Followup: Troll Physics Solved

A month ago, we saw a marvelous demonstration of troll physics from YouTube user [Fredzislaw100]. In his video, we saw a circuit of three switches and three LEDs wired in series and but not acting like the should. A lot of the comments for this post elicited reasonable explanations like modifying the battery or pure camera wizardry via After Effects. Thankfully, [Alan] stepped in and showed us how it was done. The solution uses two AC power sources with diodes in two of the switches and LEDs and inductors in the third pair. [Alan]’s build was rather large compared to the original video, so we were wondering how this circuit could be made invisible.

[Fredzislaw100] just posted a video on how he did it. Like [Alan]’s build, it uses two AC power sources, diodes, and inductors. In contrast to every single guess about where the circuit is hidden, the majority of the build is inside the battery connector. [Fredzislaw] did some amazing work hiding a 74LV132 quad NAND Schmitt trigger inside the battery connector. The diodes were easily hidden on LEDs 1 and 3 with some red nail polish, but we’re amazed by the inductor built into the LED seen in the title pic.

So there you go. With a ton of electronics know-how and an extremely steady hand (and a microscope), you too can build your own troll circuit. Check out the video after the break.


48 thoughts on “Followup: Troll Physics Solved

  1. Big smile on my face, the man is a soldering ninja.

    I think that deserves nothing less than a 15 minute mega geek standing ovation.


    (and I think I claim I was “close but no cigar”)

  2. Impressive fab skills no doubt. But more importantly, how much time must he have spent perfecting that??!? I bet he must have felt a right chump at the make up counter colour matching nail varnish to a bunch of LEDs.

    Also, why low voltage TTL and a zener shunt regulator for the oscillator and not just a 556? Or a quad op-amp even?

  3. I need to build this and use it for training technicians at work! lol. That would be great.
    Great build. I thought video editing at first, but was amazed at how well the led tracking was. so this makes more sense.

  4. Epic!

    i was very scared for his fingers at the start…

    looking at my junk i have 9v bat adapter that is flexible (kind of like a bag around the tabs…you know what i mean) would have been Way easier to cut open…

    but way it was done just makes it that much more Epic

    Truly an inspiration!

  5. I’ll be honest, I was quick to blame video trickery and couldn’t fathom how three LEDs could be controlled that way.

    I’ll eat my humble pie and bow before this master. ;) Major kudos!

    1. Some of us have actually been raised close enough to special effects that we can spot Hollywood-grade ones a mile away, let alone the sort of thing an electrical engineer could make and upload to YouTube.

      Real special effects don’t look like mismatched reflections and light bleed-through. Mismatched reflections and light bleed-through are a sign that your eyes are playing tricks on you and you’re seeing things that aren’t there.

  6. now that is smd-fu


    ps: the ONLY time i do ANY smd is when it needs to fit into a small space(hack) and NOT because its fasionable to make small boards! and it is ALWAYS dead-bug. i have given up on smd and if u want to sell smd parts i will not buy em by themselves, and i certainly wont pay twice as much so someone can make a 1-part board lolz i’d rather not bother. i mean im paying you more to develop a smaller part so it takes more of my time and effort cough: burnt out parts.

    why dont i do board etching? its not hacky enough for me and to me is boring, i’d rather have something that proves i made it with my own hands, not someone else’s robot’szs hands. cough: board-house

    1. A valid assumption given a 9V battery has 6 1.5V cells similar in size to AAAA cells inside. Removing three and running the circuit from 4.5V would give you heaps of room to work with.

    1. There are two different AC frequencies generated inside the battery connector. The first switch has parts to filter out one half cycle of one of the frequencies, the next has components that filter all of the second frequency, and the last has components that filter out the other half cycle of the same frequency as the first switch.

      When the switches are closed the filters are shorted and the corresponding frequency components pass through.

      The LEDs are wired in the opposite way. They are set up so that they short any frequencies which are not of interest around them to make sure they don’t light up, while still passing the frequency of interest through the LED itself.

      All of this takes advantage of basic analogue filtering via L and C circuits, as well as the properties of diodes only passing current one way.

  7. Interesting idea, winding an inductor round a sanded down LED.

    Wonder if this idea could be used to make an LED that lights off 1.5V by using the JFET from an electret microphone as a low frequency blocking oscillator, with iron wire or tape wound just under the inductor to increase the inductance?
    This would also work with iron powder and cycle tyre repair cement painted over and under the windings.

  8. Interesting hack *2, using a series JFET from electret microphone with gate connected to source as a constant current of around 25-30mA.
    Works well, allows a cheap LED to work from a PP3 without a resistor.

  9. Soldering like that is impossible, and if you look closely, the shadows on the parts, and reflections off his scalpel are all wrong. Still, nice use of video editing. :)

    Seriously though, i find both Alan and Fredzislaw100 to be inspirational. This is amazing work. And Fredzislaw100 demonstrates quite an array of talents here. This is true hackmanship.

  10. That is some precision work. Modelmakers and forgers around the world are probably jealous of his skill.

    This isn’t just a hack. This has graduated to a work of art. Part performance art, part forgery, part electronic wizardry, etc., but art through and through.

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