$12 Plant Bot is an ESP32-C3 soil sensor and pump driver for fully automated indoor plant care

The Plant Bot is an open-source, Internet-enabled plant monitor powered by the ESP32-C3 microcontroller and integrating a corrosion-resistant capacitive moisture soil sensor and a pump driver on a single printed circuit board, eliminating the need for additional cabling.

The Plant Bot is designed to automate indoor plant care by combining moisture sensing, light sensing, and pump activation. It can be powered via USB or a single coin cell battery which lasts up to a week with daily updates. An onboard multi-color LED visually represents the current soil condition, ranging from red (dry) to blue (moist).

The “Soil Level” line on the board indicates the maximum depth to which the sensor or device should be inserted into the soil. According to the maker, the Plant Bot will remain unaffected by corrosion if the soil level does not exceed this line. Other solutions we’ve covered with a soil sensor usually separate the main board and the sensor which are connected with some wirings. Some examples include the Maker Uno RP2040 kit, the ANAVI Gardening uHAT, and Eduponics Mini v2.0. One exception is the ESP32-powered TTGO T-Higrow with a design somewhat similar to the Plant Bot.

Plant Bot specifications:

• Wireless Module – ESP32-C3-MINI module
  • ESP32-C3 SoC 32-bit RISC-V single-core processor, @ up to 160MHz; 2.4GHz and Bluetooth (BLE) 5.0 connectivity
  • Memory – 384 KB ROM, 400 KB SRAM (16 KB for cache)
  • Storage – 4MB flash
• USB – USB-C port for power and programming
• Connectivity – 2-way screw terminal for water pump
• Sensors
  • Vishay TEMT6000X01 ambient light sensor
    • Angle of half sensitivity: ± 60°
    • Peak sensitivity: 570nm (suitable for plants)
  • Capacitive moisture sensor
• Pump Driver – Texas Instruments DRV8837C motor driver
• Misc – Multi-color LED for moisture level representation, 1x LED for pump activation, 2x buttons
• Power Supply
  • 700mA 3.3V LDO via USB or coin cell battery
  • Texas Instruments BQ24073RGTR Battery Charger
    • Over Temperature, Voltage & Short Circuit Protection
    • Charge Current: 1.5A
• Mounting – FR-4 stake into the soil

The Plant Bot is an open-source project and schematics, source code, and demos are hosted on GitHub. The ESP32-C3 plant monitor can be programmed using ESP-IDF (advanced users), MicroPython, and Arduino. The available demos allow the Plant Bot to send notifications to Telegram or relay measurements to IoT platforms like Thingspeak or Firebase. The Hackaday project page has more information about the device.

The Plant Bot is priced at $12 on Tindie and Lectronz by ElektroThing who also previously designed the Spark Analyzer USB-C PD analyzer and power supply.

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