Admu.
FR
IoT · Engineering2023

Connected CO₂ sensor

Engineering Science project built by a team of three: measure air quality and regulate it automatically.

Period
Jan – Feb 2023
Team
3 students
Context
Engineering class
Boards
2 × micro:bit

01Goal

A senior-year Engineering Science project built by a team of three: design a system that measures a room's CO₂ level and regulates air quality by automatically opening or closing a window.

02Architecture

The system is built on two micro:bit boards (a main one programmed in Python, plus a secondary one), wired to the sensors and actuators.

  • Input: CO₂ sensor;
  • Outputs: LCD screen, RGB LED (color-coded air quality), DC motor;
  • Modeling: SysML (use cases, requirements, block definition);
  • Mechanical design: enclosure modeled in 3D with SolidWorks.
CAD overview of the enclosure
Enclosure modeled in SolidWorks
Final build with LCD screen
Final build: board, sensor and screen
SysML use case diagram
SysML: use cases
Python code of the main board
Main board code (Python)

03In hindsight

This was my first connected device, designed to work. Today, the first questions I'd ask would be an attacker's: how do the two boards talk to each other, and what stops a third party from sending a fake "open" command? What does the system do if the sensor returns an absurd value? Authenticating messages and planning a safe fallback state is exactly what separates a connected device from a secure one.