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For Heater: Mechanical Fourier Transform — Parallax Forums

For Heater: Mechanical Fourier Transform

potatoheadpotatohead Posts: 10,261
in General Discussion


This machine is very cool. And it makes for a visual, intuitive understanding of the core FFT.

Comments

  • Heater.Heater. Posts: 21,230
    Thanks Spud,

    I have seen that before. I love that machine would love to see it for real!

    However, it is not doing an FFT. Yes it is an excellent demonstration of how the Fourier transform/Fourier analysis works. It does nothing to enlighten one as to the magic of the FFT algorithm.

    That thing is doing a lot of calculation, in analog, in parallel though. Amazing!
  • potatoheadpotatohead Posts: 10,261
    edited 2015-12-01 17:53
    Did you look at the analysis video? I think it's the third one.

    I'm very seriously tempted to make a CAD model of this thing. Modern CAD can animate and or allow "use" of the thing from the solid model...

  • Heater.Heater. Posts: 21,230
    Yep, I have to watch it again to remind myself what goes on there.

    I don't recall any complex numbers, or divide and conquer algorithm, or bit reversal reordering of inputs. I see no FFT there.

    I do recall a lot of processing going on in parallel, in analog, though.

    For example, that beam with all the springs attached is adding all the forces applied to it, all in one go, in parallel, in analog.

    Or that huge gear train is generating all possible frequency components at the same time, in parallel, in analog.

    Brilliant.

    We could build that with an array of oscillators and op amps!

    Must not think about that, must not think about that....

  • Heater.Heater. Posts: 21,230
    It would be interesting to see what rate a CAD model could produce transforms at?

    Certainly would be a impressive demo.
  • ercoerco Posts: 20,256
    Late to this FFT party, but that machine is freakin' AMAZING.
  • Heater.Heater. Posts: 21,230
    I'm going to revise what I said above a little bit.

    Perhaps we can call this machine a "fast Fourier transform". As in, it probably gets the transform done faster than the other alternative for the time, calculating by hand with pencil and paper!

    Still not an FFT as we know the algorithm today.

    Also, for a CAD model to run that the CAD system would have to have some physics awareness built in. For example knowing about Hook's law and adding up all those forces.


  • MikeDYurMikeDYur Posts: 2,176
    This link in the series of videos gives a detailed explanation of how this fantastic machine operates.

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