Build a Secret Tripwire Alarm

Stretch the fishing line across a doorway - when someone walks into it, it will trigger a buzzer to go off, alerting everyone that your security has been breached!

Protect your bedroom or your locker - protect your campsite - protect your stuff!

Kit Contents:

tripwire kit contents

Your kit contains the following parts:

  • 1 Clothes peg
  • 1 Buzzer
  • 1 Lithium battery (CR2032)
  • 2 Sticky pads
  • 1 Twist tie
  • 1 Length fishing line
  • 1 Piece copper foil tape

Step 1 Open the clothes peg and hold it open by wrapping a twist-tie around it like this

Tripwire Build 01

Step 2 Peel the backing off the copper tape and stick the tape around one of the open jaws of the peg, as in the next picture.


Make sure the copper tape is firmly stuck down all the way around; use the back of your nail to press it down firmly.

Tripwire Build 02

Step 3 Peel the backing off one side of a sticky pad and use it to stick the bare metal end of the RED wire to the copper, like this…

In this shot you can see that we shortened the red wire (perhaps a bit too much) to make the finished device a bit tidier. If you want to do this, you will need to strip the insulation off the end of the trimmed wire using wire strippers.

Tripwire Build 03

Step 4 Peel off the backing on the sticky pad and stick the buzzer down onto it, like this:

Tripwire Build 04

Step 5 Stick the other pad to the other side of the peg and position the stripped end of the black wire on top of it:

Tripwire Build 05

Step 6 Stick the battery down on top of the black wire. Try to make sure that the metal end of the wire is near the centre of the battery.

NOTE: The positive (+) side of the battery goes UP, towards the buzzer!

Tripwire Build 06

Step 7 Now take the backing from the copper tape that you saved from step 2. Fold it in half with the smooth waxy side outwards. Push a sewing needle or another fine-pointed sharp tool through the folded paper to make a small round hole. Make the hole in the end without the fold. Don’t use a knife and don’t try to enlarge the hole. Push the end of the fishing line through the hole and tie it off with a double or triple knot. It should look like this:

Tripwire Build 07

Step 8 Remove the twist-tie and place the wax paper in between the battery and the copper foil. When you pull the paper out, the alarm sounds! Choose a place to install the alarm. You can probably think of lots of ways to rig it up - one of the simplest is to tape the clothes peg down and tie the other end of the fishing line to a point on the other side of a doorway or other gap. Make sure the fishing line is pulling straight out of the peg like this, not on too much of an angle.

Tripwire Build 08

That’s it - You’re done!

Drop us an email or tweet us a pic to let us know about fun stuff you get up to!




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