.. note::

    Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts.

    **Why Join?**

    - **Expert Support**: Solve post-sale issues and technical challenges with help from our community and team.
    - **Learn & Share**: Exchange tips and tutorials to enhance your skills.
    - **Exclusive Previews**: Get early access to new product announcements and sneak peeks.
    - **Special Discounts**: Enjoy exclusive discounts on our newest products.
    - **Festive Promotions and Giveaways**: Take part in giveaways and holiday promotions.

    👉 Ready to explore and create with us? Click [|link_sf_facebook|] and join today!

.. _2.2.4_js:

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.

.. image:: ../img/2.2.4reed_switch.png
    :width: 300
    :align: center

Required Components
------------------------------

In this project, we need the following components. 

.. image:: ../img/2.2.4component.png
    :width: 700
    :align: center

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

.. list-table::
    :widths: 20 20 20
    :header-rows: 1

    *   - Name	
        - ITEMS IN THIS KIT
        - LINK
    *   - Raphael Kit
        - 337
        - |link_Raphael_kit|

You can also buy them separately from the links below.

.. list-table::
    :widths: 30 20
    :header-rows: 1

    *   - COMPONENT INTRODUCTION
        - PURCHASE LINK

    *   - :ref:`cpn_gpio_board`
        - |link_gpio_board_buy|
    *   - :ref:`cpn_breadboard`
        - |link_breadboard_buy|
    *   - :ref:`cpn_wires`
        - |link_wires_buy|
    *   - :ref:`cpn_resistor`
        - |link_resistor_buy|
    *   - :ref:`cpn_led`
        - |link_led_buy|
    *   - :ref:`cpn_reed_switch`
        - |link_reed_switch_buy|

Schematic Diagram
-----------------------

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

.. image:: ../img/reed_schematic.png
    :width: 400
    :align: center

.. image:: ../img/reed_schematic2.png
    :width: 400
    :align: center

Experimental Procedures
-------------------------------

**Step 1:** Build the circuit.

.. image:: ../img/2.2.4fritzing.png
    :width: 700
    :align: center

**Step 2:** Go to the folder of the code.

.. raw:: html

   <run></run>

.. code-block::

    cd ~/raphael-kit/nodejs/

**Step 3:** Run the code.

.. raw:: html

   <run></run>

.. code-block::

    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**

.. code-block:: js

    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**

.. code-block:: js

    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.

.. code-block:: js

    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.   

.. code-block:: js

    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
------------------------

.. image:: ../img/2.2.4reed_switch.JPG
    :width: 500
    :align: center