A Singing Arc Lighter

We’ve all been guilty of buying things we want, but don’t need. And that’s how [PodeCoet] found himself in possession of a couple of double-arc electric lighters, thanks to those far-eastern websites purveying cheap goods. ‘Tis the season of giving after all, justified [PodeCoet]. Being a hacker, the obvious thing to do was to make them belt out tinny tunes. If you’re still holding on to your gas lighters, don’t — because these electric ones are ‘oh so hackable’. Dual-arcs are the same, but twice the fun.

[PodeCoet] starts off with a tear down of the lighter, to figure out the schematic and understand how it works. There’s a charger IC for the LiPo, an unidentifiable micro-controller, a pair of FET’s driving a pair of power transistors, which in turn drive the HF output transformer at around 15.6kHz. He guesses that the “original micro-controller is probably an OTP part like a 12C508” but in the absence of a chipID he couldn’t be sure.

Instead of trying to break his head over it, he just swapped in a pin-compatible PIC12F1840. All that’s left to do is to write some quick-n-dirty code and sprinkle it with funny comments in order to modulate the output signal at audio frequencies. His first choice of tune was “We are Number One” by Lazy Town, the Icelandic educational musical comedy children’s television series (phew). But redditors are awesome, and someone asked him to add the “Imperial March” and [PodeCoet] obliged.

Since he was going to gift these lighters, the sneaky hacker added a prank in the code. Every time the button is pressed for more than two seconds, it works as normally expected and a counter is incremented. On the 20th count, and for one time only, the tune is played. No amount of pressing the button will play the tune again, confounding the user to wonder if he was hallucinating. This also helps ensure the lighter does not self-destruct prematurely, since the output transformer is likely designed for low duty cycles. His blog post contains all of the information needed to do this hack along with handy tips to avoid the problems he faced. A “Happy Birthday” tune would be great when lighting some birthday candles, we think.

[PodeCoet] has a fancy for high voltage stuff – check out “Home built Stun Baton turns you into a cop from Demolition Man“. This man surely loves his pranks, as evidenced by “Hacking your Co-Workers Label Makers“. And the farce is strong in this one — “Student trolls anti-Arduino Prof with parasite MCU“.

Thanks to [ryg] for tipping us about the reddit thread.

51 thoughts on “A Singing Arc Lighter

    1. Hell yeah ;)

      I love these. While I totally respect the hacks that solve problems in creative ways, ones like this – taking a Thing, and making it more awesome solely for the purpose of making it more awesome? That’s golden.

      And this does take a pretty cool Thing, and make it a damned awesome Thing.

  1. Good reuse of an electric lighter (and a funny prank idea at least).
    Could cram allsorts of extra functionality into one of these as a bit of a Mr Bond gadget.

    Though, here in England due to the laws on these devices being grey enough as it is… One cop catches someone would see it as a taser where as another cop wouldn’t (and rightfully see it as a lighter).

      1. Having an arc doesn’t make something a taser.

        If you crammed your finger in there, it’d hurt and probably burn you severely, but it wouldn’t put you down like a taser would.

        1. True… Cops here, though…. Thinking is a weapon of mass destruction in their eyes it seems or “looking black” (Yep, that still happens as of late 2014, oh and I’m a genetically diverse form of “white”, can explain either or both how I was pulled over for being black or what I meant by genetically diverse if you want).

          1. Yep the looking black, It was cold and I was going through an estate that is supposedly rough (quiet ghost-town like IMHO).
            Had a flat tyre and the day was cold so I had my hooded jumper on with the hood covering the face to keep the icey wind out.
            A policy enforcement officer pulled me aside as I was about to cross a road.
            Before anything, he said he pulled me over because he, “was looking for a black guy on a pushbike in a high crime area.”

            I opened the drawstrings and lifted over my hood and said, “I’m clearly the wrong guy then.” and I started to walk off.
            Before he could accuse me of resisting arrest I quickly mentioned, “We’re all internet connected, microphones and all, you have no valid arrest!”

            See below about the mixed-geno bit

          2. About the mixed-geno (aka almost mixed race, however you look at it)

            My father’s great grandfathers grandmother was a prostitute back then and it is her where we get our family name from. Not sure about her background much, however along the lines down from there has been a mix with some Indian blood, further from the father’s mother side there were some stem off from some royalty stemming several generations and some Mediterranean blood mixed into the family.

            From my mother’s side since I know my mother’s mother (I just don’t know much about my mother). Pictures of my mother next to my father, She made Casper look dark. The said grandmother has Nomad-Celtic era roots and my mother’s father is a Roman-Saxon mix through tracing back his name and by facial features and other body shape giveaways. Alot of this is speculation anyway since I wasn’t around back then to fully confirm (obviously), Though this is the best I can work out so far.

            Some Roman era blood would of likely been Mediterranean/middle eastern and other possible mixes (though this is now purely guesses).

            During winter my skin goes lighter and my hands essentially turn to sandpaper. Enough sun during summer and I have (twice AFAIK) became darker skinned than a descendant of the Gujarat state of India (an ex colleague at work). And I now have a rough idea where that came from (amongst other things like a family long tradition of mild OCD, quick learning, ect…)

            (proof read my post several times, mistakes and inaccuracies may still be present, take with a pinch of salt!)

      2. There are laws and regulation that should cover this grey area (AFAIK), but even the coppers (usually pretend not to..) don’t always know.
        Something like this may get an on the spot caution+confiscation or get as far as a court room… and thrown out as soon as the device is shown to the judge with the device returned thereafter.

        It takes one random stop-search (usually falsely made under some anti-terror act, I have a small history of being stop-searched… less so these days as I made a fool enough out of them. LOL).

        IMHO, not worth the hassle.

        Oh and over here tasers were (still are?) classed as a fire-arm, standard run of the mill policy enforcement officer are not allowed fire-arms AFAIK… however: This link says otherwise [Official MET-POL]

        Corrections/confirmations/etc are welcome…

    1. TLDR:
      Current limit or square wave rounder.
      .
      .
      .
      .
      Further info….
      Some kind of current limiting bodge.
      I say bodge because the thing sets a current for a given voltage, but the battery voltage will vary quite a bit (relatively).

      Or on second thoughts it could be to round off the squareness of the wave form.

      R7 and R8 set their transistors’ base current thus limiting the current through the transistor. However they are before the FETs and thus would seem to respond by how much on-resistance the FETs have.
      The FETs are driven by PWM thus full-on full-off and thus seems not to allow the MJD3055s from smoothing the square edges.

      That’s my guess. Someone with more a clue may better answer your question.

    2. To protect the driver chip from the back EMF of the transformer. This can be done other ways but the other ways dampen the oscillation of the transformer and this way allows the transformer to ‘ring’ or oscillate longer.

    3. This looks like a “Cascode” Amplifier stage, In this case MOSFET + BJT. The common-base section amplifies the voltage, but not the current (all current flows through both transistors. The MOSFET has only a 20V rating, the MJD3055 has 70V VCB, it’s low current gain does not matter in this case and it has good high frequency properties. Perhaps there were no cheap 70V MOSFETs with sufficiently low On-resistance or gate capacity so the designer went for a two stage amplifier approach. Of course in a flyback the peak voltage can be much higher than the battery voltage and you want this to strike the arc.

    1. I imagine through heating it. It doesn’t take much energy to make audible sound, so even a few thousand micro-heats per second should move the air around a bit.

      The tones are produced by turning the spark on and off at audio frequencies.

    1. He should try to fit a polyphonic/chiptune-esque (beep-beep-boop-boop) remake/remix of (or most of) H0ffman’s – Pattern Skank tune.
      at least however much could fit into 1KB (compressed if needed).

      That would place it high up in the 1KB challenge.

      1. forgot to mention:
        The two arcs are independently driven by two seperate “GPIO” according to the schematics, so one output could do bassline-voices and the other the faster moving beat/melodies.

    1. are you me??? I asked this via email, reply is below

      “Absolutely agree that it would have been better with a continuous arc, but (at least this time) it was a /deliberately/ shit implementation:

      First up, there are other super-cheesy lighters out there with LED illumination and piezo buzzers, you know, the type they sell at the dollar shops (or $2.80, if you’re Daiso). My first implementation /was/ actually continuous arc… But when I demonstrated it to my dad (because nothing means anything without dad’s approval, even when you’re 33 and live away from home, and the approval never usually comes), he immediately thought that I just stuck a piezo speaker in there, as there are no visual cues to show that the arc is emitting the sound

      Second, my other lighter completely died on me with a shorted secondary. This was prior to modification, I was just using it to set fire to everything that I possibly could; completely transfixed by the arc. It turns out that they’re meant to be used briefly for no more than a few seconds at a time otherwise damage can occur. I figured as much, since they’re obviously pushing the components beyond their intended limits. The thing draws four bloody amps!

      So, there’s all that. Either your friends and family think you’re full of shit, or your lighter implodes (or both, that’d suck)”

  2. I can imagine the reciever telleng all the friends “I promice, once it played the imperial march” and all the friends going “sure, show me then…”

    Evil prank this is -Yoda

    1. Yes. There are two arc driver stages and two separate GPIO pins used and that is enough to get to two-frequency poly-phonics. You could also use software to get more channels (mixed). Even XORing two frequencies for each hardware channel could result in four channel poly-phonics.

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