Magnet Activated Led Pen




About: I love the TV shows Psych and Monk Bands Relient K and Anberlin destroying things making things swimming and having fun.

A handy Light in a pen activated by a magnet. Easy project

Step 1: Materials

What you need:

- drill
- electrical tape
- 3/16 in drill bit
- LED about 2.7v
- expo marker
- exacto knife
- reed switch
- soldering iron
- solder
- 9v battery
- wire cutters
- needle-nose pliers
- about 26ga red wire
- black sharpie

Step 2: Dissasembleing

Carefully cut the edges of the 9v battery off to reveal 6 AAAA batteries. Cut two off from the group and be sure that they are connected by metal at the bottom and it would be helpful if there was metal sticking out of the other sides also.

Take your needle nose pliers and remove the end cap and ink cartridge from the back of the marker.

Step 3: Casing

Solder the negative end of the battery pack to the reed switch with the red wire .The positive end has a piece of metal left on it from the 9v battery, if not quickly solder on a strip of tin. Making sure that the end of both pieces of metal are the same length, wrap the bundle in electrical tape (you may also apply a layer of scotch tape for a better fit).

Step 4: LED Placement

use a sharpie and color a wire black (about 3 in) and leave another red. solder one black end to the reed switch (+) and the other end to the cathode part of the LED (the side with the short wire or flat side). solder a red end to the strip of metal (-) and the other end to the anode side of the LED.

Step 5: Assemble

Insert pack as far back as you can with a pencil. Drill a hole in the end plug so that you can fit the LED through it. Leave the LED in the cap and carefully roll up the wire and fit the cap on.

Step 6: Finished

Now that you are finished try it out by putting a magnet by the marker and the LED will, if you did it properly, turn on.

Of course there are many variations of this project. you could use different colored LEDs. (I used red because that's all they had at Radioshack at the current time.) You could use UV LEDs in a highlighted because yellow halters glow when exposed to UV light. I would like to see that.

UV nightlight

telekenetic pen

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    19 Discussions


    10 years ago on Introduction

    Nice idea and done well but the limited life of the batteries kill your project.... For the idea 5/5 for the job 3/5 total (average) lets say 4/5...:)

    1 reply

    Reply 6 years ago on Introduction

    Both ordinary and rechargeable AAAA batteries are available to buy.

    (The rechargeables are rare as yet, e.g. only one supplier on Ebay, from Thailand.)


    10 years ago on Introduction

    Hi QuicksilverRox, I have to say that this is a most excellent instructable! Partly the reason being that I have made an almost exactly similar highlighter LED light a couple of months ago! I also used 9V battery cells and a reed switch! You may think I am just trying to steal your shine, but honestly that is not my intent! It's just amazing how similar our ideas are... as they say, grate minds think alike! I mounted two small pieces of broken magnet in the cap thus the light will only shine when the cap is stuck on the back! Wonderful instructable anyway! Kind regards. (PS - I have added some pictures of mine I took as soon as I saw yours to prove it exists. I unfortunately don't have assembly pics. If you would like some pics I could disassemble it and post a instructable with some video as well.)

    1 reply

    10 years ago on Introduction

    can it be done so that a magnet is attatched to the unit, and the led turns on when it is put on a metal surface? kind of like a fridge magnet light that turns on when u put it on the fridge and goes off when u take it off


    10 years ago on Introduction

    I have finished a similar project. Guys with Macbooks (not PRO), you know of the magnets in the corners of the screen of a macbook. You need a reed switch, a keychain LED mini-torch, and a tiny metal plate (glued to the minitorch, to hold it on the magnet. Better glue a tiny piece fabric or leather on the surface of metal plate to protect Mac from scratches). Connect and enjoy the visible keyboard on those dark nights of chatting. Advice: might sandpaper LED to diffuse the light to a wider angle. When you stick the torch to the magnet, light goes ON. Take it off, light is OFF

    1 reply

    10 years ago on Introduction

    oh oh oh! If your reed switch behaves like mine, they're also sensitive to a magnet being brought near one of the leads, rather than at the center (mine seem to be MORE sensitive in that direction!) So you might be able to put the magnet in the cap and carefully arrange the components so that when the cap is "on" the light is off, and when the cap is in the "on rear" position, the light is ON. Sorta like shown in the pic. Let us know if you try it!

    2 replies

    Reply 10 years ago on Introduction

    You give out 5 stars like no tomorrow my friend... kinda defeats the exclusiveness of a 100% rating... 3.5/5


    Reply 10 years ago on Introduction

    Sorry, I will stop giving out so many stars :-\. Best Regards, plane phanatic