higher concentrations of CO2 inside will make you sleepy and have an impact on your wellbeing. during the current pandemic higher CO2 concentrations inside are also a pretty good indic ation for higher levels of aerosol and as such a higher risk for infection. the 'CO2 Ampel' (CO2 traffic light) will give you a visual representation of the current situation and remin d you to open windows to keep you happy and healthy
| description | part | link |
|---|---|---|
| ESP32 | ESP-32 30Pin | Aliexpress Link |
| Infrared CO2 Sensor | mhz-19 | Aliexpress Link |
| Active piezzo buzzer (optional) | KY-012 | Aliexpress Link |
| OLED Display | SSD1306 | |
| LED-Ring (9 Pixel) | WS2812 | Aliexpress Link |
- solder everything according to the connection schema
- get yourself a copy of esphome (https://esphome.io/)
pip3 install esphome - compile the firmware with
co2ampel=USER_ROOM esphome co2sensor.yaml run- replace user with a nick that identifies you or your organisation
- replace room with the place the sensor is located at
- e.g. unhb_hackspace or unhb_001 for obfuscation
- these will be used for online graphing! if sensor has wifi access
- hold boot on your esp32 until fw upload starts.
- place the sensor in your room, keep it away from direct exposure of breath (give it at least 1-2m distance to humans or other co2 sources to get the average co2 level of the room)
- when there is a freifunk wifi around there is nothing to do for you, same when you defined your own wifi via secrets.yaml.
- else just wait a bit and the sensor will spawn an wifi without a password. connect with your phone and choose to login or open http://192.168.4.1 in a browser to enter your wifi credentials
- when everything is done, the default config will send the sensor readings back to the project where you can view online graphs (see grafana)
there is a quick setup on here your sensor should apper in the list on the left as soon it is connected via wifi.
| ESP32 PIN | peripherals | note |
|---|---|---|
| VIN | mhz-19 (VCC) | |
| GND | mhz-19 (GND) | |
| GND | KY-012 (GND) | passive buzzer will do as well |
| D12 | KY-012 (Signal/+) | |
| 3V3 | SSD1306 (VCC) | |
| 3V3 | WS2812 (VCC) | |
| GND | WS2812 (GND) | |
| GND | SSD1306 (GND) | |
| D4 | WS2812 (DI) | |
| RX2 / D16 | mhz-19 (TX) | |
| TX2 / D17 | mhz-19 (RX) | |
| I2C SDA / D21 | SSD1306 (SDA) | |
| I2C SCL / D22 | SSD1306 (SCL) |
if your ws2812 don't work on 3.3V power (most will do) you can try to use 5V instead. there are plenty different ws2812 builds so ymmv... if the leds don't work with 5V try to add a pullup resistor to your data line and a diode towards D4 to raise your high level while protecting your GPIO (https://forum.arduino.cc/index.php?topic=578735.msg3941756#msg3941756)
looks like this:
either way it might be a good idea to have a capacitor between VCC and GND. my prototype worked without any of these, but from time to time some LEDs just randomly turn on...
| CO2 measure | light | buzzer | meaning |
|---|---|---|---|
| 400 ppm | none | no | more or less the baseline of the sensor hardware and means 'outside air quality' |
| 400-800ppm | none | no | safe zone and can be considered good air quality |
| 800-1000ppm | yellow | no | warning zone (consider to open windows) and is between medium and bad air quality |
| > 1000ppm | red + blink | no | hygienic bad air quality, chance for infections rise |