This is something I thought up while browsing the shelves at the local thrift store. I had been more or less randomly grabbing fun and inexpensive things which might be fun to hack and/or add to the junk box when I suddenly had an idea. I had in my hands at that time an old 35mm camera and a Magic 8 Ball. The combined cost of these two items was $1.35. So I decided I had to realize my idea.
-an innocent magic 8 ball
My idea was to make a magic 8 ball which would blind an unsuspecting victim with the camera flash. I had an old Honeywell thermostat at home which had a mercury tilt switch inside, and after cutting open the 8 ball and removing the blue goo tube I stuffed the camera flash guts and the tilt switch inside:
I also added a "safety switch" to the ball, which can be toggled without opening the ball and which disables the charging circuit, making it so the ball can't recharge for another flash. I had a dead Commodore 64 that I had been gradually pillaging for parts and I stole the power switch and installed it facing out the bottom next to the flash tube and reflector. You can kinda see it in the first of the two pictures above.
Of course camera flash circuits usually vary pretty widely so I didn't really document that part of the hack. In general you just have to find out what wires to cross to make the flash fire, and then rig those up to the mercury switch so that when you tip the ball upside down the mercury will close the switch and fire the flash.
And just as a side note: this project took me about 2 hours to do. 90% of that time was spent trying to get the Magic 8 Ball open in one piece, which was an arduous process involving a large vice, chisels, screwdrivers, lots of prying, and general frustration. Hopefully you can figure out how do it better than me, as I eventually just wound up crushing the thing in the vice until the seam popped open and then bending the shell back to shape. It worked surprisingly well, but did leave some nasty gouges in the plastic in a couple places. The last 10% of the time was spent disassembling the camera, soldering in the tilt switch, and hot-gluing everything into the shell.
In all, it's a very effective little prank device, and has been the source of great amusement so far.