Lesson 21 Flame Sensor

Introduction

A flame sensor (as shown below) performs detection by capturing infrared rays with specific wavelengths from flame. It can be used to detect and warn of flames.

Required Components

• 1 * Raspberry Pi

• 1 * Breadboard

• 1 * Flame sensor module

• 1 * PCF8591

• 1 * 4-Pin anti-reverse cable

• Several Jumper wires

Experimental Principle

There are several types of flame sensors. In this experiment, we will use a far-infrared flame sensor. It can detect infrared rays with wavelength ranging from 700nm to 1000nm. A far-infrared flame probe converts the strength changes of external infrared light into current changes. And then it convert analog quantities into digital ones. In this experiment, connect pin D0 of the Flame Sensor module to a GPIO of Raspberry Pi to detect by programming whether any flame exists. The schematic diagram:

Experimental Procedures

Step 1: Build the circuit.

Raspberry Pi	GPIO Extension Board	PCF8591 Module
SDA	SDA1	SDA
SCL	SCL1	SCL
3.3V	3V3	VCC
GND	GND	GND

Flame Sensor	GPIO Extension Board	PCF8591 Module
DO	GPIO17	*
AO	*	AIN0
VCC	3V3	VCC
GND	GND	GND

For C Users:

Step 2: Change directory.

cd /home/pi/SunFounder_SensorKit_for_RPi2/C/21_flame_sensor/

Step 3: Compile.

gcc flame_sensor.c -lwiringPi

Note

If it does not work after running, or there is an error prompt wiringPi.h: No such file or directory, please refer to WiringPi to install it.

Step 4: Run.

sudo ./a.out

Code

#include <stdio.h>
#include <wiringPi.h>
#include <pcf8591.h>
#include <math.h>

#define             PCF     120
#define             DOpin   0

void Print(int x)
{
    switch(x)
    {
        case 1:
            printf("\n*********\n"  );
            printf(  "* Saft~ *\n"  );
            printf(  "*********\n\n");
        break;
        case 0:
            printf("\n*********\n"  );
            printf(  "* Fire! *\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;

    if(wiringPiSetup() == -1){
        printf("setup wiringPi failed !");
        return 1;
    }
    // Setup pcf8591 on base pin 120, and address 0x48
    pcf8591Setup(PCF, 0x48);

    pinMode(DOpin, INPUT);

    status = 0;
    while(1) // loop forever
    {
        analogVal = analogRead(PCF + 0);
        printf("%d\n", analogVal);

        tmp = digitalRead(DOpin);

        if (tmp != status)
        {
            Print(tmp);
            status = tmp;
        }

        delay (200);
    }
    return 0;
}

For Python Users:

Step 2: Change directory.

cd /home/pi/SunFounder_SensorKit_for_RPi2/Python/

Step 3: Run.

sudo python3 21_flame_sensor.py

Code

#!/usr/bin/env python3
import PCF8591 as ADC
import RPi.GPIO as GPIO
import time
import math

DO = 17
GPIO.setmode(GPIO.BCM)

def setup():
    ADC.setup(0x48)
    GPIO.setup(DO, GPIO.IN)

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

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

        tmp = GPIO.input(DO);
        if tmp != status:
            Print(tmp)
            status = tmp

        time.sleep(0.2)

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

Now, ignite a lighter near the sensor, within the range of 80cm, and “Fire!” will be displayed on the screen. If you put out the lighter or just move the flames away from the flame sensor, “Safe~” will be displayed then.