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.

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: 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.