Simplest Most Useless Machine


[Brett] posted about his most useless machine build. His project gives us a chance to massacre the language in the title because it uses the lowest parts count we’ve see with these machines. The logic is controlled by our friend, the 555 timer. Add to that just one servo motor, two switches, three resistors, two caps, a diode, and a battery pack and you’re in business. The hardest part to find locally is the servo but check at a hobby/RC store. If you don’t have to put in a parts order this can be your next impulse project.

42 thoughts on “Simplest Most Useless Machine

  1. @pwd

    “The only design I could find uses a microcontroller but I consider this to be overkill (not knowing how to write code for micros may have had some influence on my humble opinion…).

    Additionally, the microcontroller version really doesn’t shut itself off. It’s circuit remains powered even when the switch is in the off position.

    Knowing a little bit about servos and basic electronics, I felt sure that I could build the machine using a simple analog circuit. My main goal however was to have the machine REALLY turn itself off.

    The machine in THIS instructable accomplishes that!” –

    So there is a difference….just…not much of one.

    This is neat though, I’ve been thinking of building one to sit on my desk but it would distract me from work quite a lot.


  2. I’m pretty sure I can come up with a simpler one, no servos, no 555. Using this, very simple circuit:

    The arm holds the push-to-break switch on the left at the bottom of its journey. When the switch at the top is changed, the arm rotates, releasing the push to break, hits the switch which changes the direction of the motor, until the arm rests on the ptb switch again, turning it off.

    I can’t be bothered to build this though so if anyone else does, let me know.

  3. clicking on that link gave me malware, I had to restore my system. Chromium has the page flagged as containing elements from the website “”

    Please remove the link, its dangerous.

  4. No not yours (sorry about my clarity), the instructibles page link brought up a chrome warning, I passed it and got a nasty spot of malware. Seems that instructibles has a malware advertiser or something that randomly appears…

    …offending website is “”

  5. idk guys, lowest parts count? i could make one with just wire(7 pieces, we’ll count it as 1), 1 DPDT toggle switch, 1 DC motor (plus gearbox) , 1 battery, and 1 normally closed pushbutton switch. LOOK MA, NO SEMICONDUCTORS!!

  6. Waste of space. I mean seriously ou guys, how many of these retarded boxes do we need to see? We get it, it’s useless and easy to build.

    Just leave the space blank next time instead of posting the same crap over and over and over and over and over… suprised it isn’t built of Legos and using an Arduino somehow. sigh

    Has the hacking community really gone this half-baked, or do I just need to find another board to frequent? Jeez guys let’s pull it together, you’re not doing much to continue your predecessors legacy.

  7. I was thinking about a different sentence every time.
    “Hands off”
    “Don’t do that”
    And if you push the switch a couple of times in a row:
    “what do you think you’re doing”
    And then the lid would lock itself for a while

    So useless, so much fun :-)

  8. @bencoder – looks right, there’s absolutely no need for any semiconductors here.
    Although the idea of the 555 timer chip is good for learning electronics in general, I think its important to keep some perspective on when to employ mechanics to reduce circuit complexity, and your schematic is a great example.
    One point of note, am I right in saying that one of your batteries should be wired in reverse to make the dc motor move backwards? I’m not sure your schematic makes that clear.
    Gearboxes though are a pain to source if you want a new one, its best to rip up an old RC toy but then you usually end up with a gearbox of arbitrary ratio.
    Its so difficult to source the perfect gearbox without making your own gears and shafts on both a CNC mill and lathe, or something. And if you do find one, its for industry, and costs a small fortune.
    And therein lies some advantages of a servo and microcontroller because you can control the speeds yourself!
    Great little project, the wooden box helps a lot because if you hadn’t seen one before, like I hadn’t, its all that more amusing! :-)
    I’m seriously thinking of adding that one to my list of stuff to make, but it would get very boring very quickly unfortunately.

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