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Home-Built Turing Machine
stronghawk writes "The creator of the Nickel-O-Matic is back at it and has now built a Turing Machine from a Parallax Propeller chip-based controller, motors, a dry-erase marker and a non-infinite supply of shiny 35mm leader film. From his FAQ: 'While thinking about Turing machines I found that no one had ever actually built one, at least not one that looked like Turing's original concept (if someone does know of one, please let me know). There have been a few other physical Turing machines like the Logo of Doom, but none were immediately recognizable as Turing machines. As I am always looking for a new challenge, I set out to build what you see here.'"
Hot Tub Turing Machine!
I don't think it has been done before though. At least not as a hardware implementation. The reason being that while it's an interesting hypohetical machine, it's extremely inefficient means of computing anything. But it is very nice to actually see a visualisation of such a machine
For social reasons I will refrain from mentioning this to my friends (which I have) later tonight. Baaaah, I want one! This is so pointless but nifty, my inner collector is crying out. Damn fiscal responsibilities in life tell me it's a waste of money, but oh, the geeky child inside cries out!
"Sorrow is better than laughter, for by sadness of face the heart is made glad." [Ecclesiastes 7:3]
Purely technically, a Turing Machine that hasn't infinite tapes is simply a Finite State Machine. You cannot build a "real" Turing Machine. Doesn't make his creation less interesting though :-)
For the ultimate in coffee table extravagance, you need this turing machine running an implementation of Conway's game of life, ideally using a chessboard as the display device for that: full cells would rise slightly above the board, moving back down when declared empty.
To provide randomized starting positions for your game of life simulations, without sinning against Von Neumann, a vintage mahogany-clad Geiger-Müller counter would of course be included...
And you'd be wrong.... Computers are Finite State Machines with an insane number of states.
RTFA. I know that's a sin, but seriously, do. You'll discover you are wrong.
The microcontroller loads the program as written in ascii on an SD card. It also can write the initial data onto the tape. After that, the computation is, indeed, performed by the "machine". Hence the optical reader for the characters on the tape.
A Turing machine is supposed to represent what an infinitely patient mathematician with no insight can achieve when he has an infinite amount of paper and pencils. Obviously, the infinity here poses some problems, but you can build a finite Turing machine by finding a mathematician that has no insights,giving him tranquilizers to make him more patient, and locking him into your basement with some food and papers and pencils.
The hardware is very elegant and well-done. The guy is a multi-talented geek of the highest order.
"Eve of Destruction", it's not just for old hippies anymore...
Now, let's look at how this works. It reads a symbol from the tape using the camera. Then it checks its internal state, and sees what it should do with that symbol (should it change the symbol, change the state, and/or how should it move). Then it does that action and moves on to the next symbol as instructed by the last "rule". Considering that the only thing that the machine keeps track of from position to position is the state, it is indeed a Turing machine. The microprocessor's job (as he states) is to act as the read/write head for the machine. Turing never described HOW the head worked, just WHAT it did. And this head performs EXACTLY what Turing described. And that's why this is a Turing machine. If you wrote a program on your computer that did this, it too would be a Turing machine. The delineation is in how it handles and stores states, not the method in which it "processes" data... And Turing's original work described a Turing machine as using a person to perform the actions (but strictly following the ruleset). So I fail to see how this could possibly NOT be a Turing machine...
If a man isn't willing to take some risk for his opinions, either his opinions are no good or he's no good
Well, if you're going to make a Turing machine run something equivalent to Conway's Game of Life, forget the random: have the simulation be A Turing Machine in Conway's Game of Life.
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Im impressed: For an infinite tape, the reels look very compact.