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
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
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.