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Description

Imported from GitHub: ducktec/usense_v2 · commit 3797cee · license CERN-OHL-P-2.0

Description

An ultra-compact low-cost environmental indoor air quality sensor node for CO2, temperature and humidity.

README

uSense v2

[!CAUTION] This design is in a very early stage. The PCB has not yet been finalized, manufactured and tested. It is likely that nothing will work as expected. Use at your own risk.

uSense v2 Render

An ultra-compact low-cost environmental indoor air quality sensor node for CO2, temperature and humidity with a simple RGB LED for status indication. Optional BLE connectivity.

Overview

uSense v2 is a battery-powered environmental sensor that measures temperature, humidity, and CO2 concentration. The device makes use of two Sensirion sensors (SHT45 for temperature and humidity, STCC4 for CO2). The ANNA-B402 module from u-blox integrates a Nordic nRF52833 microcontroller with onboard memory and a PCB antenna for BLE connectivity.

Features

  • Sensor Values: Temperature, humidity, CO2
  • Battery-powered: Optimized for long battery life with coin cell power or, alternatively external power, e.g. with a 2x AAA battery holder
  • Compact: 35mm x 25mm raw PCB, ~30mm x ~40mm x ~13mm with 3d-printed case
  • LED: Simple RGB LED for status indication, BH1750 ambient light sensor for adaptive brightness control (e.g, dimming or disabling LED in dark light conditions)
  • User Button: Single button for user interaction (e.g., pairing, reset, etc.)
  • Optional BLE Connectivity: Bluetooth 5.0 Low Energy support with u-blox ANNA-B402 module

Hardware Specifications

Sensors

  • SHT45: Temperature and humidity sensor with ±1.5%RH and ±0.1°C accuracy
  • STCC4: CO2 sensor using photoacoustic measurement principle, linked to SHT45 for temperature and humidity compensation
  • BH1750: 16-bit ambient light sensor (within center of case, effectiveness for light condition detection TBC)

MCU

  • u-blox ANNA-B402: Nordic nRF52833 low-power SoC with integrated BLE support and antenna, openCPU variant
  • SWD port: Compatible with RPI Debug Probe and other SWD programmers
  • Software: To be developed (embedded Rust/embassy)

Power Management

  • CR2032 coin cell battery holder on the under side of the PCB (optional)
  • JST-SH 2-pin connector for external power (e.g., 2x AAA battery holder)

Case

uSense v2 Case Render

  • Compact case designed in FreeCAD to be 3d printed
  • Separate chamber for sensors to minimize thermal interference
  • Button passthrough
  • LED should be nicely visible by diffusion through case when printed with bright filament (white, marble) (TBC)

Project Structure

uSense_v2/
├── pcb/                    # KiCad PCB design files
│   ├── uSense_v2.kicad_*   # Schematic and PCB layout
│   └── sketches_edge_cuts/ # Mechanical outline files
├── case/                   # FreeCAD case design
│   └── compact_case.FCStd  # 3D printable enclosure
├── docs/                   # Documentation and images
└── README.md              # This file

License

Both the PCB and the case designs are released under the CERN Open Hardware License Version 2 - Permissive.

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