Ready to bring your KojiGotchi to life? Our assembly guide provides the steps to construct your own device. Please note, this guide is a work in progress and may not be as clear as we’d like just yet. We’re actively working on improving it, but in the meantime, please don’t hesitate to reach out if you encounter any difficulties or have questions about the steps. Your feedback is invaluable in making this process smoother for everyone!

Two KojiGotchi Versions

We offer plans for two distinct KojiGotchi versions:

• The Essentials Version: This portable prototype includes the bare minimum sensors necessary to provide a meaningful learning experience. It’s equipped with an ENS160 + AHT22 sensor module, offering readings on air temperature and humidity, along with approximate concentrations of CO2 and volatile organic compounds (VOCs). This version has been successfully constructed and is fully functional.
• The Advanced Version: As tested in our experiments, this version incorporates a more comprehensive sensor suite. It features the ENS160 + AHT22 air quality sensor, a DS18B20 temperature probe for internal readings, and an HD-38 Soil Moisture Sensor. This advanced prototype was designed for display at the BDC 2025 finals and, in its current iteration, is not yet portable. We welcome your input and ideas on how to make this version more compact!

Both versions share core electronic components: an SD card reader module, an SSD1306 OLED Screen for visual feedback, and three tactile buttons for interaction. They are both powered by the versatile ESP32-C3 Mini LOLIN microcontroller.

Open-Source 3D Files

To help you get started, we’ve provided all the necessary 3D files. You’ll find STL files for the case_front and case_back of the device, as well as the comprehensive Fusion360 file for the entire assembly. For those working with visuals, feel free to reach out to us for the textured device model suitable for Blender. Additionally, the mold for the transparent growth chamber is included, designed for vacuum forming. We used a Mayku Formbox, but any vacuum former should work, provided you use HIPS (High Impact Polystyrene). We found HIPS to be the only material capable of maintaining full transparency after the molding process, which is crucial for observing your koji’s growth.

Dive into the KojiGotchi’s circuitry with our comprehensive electronics resources! We’re providing detailed Fritzing files that illustrate all three possible configurations of the KojiGotchi in one clear, annotated file:

1. Essentials Version: The schematic for our portable prototype, featuring the core sensors for a basic learning experience.
2. Advanced Version (Breadboard Layout): A clear, organized layout of the advanced sensor suite on a breadboard, designed for easy understanding and experimentation.
3. Advanced Version (Prototyping Board Layout): The compact layout of the advanced setup on a prototyping board, optimized for maximum space efficiency (though still not fully portable in its current iteration).

In addition to the device configurations, you’ll also find the Fritzing file for Experiment #3. This specific setup was crucial during our design process, as it allowed us to meticulously determine the sensitivity and performance of various standard component sensors, directly informing our final choices.

Accompanying these schematics, we’ve provided the codebases for all of the aforementioned setups. These open-source files allow you to explore, modify, and understand the logic driving each KojiGotchi configuration.