applications and implications, project development

Final Project Plan – CO₂ Monitoring System for Indoor Air Quality

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inlaywithoutacryl

What will it do?

The project continuously measures the CO₂ concentration in the lab’s air and indicates the air quality using a traffic light system (LEDs in red, yellow, and green). In addition, the measured values are shown on a small display. When the room is ventilated and the air quality improves, the device signals this with a green light. The goal is to provide a timely and clearly visible warning of poor air quality without the need for complex installations – the system is discreetly integrated into the existing acoustic insulation panels.

Who has done something like this before?

There are several DIY air quality monitoring projects, especially from the time of the COVID-19 pandemic, when CO₂ traffic light systems became common.

One example is a sound-based air quality alert developed by the Wuppertal Institute, which used bird chirping sounds to signal CO₂ levels (source). While the idea is charming, it is not suitable for office or FabLab environments where sounds might disrupt meetings – which is why I chose a visual traffic light system instead.

Within the Fab Academy community, I was inspired by the “Cloud” project by Jesús Lucero from FabLab Lima (Fab Academy 2021 – Jesús Lucero).

His design used a stylized cloud to represent air quality and worked with colorful light patterns in a tabletop object. Although that format didn’t fit my use case, the idea of using a natural element as a metaphor resonated with me.

Inspired by his use of a cloud, I chose to integrate the structure of a beehive as a visual and structural motif. It fits conceptually, symbolizing air flow, order, and environmental awareness – and technically, it allowed me to embed the system subtly into acoustic wall panels.

Another strong influence was the portable CO₂ monitor developed by Nicole Bakker at Waag FabLab (Fab Academy 2021 – Nicole Bakker). Her use of transparent materials and clean cable management directly inspired parts of my honeycomb design, where components remain visible yet neatly integrated.

My project builds on these references and merges them into a functional, calm, and visually unobtrusive system tailored for everyday use in shared creative spaces like a FabLab.

What sources will you use?

For the development of my project, I will use a combination of hardware components, datasheets, library documentation, and previous Fab Academy project references. Specifically:

  • The MQ-135 CO₂ sensor for measuring air quality. I will refer to datasheets and integration guides to calibrate it for reliable indoor CO₂ detection.

  • An LCD module (Joy-it COM-LCD 16x2, 16x4 pixels) for displaying real-time CO₂ levels and system states. I will use Arduino-compatible libraries to interface it with the microcontroller.

  • An RGB LED strip (Neopixel) for the traffic light-style visual feedback. I’ll use the Adafruit Neopixel library and follow tutorials for integrating it with ESP32 boards.

  • Bluetooth communication, as an optional feature, for remote debugging or integration with a potential mobile app interface.

  • Two Seeed Studio XIAO ESP32-C6 boards will be used – one for sensing and display logic, and another for control and communication. Their small form factor is ideal for embedded integration.

  • I will design and manufacture two custom PCBs for clean integration of the electronics into the housing and to minimize cable clutter.

What materials and components will be used?

The final CO₂ monitoring system will consist of the following materials and electronic components:

Electronic Components

  • MQ-135 CO₂ sensor – for continuous measurement of indoor air quality.
  • Joy-it COM-LCD 16x2 display module (6.6 cm / 2.6 inch, 16x4 pixel) – used to display live CO₂ readings and system status.
  • Neopixel RGB LED strip – for traffic-light-style visual feedback (green = good air, yellow = medium, red = poor).
  • 2x Seeed Studio XIAO ESP32-C6 – one microcontroller for sensor handling and one for display/control logic.
  • Bluetooth communication module (via ESP32-C6) – optional feature for wireless data transfer or configuration.
  • 2 custom-designed PCBs – to integrate the electronics cleanly and reduce wiring inside the housing.

Materials for Enclosure and Mounting

  • RPLA filament from Redline – used for 3D printed parts such as mounting brackets, light diffusers, or structural supports.
  • Multiplex wood panel – used for laser-cut housing elements and to blend the system with acoustic wall panels.
  • Transparent acrylic sheets – used for visual inspection windows and subtle integration of internal elements like the LEDs or electronics.

These materials were chosen for their functionality, aesthetics, and their suitability for digital fabrication processes (e.g., laser cutting, 3D printing, PCB milling). The combination allows the system to be unobtrusive, modular, and well-integrated into a FabLab or office environment.

What will you design?

The following elements will be custom designed for this project, combining additive and subtractive fabrication techniques, as well as embedded programming:

Additive (3D Printing)

  • Inner housing inlay
    A 3D-printed component that holds the electronics in place within the wooden enclosure. It ensures a secure fit and modular assembly for maintenance or upgrades.

Subtractive (Laser Cutting & CNC Milling)

  • Outer enclosure
    Made from multiplex wood, milled with a CNC machine to fit precisely into existing acoustic panels. It provides structural stability and visual integration into the lab environment.

  • Mount and cover for LEDs and display
    Cut from semi-transparent and clear acrylic using a laser cutter. These elements diffuse the light from the Neopixel strip and protect the LCD display while keeping it readable.

  • Custom PCB
    Designed for:

  • Sensor integration (MQ-135)
  • LED driver connection
  • Power distribution
    Milled using a CNC PCB milling machine.

Programming

  • Embedded code
    The firmware will be programmed to:
  • Read CO₂ values from the MQ-135 sensor
  • Control the RGB LED strip according to air quality thresholds
  • Display values and status information on the LCD
  • Optionally manage Bluetooth communication via ESP32-C6

All designs will be created using tools such as Fusion 360 (CAD), KiCad (PCB), and standard Arduino-compatible programming environments.

Where will the materials come from?

The materials and components for this project will be sourced from the following suppliers:

Electronics

  • All electronic components (e.g., MQ-135 sensor, Neopixel strip, LCD module, Seeed XIAO ESP32-C6 boards, connectors, etc.) will be sourced from BerryBase – a reliable German supplier for maker and IoT components.

3D Printing Material

  • The filament for 3D printed parts (specifically RPLA filament) will be sourced from Redline Filament – known for high-quality recycled PLA material made in Germany.

Acrylic

  • The semi-transparent and clear acrylic sheets used for light diffusion and protective covers will be sourced from Acrylglas-Shop.de – a specialized supplier for laser-cuttable acrylics.

Wood

  • The multiplex wood panels (used for CNC-milled enclosure parts) will be purchased from Hornbach – a widely available hardware and building materials store offering suitable birch plywood panels.

All sources were chosen based on availability, sustainability, quality, and compatibility with digital fabrication workflows.

How much will it cost?

The total estimated cost of the project is between €30–50, depending on specific component choices and quantities. Here is a breakdown of the expected costs:

  • CO₂ sensor (MQ-135): approx. €15–25
  • 2x Seeed Studio XIAO ESP32-C6 microcontrollers: approx. €14–20 (about €7–10 each)
  • Neopixel LEDs + LCD display (Joy-it 16x2): approx. €5–10
  • Housing materials (wood, acrylic, 3D printing filament): approx. €5
  • Miscellaneous (wires, connectors, resistors, soldering supplies): approx. €5

These prices are based on current listings from BerryBase, Redline Filament, Acrylglas-Shop.de, and Hornbach.

And I get some Wood and acrylic for free at our FabLab. Thanks HRW FabLab for this suppoprt.

What parts and systems will be made?

The following parts and systems will be self-designed and fabricated as part of the project:

  • The complete enclosure, including both 2D (laser-cut and CNC-milled) and 3D-printed components.
  • A custom PCB to connect the CO₂ sensor, Neopixel LEDs, LCD display, and the ESP32 microcontroller.
  • The control logic and embedded programming for the ESP32-C6, handling sensor data, visual output, and optional Bluetooth communication.
  • Integration into existing infrastructure, such as mounting the system within soundproofing panels in the lab environment, making it both discreet and functional.

Basically, all parts of the project — except for the electronic components themselves — are fully self-made. This includes the complete housing (2D and 3D design), custom PCB production, embedded programming, and mechanical integration.

The only pre-manufactured elements are the standard electronic modules such as the sensor, microcontroller, and display.

What processes will be used?

The project involves a variety of digital fabrication and programming processes, combining both additive and subtractive methods:

  • 2D Design using Inkscape or Fusion 360 for laser-cutting the outer shell (wood and acrylic).
  • 3D Design in Fusion 360 to create mounting components and inlays for holding electronics.
  • Laser cutting for acrylic and wood components.
  • 3D printing using RPLA filament for structural and internal parts.
  • PCB design in KiCad, followed by PCB milling using the LPKF software and a CNC PCB milling machine.
  • CNC milling of multiplex wood using a portal milling machine for precise large-format housing elements.
  • Programming with the Arduino IDE for the Seeed Studio XIAO ESP32-C6, including:
  • Reading and processing sensor data (MQ-135)
  • Controlling RGB LEDs and LCD display
  • Handling I²C communication
  • Optional Bluetooth communication

These processes ensure the project is fabricated and programmed almost entirely in-house, using FabLab tools and techniques.

What questions need to be answered?

Several technical and design-related questions still need to be resolved during development:

  • How can the CO₂ sensor be calibrated, and what CO₂ values realistically represent “good” air (e.g., after ventilation) and “poor” air (e.g., in an unventilated room) in our specific lab environment?

  • How can the traffic light-style LED display be positioned to ensure visibility for everyone in the room?

  • What type of power supply (USB, rechargeable battery, or fixed power adapter) is most stable and practical for long-term use?

  • How can the device be securely mounted inside the wooden enclosure and inlay without affecting its functionality or stability?

  • How should the threshold values for the LED color indicators (green/yellow/red) be defined to reflect meaningful air quality levels?

These questions will guide iterative testing, user feedback, and final design decisions.

How will the project be evaluated?

The project evaluation will focus on the following criteria:

  • Does the display work reliably and accurately under different air quality conditions?

  • Are the CO₂ measurements consistent, understandable, and plausible?

  • Is the system stable during continuous operation over an extended period?

  • Is the visual indication intuitive and easy to understand (colors and numeric values)?

  • How well is the device integrated into the lab environment in terms of discretion, usefulness, and robustness?

  • Have the Fab Academy-relevant technologies and processes been applied independently and thoroughly?

The project fulfills all core areas of the Fab Academy:

✅ 2D and 3D design
✅ Additive and subtractive manufacturing
✅ Electronics design and production
✅ Programming and microcontroller interfacing (ESP32)
✅ System integration and enclosure construction
✅ Make > Buy principle (manufacturing as much as possible independently)

The project is realized individually, clearly demonstrates the acquired skills, and is fully independently operable.