After Hours

Lego Turing Machine: The building blocks of computing in play

By // June 22, 2012, 1:38 AM PST // nickjheath

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  • The Turing Machine is a theoretical model of how computation takes place. It dates from 1936 and inspired the pioneers who created the modern digital computer. The machine was described in a paper, On Computable Numbers, written by British mathematician Alan Turing.

    Researchers at the Centrum Wiskunde & Informatica (CWI) or Centre for Mathematics and Computer Science in Amsterdam in the Netherlands decided to demonstrate the principles of the machine's operation by building a Turing Machine using a Lego Mindstorms NXT set.

    The machine is part of the Turings Erfenis exhibition at the centre, which is running until October to mark the centenary of Turing's birth.

    Photo: Centrum Wiskunde & Informatica

  • The Lego machine is based on the theoretical device set out by Turing in his paper.

    Turing described the hypothetical machine as being able to move backwards or forwards over a strip of infinite tape, which is divided into cells. The machine could read, write or erase symbols inside each cell.

    The machine would be controlled by a series of rules that tell it whether to move the tape, how to manipulate a cell's contents and which rule to jump to next.

    In the Lego Turing Machine each cell on the building-block tape, seen above, is made of a black switch, which can be switched on to represent a symbol or turned off to represent a blank cell.

    Photo: Centrum Wiskunde & Informatica

  • As the Lego machine moves along the tape, it checks the contents of each cell using a light sensor. The sensor detects the light reflected from each cell to check whether it contains a black switch, representing a symbol, or a white Lego block, representing a blank cell. The Lego tape is made up of 32 cells.

    Photo: Centrum Wiskunde & Informatica

  • A rotating beam with two orange arms mounted above the Lego tape can flip the black switches in both directions - either inscribing a symbol on the tape or erasing it.

    Photo: Centrum Wiskunde & Informatica

  • The machine reads from the Lego tape.

    Photo: Centrum Wiskunde & Informatica

  • Here you can see the machine representing the computation of 2 + 2.

    Photo: Centrum Wiskunde & Informatica

  • And here the machine is representing the result of the 2+2, which is of course 4.

    Photo: Centrum Wiskunde & Informatica

  • The movement of the Lego tape and the operation of scanner are controlled by a series of corkscrews and rotors.

    Photo: Centrum Wiskunde & Informatica

  • A side view of the machine.

    Photo: Centrum Wiskunde & Informatica

  • Another close-up of the machine.

    Photo: Centrum Wiskunde & Informatica

The Turing Machine is a theoretical model of how computation takes place. It dates from 1936 and inspired the pioneers who created the modern digital computer. The machine was described in a paper, On Computable Numbers, written by British mathematician Alan Turing.

Researchers at the Centrum Wiskunde & Informatica (CWI) or Centre for Mathematics and Computer Science in Amsterdam in the Netherlands decided to demonstrate the principles of the machine's operation by building a Turing Machine using a Lego Mindstorms NXT set.

The machine is part of the Turings Erfenis exhibition at the centre, which is running until October to mark the centenary of Turing's birth.

Photo: Centrum Wiskunde & Informatica

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By Nick Heath

Nick Heath is chief reporter for TechRepublic. He writes about the technology that IT decision makers need to know about, and the latest happenings in the European tech scene.