Setting up the MH-Z14A CO2 sensor with Raspberry Pi
17 May 2020
After feeling tired for days (yay for COVID-19 and being at home all day every day), I wanted to see if the indoor air was at fault.
So I bought an an MH-Z14A sensor to get CO2-levels at home, by attaching it to a Raspberry Pi 3.
Indoor CO2-levels have pretty large impact on sleep and concentration. Usually measured in ppm (parts per million), the desired values are below 1000ppm.
You'll need a CO2-sensor, a Raspberry Pi and some jumper cables.
Log into your Pi and run sudo raspi-config.
Go to 5 Interfacing Options, then P6 Serial.
Select No on the login shell and Yes on the serial port hardware.
Then install pyserial for the sensor code.
sudo apt install python3-pip
pip3 install pyserial
The sensor has three interfaces, analog output, PWM output and a 9600 baud 3V/5V TTL UART interface. You basically send a request and the sensor responds.
I manually rewired the cable that came with the sensor, to have female jumper DuPont wires to attach to the Pi's GPIO pins.
You can also use F-M jumper wires and use the PWM interface instead.
The sensor pins are:
PWM (yellow) TXD (green) RXD (blue) VCC (red) GND (black) | AnalogOutput (white) HD (brown)
and need to be attached to the Pi's pins like this:
Here's a simplified version of the code, for the full version check here.
Now if you run python3 filename.py, you'll get the time, the current ppm value and the current temperature.