Moisture sensor

Watering Controller

A tinkering project to automate watering plants in a greenhouse and analyzing data afterwards.
Current Progress can be seen in "Status" at the bottom.

Codewise: an exploration of using embedded rust, specificaly embassy.

Short Overview

Hardware

Per pot:

• 1 STM32F103C8#
• capacitive moisture sensor
• valve
• mcp2551 can RX/TX
• Mosfet IRFB3006 (there are alternatives, this one worked for us)

Central Controller:

• Pico 2 W (pico 1 2 would be enough)
• 2x16 LCD Display
• MCP2515 for can communication.
• UX to be determined

Additional Hardware needed:

• Some kind of reservoir
• Silicone tubes for delivering water to valves

System Design

The central controller communicates with each moisture sensor over CAN-Bus. The Specs for this Communication can be found here. The implementation is found here. The moisture sensors get a threshold and use their valves to hold that threshold, currently through a simple comparision (potential PID).

Current Status

August '25: Web-functions added, central controller accesses WLAN. Sensorreadings possible through network with webinterface-prototype.

Story and some Context

After building a greenhouse on our little roof terrace for my fiancée, I stumbled upon the biggest problem in the private greenhouse industry. While tomatoes and cucumbers thrived, the biggest recurring problem was watering the plants, as you have to do so every day; on hot days, multiple times a day. The solution was obvious: I turned to my good friend Bendix and we started engineering the hell out of this seemingly small problem. The idea got bigger and bigger, until we suddenly had the first prototype running on a cheap patch panel. Our system was actually reading live moisture data and maintaining a moisture level for several days. The next step was soldering prototype v2, which is currently running in the greenhouse.
Throughout the process, I had lots of ideas for little extras, such as a menu operated through a rotary encoder on an LCD display or RGB LEDs. Because everything is better with RGB. The final version is supposed to support up to 256 pots (far too many for the 2 x 1.2m²), so the system is adaptable for larger greenhouses. We are planning to implement a web interface and push notifications to smartphones, so even while being abroad, there is no need for close monitoring by a third party. But these are future dreams. Our current priority is the watering and monitoring functionality – all while the CAN network does its job.
Bendix has been documenting his progress in code here since day one. I joined GitHub mainly to be a part of it. To be honest: I have absolutely no clue about coding other than basic principles and a rough idea of what computers can do. My main background is being a mechanic by trade. Now I do my part by trying to document our progress and give a little context about what we do. I'll try to update regularly – who knows, this might one day attract public interest.

Small Addition: I startet building a webinterface, all while learning how to work with HTML and JavaScript. If you're interested, click here.

-Philipp

Milestones

June '25: working menu on LCD-Display with individual IDs and live data, navigation possible through rotary encoder and "return"-button
June '25: data saved, showing 9 day continuous watering without crashes or similar issues; moisture level plausible
July '25: Hardware for easier refilling added, also new water container
July '25: Webinterface concept working, reference here.
August '25: Access to live data possible through Webinterface concept.

Status History

Up to July '25: Two pot-sensors together with central controller, currently set up in greenhouse, with CAN-Network and watering function working as far as assessable. Menu working, displayed on LCD.
Up to August '25: Three pot-sensors together with central controller, currently set up in greenhouse, with CAN-Network and watering function working fairly reliable. Menu working, displayed on LCD. RGB-LEDs added for easier identification while changing thresholds. Humidity/Temperaturesensor added. All data is logged on SD-Card.