Arduino analog read at 77 kHz, no interrupts needed. Graphical representation of data on Serial Monitor.
Project showcase by ArduinoKoen
CO2 monitor and log based on MQ-135 with temperature and relative humidity correction.
An ultra flat screen built out of single row of LEDs.
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Don't throw away those old TV, DVD, etc., remotes because they can control your house's electrical devices!
Project tutorial by VE1DX
Amazing how you can trick the eye!
I have derived my formulas from datasheets on mq135. The measurement is corrected for water content in the air and temperature.
Since I used the monitor inside, RH and T did not really vary much. The meter readings however were highly fluctuating. One would expect that during the night the value gradually will come back to the background CO2 concentration. This value however is different every day. It seems that some pollutants adsorb on the element that do not come off easily.
Good about MQ 135 is that it senses human presence quite well. As soon as someone enters the room, the readings go up. Especially when all windows and doors are closed. From the time needed to reach a new steady state I have derived that our house needs better ventilation.
I also found datasheets stating that mq135 is sensitive to many more gasses than only CO2.
So, MQ135 shows large measuring drift, is not selective and can still give an impression on ventilation in your house and air quality (good/reasonable/bad). Sensitivity should be set via calibration, not with data from the datasheet as it varies from sensor to sensor and from time to time.
For me it was a fun project and I had in mind to do an update of my project with my experiences...
Van: Hackster.io email@example.com
Verstuurd: maandag 26 oktober 2020 11:29
Onderwerp: New comment for CO2 Monitor
Nice way to confront people!
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