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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.

../_images/2.2.4reed_switch.png

Required Components

In this project, we need the following components.

../_images/2.2.4component.png

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

Name

ITEMS IN THIS KIT

LINK

Raphael Kit

337

Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION

PURCHASE LINK

GPIO Extension Board

BUY

Breadboard

BUY

Jumper Wires

BUY

Resistor

BUY

LED

BUY

Reed Switch Module

BUY

Schematic Diagram

T-Board Name

physical

wiringPi

BCM

GPIO17

Pin 11

0

17

GPIO27

Pin 13

2

27

GPIO22

Pin 15

3

22

../_images/reed_schematic.png ../_images/reed_schematic2.png

Experimental Procedures

Step 1: Build the circuit.

../_images/2.2.4fritzing.png

Step 2: Change directory.

cd ~/raphael-kit/python/

Step 3: Run.

sudo python3 2.2.4_ReedSwitch.py

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.

Code

Note

You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like raphael-kit/python. After modifying the code, you can run it directly to see the effect.

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

ReedPin = 17
Gpin    = 27
Rpin    = 22

def setup():
    GPIO.setmode(GPIO.BCM)       #
    GPIO.setup(Gpin, GPIO.OUT)     # Set Green Led Pin mode to output
    GPIO.setup(Rpin, GPIO.OUT)     # Set Red Led Pin mode to output
    GPIO.setup(ReedPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)    # Set ReedPin's mode is input, and pull up to high level(3.3V)
    GPIO.add_event_detect(ReedPin, GPIO.BOTH, callback=detect, bouncetime=200)

def Led(x):
    if x == 0:
        GPIO.output(Rpin, 1)
        GPIO.output(Gpin, 0)
    if x == 1:
        GPIO.output(Rpin, 0)
        GPIO.output(Gpin, 1)

def detect(self):
    Led(GPIO.input(ReedPin))

def loop():
    while True:
        pass

def destroy():
    GPIO.output(Gpin, GPIO.HIGH)       # Green led on
    GPIO.output(Rpin, GPIO.LOW)       # Red led off
    GPIO.cleanup()                     # Release resource

if __name__ == '__main__':     # Program start from here
    setup()
    detect()
    try:
        loop()
    except KeyboardInterrupt:  # When 'Ctrl+C' is pressed, the child program destroy() will be  executed.
        destroy()

Code Explanation

ReedPin = 17
Gpin    = 27
Rpin    = 22

def setup():
    GPIO.setmode(GPIO.BCM)       #
    GPIO.setup(Gpin, GPIO.OUT)     # Set Green Led Pin mode to output
    GPIO.setup(Rpin, GPIO.OUT)     # Set Red Led Pin mode to output
    GPIO.setup(ReedPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)    # Set ReedPin's mode is input, and pull up to high level(3.3V)
    GPIO.add_event_detect(ReedPin, GPIO.BOTH, callback=detect, bouncetime=200)

Set the GPIO modes to BCM Numbering. ReedPin, Gpin and Rpin connects to the GPIO17, GPIO27 and GPIO22.

GPIO.add_event_detect() is used to add an event that is triggered by a change in the value (level) of ReedPin, at which point the callback function detect() is called.

def Led(x):
    if x == 0:
        GPIO.output(Rpin, 1)
        GPIO.output(Gpin, 0)
    if x == 1:
        GPIO.output(Rpin, 0)
        GPIO.output(Gpin, 1)

Define a function Led() to turn the two LEDs on or off. If x=0, the red LED lights up; otherwise, the green LED will be lit.

def detect(self):
Led(GPIO.input(ReedPin))

In this callback function, the value of the reed switch is used to control the 2 LEDs.

Phenomenon Picture

../_images/2.2.4reed_switch.JPG