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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.

codongolev3 years ago
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....
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 Paz7 years ago
where can i buy a reed switch at and how much is it
you can find them here $1.00-$1.25 USD
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
if i tried that id get expelled for something like ppl thinking its a bomb
id probably make mine explode 10 seconds after moving it
Wish I could do that and say it was my science project. That would be HILARIOUS!!!
photozz (author)  golddigger15596 years ago
\o/ Hooray! Its Science!
Saturn V5 years ago
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.
bounty10125 years ago
Imagine having one of these that Rickroll'd people when they picked it up, or if it screamed, that would be freaking hilarious.
neardood7 years ago
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.
He did say that he didn't have one of those lying around, so he improvised one.
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?
I have yet to see a four-cent reed switch in Radio Shack.
4 cents. Wow. Its so much cheaper in America.
because it is fun.
but(t) you could do something ten times as coll in the same time...
I agree, and its even funner on the last day
Gamer9176 years ago
make one out of a toy car and let a little kid in your school pick it up
A good name6 years ago
Does this fall under the same basic concept of a landmine? Or tripmine?
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.
Get a life.
You fail.
Who? Me?
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.
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.
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 name7 years ago
Put this into the Instructable book contest!
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.
Interesting Revenge
minimidget7 years ago
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?

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.
eeeXsmart7 years ago
very cool!!!!!!!!!!!!!!!!!!!!!!!
neardood7 years ago
Also, why does evry image reset the page scroll to the top? Is this some kind of cruel joke????!
Nice goodbye for your coworkers. :-)
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
people can be really stupid - they think everything is a bomb, remember the "boston bomb" scare? yeah...
RFilyaw bgugi7 years ago
"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.
It had batteries and wires. It was terrifying.
Yup, batteries and wires:
Mooninite Bombs Made Of Batteries and Wires (Wired blog).
Can you imagine the horror?! :P
wasn`t it a cartoon from adult swim?
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 bgugi7 years ago
The same thing happened when two girls decided to place Mario Bros. style "question boxes" around a town in Ohio...
bumpus bgugi7 years ago
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
good one lol
i was kidding lol
BlueFusion7 years ago
Nice work. But a better and simpler idea would have been a magnetic reed switch and a simple circuit to latch a relay so a magnet could not turn it off again. :) Waaay simpler and doesn't leave bits to clunk around that could allow it to turn off again if say, it was inverted...
Sorry, BlueFusion, how does it turn off if you turn it upside down? Anyway, he does mention that he scavanged all the parts from work. That small fact makes it an even better prank!
Well the way I interpret it is that the weight holds the switch down... either on or off until the magnet moves it... kinda confusing there. But if you released or pressed the switch depending on how you look at it... no power to the alarm therefore no more noise.
Not so. The magnet pulls the lever down onto a switch. He is using the "normally closed" portion of the switch, which means that it is closed when NOT pushed. So, when the person lifts the box away from the magnet, the switch pops up and alarm goes off. If you flipped it upside down, the switch would still be popped up and would still go off. The only way to stop it is to push the switch in again, which means disassembling it or laying it on the sweet spot again.
Oh, I truly, truly wish I had seen this instructable last Thanksgiving when I lost my job a week after receiving an award for running a very successful project at my company. "Oh, it's nothing personal." Well, it felt pretty personal to me. Anyway, I think this is brilliant. You're not doing any real damage (at least, nothing prosecutable), but you're reminding them you're gone, with a sense of humor. Definite + vote.
fd937 years ago
another thing. wouldn't it be easer to make a hairline motion swich with one of those little shild-things that come on the batery cases of like hess trucks so that you could arm it and then any motion would irreperably set it off
fd937 years ago
You could do a small ruber pin on a string that when moved would pull out and not be reinsertable, like those clear plastic tabs on laser pointers and things
paulm fd937 years ago
that is visible
fd93 paulm7 years ago
Dental floss
xproplayer fd937 years ago
fishing line
gripes7 years ago
you can get these at the dollar store. you put them on doors. just hide the top piece in (whatever you want) and tape the bottom piece to the bottom of the desk.
Dr.Paj7 years ago
If you really wanted it to last longer you should have put some bondo/spackle over the screw holes and painted the whole thing (after sanding the bondo/spackle smooth) so that it couldn't be taken apart without destroying it.
u think this would be a good speaker for it
its like 103db or something insane and its cheap
That's so cool! And I like the update. First sentence... yeah. ;-) Nice job, and great photos. +1 rating.
Comeaja7 years ago
Now see, lots of extra effort, but make it reflective with a ton of those mega0bright LED's all over it. Good luck trying to find how to even open the case to turn it off. Not to mention, it'd be shiny. And people love shiny things.
Tippler8 years ago
This reminds me of the old "Panic Box" prank. It is basicaly the same thing, except the panic box has a large red button marked "Do not press", an on/off switch, and an ac plug. The button sets off the alarm, the switch and plug are dummies. It turns off with the reed switch. I imagine the electronics would just be a one shot 555 setup.
hcold Tippler7 years ago
Huh, I thought of a similar thing to set off a bomb, but when the button was pushed, it "pulled the pin" and set the thing off. That's what they get for pressing my buttons, if you know what I mean.
redskinsjbs7 years ago
I made something like this a while ago. I had the same sweet spot idea, but instead of having the alarm placed inside of the *box* (I used a chicken paper weight) there was a transmitter that sent one of four signals to to one of four receivers. These receivers were conveniently placed under my colleagues desks, and they would then cause an alarm to go off in their respective positions.
TheInventor7 years ago
Thats too funny and awesome! +1/added to favs
Aerospaced7 years ago
All you really need is a normally closeed magnetic switch and a magnet. The same thing burlar alarms use.
photozz (author)  Aerospaced7 years ago
Yes, but I could *not* find one on the scrap pile or in my parts box anywhere. I made do with what I had in true hacker form.
reedzilla8 years ago
I'm not entirely clear, given the pictures, what causes the weight to go up and complete the circuit from the battery to the alarm when the box is removed from the magnet. Is there a counterweight on the other side of the lever bar we can't see, or is the whole assembly on a springarm or something?
photozz (author)  reedzilla8 years ago
Yeah, I need to ad some clarification to the pictures. the switch is under the bar, it is holding th bar up on it's own, as it's just a momentary push button, kinda like a doorbell. the weight is not enough to push it down normally, but with the pull from the magnet, it's just enough to trip it.
but y doesnt it go back off when put back?
If you guys skipped step 1(i have no trouble beliving you did), its a magnetic switch that so when the box is moved away from the hard drive magnet, the magnetic field is broken, causin the bar to gu up and connect with the alarm.
nvm that last comment i didnt see that photozz explained it. it would be gone but some glitch keeps it from being deleted .
PR228 years ago
Couldn't you just stuff the holes that let out the sound, thus rendering it useless? We need a way around that.
photozz (author)  PR228 years ago
you could. I was thinking of making a coffee can with a motor driven rattle inside instead. that would be almost impossible to muffle without just smashing the whole thing. ... For the siren, if you drilled holes in all sides of the cube, it would e tough to block them all at once
LOL, this is pure GENIUS! I play airsoft, and I think this has considerable applications in our games! I'll probably end up making one of my own, to annoy people, and maybe try it out with a tripwire type deal in an airsoft game! Great instructable.
Heh. I need to do this on the last day of school, like hook it up on the toilet seat or under the teachers desk. when there cleanin up in the summer that would be funny if some1 bumped it and they went into a cuss-fest tryin to turn it off
benhudson8 years ago
Nice instructable. For lazy buggers (ie me) you could do the same thing with a rape alarm thingy built into a tough box. As far as I know they work by pulling out a tab, and putting it back in to deactivate, but if you have it so that a ribbon or some kind of cord pulls out the tab (from the alarm which is epoxied to the bottom of the case) you couldn't get it back in. Sorry about the vagueness and verbosity.
Oooh, and (with your design, not mine) if you had a thin(ish) non-ferrous desk and a strong magnet, you could have it so that removing the SLM lets the magnet fall (discreetly, of course) so that you couldn't stop it by putting it back. Then again, I like the idea of having the cube left on the desk for years because they can't move it anywhere else.
jtobako8 years ago
there's a psychological part that's missing-why would they put it back (or even know to try)? you need some sort of warning to leave it in place, something like putting a mattress tag (do not remove under penalty of law) on it.
photozz (author)  jtobako8 years ago
Thought about that.. decided they need to figure it out on their own. :) Besides, you can feel the magnetic pull a little when you lift it, that *may* be clue enough.
jtobako photozz8 years ago
not if you are doing a quick cleanup. i think that it's going to be a lot less annoying than you hope. once it goes off, it's just going to be circular filed.
photozz (author)  jtobako8 years ago
ho no.. apparently it was quite annoying. went off this morning for about ten minutes. they had to disassemble it to kill it. totally worth the effort.
yea i agree i had something basicly like this sept with light and it woke me up at midnight just cuase it screwed up so i got pissed punched the window screen out and threw it into the road next to my house.
crapflinger8 years ago
hehe...an even more annoying modification! just thought of it....mount a magnet switch remotely...i.e. run some wire out of the box over to a magnet switch somewhere else on the desk...when they pick up the box...it's not likely that they would have seen where the remote switch was at...so they'd have to search harder to turn the thing off
photozz (author)  crapflinger8 years ago
I made it self-contained, as I was giggling about the idea of someone running around the office with this thing trying to figure out how to shut it up. At this point, they will either have to disassemble it, or smash it to shut it up. It's built for industrial applications, so smashing might not be an option. :)
So if you say, dropped some solder into the screw holes during assembly, nothing short of a sledge hammer would do the trick? Fantastic! Perfect blend of subtlety and high decibel speakers.
Ibanezfoo8 years ago
Another source for a magnetic switch is the little glass ones inside security system door and window sensors. They look similar to a germanium diode, except bigger. They are basically two wires touching inside the glass... when you pass a magnet over them you can watch them separate. So as long as its sitting over a magnet the circuit is open, when you move it away the circuit will close and your alarm will go off.
photozz (author)  Ibanezfoo8 years ago
Yeah, That is an ideal solution. I actually had one of those, but it was a "NO" (normally open) type, so it was not working for me. I'm noticing that I get more satisfaction out of the McGuyver approach to these things. Why take the easy way out when you can do it the hard way.
ewilhelm8 years ago
So, it's Friday. Tell us what happened! If it wasn't exciting, make something up (or don't respond so we'll speculate that you're in jail).
photozz (author)  ewilhelm8 years ago
It worked! I called one of my friends today to check up, she answered with a loud "DUDE!" she sits on the other side of the floor and said they hear it go off this morning. They said it went off for quite a while. Later when they ran past my desk, the case screws for the alarm enclosure were laying there and no one was around. I giggled for a good ten minutes.
photozz (author)  ewilhelm8 years ago
Hehe. I have no idea yet what hapened. I literally plugged the battery in, picked up the last box of crap and walked out the door. I'm sure I will hear about it next week when someone gets curious.
so all this does is when you take the box off the desk it goes weee-wooo-weee-wooo right?
photozz (author)  ich bin ein pyro8 years ago
Right, but it does it at 80db in a quiet office. :) it's pretty piercing. scared the bejesus out of the cats.
crapflinger8 years ago
ahh office torment...one of the best things there is....nice instructaable...though some clarification on your magnet switch would be nice (not the most complex thing to build but...)
photozz (author)  crapflinger8 years ago
Clarified.. added another pic and some more text.
Operandi8 years ago
Next time mark the spot on your desk with a Sharpie where it has to stay. With a warning. Then leave a picture of yourself or message permanently attached. Say some piece of cryptic info about the owner or your boss. Something that isn't slander. But sooner or later someone will figure out. Or maybe a clue leading to a clue etc. etc. All with cryptic secrets about the sordid lives of those you left behind. (Ok! So this is getting twisted! But what a great idea to expand on. "Last day of work pranks!" lol!) I could just see it two years from now. "Hey. What's that "thing!" on your desk?" Reply "I don't know. But don't move it or even touch it! It will go off!" LOL! Great Instructable! Especially considering you made this from parts on hand at the last minute!
photozz (author)  Operandi8 years ago
Thanks.. I was going to leave a post-it under there, but I decided leaving it a mystery would be more fun. I can't wait to hear the results from my friends on Mon. ...
AymericRdV8 years ago
That is a great prank. When I left my last job had the whole weekend to clean out my desk. I went to all the labs and collected every single timer I could find. I hid the timers behind books and every other hard to find corner and set them to go off one after the other in 5 minute intervals. The timers usually go of for exactly a minute but you can mod them to go off untill either the batteriy dies or you turn them off. For two hours on monday morning a lot of people hated me a whole lot....hahaha
knexer18 years ago
Nice!!! That will make an awesome prank for april first.
photozz (author)  knexer18 years ago
Kiteman8 years ago
How about a switch held open by a lump of iron held in place by the magnet?

When they move the box, the iron falls off the switch, letting it close and start the alarm, but, when they put the box back, the alarm keeps going.

BTW - glue the box shut!
photozz (author)  Kiteman8 years ago
not a bad idea. I had put this together at the last minute, with crap I had laying around, so I had to work with what I had. I'll think about it for next time though. The box is screwed shut, and I was the only one that had screwdrivers. :)
irwinner8 years ago
hey this looks remarkable similar to those cheap house alarm things, i bought one at the dollar store a while ago (and rigged it so every time my teachers door opens it sounds) but any way. it has two major parts the noise maker and a magnet. they have to small metal strips that get pulled toward each other (and short the circuit) when the door is closed(and the alarm is next to the magnet) when the door is opened the metal strips separate, open the circuit, and the alarm sounds. now i just telling you all this so you can go down to the dollar store and make one of these with out having to rig up your own sensor.
photozz (author)  irwinner8 years ago
pretty much. The only real difference is stealth. No one will expect this part to go off like that. there are a lot of these laying around, and none are wired in this way. Call it a ISD (Improvised Sonic Device). It also seems more sensitive, as the magnet is almost an inch away. the dollar store version usually requires less tolerance than that.
Drackar8 years ago
Vindictive reminder of your parting :p
photozz (author)  Drackar8 years ago
Somewhat, in a mostly harmless way. I was originaly thinking of filling all the cabinets up with cups of water stapled together.
royalestel8 years ago
I guess if you shook the box you could get the alarm to go on and off, though not off permanently. This is pretty fun. Mad hacker. Heh.
photozz (author)  royalestel8 years ago
yeah. That will make it even more confusing. Only one other person at the job knows about it and how it works. and I am sure that he is not going to say anything.
zachninme8 years ago
Why not use a reed sensor? That would seem to make more sense, as it is only activated by magnetism (yours is affected by acceleration) and can't be unhooked.
xboxteen018 years ago
pretty cool,i especially like how it can only be shut down by putting it in the same spot,nice touch and good luck with your new job
This is pretty interesting. Tell us if you get any calls from the office.