Quick and Dirty Homemade Reed Switch

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Introduction: Quick and Dirty Homemade Reed Switch

About: I'm a husband and a father and I make stuff.
A reed switch is an electronic device that closes a circuit when a magnet passes close to it. You have probably used devices that contained reed switches in your day to day life. Alarm systems use reed switches to tell if a door or window has been opened. A bicycle computer uses a reed switch to count the frequency of passes of a spoke mounted magnet to determine speed and distance. Once you start using them, you'll find hundreds of uses for reed switches.

In this instructable I will show you one way to make quick and dirty reed switches.

***Warning: The reed switches you make at home are vastly inferior to store bought. If you have a serious project that needs a reed switch i highly recommend you buy one rather than cobbling one together in your garage. I made this Instructable to demonstrate a concept but I will be the first to admit that the finished product is lacking in quality and reliability. With that said; lets make some switches!

We'll start with a parts list:

a 3" piece of copper pipe
a spool of steel craft wire (or) a small steel spring
some mini zip ties
a rare earth magnet
a sheet of 'Plastic Canvas'*
scissors

  • Plastic canvas is a plastic mesh used for some type of latch-hooking. It costs about $1 a sheet and is available at craft stores in the needle-art section. I've never done needle art but this is very handy stuff to have around. Plastic Canvas @ A.C.Moore

EDIT: I added an animation to show how a reed switch works. I just purchased some reed switches from Mouser so stay tuned for some upcoming reed switch based instructables.

Step 1: Make It!

1. Once you gathered your materials you should start by drilling a small hole near the end of the copper pipe. This hole will allow you to solder a wire to this side of the switch.

2. Next, cut a small piece of plastic canvas to insulate the spring from the pipe.

3. If you are not using an existing spring, wrap a tight coil of steel wire around a pencil or similar item to make a tightly wound steel spring.

4. Zip tie the spring to the plastic canvas.

5. Insert into the pipe.

6. Attach a wire to the spring and one in the hole drilled in the copper pipe.

When the magnet comes close to the top of the pipe the spring gets pulled over and makes contact with the copper pipe

When the magnet is removed, the spring goes back to the rest position cradled in the plastic canvas insulation.

Congratulations, you just made a quick and dirty Reed Switch!

Please leave (constructive) comments if you have ideas to make this better.

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32 Comments

this is perfect for me to share with my students thank you.

Not about the instructable but i like u use ms paint. Do u by chance follow ms paint adventures? I myself like homestuck. Srry this is in no way related to the project

good project this is my reed switch it is more simple
https://www.instructables.com/id/how-to-make-a-magnetic-sensor/

test.jpg
user

Ahh. I just bought a box of mixed springs (just for the compression springs), and I didn't have anything to do with the extension springs, but now It looks like I will.

You could also, in theory, use this same device as a sort of crude vibration sensor..

1 reply

Absolutely. I hadn't thought of a vibration sensor but it would certainly work for that. I'd love to see pictures of anything you put together.

Aaaah!!! I see! Thanks! I undesrstand already! :D

Umm... excuse me, I just wanted to ask about the instructions in the last part. You said to solder the wire into the hole drilled in the pipe. Just want to ask. I don't really understand this part. You will insert the wire into the drilled hole or to the side of the hole? And where exactly do you solder the wire?

1 reply

Insert the wire into the hole and solder to hold it in place. I hope this helps.

 can i use something instead of a 'rare earth magnet'?

1 reply

You could use a standard magnet but they don't have as much "pull" so you might need a larger magnet or to hold it closer.

If you wanted to make it normally closed you could just pack some paper or something under the spring right after the zip ties, to bend it just enough to make it touch the copper tube. Then when the magnet hits the opposite side the spring will be pulled away from the tube and it will be open.

could you make it so that the device would be turned on instead of off? please help me!!

2 replies

I'm not sure I understand what you mean turner22? You want the switch to be normally closed and open only in the presence of a magnetic field? Reed switches are divided into 3 basic types- Normally Open (as built in this 'ible) Normally Closed (the opposite of this 'ible) -and- Single Pole Double Throw (which can be wired either way) I hope this helps.

yeah i think we re all wondering how to make a normally closed one because most of the ones on sale are expensive, big, and are designed for security system use, not pcb mount (but they can still be used that way)

you can buy a window alarm at the dollar store which includes a magnet and a reed switch, and its a lot smaller than this one. Only problem is im not sure what kind of power u could run through it, this one built here lokts a little beefier and could handle more amps.

1 reply

yep i got 1 of those for $2 :D but the magnet mine came with was crap, only sets the swtich off from 5 - 10 mm.

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3 replies

I can't see your comment, it only shows up as a line of 'missing character' boxes.

that was what i typed actually

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