MQ-135 Air Quality Sensor Module

Main usage: harmful gas detection device for home and environment

Main chips: LM393, MQ-135 gas sensor

Steps for usage:

  ①Download the supporting program to the corresponding development board.

  ②Connect the serial cable and module to the development board, and power on the development board.

If DOUT, TTL high and low level terminals are selected, the output signal can be directly connected to the IO port of the microcontroller or an NPN transistor to drive the relay. The potentiometer RP is used here to adjust the threshold of the output level transition. When the sensor detects the measured value In the case of gas, the voltage value of the comparator LM393 pin 2 is proportional to the concentration of the gas detected by the sensor. When the concentration value exceeds the threshold set by the potentiometer RP, the comparator 2 pin is higher than the 3 pin. Point, at this time, the comparator pin 1 outputs a low level, the LED light is on, R3 is the LED light current limiting resistor, and C1 is the filter capacitor. The sensor outputs a low level, on the contrary, when there is no signal, the sensor outputs a high level, which is equal to the power supply voltage.

    If you choose AOUT, analog output, then you don't need to control the potentiometer, you can directly connect the AOUT pin to the input terminal of AD conversion or a microcontroller with AD function. According to our experience: in a normal environment, that is, an environment without the gas to be measured, set the output voltage of the sensor as the reference voltage. At this time, the voltage of the AOUT terminal is about 1V. When the sensor detects the gas to be measured, the voltage will be When the increase of 0.1V, the actual concentration of the measured gas increases by 20ppm (simply put: 1ppm=1mg/kg=1mg/L=1×10-6 is often used to represent the gas concentration, or the solution concentration.), according to this parameter, you can In the microcontroller, the measured analog voltage value is converted into a concentration value. Note: If you use it as a precision instrument, please buy a standard calibration instrument on the market, otherwise there will be errors, because the ratio of the output concentration and voltage relationship is not linear, but tends to be linear.

  ③Let the sensor warm up for one minute.

  ④Put the sensor into the device containing sensitive gas, and the signal indicator on the module will light up. Take the sensor out of the sensitive gas device, the signal indicator on the module goes out.