A very simple CO2 measurement device for about than 40 Euros or 50$. This is the most simple design. It can be build in a few minutes without soldering. Only minimal technical understanding is required. You need a calculator to get the CO2 concentration.
You may use this design after you bought the MH-Z19B sensor to test it and to get a basic understanding of CO2 measurement.
Please read this document carefully to see what restrictions follow from this design.
This is the very simple design. It needs a conversion table to get the ppm value from the reading. No soldering needed, the connection is made with screw terminals:
Parts needed:
Tools needed: