Love Open Source but Hate People? Get OpenKobold

[Tadas Ustinavičius] writes in to tell us of his latest project, which combines his two great loves of open source and annoying people: OpenKobold. Named after the German mythical spirit that haunts people’s homes, this tiny device is fully open source (hardware and software) and ready to torment your friends and family for up to a year on a CR1220 battery.

The design of the OpenKobold is quite simple, and the open source nature of the project makes this an excellent case study for turning an idea into a fully functional physical object.

Beyond the battery and the buzzer module, the OpenKobold utilizes a PIC12F675, a transistor, and a few passive components. This spartan design allows for a PCB that measures only 25 x 20 mm, making it very easy to hide but fiendishly difficult to try to track down later on.

But the real magic is in the software. The firmware that [Tadas] has written for the PIC not only randomizes how often the buzzer goes off, but how long it will sound for. This makes predicting the OpenKobold with any sort of accuracy very difficult, confounding the poor soul who’s searching their home or office for this maddening little device.

Hackers have a long and storied history of creating elaborate pranks, putting the OpenKobold in very good company. From randomly replaying signals from a remote control to building robotic cardboard burglars, we’ve seen our fair share of elaborate pranks from the community.

47 thoughts on “Love Open Source but Hate People? Get OpenKobold

  1. Could that be made smaller? Deadbug a programmed ATTiny10 with battery and buzzer. Program it to sleep for random x hours, make noise for random x seconds, repeat until discovered and smashed by irate victim(s).

    1. Ah! the dreaded mosquito siulator. This has been in magazines since the 1960′. Using a PIC instead of a NE555, the sound could be modulated to simulate doppler shift from the mosquito flying around and periodically stop, to emulate the mosquito landing on your face.

      1. Oh wow, trying to mimic Doppler shift would be brilliant for something like this.

        Even just messing with the frequency so that each “beep” sounds different, occasionally right at the limit of hearing, would be a great use of the flexibility afforded by the PIC.

      2. Now that is diabolical. If it was done right, it would make the source of the sounds appear to be from different places at different times…no one could ever find it just by listening to it. Excellent!

          1. Not a bad idea…BUT…what if the device only beeped twice quickly, and then did not beep again for 3 hours…then beeps…then 5 hours…etc? You would need a lot more patience to sit there waiting with a tube in your ear than I have, ha ha.

  2. What a nasty and mean project. This person needs treatment.
    If anyone did that to me they would be no longer welcome in my house and I would not want any contact with them.

      1. @evilmadscience I agree with you. And so many people prepared to do this bloody awful idea. I suppose it reflects on society – The meanness – The wish to annoy – The enjoyment when others suffer. This what we have now -Childish and very mean.

    1. I got all the detectors here at about the same time so when one starts beeping the next time I go into town I get a couple cards of batteries and replace the batteries in all of them.

  3. Did that a couple of years back as a wedding prank. They needed two weeks to find it. Was based on NE555, so even without randomization, finding these things takes long. The trick is certainly to use a relatively high pitched sound to mess with directional hearing.

      1. Joke? I am deadly serious. If you think this is a good project then there is no hope for you. Perhaps a visit to an anti-social correction class may point you in the right direction.

          1. I do have both humour and a soul – but I doubt if who perpetrate such a prank have one.
            One thinks this is a harmless prank, but what it actually is an annoying invasion of privacy at the highest level.
            Nothing funny about it all.
            There seems to a lot of people like you in this discussion around which is not exactly speaking out for the quality of those people. A bit sad, really –

    1. Ooh! Make it sound like a smoke alarm with a dying battery!
      After they replaced all the batteries in their smoke alarms, they still hear it.
      (and go about replacing all the batteries again thinking one of the replacement batteries was bad).

  4. As a kid I remember wanting to build something like this which I saw in a magazine. I believe it was the 1989 or maybe 1990 Electronics Handbook, which was just a yearly ‘best of’ publication for Popular Electronics. It was called the Tormentor, it was supposed to be randomized both in time and in exactly what sound it makes. That one didn’t even use a 555, just a couple of transistors and a handful of passives!

    i finally did try to build it, probably 7 or 8 years ago now. I couldn’t get it to work but it may be because I had a hard time finding the original transistor types and attempted substitutions.

    1. I saw that one too – or something just like it in Popular Electronics – Sounded like a water drip – booweep (rising tone). I built it and placed it in the hung ceiling of a classroom at school inhabited by a particularly annoying teacher…
      After a month or so of driving her nuts (kids are MEAN) – it started to annoy us too, so we removed it. It was never found despite the teacher, janitors, and plumbers looking for it.

  5. Why not TWO of them to really mess up direction finding? Hide them in different locations in the room. The first one goes off randomly, slowly decreases in amplitude, the second one detects the first signal then slowly takes over. Yes, it IS “antisocial”, that dreaded universal perjortative adjective of Britain and other humorless member countries of the worldwide socialist utopia.

  6. “Love Open Source but Hate People?”

    TBH, I feel the opposite.

    Specifically copyright shouldn’t extend to instructions and it’s because of other people that you’re reading this.

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