Hot selling original MQ-135 air quality sensor module, harmful gas detection sensor, alarm module, air pollution

Brief Explanation

1、 Size: 32mm X22mm X27mm Length X Width X Height

2、 Main chips: LM393, MQ-135 gas sensor

3、 Working voltage: 5 volts DC

Characteristics

1. Has signal output indication.

2. Dual signal output (analog output and TTL level output)

3. TTL outputs a valid signal at a low level. When the signal light is on when the output is low, it can be directly connected to a microcontroller

4. Analog output voltage of 0-5V, the higher the concentration, the higher the voltage.

5. It has high sensitivity and good selectivity towards carbon monoxide.

6. Long term service life and reliable stability

Application

Carbon monoxide detection device for households and environments. Suitable for detecting carbon monoxide, coal gas, etc.

Applicable occasions: microcontroller learning, electronic competitions, product development, graduation project...

Instructions

Explanation: This module is an MQ-135 air quality sensor. Please preheat it for about 20 seconds before use

Step: Supply 5V DC power to the module (be careful not to connect the positive and negative poles in reverse, otherwise it may burn out the chip).

Step 2: If DOUT or TTL high and low level terminals are selected, the output signal can be directly connected to the IO port of the microcontroller or connected to an NPN transistor to drive the relay. The potentiometer RP is used here to adjust the threshold of the output level jump. As shown in the schematic diagram below, when the sensor detects the gas being measured, the voltage value at pin 2 of the comparator LM393 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 point of pin 2 of the comparator is higher than the point of pin 3. At this time, pin 1 of the comparator outputs a low level, the LED light is on, R3 is the current limiting resistor of the LED light, and C1 is the filtering capacitor. The sensor outputs a low level. Conversely, when there is no signal, the sensor outputs a high level, which is equal to the power supply voltage.

Step 3: If AOUT is selected for analog output, there is no need to use a potentiometer. Simply connect the AOUT pin to the input terminal of the AD conversion or a microcontroller with AD function. Based on our experience, in a normal environment where there is no gas being measured, the sensor output voltage is set as the reference voltage. At this point, the voltage at the AOUT terminal is around 1V. When the sensor detects the gas being measured, for every 0.1V increase in voltage, the actual concentration of the gas being measured increases by 20ppm (in simple terms, 1ppm=1mg/kg=1mg/L=1 × 10-6 is often used to represent gas concentration or solution concentration), Based on this parameter, the measured analog voltage value can be converted into concentration value in the microcontroller. Attention: If you are using precision instruments, please purchase standard calibration instruments on the market, otherwise there may be errors, because the ratio of output concentration to voltage relationship is not linear, but tends to be linear.

Special reminder: After the sensor is powered on, it needs to be preheated for about 20 seconds for the measured data to stabilize. Sensor heating is a normal phenomenon because there are electric heating wires inside. If it is hot, it is not normal.

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