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CorO₂Sens

Disclaimer and credits: this repository is a fork from https://github.com/kmetz/coro2sens.

Several changes have been made in this fork. Please also consult the README file of the original version.

The following sections have been updated for this repository:

Build a simple device that warns if CO₂ concentration in a room becomes a risk for COVID-19 aerosol infections.

  • Measures CO₂ concentration in room air.
  • Controls two LEDs (green + orange/red) for indication of warning/critical CO2 level.
  • Controls a NeoPixel ring for indication of CO2 level and its criticality (optional).
  • A buzzer can be connected that alarms if levels are critical (optional).
  • Also opens a WiFi portal which shows current readings and a graph (not connected to the internet; optional).
  • Can be built for ~ $60 / 50€ (parts cost).

This project was heavily inspired by ideas from Umwelt-Campus Birkenfeld.

You can also find a good overview of the topic by Rainer Winkler here: Recommendations for use of CO2 sensors to control room air quality during the COVID-19 pandemic.

Sensors

The sensor used here is the Sensirion SCD30 (around 70 USD / 60 €).

The pressure compensation by an additional sensor BME280 is currently no longer supported in this forked repo.

Threshold values

LED color CO₂ concentration
Green ("all good") < 800 ppm
Yellow ("open windows") 800 – 1000 ppm
Red ("leave room") > 1000 ppm

Based on a Recommendation from the REHVA (Federation of European Heating, Ventilation and Air Conditioning associations, rehva.eu) for preventing COVID-19 aerosol spread, especially in schools.

Web server

You can read current levels and a simple graph for the last hour by connecting to the WiFi coro2sens_<serialno> that is created. Most devices will open a captive portal, immediately showing the data. You can also open http://10.0.0.1/ in a browser. You can also control most of the settings via the web interface. Visit http://10.0.0.1/config in a browser.

You need

  • A NodeMCU board (any other ESP8266 based board might also work).
  • Sensirion SCD30 I2C carbon dioxide sensor module (mouser, digikey).
  • (optional) NeoPixel ring
  • (optional) 2 LEDs (green + yellow/red); the green one indicates "all good" (< 800 ppm) the other one that this limit has been exceeded
  • (optional) A 3V piezo buzzer or a small speaker.
  • (optional) You may want to work with Guido Burger's IoT Octopus PCB. This helps fixing the sensor and the NodeMCU, as well as the LEDs.
  • (optional) A nice case :) Make sure the sensor has enough air flow.
  • An Arduino IDE (select the board "NodeMCU 1.0 (ESP-12E Module)", v2.7.1 and v2.7.4 have been tested and should work; you may need to install the board support for the "esp8266")
  • Arduino libraries:

Wiring

ESP8266 pin goes to
3V3 SCD30 VIN
GND SCD30 GND, Buzzer (-)
SCL / D1 SCD30 SCL
SDA / D2 SCD30 SDA
D3 LED DIN
D5 Green LED
D6 Buzzer (+)
D7 Warning LED (yellow or red is a good idea)
D8 NeoPixel ring