A carbon dioxide (CO2) meter is probably the most underrated device that, in my opinion, should be in every apartment, because it shows how breathable the air is and with the help of it you can always see when it's time ventilate.
Such a meter is very rare in apartments, primarily because of the high price. I bought my first AZ Instruments 7798 CO2 datalogger for $ 139 and it was the cheapest model on the market.
Now a ready-made CO2 meter costs about 4,000 rubles, and a home-made one will cost half the price.
I figured out how to connect carbon dioxide sensors from Aliexpress, found examples of their use and made the simplest CO2 meters that are very easy to repeat.
Most homemade products use the MH Z19B sensor, but it has a bad feature - if the room is not ventilated to the state of the street air every day, the readings begin to "float" (the sensor is automatically calibrated every day and calculates the minimum CO2 level in the room as 400 ppm). I ordered two more advanced sensors - Sensair S8 004-0-0053 (it cost me $ 28.86, now
costs $ 32.30) and Telaire T6703 (I bought it for $ 19.41, now it costs $ 28.35).I connected the sensors to the Arduino Nano (you can buy it for $ 2.98), but you can use another Arduino board. A cheap TM1637 LED screen is used to display the CO2 value (it costs $ 0.67). For connection, it is convenient to use ready-made wires with Dupont F-F connectors (20 pieces of 10 cm cost $ 0.87), to connect sensors they can be cut in half and soldered.
In addition to the indication on the screen, my meters transmit data to the port, so they can be connected to a computer, go into the Arduino platform mode "Monitor port "(speed 9600), observe the CO2 values and use the meter as a datalogger (you just need to copy the data from the port monitor window to Excel).
By the way, you don't have to connect the screen and use only the port monitor.
Both sensors give accurate results (I compared with good carbon dioxide meters Dadget MT8057s and AZ Instruments 7798 CO2 datalogger). I liked the cheaper Telaire T6703 even more - it reaches the correct readings in seconds thirty after switching on and its results are closer to the results of expensive devices with two-beam sensors.
If you want to repeat one of these simple constructions, I have collected everything you need in one archive - there are sketches for Arduino, and wiring diagrams and the necessary library.
I plan to add support for a cheap TFT color screen to my meters (https://ammo1.livejournal.com/1191683.html) and three or four relays for ventilation control depending on the level of carbon dioxide in the room. As soon as I do this, I will write the same instructions for repeating these homemade products.
© 2021, Alexey Nadezhin
For ten years I have been writing every day about technology, discounts, places of interest and events. Read my blog on the site ammo1.ru, in LJ, Zen, Mirtesen.
My projects:
Lamptest.ru. I test LED lamps and help figure out which ones are good and which are not so good.
Elerus.ru. I collect information about domestic electronic devices for personal use and share it.
You can contact me in Telegram @ ammo1 and by mail [email protected].