This Useless Machine Now Plays with Fire

The Useless Machine, Candle Edition

Useless machines are a lot of fun, if not just a little overdone. Looking for a new twist, [bd594] decided to try making one that integrates a candle — it works quite well!

While not quite as impressive as some of [bd594's] previous projects, like his rendition of Bohemian Rhapsody on old school computer equipment, we like how he used regular DC motors in this design, instead of servos (the easy way).

A PICAXE14M2 microcontroller controls the H-Bridge responsible for the geared DC motors (taken from a Mac floppy drive), and a light sensor checks for the flame. He’s also made use of some NPN transistors to invert some logic levels to show you if you’re running low on I/O pins, its always possible to incorporate some other discrete components like a transistor to achieve your design.

Among others, some great alternative spins on the “useless machine” include the moody useless machine, an even more useless machine (featuring 8 switches!), a pull-string version, and even a rather ridiculous elevator button pressing useless machine!

Stick around to see this one put out the candle (Caution: Very exciting).

Comments

  1. Matt says:

    Nice! Though, a suggestion for an upgrade: cut out a portion of the bottom of the candle holder and put a more sensitive light sensor facing up, though the semi-transparent wax, so one can’t tell how the candle light is being sensed.

  2. Mike Szczys says:

    I love it… now make it powered by a Peltier device.

  3. JoeGTN1 says:

    Now someone only needs to add a Stirling Engine or a peltier so it’s self powered. Maybe even one that re-lights itself so the only input is paraffin.

  4. henry says:

    Cool. Perhaps further versions will be adjusted so the flame is smothered out, rather than pushed into the wax

    • Andrew says:

      Aha! Very “meta”. You have made the leap from “useless machine” to “useless comment”. Either that or you have not actually watched the video. The candle is snuffed out. The wick is not pushed into the wax.

  5. Joey Sheldon says:

    Next, I’d like to see a version using a CO2 cartridge blowing it out.

    Cool twist on the useless machine, though!

  6. Dax says:

    I’m just thinking how this does not need a microcontroller at all.

    An ambient light comparator can be made with two LDRs in a Wheatstone bridge that turns out a voltage differential when one gets more light than the other. A small capacitor provides for delay. This voltage differential can be used to run a simple four transistor H-bridge where both legs have a microswitch that cuts the current at the extremes of movement.

    When one LDR gets more light, a voltage differential appears in the bridge, which triggers a comparator, which changes the logic level controlling the H-bridge direction at a delay provided by the capacitor, which moves the motor forward until it hits the limit switch, stays there until the capacitor delay, then winds back and hits the other limit switch and stops until there’s enough difference in light at the LDR for long enough to trigger the circuit again.

    • Jumping Jeremy says:

      A small micro is infinitely more flexible than a straight hardware solution. Just saying.

      • Dax says:

        So when are you going to upgrade your useless machine with new functionality?

      • Arduino Noob says:

        a desktop pc is infinitely more flexible than a small micro, get to work!

      • justice099 says:

        What is the real justification for NOT using a micro? You keep hearing this kind of comment, but I don’t get it. Yeah, there was a time not very long ago where a microcontroller system was more expensive and more complex. But now, this just doesn’t even make sense. Just do it the ‘hard way’ for the hell of it? Does it make one feel smarter? Do you think people that use micros DON’T know how to do it the hard way just because they used a micro?

        It is cheaper and more simple, and perhaps even far more reliable to use a micro to replace a ton of components with just 1.

        I am not busting your chops. I am genuinely curious. Why?

        • Dax says:

          Engineering challenge and better understanding of electronics, rather than just throwing some chip and software at the problem.

        • Dax says:

          ” Do you think people that use micros DON’T know how to do it the hard way just because they used a micro?”

          Yes. Mostly.

          Probably about 80% of the people who do these kinds of hobby projects don’t really have a working knowledge of analog/discrete electronics because they’ve never had to try and engineer something out of discrete parts. Even more people just throw an arduino at it, and hold it “advanced stuff” to use just the IC on its own because they couldn’t wire the board for their life.

          And if the thing ever breaks, it’s easier to find a replacement BCxxx transistor than a microcontroller and a programmer and compatible software and reverse engineer the original. You know flash memory has finite data retention time and may corrupt over time, right?

          • Dax says:

            Although fundamentally your question is like asking “Why paint when you can just apply a paintbrush filter in photoshop and print it?”

          • justice099 says:

            Really? No. I didn’t know that! Only you do, because you’re special. ;)

            Us engineers use the KISS principle, well, because apparently we’re stupid.

  7. tekkieneet says:

    Would be far more entertaining if the box lights the candle instead of snuffing it out and put the box near flammable materials.

  8. BB Gun says:

    +1 to [justice099] and [tekkieneet]

    Props to [bd594], though. This is awesome. These useless machines always seem to have a personality, and this one somehow kicks it up a notch. Loved it.

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