Fabulous Magic 8 ball prank

Hackaday forum user [arfink] has shown us a brilliant practical joke he built. This is a magic 8 ball that will blind you with a flash when you flip it over. Have you ever been in a room with one of these and not flipped it over? Neither have we. Using a basic flash circuit ripped from a disposable camera in conjunction with a mercury switch, this project took him about 2 hours to make. Admittedly, most of that time was just trying to split the 8 ball in half without completely destroying it.  The circuit is pretty simple. Just figure out what 2 wires need to be crossed to trigger the flash and install your tilt switch there. He added a power cut off so you could disable it as well.

UPDATE: video added after the break!


  1. Spork says:

    Haha sounds like a fun thing to leave in the living room for guests.

  2. Gav says:

    Love it. Tempting to make one for myself

  3. mccoywm says:

    I was really expecting a miniature screen with custom, lets say negative, messages that randomly appear. I guess this works too.

  4. M says:

    My trick would have just been to take out the little plastic thing with the responses and put it back together.

  5. 3vi1 says:

    That’s brilliant. God I wish I had thought of it first.

  6. Bill Porter says:



  7. Renee says:

    I thought they were going to replace the answer Icosahedron with negative answers.

    “Will I ever find true love?”

    “No, go f^*( yourself”

  8. tlalexander says:

    Pretty nice simple hack.

    The only improvement I can see is changing the flash to a high powered LED. The big ones can put out a blinding amount of light, but don’t require a high voltage capacitor to stay charged like I think most flash circuits do.

    That might reduce the idle power consumption.

    Also, to disassemble it, just break out the clear window. Since, by the time the user sees that part of the 8 ball, it doesn’t matter what it looks like, you don’t have to worry as much about what you replace that section with. As long as its flat so that when they pick it up they don’t feel anything weird.

  9. zool says:

    heh, they’d probably notice when shaking it and it didn’t sound or feel right
    also if you shake it before, wouldn’t that set off the mercury switch

  10. t&p says:

    needs a delay so it doesn’t go off when not facing the person when picking it up.

  11. t&p says:

    oh next post reads for a 555 timer circuit delay in the future. NOW this guy is thinking. I love it.

  12. cde says:

    @Zool, they will definetely look at it, if it doesn’t feel right when shaking, if the flash doesn’t trigger first. Hell, even if it triggers, they will still look at it to try to figure out wtf just happened.

  13. Oren Beck says:

    Nice hack on tech merits and unexpected “WtF?” aspect. Getting too elaborate and having a hack never get built is a fail that’s had many projects die stillborn. Arfink scores points for e job done more than just “Good Enough” that actually got built.

    Perhaps an expansion of the concept might be tucking a cam into the ball for capturing those Wtf? expressions.

  14. Dave says:

    That is full on awesome. Great job.

    ++ to Renee for knowing the word Icosahedron.

  15. Random reader says:


    to slow the flash a little a resistor and capacitor at the mercury switch? i meen how longs it take u to grab one off a table to get a gd view of what its gonna say?

  16. Hirudinea says:

    “I see a white cane in your future.” Another fun thing would be to put a spray pump from one of those automatic air fresheners and fill it with this…


  17. PocketBrain says:

    Is it such a good idea to cause injury to people?

  18. Jeditalian says:

    Nice Prank! i also enjoy packing vials of mercury into things that people will drop or throw when they get startled!

  19. ho0d0o says:


    There is no more injury happening here than any that might occur from a close up picture taken at night…although if someone were epileptic this could cause them to go into a seizure since the flash is obviously a surprise.

    I fairly certain that it takes multiple flashes of light to trigger an epileptic’s seizure response. (I’m a RN at a state mental hospital so I know a few things about epileptics).

    Side-note: My great aunt was epileptic and she took group pictures with us all the time involving multiple flashes, so in totality I really don’t see how this could harm anyone.

  20. Brian Neeley says:

    I’m with Oren for version 2. The camera would be an awesome add. But, if I were going to go to that much work, I would replace the flash and mercury switch with an accelerometer and high power LED. That way, it won’t fire off before faceing up.
    Then I’d add a weight so that feels right when picked up, and then…

    Yes, long before this point it would never get finished, just like Oren said…

  21. moo says:

    He posted a video too.

  22. arfink says:

    Thanks for the feedback. Yeah, this was a cheap no-brains hack. Also, as a side note, the mercury tube does make a sloshing noise which is somewhat like what the blue goo tube does. It’s fairly convincing.

  23. arfink says:

    Oh, and the weight is pretty much spot on too.

  24. bluewraith says:

    I just noticed this and have to ask.. what happened to your “3” key? Seems to be AWOL.

  25. arfink says:

    Book took a nose dive off the shelf. Smashed the key clean off. It never would go back on. :) I have used the computer like that for 5 of the 6 years I have owned it.

  26. medwardl says:

    I was kind of expecting an LCD screen with some programmable smart remarks possibly with wireless on the fly ability to change them.

  27. TheCreator says:

    Now you need to throw in a camera to catch that “wtf?” response. Lighting would be perfect :-p

  28. Dan L says:

    Better make it drop resistant.

  29. pRoFlT says:

    I would put metal contacts on the side and make it shock people when they turn it over! hahaha.

    Like my shocking mouse(http://www.practical-jokes-and-pranks.com/shocking.html) and flash light(http://www.shockinglighters.net/shockflashlight/index.htm). People just love to pick things up on your desk and play with them. Notice flash light has real LED button at top but shocking button in the normal postion. I love that flashlight!

  30. Frogz says:

    go with my version
    buy http://cgi.ebay.com/110632493890 for $75
    add 2 d cell batteries and a driver circuit, make sure to include a small delay after mercury switch is tripped, so the person can see the little note “goodbye light, hello world of darkness”


  31. ali says:

    LOL.. It’s funny isn’t it? :D

  32. Mar says:
  33. stormdog says:

    I’d love to see the addition of an alarm sound or a ‘bang’ noise.

  34. grenadier says:

    Heh, I made one of these about 7 years ago using a cigar box. I think I did it because I saw a flashy trap box on hey arnold or something.

  35. Xb0xGuru says:

    Sorry to be a party pooper, but pretty irresponsible IMHO. Even putting epilepsy to one side (which can still be triggered by a very bright flash – just because your aunt/gran/uncle/etc – delete as appropriate – doesn’t suffer from a single flash, doesn’t mean no-one else does), you can easily give someone a migraine with this. If you’ve not had one before, I suggest you look it up. it would have been much funnier to just build a camera into the bottom with a small white LED which came on enough to illuminate the subject and have the obscene answer to be captured on digital memory inside.

  36. arfink says:

    Xb0xGuru- again, as with any prank: know thy victim.

  37. Frogz says:

    or toss all legality/people’s health aside and just build my version with the 1 watt bluray diode

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