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

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: Go to the folder of the code.

cd /home/pi/raphael-kit/nodejs/

Step 3: Run the code.

sudo node reed_switch_module.js

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

const Gpio = require('pigpio').Gpio;

const led1 = new Gpio(22, {mode: Gpio.OUTPUT});
const led2 = new Gpio(27, {mode: Gpio.OUTPUT});

const reedSwitch = new Gpio(17, {
    mode: Gpio.INPUT,
    pullUpDown: Gpio.PUD_DOWN,
    edge: Gpio.EITHER_EDGE
});

reedSwitch.on('interrupt', (level) => {
    led1.digitalWrite(level);
    led2.digitalWrite(!level);
});

Code Explanation

const Gpio = require('pigpio').Gpio;

const reedSwitch = new Gpio(17, {
    mode: Gpio.INPUT,
    pullUpDown: Gpio.PUD_DOWN,
    edge: Gpio.EITHER_EDGE
});

Import the pigpio module, create a ReedPin object to control the IO port, set it to input mode, pull down (initially low level), and set an interrupt.

const led1 = new Gpio(22, {mode: Gpio.OUTPUT});
const led2 = new Gpio(27, {mode: Gpio.OUTPUT});

Create two objects led1, led2 to control the IO ports Gpio22 and Gpio27, and set them to output mode.

reedSwitch.on('interrupt', (level) => {
    led1.digitalWrite(level);
    led2.digitalWrite(!level);
});

When the interrupt is triggered, write the same level to led1, and write the opposite level to led2.

Phenomenon Picture

../_images/2.2.4reed_switch.JPG