Coin shrinking with high voltage in slow motion

Craft & Design Science Technology
Coin shrinking with high voltage in slow motion

Recently Hackerbot Labs was invited by Intellectual Ventures to demonstrate their Maker Faire Editor’s Choice Award-winning high voltage coin shrinker in front of a Vision Research Phantom 100k fps high-speed camera.

Discharging about 10 kV (15,000 joules!) from enormous 300 µF capacitors the team at Hackerbot Labs “Turn half dollars into quarters! Turn quarters into dimes! Turn dimes into little semi-molten balls of metal!” with their custom built apparatus through a process known as “Magnaforming”.

Passing current through a coil of wire produces a magnetic field. In this case, with so much current, the magnetic field produced is gigantic: the coil becomes a magnificently powerful electromagnet.

The creation of a magnetic field in the coil-now-magnet induces a circling current to flow around the coin sitting inside the coil. This current in the coin also produces a magnetic field (i.e., the coin becomes another electromagnet). The kicker is that the coin’s magnetic field and the coil’s magnetic field point in opposite directions, so the coin and the coil repel each other furiously.

This repulsion creates forces which overcome the strength of the metal; the coil is expanded out and explodes, and the coin is pushed in and shrunk.


Some interesting facts were gathered as a result of the demonstration:

  • Filmed at 100,000 fps, the coin will shrink in just 30-40 microseconds
  • The coin will have shrunk prior to the coil exploding
  • A loud 135 dB shockwave is produced as the coil explodes
  • When shrinking the edge of the coin moves at about 400 mph

High Speed Coin Shrinking
[via Intellectual Ventures]

28 thoughts on “Coin shrinking with high voltage in slow motion

  1. hurf durf says:

    … that this is completely not green and TOTALLY ****ING AWESOME.

  2. Jason says:

    Is 300 microfarads a misprint? Seems a little small.

    1. Coin shrinking with high voltage in slow motion Becky Stern says:

      That’s what it says on their site, I just left a comment with the same question.

      1. Dan Heidel says:

        That’s not a misprint. Remember that while it’s only 300 microfarads, it’s also at 10,000 volts.

        1. says:

          Three 100uF energy storage capacitors on parallel bus, a great find at STI Optronics auction. Makes conductive objects explode like bombs.

          A small camera flash capacitor might pack five joules. But 10 kilovolts gives 1/2*C*V^2 = .5*.0003*1e8 = 15000joules

  3. Colecoman1982 says:

    The finished product looks like it would make awesome buttons for clothing.

  4. Volkemon says:

    A W E S O M E !!!

    And…the button idea is a good one too…

    We were just in the hall during lunch trying to think of any use for this :)

  5. fraser says:

    What a trite, pointless, waste of time and energy.

    1. Mark Frauenfelder says:

      Hi Fraser! Thanks for your comment, which was profound, relevant, and a worthy use of time and energy. With a remarkable talent such as yours, do you ever tire of having to point out all that is unworthy of your praise? I doubt it, because you are Fraser!!!

      Would you mind sending a photo of yourself so I can use it in the What Would Fraser Do fan club I’m working on?

  6. Nathan says:

    FYI: The camera is actually capable of 1 million fps.

  7. Dan says:

    Likes like a good way to turn a quarter into something that looks like it was made in by the Roman Empire.

  8. Keith says:

    That is EPIC!!!

  9. Jordan Bartholme says:

    It’s illegal to deface U.S. currency.

    “United States Code
    TITLE 18
    PART I
    CHAPTER 17
    § 331. Mutilation, diminution, and falsification of coins—-000-.html

    Whoever fraudulently alters, defaces, mutilates, impairs, diminishes,
    falsifies, scales, or lightens any of the coins coined at the mints of
    the United States, or any foreign coins which are by law made current
    or are in actual use or circulation as money within the United States;
    or whoever fraudulently possesses, passes, utters, publishes, or
    sells, or attempts to pass, utter, publish, or sell, or brings into
    the United States, any such coin, knowing the same to be altered,
    defaced, mutilated, impaired, diminished, falsified, scaled, or
    lightened. Shall be fined under this title or imprisoned not more than
    five years, or both.”


  10. Liz Doucette says:

    In shrinking does it elimate the impurities within the coin such as gold and silver ones????

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