An el-cheapo small-scale irrigation system for watering my zucchini plant.

It uses an ESP8266 module (the cheap ESP-01 module, to be exact) and a relay board, both of which can be bought at your favourite chinese marketplace for less than three bucks. Oh yea and it uses micropython.

Together with a small water pump that is driven by the relay, and some hose which I drilled holes into, this makes for a really feature-rich dead cheap irrigation solution.

It automatically adjusts irrigation time based on the estimated evaporation which depends on the weather, and supports multiple irrigation events (e.g. in the morning and in the afternoon on hot days).

Throw in a 5V linear regulator and a 12V/1A power supply to the mix and we're talking less than 20 bucks in total. Yea and hot glue. Always use more hot glue.

And the best is: Of course it's internet of things, and of course it speaks a REST-ish API!

Download the "ESP8266 with 1MiB flash" version from micropython's download page. Erase the chip's flash and flash the firmware, e.g. using esptool.

Attach a serial adapter and set it to 115200 baud. Press enter for a python shell. Follow their guide to enable webrepl.

Create wifi_config.py with the following lines:

wifi_ssid = 'YOUR WIFI SSID'
wifi_key = 'YOUR WIFI KEY'

Use Webrepl to upload the main.py, index.html and wifi_config.py files.

Upon rebooting, the device should connect to your WiFi and you should be able to point your browser to http://device's ip address. Additionally, it exposes the following HTTP endpoints:

• GET /status.json gives you information about the current state of the system.
• GET /log.csv returns a log of past activations.
• GET /config.json reads the current config as JSON.
• GET /factor retrieves the current irrigation scaling factor for debugging.
• GET /main.py delivers the code running on the micro controller, for AGPL compliance.
• GET / or GET /index.html delivers the control website.
• PUT /config.json sets a new config. See below for the configuration format.
• POST /ntp forces the system to re-fetch its time via NTP. Note that this is done on startup anyway and should not be neccessary.
• POST /water?seconds=42 will turn on the pump relais for 42 seconds.

{
  "day_length": 86400,          // Optional and mainly useful for testing

  "schedule": [
    {
      "start": 28800,           // When the irrigation starts in seconds after the start of a
                                // day. 28800 = 8 * 3600.

      "duration": 5,            // Irrigation duration in seconds at the reference evaporation. If
                                // the current evaporation is higher(lower), this gets scaled up(down)

      "subtract": 0,            // Optional: Subtract this value from the calculated duration (i.e.,
                                // calculate max(0, duration * factor / 100 - subtract). Default: 0

      "max": 999,               // Optional: Maxium irrigation duration for this event, wo which the
                                // duration is clamped. Default: 10*duration
    }
  ],


  "reference_evaporation": 6,   // Reference evaporation in mm/day.

  "latitude": 49.5529,          // Your location (required for the weather forecast)
  "longitude": 11.0191559,
  "elevation": 279              // Elevation in m above NN
}

Note that the wifi_ssid and wifi_key must be changed by re-uploading the wifi_config.py file.

You can split up your desired total irrigation times into multiple events, e.g. one at 10am and one at 4pm: Create two schedule entries with the same duration, but set a max value on the first and the same number as subtract value on the second, e.g.:

"schedule": [
  {
    "max": 30,         // The first event will run for the calculated time, but at most 30 sec.
    "start": 28800,
    "duration": 55
  },
  {
    "subtract": 30,    // The second event will run for the remainder of the calculated time.
    "start": 57600,
    "duration": 55
  }
]

AGPL, are you serious?!

Dead serious. You can retrieve the source code via HTTP using the /main.py and /index.html endpoints.

This is Zucchini, a cost-effective™ smart home irrigation solution. Copyright (C) 2022 Florian Jung

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License version 3 as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/.