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1 简介

Hi，大家好，这里是丹成学长，今天向大家介绍一个学长做的单片机项目

基于单片机的空气质量分析仪

大家可用于 课程设计 或 毕业设计

单片机-嵌入式毕设选题大全及项目分享:

https://blog.csdn.net/m0_71572576/article/details/125409052

2 主要器件

本项目使用了的6个气体传感器，可测量12种气体的气体浓度。

在开始工作之前，应该给传感器供电，让它发热至少24小时。这一步非常重要，因为MQ传感器受到了污染，发热可以帮助它们自我清理。必须用5V给传感器供电然后把它们放在干净的地方。

MQ传感器输出模拟电压，该电压随某些选定气体的浓度而变化。所以可以通过Arduino ADC读取模拟值，得到空气中的气体浓度。

使用6个MQ传感器(MQ3、MQ4、MQ7、MQ8、MQ9和MQ135)。

传感器的用途：

• MQ3用于测量酒精，苯和己烷
• MQ4用于测量甲烷和烟雾
• MQ135用于测量CO2, NH4，甲苯和丙酮
• MQ7 测量CO
• MQ8用于测量H2
• MQ9用于测量可燃气体

3 实现效果

4 设计原理

4.1 电路接线图

这里主控学长选择的是arduino，你们可以选其他自己熟悉的主控，比如stm32，51等…

将传感器连接到Arduino nano，因为它有8个ADC，6个ADC用于传感器，2个用于I2C与LCD通信。

Arduino与传感器连接：

• MQ3 Ao - Arduino A0
• MQ4 Ao - Arduino A1
• MQ135 Ao - Arduino A2
• MQ7 Ao - Arduino A3
• MQ8 Ao - Arduino A6
• MQ9 Ao - Arduino A7
• Arduino与LCD 连接：
• Arduino A4 - LCD SDA
• Arduino A5 - LCD SCL

5 气体传感器数据解析算法

参考这篇文章：
https://jayconsystems.com/blog/understanding-a-gas-sensor

#include <SPI.h> //Library for SPI interface 
#include <Wire.h> //Library for I2C interface 
#include <Adafruit_GFX.h> //Core graphic library for displays 
#include <Adafruit_SSD1306.h> //Library for OLED display
 
#define OLED_RESET 11 //Reset pin 
Adafruit_SSD1306 display(OLED_RESET); //Set Reset pin for OLED display 
 
int led = 10; //LED pin 
int buzzer = 9; //Buzzer pin 
int gas_sensor = A0; //Sensor pin 
float m = -0.318; //Slope 
float b = 1.133; //Y-Intercept 
float R0 = 11.820; //Sensor Resistance in fresh air from previous code
 
void setup() {
  Serial.begin(9600); //Baud rate 
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C); //Initialize screen 
  display.setTextColor(WHITE); //Set text color 
  display.setTextSize(3); //Set text size 
  pinMode(led, OUTPUT); //Set LED as output 
  digitalWrite(led, LOW); //Turn LED off 
  pinMode(buzzer, OUTPUT); //Set buzzer as output 
  digitalWrite(buzzer, LOW); // Turn buzzer off 
  pinMode(gas_sensor, INPUT); //Set gas sensor as input 
}
 
void loop() {  
  display.clearDisplay(); //Clear display 
  display.setCursor(0,5); //Place cursor in (x,y) location 
  float sensor_volt; //Define variable for sensor voltage 
  float RS_gas; //Define variable for sensor resistance  
  float ratio; //Define variable for ratio
  float sensorValue = analogRead(gas_sensor); //Read analog values of sensor  
  sensor_volt = sensorValue*(5.0/1023.0); //Convert analog values to voltage 
  RS_gas = ((5.0*10.0)/sensor_volt)-10.0; //Get value of RS in a gas
  ratio = RS_gas/R0;  // Get ratio RS_gas/RS_air
 
  double ppm_log = (log10(ratio)-b)/m; //Get ppm value in linear scale according to the the ratio value  
  double ppm = pow(10, ppm_log); //Convert ppm value to log scale 
  double percentage = ppm/10000; //Convert to percentage 
  display.print(percentage); //Load screen buffer with percentage value 
  display.print("%"); //Load screen buffer with "%"
  display.display(); //Flush characters to screen 
  
  if(ppm>2000){ //Check if ppm value is greater than 2000 
    digitalWrite(led, HIGH); //Turn LED on 
   digitalWrite(buzzer, HIGH); //Turn buzzer on  }  else{ //Case ppm is not greater than 2000    digitalWrite(led, LOW); //Turn LED off    digitalWrite(buzzer, LOW); //Turn buzzer off  }   }  

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单片机-嵌入式毕设选题大全及项目分享:

https://blog.csdn.net/m0_71572576/article/details/125409052

6 最后