2.2.4_reed_switch_c.rst

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2.2.4 Reed Switch Module

Introduction

In this project, we will learn about the reed switch, which is an electrical switch that operates by means of an applied magnetic field.

Required Components

In this project, we need the following components.

It's definitely convenient to buy a whole kit, here's the link:

Name	ITEMS IN THIS KIT	LINK
Raphael Kit	337

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
cpn_gpio_extension_board
cpn_breadboard
cpn_wires
cpn_resistor
cpn_led
cpn_reed_switch

Schematic Diagram

T-Board Name	physical	wiringPi	BCM
GPIO17	Pin 11	0	17
GPIO27	Pin 13	2	27
GPIO22	Pin 15	3	22

Experimental Procedures

Step 1: Build the circuit.

Step 2: Change directory.

cd ~/raphael-kit/c/2.2.4/

Step 3: Compile.

gcc 2.2.4_ReedSwitch.c -lwiringPi

Step 4: Run.

sudo ./a.out

The green LED will light up when the code is run. If a magnet is placed close to the reed switch module, the red LED lights up; take away the magnet and the green LED lights up again.

Note

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

Code

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

#define ReedPin     0
#define Gpin        2
#define Rpin        3

void LED(char* color)
{
    pinMode(Gpin, OUTPUT);
    pinMode(Rpin, OUTPUT);
    if (color == "RED")
    {
        digitalWrite(Rpin, HIGH);
        digitalWrite(Gpin, LOW);
    }
    else if (color == "GREEN")
    {
        digitalWrite(Rpin, LOW);
        digitalWrite(Gpin, HIGH);
    }
    else
        printf("LED Error");
}

int main(void)
{
    if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
        printf("setup wiringPi failed !");
        return 1; 
    }

    pinMode(ReedPin, INPUT);
    LED("GREEN");

    while(1){
        if(0 == digitalRead(ReedPin)){
            delay(10);
            if(0 == digitalRead(ReedPin)){
                LED("RED"); 
                printf("Detected Magnetic Material!\n");    
            }
        }
        else if(1 == digitalRead(ReedPin)){
            delay(10);
            if(1 == digitalRead(ReedPin)){
                while(!digitalRead(ReedPin));
                LED("GREEN");
            }
        }
    }
    return 0;
}

Code Explanation

#define ReedPin     0
#define Gpin        2
#define Rpin        3

Pin GPIO17, GPIO27 and GPIO22 of the T_Extension Board is corresponding to the GPIO0, GPIO2 and GPIO3 in wiringPi. Assign GPIO0, GPIO2 and GPIO3 to ReedPin, Gpin and Rpin.

void LED(char* color)
{
    pinMode(Gpin, OUTPUT);
    pinMode(Rpin, OUTPUT);
    if (color == "RED")
    {
        digitalWrite(Rpin, HIGH);
        digitalWrite(Gpin, LOW);
    }
    else if (color == "GREEN")
    {
        digitalWrite(Rpin, LOW);
        digitalWrite(Gpin, HIGH);
    }
    else
        printf("LED Error");
}

Set a LED() function to control the 2 LEDs, the parameter of this function is color.

When color is "RED", set Rpin to HIGH (light up the red LED) and Gpin to LOW (turn off the green LED); when color is "GREEN", then light up the green LED and turn off the red LED.

while(1){
        if(0 == digitalRead(ReedPin)){
            delay(10);
            if(0 == digitalRead(ReedPin)){
                LED("RED"); 
                printf("Detected Magnetic Material!\n");    
            }
        }
        else if(1 == digitalRead(ReedPin)){
            delay(10);
            if(1 == digitalRead(ReedPin)){
                while(!digitalRead(ReedPin));
                LED("GREEN");
            }
        }
    }

Read the value of the reed switch module, if the value read 2 times is 0, call LED("RED") to light up the red LED and print "Magnetic material detected!".

If the value is 1, the green LED is lit.

Phenomenon Picture