TheMainBoard

The Thermometer

An analog temperature & dew point gauge — part of the AQI Board

Overview

This repository is a part of the AQI Board project by @RolandThsive — a wall of analog-style instruments (hygrometer, thermometer, AQI meter and VOC meter) that are as much a showpiece as they are useful.

The Thermometer shows room temperature and dew point with two independent mechanical ticks, each driven by its own N20 motor and tracked by its own absolute encoder.

Both ticks are read 1 : 1 by AS5600 magnetic encoders on the main board, so the gauge always knows exactly where its needles are. Gear visibility and a symmetrical face were the top design priorities.

Features

• Absolute positioning on both ticks with AS5600 magnetic encoders
• Planetary gear set as the visual centrepiece of the face
• Custom main board built around a Seeed Studio XIAO ESP32-C3
• PCA9546A I²C multiplexer to talk to both encoders and the SHT40 sensor
• DRV8833 dual motor driver, with reverse-polarity and ESD protection on the connectors
• USART link (115200 baud) so the gauge can be polled and commanded by a master board
• 125 mm glass front and a two-part 3D-printed housing with embedded nuts

Parts Gallery

Full Assembly	Both Ticks Engaged	Main Board
Top Assembly	Bottom Assembly	Top Housing

Want to spin these around? The blog post has interactive 3D viewers for every assembly.

Instructions

For complete printing and assembly instructions, scroll all the way down to the 'Manufacturing' section on the official blog post: The Thermometer (AQI Board) Guide

[!TIP] Every part prints normally except the top housing, which has nuts embedded mid-print. The layer they sit on must be perfectly flat — use the Sharpie technique on the supports.

Bill of Materials (BOM)

Electronics

Schematic PDF: Electronics/TheMainBoard_Schematic.pdf · KiCad project, custom symbol/footprint libraries, Gerbers and datasheets are all in Electronics/.

Firmware

Built with PlatformIO on the Arduino framework for seeed_xiao_esp32c3.

cd Firmware/temperature_level_device
pio run -t upload
pio device monitor -b 115200

Between commands the gauge refreshes itself on its own, so it also works standalone.

Firmware/Testing Programs/ holds the bring-up sketches used along the way: motor silence tests (plain and PID), USART master communication, and a PCA9546A device scanner.

Repository Structure

Thermometer/
├── CAD/
│   ├── Blender Projects/        # Source .blend files for every assembly
│   ├── GLB-GLTF FIles/          # Web-ready 3D models + model-viewer pages
│   ├── Printables/              # STL files to print
│   └── Step Files/              # STEP assemblies (with and without electronics)
├── Electronics/
│   ├── The Main Board/          # KiCad project + Gerber files
│   ├── Libraries/               # Custom KiCad symbols, footprints & 3D models
│   ├── Documentations/          # Component datasheets
│   └── TheMainBoard_Schematic.pdf
├── Firmware/
│   ├── temperature_level_device/     # Main firmware
│   ├── temperature_level_device_2/   # Alternate firmware revision
│   └── Testing Programs/             # Bring-up & test sketches
├── LICENSE.txt
└── README.md

The AQI Board Family

Gallery

Full Assembly	The Face

The Mechanism	The Main PCB — Assembled	The Backside

The Internals	The Main PCB — Front & Back

The Main Board Schematic

Click any picture to see it full size.

Connect With Me

• Blog: ro-h-bots.blogspot.com
• Insta: @ro_h_bots

License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.