you should see the contents of run.crontab appear. If you see nothing, you'll need to reinstall the crontab. If you ever want to remove the crontab, enter sudo crontab -r.

Good luck!