CO₂ Indicator Light

Hardware

• ESP32 Development Board
• MH-Z19B or MH-Z19C (400-5000ppm) Infrared CO₂ Module (needs calibration!!!)
• BME280 3.3V Temperature Humidity Barometric Pressure Sensor Module
• WS2811 Full Color LED Pixel Lights 5V (usually logic level is 5 V but work with ESP32 3.3 V, see notes
• Fully 3D-Printed Case

You should be able to do a build for around USD 22,00

Software

• The software should work with or wihout WIFi
• If no WIFI is available, you can still query the measurements over Bluetooth
• Using 8 LEDs Color/Lighting scheme will be as follows

  • Temperature (b … blue, c … cyan, g … green, r … red), there are a litte more shades, but overall lighting is as follows:

    °C	LED 1	LED 2	LED 3	LED 4
    < 19	b	c	g
    < 22		c	g
    < 25			g
    >=25			g	r

  • CO₂ ppm (g … green, y … yellow, o … orange, r … red), there are a litte more shades, but overall lighting is as follows:

    ppm	LED 5	LED 6	LED 7	LED 8
    < 800	g
    < 1400	g	y
    < 2000	g	y	o
    < 2600	g	y	o	r
    >= 3000	g	r	r	r

  So LED 3 and 8 can be seen as indicator for proper cabling/powering of the LEDs. 800 ppm is some target referred to in some publications, for classroom-settings this is rather hard to achieve.

• Use a Bluetooth client like NRF Connect to connect. CO₂ ppm will be the only characteristic available right now.

Config

If you want to configure initial WIFI and InfluxDB you may want to set following environment variables:

• WIFI_SSID - WIFI access point name
• WIFI_PASS - WIFI password
• INFLUXDB_URL - URL of your Influx-DB
• INFLUXDB_DB_NAME - Name of the Influx DB to write to

If you don’t set the vars, WIFI or INFLUX DB client will fail gracefully and you will still be able to get a reading using the LEDs or Bluetooth

Wiring

For 38 Pin ESP32 see docs/wiring38.md