[Ovidiu] cares for their house plants, trying to dial in the perfect soil humidity and light levels. However, many cheap monitors tend to rust after a few weeks of sitting in a damp, slightly acidic environment. By creating a custom plant monitor with a removable probe, not only can [Ovidiu] integrate better with their Home Assistant setup, but it will also be less wasteful.
The build starts with an ESP32-S3, a TP4056 charging circuit, a small e-ink display, and an AHT20 IC for air humidity and temperature. The ESP32 reads the probe using the capacitance measuring devices for touchpads built into the chip. Or course, a 450mAh battery provides a battery life of about 11 days. The probe is just a bare PCB with a connector at the top, making them cheap and easy to swap. They included pads on the probe for a thermistor for reading soil temperature, but this is optional. A handsome 3D-printed case wraps it all up nicely.
To further extend the battery, [Ovidiu] added a small solar panel via the header they left on the top of the project for expansion. All the code, schematics, and STL files are up on GitHub for your perusal. Of course, this isn’t the first project we’ve seen that uses swappable capacitive probes, but we love seeing people continue to iterate on good ideas.