There have been plenty of projects designed to automate lawn irrigation, however these normally refer to systems that open a single valve and turn on the sprinklers — all the sprinklers — at one time. Due to an irregularly shaped yard and a limited water supply, Sebastian Staacks wanted a bit more granular control.

Staacks’ setup consists of a half dozen Gardena valves, which are housed in underground boxes, while the brains and power supply are screwed to a wooden board on a wall in his garage. An Arduino Nano 33 IoT is employed to activate the sprinklers in six zones with an eight-channel relay bank. Relay channels 1 to 6 correspond to the valves controlling the sprinkler groups, the seventh is used for the main valve, and the eighth is saved for a “bonus” function that may be disclosed later.

The device operates over WiFi using MQTT via an OpenHAB installation. It also features a pair of buttons and a small OLED screen for manual interface, especially useful when he’s on vacation and someone else is taking care of the house.

Code for the build can be found on GitHub, and more details are available in Staacks’ blog post.