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Monitor Your Door Using Magnetic Reed Switch and Arduino

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This tutorial demonstrates how to use a magnetic reed switch. I’ll do a quick overview on how it works and show a project example using an Arduino.

Description

A magnetic contact switch is basically a reed switch encased in a plastic shell so that you can easily apply them in a door, a window or a drawer to detect if the door is open or closed.

The switch that we are going to use has two parts: the switch itself, that usually comes opened and the magnet. When you buy this switch, it also comes with 4 screws, so that you can attach it to your door.

label

How does it work?

It’s very very simple.

The electrical circuit is closed when a magnet is near the switch (less than 13 mm (0.5’’) away). When the magnet is far away from the switch, the circuit is open. See the figure below.

magnetic_reed_switch_howitworks

Where to buy?

These switches are very cheap. You can buy them on ebay here.

Project Example

In this example, we will turn on a red LED if your door is open and a green LED if your door is closed.

You’ll need the following components:

  • 1× Magnetic Reed Switch (ebay)
  • 1× Arduino (ebay)
  • 1× green LED
  • 1× red LED
  • 2× 220Ω resistor
  • 1× 10kΩ resistor
  • 1× breadboard

Schematics

Here’s the schematics for this example.

magnetic contact switch_bb

Uploading Sketch

For this example, upload the following code:

»» View and download code on GitHub!

Demonstration

Here’s a video demo showing this project working.


I hope you found this tutorial useful.

Are you thinking of including a magnetic reed switch in one of your projects? Share your thoughts writing a comment below.

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Thanks for reading,

-Rui Santos

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