Arduino

/**************************************
 * name: Flammable Gas Detection
 * function:ingite a ligther. Then the sensor detects the gas emitted.
 * Thus, the led on the gas sensor and that attach to pin 13 on the arduino Uno
 * board will light up.Also you can see the value at A0 and D0 printed on Serial Monitor.
 * connection:
 * MQ-2 gas sensor   Uno R3
 * D0                   7
 * A0                   A0
 * GND                  GND
 * VCC                  VCC
 **************************************/
 const int ledPin = 13; 
 const int analogPin = A0;
 const int digitalPin = 7;
 const int buzzerPin = 8;
 int Astate=0;
 boolean Dstate=0;

 void setup()
 {
  //set the pins state
  pinMode(digitalPin, INPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
 }

void loop()
{
  Astate = analogRead(analogPin);
  Serial.println(Astate);
  Dstate = digitalRead(digitalPin);
  Serial.println(Dstate);

  if (Dstate == HIGH)
  {
    digitalWrite(ledPin,LOW); //turn off
     noTone(buzzerPin); //if you want to play different pitches on multiple pins, you need to call noTone() on one pin before calling tone() on the next pin.
  }
  if (Dstate == LOW)
  {
    digitalWrite(ledPin, HIGH); //turn on
    tone(buzzerPin,320,200); //in pin7 generate a tone, it's frequency is 320Hz and the duration of the tone is 200 milliseconds
  }
  delay(200);
}

树莓派

C

#include <stdio.h>
#include <wiringPi.h>
#include <pcf8591.h>
#define  PCF  120
#define  D0pin 0
#define  Buzz  1

void Print(int x)
{
    switch(x)
    {
        case 1:
                printf("\n*******\n");
                printf("* Safe~ *\n");
                printf("*********\n\n");
                break;
        case 0:
                printf("\n*************\n");
                printf("* Danger Gas! *\n");
                printf("***************\n\n");
                break;
        default:
                printf("\n********************\n");
                printf("* Print value error. *\n");
                printf("**********************\n\n");
                break;
    }
}

int main()
{
    int analogVal;
    int tmp, status, count;

    if (wiringPiSetup() == -1){
        printf("set up wiringPi failed !\n");
    }
    pcf8591Setup(PCF, 0x48);
    pinMode(D0pin, INPUT);
    pinMode(Buzz, OUTPUT);
    digitalWrite(Buzz, HIGH);
    status = 0;
    count = 0;
    
    while(1)
    {
        analogVal = analogRead(PCF + 0);
        printf("%d\n", analogVal);
        tmp = digitalRead(D0pin);
        if (tmp != status)
        {
            Print(tmp);
            status = tmp;
        }
        if (status == 0)
        {
            count ++;
            if (count % 2 == 0)
                    {digitalWrite(Buzz, HIGH);}
            else
                    {digitalWrite(Buzz, LOW);}
        }
        else
        {
            count = 0;
            digitalWrite(Buzz, HIGH);
        }
        delay(200);
    }
    return 0;

Python

#!/usr/bin/env python
import PCF8591 as ADC
import RPi.GPIO as GPIO
import time
import math

D0 = 17
Buzz = 18
GPIO.setmode(GPIO.BCM)

def setup():
    ADC.setup(0x48)
    GPIO.setup(D0, GPIO.IN)
    GPIO.setup(Buzz, GPIO.OUT)
    GPIO.output(Buzz, 1)

def Print(x):
    if x == 1:
        print('')
        print('*********')
        print('* Safe~ *')
        print('*********')
        print('')
    if x == 0:
        print('')
        print('***************')
        print('* Danger Gas! *')
        print('***************')
        print('')

def loop():
    status = 1
    count = 0
    while True:
        print(ADC.read(0))

        tmp = GPIO.input(D0)
        if tmp != status:
            Print(tmp)
            status = tmp
        if status == 0:
            count += 1
            if count % 2 == 0:
                GPIO.output(Buzz, 1)
            else:
                GPIO.output(Buzz, 0)
        else:
            GPIO.output(Buzz, 1)
            count = 0

        time.sleep(0.2)

def destroy():
    GPIO.output(Buzz, 1)
    GPIO.cleanup()


if __name__ == '__main__':
    try:
        setup()
        loop()
    except KeyboardInterrupt:
        destroy()