> MQ135 is mainly used to detect the concentration of carbon dioxide, alcohol, benzene, NOx, ammonia and other gases in the air.
The MQ135 board has 4 pins: Vcc (5v), GND, A0 (Analog voltage), and D0 (digital signal). It has several components, including the MQ135 sensor, a power LED, an alarm LED, a variable resistor to adjust ...