Using Pulleys and Weights to Explain Binary Logic Gates

pulley computer

To demonstrate how computers work, [Alex Gorischek] has made a physical example of how binary logic gates work using pulleys and weights.

For anyone who doesn’t know much about logic gates (Wikipedia), it’s a great lesson in one of the fundamentals of circuitry. Using an old chessboard, eyelets, rings, weights, and string, [Alex] has designed a system that can show off all of the logic gates. This includes: NOT, BUFFER, NAND, AND, OR, NOR, XOR, XNOR. He’s also included a gallery of all his examples here.

The neat thing about this demonstration is it is shown in a way that anyone can understand, heck, it’s also something anyone can play with in order to learn! Stick around after the break and see for yourself.

Understand everything about logic gates now? Are you ready for the test? Do you think you’re ready to make some using live crabs?

[via Adafruit]


  1. Hirudinea says:

    Oh wow, that is so cool! This would be a great kit for schools or just kid at home, they could even build their own gates (well maybe not the X gates) to get a good handle on logic gates. Again this is great!

  2. Andrew says:

    I forsee a ‘keyring-and-weight’ 8-bit ALU. Anyone?

  3. denis says:

    Not dissing the idea, but i don’t think i would have found this helpfull, its like an extra layer of learning. the function of the gates is explained in there name. look at the logic tables, look at the name. repeat till you realize why the table = the name. job jobbed. Obviously a good lecturer/tutor will help the whole thing “click” sooner. having to think though an abstracted layer of pulleys and string is convoluted imho. In my last job i spent a vast amount of time training people on technical matters, i found if you didnt present the appropriate explanation right off the bat it only confused matters, and made subsequent explanation on further complexities harder.

    • Sobiguy says:

      I have to agree with “denis “, I congratulate Alex Gorischek on an awesome job at representing logic gates with weights and pulleys. I myself really enjoyed the demonstration, course I already know my logic gates so at least speaking for myself I was more intrigued by the pulley system. So to teach a beginner about logic gates with this I would probably end up having a much longer than needed conversation, having to include pulley and leverage theory on top of it all..

    • HC says:

      Thirding denis. This reeks of someone who knows a lot about a subject trying to come up with a fun way of explaining it to someone who already knows how it works. This is way, way more difficult than the way textbooks explain it. KISS.

    • rasz_pl says:

      you are missing the point and not distinguishing procedure from operation theory

      its one thing to know what cellphone does, its the other to know HOW id does it.

      This not only shows you what any gate does, it shows you how its realized. Its using physical process of moving cables, but the same thing happens inside gates, only with electricity.

      give a man a fish …

      • John says:

        So does drawing resistors, switches and power/ground rails on a piece of paper. No need to learn things like gravity, mass, density, friction and all the other things that go with the pulley logic. It is however very neat, fitting perfectly into that brand of hacking where “why” cannot be answered, cool and useless. :)

    • default_ex says:

      It is a pretty system but logic functions are the fundamentals of logic in general, it’s really not hard to understand as long as you explain it to people clearly without wrapping it in jargon.

      • rasz_pl says:

        another fail

        ok so you know how logic works, yay you. Now I drop you on a Gilligan’s Island, build me a nand gate. Whad did you say? oh you understand the high level concept of logic, the broader picture of things :)))) let the Oompa Loompas take care of the pesky details of actually implementing the technology, right? :/

        I recommend this:

        • sobiguy says:

          Having a good understanding of weights and pulleys in an island scenario, tho beneficial, you would still need a firm gasp on logic gate principals and their uses first to know How to use what you were building… That is to say if you were trying to build a hut on your island with a combination lock using only ropes and coconuts…:) I like the representation idea just saying this method would not be my first choice to teach an absolute beginner…

          I did look up the SciAm article tho..which was behind a sign up wall….
          Here’s a ref. to it along with some cool pix of some other pulley logic systems

        • pff says:

          nand gate is all well and good but why would i need one on an island? to confuse animals long enough to kill and eat them?
          do people really not know what a bike looks like?
          i’m sure you could show someone this before you dropped them on an island and they wouldn’t remember that either.

  4. cr0sh says:

    Back in the April 1988 issue of Scientific American was (presented in that grand tradition which we all love and know from that time of the year) an article in the Computer Recreations column, by A. K. Dewdney – exploring this very subject:

    That of a “rope and pulley” computer invented by an ancient civilization in the jungle of Apraphul…

    Seriously – if you liked the presented demonstration here, you will love the SciAm article…

  5. Dr. Shenanigans says:

    Maybe I’m missing something, but I am kinda stumped as to how the NAND gate of his pulley system works. If each of those rings weigh, m, then there should be a 2m tension on the output ring, and the whole system should be accelerating. Am I missing something obvious, or is it just friction?

    I can kinda see how the rest of the system works due to those nails he has by the input rings, but that NAND gate one irks me.

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