Quick and Dirty Electric Tripwire -The Home Guard Mix.

About: Making things to entertain myself comes second to entertaining my offspring, but my mind is always working something out.

Basically just a tripwire based switch made from stuff lying around the house. Can also be used as a remote switch for things you don't want to be next to when you turn them on.


Step 1: Tools and Stuff, You Will Need...

Clothes Peg
Thin copper plate
Thin card/ plastic
String/ invisible thread
Crocodile clips
Device you want power
Pen knife or some other kind of cutting implement.

Step 2: Constructing the Switch.

Cut the copper plate to size. You need two pieces, roughly the same size, big enough to stick to the inner jaws of the peg and have some hanging out the side to attach the crocodile pegs to. It's best to have some stick out of one side on the top and the other side from the bottom.

Step 3: The Trip Gizmo.

Get your piece of card/ plastic and cut to a decent size. Big enough to seperate the jaws of the peg without the copper pads touching each other.
Poke a hole through one end and tie the tripwire through it.

Step 4: Finally There.

Insert the card/ plastic break into the peg jaws. Attach the crocodile clips to the pads. The other end of the clipped wires, it is up to you. Light or sound devices will work with this.
You can either wedge it under something , but I put a string through the center of the spring to anchor it to something solid.
Simply put, the card acts as an insulator an gets pulled out when the tripwire is.. well, tripped.
The copper makes contact and the whole thing acts as a switch. Done.
Works well with my Quick and Dirty Squib instructable (but only when used with caution). Check it out, NOW.



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    24 Discussions

    This is wonderfully simple, not to mention high current too! I built a similar gizmo out of a few parts and an N-channel MOSFET, its solid state but given the size only allows 300ma


    Reply 9 years ago on Introduction

    Yes, in fact aluminum is commonly used in electrical wiring.  In fact, aluminum's resistivity is only about 30% more than that of copper.  Aluminum foil can be used in this application, though it may help to use glue or a rubber band to affix the foil to the clothespin.


    10 years ago on Introduction

    We used to make these very simply. Instead of the plates and such (which are more durable I suppose) we just wrapped each wire around the jaws of the clothespin. Then when you pulled the insulator (we used half of another clothespin or a wooden peg) the two wires touched directly. Another way was to use small wood screws as the contacts. I used them in a class project in college where we had to make a rube goldberg machine. As the grand finale this is what we did with two tripwires. A falling ball bearing (about 1/2" in diameter) fell into a cup, which tripped one of these tripwire pegs, which turned on an air type popcorn popper. A bowl set on a "teeter totter" piece of wood underneath. When the bowl below the popcorn popper got full, the weight of the corn tipped the "teeter totter" which turned it off. The teacher was amazed. You can use these to turn something off very simply. Just use the insulator piece as part of the circuit. In other words, the electricity is flowing between the piece hooked to the trip wire and one side of the clothespin.. The opposite side of the clothespin has nothing. You pull on the string and the circuit is broken. One last thing, these work real well to set off those really loud "personal alarm" key chains (the ones the sell by pepper spray and such). Works well in many circumstances, such as paintball games.


    10 years ago on Introduction

    ok. so instead of the copper plates for the ports i just drove a screw into each side of the peg. the pointy parts were facing out so that the flat parts would touch each other when the card was yanked out. you would attach the clips to the pointy parts of the screws. i hooked it up to the flash component on a isposable camera and just about gave my mom a heart attack.


    11 years ago on Introduction

    what could i use to make it beep when someone trips it?

    sorta lol but you'd have to reset it every time, and you'd need to tamper with the mains voltage in the lightswitch. (something I don't suggest doing)

    Any conducting plate would do I guess. Reinforcing the foil with tape on one side would be a good idea or it could tear (obviously not the sides that need to touch to make the connection).


    11 years ago on Introduction

    i love this instructable because i hooked mine up to a buzzer and instead of yarn i used fishing line so its invisible so ive caught my brother so many times ~Nsalt94