CO₂ Sensor (ESP32 + SCD41 + 2.13in ePaper)

Battery Powered CO₂ Sensor Enclosure (ESP32 + SCD41 + 2.13in epaper) based on ESPHome (Home Assistant)

This enclosure is designed for a compact, battery-powered CO₂ sensor with an ePaper display, focused on long battery life and a clean, minimal look.

The sensor automatically measures indoor air quality and shows the current CO₂ level with temperature and humidity on the display. Sensor is connected to the HomeAssistant and uploads the values to the HA. 

With actual version of ESPHome code (link at the bottom of the text) it refreshes values on the eInk every 5 minutes and connects to HA every 15 minutes. In this mode with 2x 18650 3200 mAh is battery lifetime about 3 months. Code details are described at github. 

Print profile

• Print profile doesn't need the AMS. HASS logo and the texts are only in the 1st layer, so it is possible to print with one manual change of the filament.  
• Includes two versions of the back cover:
  • V1 hanging directly on the wall on one screw, no arretation on position
  • V2 with separate plate mounted by 2 screws on the wall with arreatation on the right position
     

What this enclosure is for

• Indoor CO₂ monitoring (bedroom, living room, office)
• Battery-powered operation – no permanent USB cable
• Wall-mounted or free-standing use
• Clean and discreet design suitable for living spaces

Key highlights

• Designed for ESP32 + Sensirion SCD41
• Space for a 2.13" ePaper display (WeActStudio)
• Optimized airflow for accurate CO₂ readings
• Easy access for charging and maintenance
• model contains 2 versions of back cover:
  • V1 for one screw directly in the wall without any back plate
  • V2 with separate wall mounted back plate

Smart behavior

• The device sleeps most of the time to save battery
• The display keeps the last reading without power
• When the battery is low, it shows a Low Battery indicator
• Automatically resumes normal operation after charging
• Firmware updates can be done wirelessly (OTA)

You don’t need to interact with it every day – it just works.

Ideal for

• Air quality awareness without distractions
• Smart homes using Home Assistant

Used Components:

• Sensirion SCD41 CO2 sensor: SCD40/SCD41 gas sensor module detects CO2, carbon dioxide, temperature and humidity in one sensor I2C communication - AliExpress
• Lolin D32 board: 1/5PCS ESP32 LOLIN32 Wifi Bluetooth Development Board ESP32 ESP-32 REV1 CH340 CH340G MicroPython Micro/TYPE-C USB For Arduino - AliExpress
• 2,13in WeActStudio epaper display: WeAct 2.9'' 2.13" 2.9 2.13 Inch Epaper Module E-paper E-Ink EInk Display Screen SPI Black-White Black-White-Red - AliExpress
• Battery holder for 2x 18650 LiIon 
• 2x 1M resistor for battery voltage measurement (voltage divider between BATT - D35 - GND)
• 8x M3x5,7 thread insert: 50pcs M3*5.7*4.6 Knurled Brass Insert Embedment Nut for 3D Printer Hot Melt Heat Injection Molding High 5.7mm Out Diameter 4.6mm - AliExpress
• 1x M2,5x4mm thread insert: 100-300Pcs M2 M2.5 M3 M4 M5 M6 M8 Heat Set Threaded Insert Brass Nut Hot Melt Knurled Inserts Double Twill Embedment Copper Nuts - AliExpress
• 4x M3x10 pan head screw
• 4x M3x16 countersunk head screw
• 1x M2,5x5 pan head screw (for Lolin D32)

ESP Home code: 

CO2-sensor-for-Homeassistant/README.md at main · OK2CME/CO2-sensor-for-Homeassistant