Introduction: "Last Day" Magnetic Sonic Cube Landmine

Picture of "Last Day" Magnetic Sonic Cube Landmine

UPDATE: It worked! Apparently someone picked it up Monday morning. It went off, and apparently went off for a while. It sounds like they had to disassemble it to shut it up. I'm ridiculously happy with the results.

At my present job, I have been known as something of a crazy hacker. For reasons too complex to explain here I have decided to leave after ten years. This Friday is my last day. I decided to leave a small present behind for anyone trying to scavenge scraps from my old cube.

Several ideas presented themselves to me, but eventually I decided on creating a small alarm that would go off mysteriously when someone moved it. Despite the elaborate title, the design is simple, and not to hard to replicate.

The alarm I used is something I pulled off the scrap dock of the job. It was originally designed to provide an audible alarm for manufacturing machines. Mine is capable of about 80db on a 9v battery, but you could replicate this with a Radio Shack buzzer or other alarm circuit.

The basic idea is to have a box siting on my desk. When someone moves it, an alarm sounds, and won't shut off. This is because the box has a magnetic trigger inside, and when the box was moved from the desk, it was also moved away from the hard drive magnet I planted under the desk, thus triggering the alarm. It will shut off again if they put it back in the same place, but there will *intentionally* not be anything to mark it's position.

Step 1: Parts

Picture of Parts

You will need:

1 Alarm circuit, buzzer, or other device to make noise.
1 project box or enclosure. Preferably plastic. The alarm I had came in an enclosure already.
1 9v battery, or a power source appropriate for the circuit you are using.
Small momentary switch. I used one out of a mouse. It needs to have a light trigger.
Hard drive magnet, or any other form of rare earth magnet. needs to be strong.
Misc hardware and some ingenuity. A genuine distaste for your co-workers is also handy.

Soldering gun and solder.
Wire stripper and/or wire cutter
Rotary tool

You could make life a lot simpler if you had a magnetically actuated switch laying around you could use, but I rarely have things work out the easy way. I was forced to do it the hard way and create a magnetic switch from a conventional mouse-button switch.

Step 2: The Switch

Picture of The Switch

The only hard part of this was getting the trigger put together and dialed in. I had to mount the switch to the side of the box, then find a small metal bar to act as a lever. Then I attached a metal weight to the other end of the bar. When a magnet is below the box, it pulls the weight down, disconnecting the battery from the alarm. When the magnet is removed, or the box moved, the weight goes up, connecting the alarm to the battery. Check the notes on the pictures.

Step 3: Final Setup

Picture of Final Setup

I don't have any fear of this causing much of a panic. It will, in fact, be exactly the sort of thing people expect of me.

The desk I use is your standard cube issue. It has areas underneath where there is only an 1/4 inch or so of metal and material thickness. the magnet sticks to it just fine, and you can feel the magnetic effect clearly through to the top.

A magnet or two will go underneath, and the box over the "sweet spot" on top. I'll plug in the battery and walk.

I'll prob expand on this one more later. Just thought I would throw this one up there for the hell of it for now.


codongolev (author)2011-09-12

sort of reminds me of a concept for a senior prank I came up with... (probably won't ever happen due to difficulty level, improbability and ridiculous stakes...)

build a large robot with several proximity sensors, powerful wheels, and a big, thick steel body. (use an electric wheelchair or something like that.) give it lots of huge batteries to keep it running for a long time (or make it seek out and plug in to outlets, but that could prove difficult). fill it with concrete so that it's somewhere around 500 lbs, then just set it loose in the halls. make it just wander around without hitting anything, maybe make it get angry if it's moved, etc....

BrefelanDesigns (author)2011-03-25

How about adding a relay wired to latch on when power is applied (or if you could find a latching relay use that) I used a relay wired to latch on for my sonic grenade (well prototype rather) and it works great once the "trigger" switch was turned on it stayed on even if you turned the switch off - the only way to stop it is either the hidden reset switch or disconnecting the concealed battery....

RGM La Paz (author)2008-07-31

where can i buy a reed switch at and how much is it

account3r2 (author)RGM La Paz2010-10-23

you can find them here $1.00-$1.25 USD

golddigger1559 (author)2009-01-22

this was great I made one of these out of an old conduit box and a reed switch I left it in the boys bathroom at school and I was across the hall when it went of the person that tripped it ran out and then a crowd gathered outside the bathroom when they figured out that it was harmless they brought it into the hall to try to turn it off and it was equipped with the most annoying buzzer I could find(fire alarm) plus as an added act of hilarity I added 4 dummy switches to throw them off they sat there for half an hour(I had a backup battery)trying different combinations for the switches it wasn't until someone from the wood shop hacked it open with a saw(I hot glued the lid shut so you couldn't simply open it)when they pulled the batteries they figured out how they should have turned it off(btw I used the same triggering system as you)I was sitting in my class trying as hard as I could not to laugh.nobody got anything done because there ears were ringing. just thought id share my sonic tripmine experience

abadfart (author)golddigger15592009-06-14

if i tried that id get expelled for something like ppl thinking its a bomb

sam1997 (author)abadfart2010-09-22

id probably make mine explode 10 seconds after moving it

Saturn V (author)golddigger15592010-08-24

Wish I could do that and say it was my science project. That would be HILARIOUS!!!

photozz (author)golddigger15592009-01-22

\o/ Hooray! Its Science!

Saturn V (author)2010-08-27

I'm going to combine this with the Annoying Beeper so that if the beeping drives them crazy enough to demolish their office, and they find this, the loud alarm will go off, sending a signal to a hidden speaker in the same room. (I took the speaker out of the device so it could be hidden.) That'd be a good "prank" for april Fool's Day. Well, more like revenge. All I need to do is wire up a prototype.

bounty1012 (author)2009-12-12

Imagine having one of these that Rickroll'd people when they picked it up, or if it screamed, that would be freaking hilarious.

neardood (author)2008-04-13

Okaaaaay. Y dont you just make life easier 4 yourselvs and put a magnetic reed N.O. (normally open) switch in the bottom of the case. You can gett any means of buzzers and alarms from radio shack or dick smith's.

TheMadTinker (author)neardood2008-04-17

He did say that he didn't have one of those lying around, so he improvised one.

neardood (author)TheMadTinker2008-04-29

no offense, but if you can't waltz into you're local electronics dealer and by a 4-cent magnetic reed switch, then you probably just dont have any common sense. However, the build is facinating and I cant understand y u would put yourself through so much strife to do something so simple?

Akoi Meexx (author)neardood2009-11-18

I have yet to see a four-cent reed switch in Radio Shack.

DavidRobertson (author)neardood2008-08-19

4 cents. Wow. Its so much cheaper in America.

Insaneisfun (author)neardood2008-04-30

because it is fun.

neardood (author)Insaneisfun2008-05-27

but(t) you could do something ten times as coll in the same time...

I agree, and its even funner on the last day

Gamer917 (author)2009-03-12

make one out of a toy car and let a little kid in your school pick it up

A good name (author)2008-09-27

Does this fall under the same basic concept of a landmine? Or tripmine?

Silvester10528 (author)2008-04-04

Interesting idea, I may try to use portions of it for some paintball projects I have had in mind for a while... As for the fake bomb pranks, I think you all need to get a firm grip on the reality that there ARE people in this world that WILL plant bombs and kill people to further their political agendas. By placing fake bombs and pulling pranks of this nature you are drawing the police away from real crimes and desensitizing the public to suspicious situations that might be real and get someone killed!! I MAY be over-reacting, as I'm sure many of you are thinking right now... But if car bombs and other terroristic devices can be detonated in England, Israel and U.S. occupied Iraq, what makes you think they couldn't be done here - in the country that is hated by more extremist societies than any other? Please keeps your "pranks" as harmless as humanly possible. It's one thing to startle or ever scare someone, it's quite another to intentionally make them fear for their life; that is really not funny, if you are laughing, you obviously need to grow up and learn empathy.

bowmaster (author)Silvester105282008-04-07

Get a life.

A good name (author)bowmaster2008-07-25

You fail.

bowmaster (author)A good name2008-07-25

Who? Me?

Pbyrd (author)Silvester105282008-07-25

Yeah taping a digital clock to some road flares and putting them in a suitcase of someone who is going on a flight soon may be funny, but it might actually let a real terrorist sneak by while airport security is busy.

wolfy02 (author)Silvester105282008-04-19

I see your point, but why live your life in fear of the unknown? Isn't the purpose of life to "live" it. You die, you die. People have such an issue with death these days. Nothing has changed all these years. Oh and about desensitizing the public, it's people like you who shove that crap down our throats that make us not care anymore. You heard it once, you ignore it again.

Silvester10528 (author)wolfy022008-04-20

I agree with your point about living in fear of the unknown; life IS there to be LIVED. But, when a joke is just for the sake of laughing AT someone else and not WITH them, is it really funny? I saw a clip once from a "bloopers" show in Isreal where a guy goes to a crowded bus stop, puts his brief case on the ground and runs away... Obviously that announcer and production crew were in stitches, while the people at the bus stop were tripping over each other and running out into traffic to get away from what they could only believe was going to be a bomb - not a funny joke to me! While I do agree that we as a society don't want to be so paranoid that we are calling in the bomb squad for every forgotten breif case or misplaced parcel, I think it's really bad form to intentionally make people think their life may be in danger just so we can laugh at how stupid they are when WE knew it was harmless.

i see what your getting at, and a fake bomb would not be funny at all, hpwever this is just a box that makes a loud noise, and he says he used the box it was already in so it probably said '(brand name) alarm' on it anyway

Yeah, I'm cool with the instructable!! It's startling funny, like a hand buzzer or shocker pen; not me personal sense of humor, but harmless. I love the way he triggers it. I might use a similar set-up for trip-wire warning alarms and strobes in scenerio paintball games.

A good name (author)2008-07-25

Put this into the Instructable book contest!

MisterMissanthrope (author)2008-07-02

hmm, the same concept could be used but instead of a using a buzzer, use a headache machine, but that seems a lot more cruel than your idea.

Sir-Jackington (author)2008-05-29

Interesting Revenge

minimidget (author)2008-05-08

Well, I just picked up the stuff to make my own! A 9-volt, a 90 Db piezo (although it only does full output on a 12-Volt..) a reed relay from radio shack ($3.00, a little expensive, but whatever...) and an aluminum project case.

I think there's some fun in store for me, whaddaya think?


minimidget (author)minimidget2008-05-08

Gah. It's not a normally open switch that's needed, but a normally closed... I put everything together, and it activates when the magnet is close, rather than when it is removed.

neardood (author)2008-04-29

try liquid cement, and even put it in a metal case, now where talking :). The problem with that is that the sound from the buzzer would not be loud enough to be noisy and annoying, so u would need to drill sound holes.

eeeXsmart (author)2008-04-23

very cool!!!!!!!!!!!!!!!!!!!!!!!

neardood (author)2008-04-13

Also, why does evry image reset the page scroll to the top? Is this some kind of cruel joke????!

gimmelotsarobots (author)2008-04-10

Nice goodbye for your coworkers. :-)

WingDings (author)2008-04-09

Yup, batteries and wires:
Mooninite Bombs Made Of Batteries and Wires (Wired blog).
Can you imagine the horror?! :P

darth acexxacer (author)2008-02-19

this is nice at my old school on the last day i left a couple of road flares with a digital clock duct taped on it it was so funny when they found it lol

bgugi (author)darth acexxacer2008-03-29

people can be really stupid - they think everything is a bomb, remember the "boston bomb" scare? yeah...

RFilyaw (author)bgugi2008-03-29

"I hope you can see this, Boston, because I am doing it as hard as I can," says Ignignokt as he flips them the bird.

pandaboy292 (author)RFilyaw2008-03-31

wasn`t it a cartoon from adult swim?

RFilyaw (author)pandaboy2922008-04-05

Indeed. Aqua Teen Hunger Force. It was a low-price marketing gimmick for the (then) upcoming movie. It was not intended to scare anyone, since it was just a flat PCB with LEDs and a pair of AA batteries, not enclosed inside a box at all. It was basically Lite Brite.

i think so

ReddWolf (author)bgugi2008-04-03

The same thing happened when two girls decided to place Mario Bros. style "question boxes" around a town in Ohio...

bumpus (author)bgugi2008-03-29

Boston Police: Putting the "Error" back in Terrorism"

HAHAHAHAHA. I wish more people knew basic electronics, and would be able to discern a prank from a real bomb. then again, us 'geeks' wouldn't have near so much fun, would we?

we could still find ways haha

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