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Finite State Machine

February 11, 2010

For this week, we each built a finite state machine: “a model of behavior composed of a finite number of states, transitions between those states, and actions” (from Wikipedia, including the following finite state diagram of a door):

I was interested in building a machine that had one input and one output, and during the output produced a secondary perceptual effect, such as an optical illusion.  I decided to work with a “found concept” at the outset, and then work on its development: I began with a zoetrope.  The input is the introduction of a force, and the output is a spinning cylinder.  The secondary effect is the persistence of vision.

I had initially wanted to introduce the force manually, by essentially treating it like a top, and pulling a string, but I ran into a couple of problems with the physical world.  The bearings I had used were for a lazy susan, and they had too much friction.  I toyed with the idea of adding mass at the perimeter so that it had more momentum once it got going, but quickly discarded the idea because the point is to be able to get up close to the zoetrope.  Hard to do if spokes are flying by in your face.  This might work if it were larger.

I suppose I could have come up with a simple hand crank, but at this juncture I knew I needed lightness and consistent speed, so I went with LEGO to prototype a mechanism:

I stuck with this design for attaching to the LEGO and balancing the wheel, but you can see below that I had to widen up the support with more points of contact.  It was too unstable otherwise, and tended to fly off its axle.

And here’s the final zoetrope, fully functional:

Greg Borenstein suggested I light the interior, and that many Victorian zoetropes had this feature.  Here’s a quick mock-up lit and close up:

Other suggestions made by the class:

• Hide the mechanism, or only reveal it selectively.  Perhaps it could be inside a polarized glass box, and only be transparent when it is active or inactive.  Active might compete with the animation, though.  Another idea is a glass bottom to the cylinder, so you see down into the mechanism as it is operating.

• Build the entire device out of LEGO.

• Make the mechanism itself into an animated circus.

I also would like to pursue the nature of the animation itself, perhaps introducing perspective or anamorphosis into it.

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