Arduino reads the analog voltage_ How mq2 gas / smoke sensor works and its interface with Arduino

arduino Read analog voltage _MQ2 Gas / How the smoke sensor works and how it works with Arduino Interface

Use MQ2 Gas sensor module , For your next Arduino The project brings an artificial nose . This is a powerful gas sensor suitable for sensing LPG, smoke , alcohol , propane , hydrogen , Methane and carbon ** carbon monoxide ** Concentration in the air .

If you plan to create an indoor air quality monitoring system ; Breathing detector or early fire detection system ,MQ2 The gas sensor module is a good choice .

 

  The analog output voltage provided by the sensor is proportional to the flue gas concentration . The higher the gas concentration , The higher the output voltage ; And lower gas concentration will lead to low output voltage . The following animation illustrates the relationship between gas concentration and output voltage .

 

come from MQ2 The analog signal of the gas sensor is further fed to LM393 High Precision Comparator （ Welded at the bottom of the module ）, Of course, it is to digitize the signal . There is also a small potentiometer used with the comparator , You can turn it to adjust the sensitivity of the sensor . You can use it to adjust the gas concentration detected by the sensor .

The sensor is sensitive to a variety of gases - But it is impossible to determine which gas it is ！ That's normal ; Most gas sensors are like this . therefore , It is best to measure the change in the density of a given gas , Instead of detecting changing gases .

calibration MQ2 Gas sensor module

To calibrate the gas sensor , The gas sensor can be kept at the smoke to be detected / Near the gas , And continue to rotate the potentiometer , Until the red on the module LED Start to glow .

Turn the screw clockwise to increase sensitivity , Turn the screw counterclockwise to reduce sensitivity .

The comparator on the module will constantly check the analog pin （A0） Whether the threshold set by the potentiometer has been reached . When the threshold is exceeded , Digital pin （D0） Will go high , And the signal LED Lighten up . When you need to trigger an action when a certain threshold is reached , This setting is very useful . for example , When the smoke exceeds the threshold , You can turn the relay on or off , Or instruct the robot to blow / Spray water . You have an idea ！

MQ2 Pin arrangement of gas sensor module
 

VCC  Supply power to the module . You can connect it to Arduino Of 5V Output .

GND  It's a ground pin , Need to connect to Arduino Of GND Pin .

D0 （ or  DIN） Provide a digital representation of the presence of combustible gases .

A0 （ or  AIN） Provide analog output voltage proportional to flue gas concentration .

connection – take MQ2 The gas sensor module is connected to Arduino UNO

take VCC Pin to Arduino Of 5V Pin , And will GND Pin to Arduino Ground pin of (GND).

Place the on the module D0  The output pin is connected to Arduino Digital pin on 8, Place the on the module A0  The output pin is connected to Arduino Analog pin on A0.

Arduino Code

The code is very simple , Basically only read A0 Analog voltage at pin . When smoke is detected , It also prints a message on the serial monitor .

#define MQ2pin (0)
 ​
 float sensorValue;  //variable to store sensor value
 ​
 void setup()
 {
   Serial.begin(9600); // sets the serial port to 9600
   Serial.println("Gas sensor warming up!  Gas sensor preheating ");
   delay(20000); // allow the MQ-6 to warm up
 }
 ​
 void loop()
 {
   sensorValue = analogRead(MQ2pin); // read analog input pin 0
   
   Serial.print("Sensor Value: ");
   Serial.print(sensorValue);
   
   if(sensorValue < 300) // threshold   Judge according to the actual situation   Greater than 300  Still less than 300 ,300 It's also a variable 
   {
     Serial.print(" | Smoke detected!   Smoke detected  ");
   }
   
   Serial.println("");
   delay(2000); // wait 2s for next reading
 
}

The output on the serial monitor is shown below ：

 

My test environment is 100 A little more   Indicates smoke   , Normally 700 many .（ What we tested was  A0  Output ）

I use   lighter   After ignition   Blow it out again .  Methane released   Gas . direct   Put it in   detector   On the edge . Detected 100 A little bit more   Output

Code instructions ：

Defines a name sensorValue To store sensor values .

#define MQ2pin (0)
float sensorValue;  // Defining variables 

  In the setting function ： We initialize with PC Serial communication , And wait for 20 Seconds to allow the sensor to warm up .

Serial.begin(9600); // sets the serial port to 9600
Serial.println("Gas sensor warming up!");
delay(20000); // allow the MQ-6 to warm up

Cycle function ： The sensor value is determined by analogRead（） Function to read and display on the serial monitor

 sensorValue = analogRead(MQ2pin); // read analog input pin 0  
 Serial.print("Sensor Value: ");
 Serial.print(sensorValue);

When the gas concentration is high enough , The output of the sensor is usually greater than 300 Value . We can use if sentence Monitor this value . When the sensor value exceeds 300 when , We will show “ Smoke detected ！”. Information .

if(sensorValue > 300)
{
     Serial.print(" | Smoke detected!");
}

notes ：

One 、println Output one line

Serial.println(" The output string   a line "); //println  Output one line 

Two 、 Upload error

  Upload error ：avrdude: stk500_recv(): programmer is not responding

Solution ：

Every time you upload code , Pull it off 0,1 Pin line . Connect it back after uploading . because arduino These two pins will be used when uploading data for interaction

Thank these two bloggers for sharing ：

Jiao Xiuwen

https://blog.csdn.net/weixin_42533120/article/details/112499307

Kappa

https://blog.csdn.net/weixin_40317528/article/details/88926989