Hackaday Links: July 24, 2011

Plasma speakers

Apparently if you run AC and DC currents through a welding torch flame you can use the resulting plasma as a loudspeaker. [Thanks Cody]

Power metering

The Google Power Meter API is no longer in development but that didn’t stop [Pyrofer] from finishing his metering hardware. It uses a reflectance sensor to read the meter instead of using clamp-based current sensing.

Music videos from inside the instrument

Filming from inside of a guitar creates the camera effect seen above which looks like the waveform you’d see on an oscilloscope. [Thanks Philleb]

Hidden messages in audio files

GhostCoder lets you encrypt and hide audio files within other audio files. The thought is, you can piggyback your own data into Torrents that are circling the interwebs.

2×4 Chair

If you’re skilled with a Skill saw you can make a chair out of one 2 by 4. You can see the pattern you’ll have to cut out from the board in the image above, wow!


  1. haexn says:

    Does anyone know about this ghostcoder software? How does it tamper with torrent files and not mess up the hash check? Wont people using the software just get marked as a bad uploader?

  2. dbear says:

    We did the torch plasma speaker thing back in 1980 in physics lab. Read about it in some magazine and rigged something up to try it. Amazing how these ideas just keep getting dug up.

    The 2×4 chair is cool though.

  3. Mojoe says:

    I believe you encode your Data into the file first then make a torrent out of it.

  4. o says:


    It doesn’t tamper with torrent files, nor does it tamper with existing torrents. You have to make an entirely separate torrent with a file of your own. It’s a neat idea in theory, but it would only work if you were the first person to upload a particular song, and only if it was the highest quality upload. Not very useful in that respect.

  5. loans says:

    It’d be nice if the plans for the 2×4 chair were some kind of legible.

  6. loans says:
  7. Oh hell yeah, that 2×4 chair looks great for $4. I’m always short a few chairs around here. And I bought like half a woodshop on the cheap a couple months ago… Time to put that bandsaw to good use I guess. :3c

    @loans: I’m guessing you didn’t download the PDF, huh?

  8. Mike Szczys says:

    @Bakamoichigel: If you make this, take pictures of the process and send us a link. I’d love to hear how it turns out for you.

  9. Tony says:

    The power meter is awesome.

    Hey, here’s a photo of a PCB! With a PIC! USB too! It measures power usage, honest it does, see the graph!

    I guess the sensor wouldn’t fit in the frame. Great ‘hack’ indeed.

  10. wardy says:

    That guitar string vid is interesting. It looks like something Apple might put in one of their trendy commercials.

  11. t&p says:

    flame is cool
    guitar is cool
    loved the comment about that stupid fat bitch.

  12. Aleks Clark says:

    Trying to be funny I see…. first off, it’s “Skil”, second, it’s a *brand* although most people associate it with a circular saw, which are cheap and ubiquitous. What you actually need is a band saw, a much more costly piece of equipment.

  13. kaoD says:

    The guitar video looks cool, but it’s not a hack and just looks-like what you’d see in an oscilloscope, but it isn’t.

    The effect is due to iPhone’s rolling shutter (http://www.youtube.com/watch?v=LVwmtwZLG88) and has nothing to do with how string actually vibrate.

  14. Pete says:

    I tried the guitar string video myself using my HD2 and did not get the same results. In my video they just looked like blurry vibrating strings.

  15. Willy says:

    Wow, I am impressed with that 2×4 chair!

    I wish I had the tools/space to build a few of those…

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