LED Clothes Peg Tampering Detector




About: YuKonstruct is a non-profit society which provides an enthusiastic community of makers and entrepreneurs affordable access to space, equipment and knowledge. This community serves to embrace the individual a...

Is your little sister sneaking into your room when you're not there? Set this little trap to tell if anyone has been through your door.

This project was created for YuKonstruct's first Build Night in collaboration with hacker-cycle and licheness.

YuKonstruct is the first makerspace in Canada's north. Our mission is to provide access to shared space, quality tools, available expertise, and a collaborative environment to help makers build anything!


Step 1: Gather Your Materials

You'll need:

  • clothes peg
  • adhesive copper tape (conductive)
  • glue gun and glue sticks
  • LED
  • Coin battery
  • Plastic, cardboard or other non conductive material (we used a business card)
  • string, twine or fishing line
  • scissors
  • hole punch
  • pliers
  • drill and small drill bit

Step 2: Drill a Hole in the Clothes Peg

Drill a hole in the end of the clothes peg.

Step 3: Take the Clothes Peg Apart

Take the clothes peg apart.

Step 4: Cut the Copper Foil

Cut the copper foil into one square and a long piece.

Cut the long piece in half lengthwise and the square in half.

Cut one of the halves of the squares in half lengthwise.

Step 5: Add the Copper to the Clothes Peg

Take a long piece of copper foil and stick it to the first half peg (side A). Begin on the inside of jaw, go around the nose and line inside the groove where the wire goes.

Take other long piece of copper, cut a 3⁄4” piece off the length and set it aside. Stick the rest to the other half peg (side B). Again, begin inside the jaw go around nose and down the back. The 3/4" piece of foil is used to line the groove with the rest laying towards the end of the peg. There will be a gap between the two pieces of foil on this side.

Put the clothes peg back together.

Step 6: Attach the Battery

Stick half of the next longest copper to the negative side of battery with excess hanging over the edge.

Place positive side of battery face down over groove (side B) and line up the overhanging foil edge with foil running towards back of the pin.

Stick foil to foil. Fold the battery back, turning positive side up.

Hot glue the negative side of the battery to the wood.

Step 7: Add the LED

Flatten LED leads out to sides in opposite directions. Place positive lead (the longer one) on positive side of battery and negative lead on foil going around the nose of the clothes peg (side B) (use pliers to shorten leads by curling ends). The light should come on.

Stick the leads securely in place with the remaining pieces of foil.

Step 8: Final Details

To turn the LED off, place non-conductive material (like a business card) between jaws of the clothespin to break the circuit.

Punch a hole in the card and attach half of the string. Attach the other half to the hole in the clothespin.

Step 9: Setting the Trap and Other Uses

Tie the two ends of the string to different objects (like a door handle and a bedpost). If one is moved, the card should pull out and the LED will light up.

You can also use this device to test whether a material is conductive or not. Pinch the material between the clothes peg's jaws; if the light comes on, the material is conductive.



  • Classroom Science Contest

    Classroom Science Contest
  • Colors of the Rainbow Contest

    Colors of the Rainbow Contest
  • Gardening Contest

    Gardening Contest

13 Discussions


4 years ago

I searched LED in walmart and ace but I couldn't find one that looked like what you used. Any suggestions

1 reply

The LED doesn't have to be exactly like the one we used. Ordering online is usually the best way to purchase LEDs, but if you need them immediately for a school project you should be able to buy some at your local Radioshack.


4 years ago

I'm doing this instructables for a project at school so please let me know asap


4 years ago on Introduction

It will also work with aluminium foil instead of copper I suppose, or have you found a problem with that?

1 reply

Reply 4 years ago on Introduction

We tried with aluminium foil, and while it works, it's trickier to put together because you need to glue down the tin foil.

YuKonstructTFS Jake

Reply 4 years ago on Introduction

This way you can hide the device somewhere where you could only see it when the light is on. But you're right that an LED isn't necessary to set a similar trap.

The primary purpose of this project was to give people an opportunity to learn about LEDs and basic circuits, and make something fun.


4 years ago

Cuantas más paridas veo como ésta... más útil me parece un rollo de papel higiénico...


4 years ago

a string or plastic in the door jamb works too.


4 years ago on Introduction

Great! =DD

Definetely a secret weapon to younger siblings! ^^


4 years ago on Introduction

Clever! I like this a lot.

Another great instructable!