Tricking an Ancient Protocol To Play Tunes

A lot of technological milestones were reached in 2007. The first iPhone, for example, was released that January, and New Horizons passed Jupiter later on that year. But even with all of these amazing achievements, Volvo still wasn’t putting auxiliary inputs on the stereo systems in their cars. They did have antiquated ports in their head units though, and [Kalle] went about engineering this connector to accommodate an auxiliary input.

The connector in question is an 8-pin DIN in the back, which in the days of yore (almost eight years ago) would have been used for a CD changer. Since CDs are old news now, [Kalle] made use of this feature for the hack. The first hurdle was that the CD changer isn’t selectable from the menu unless the head unit confirms that there’s something there. [Kalle] used an Arduino Nano to fool the head unit by simulating the protocol that the CD changer would have used. From there, the left and right audio pins on the same connector were used to connect the auxiliary cable.

If you have a nearly-antique Volvo like [Kalle] that doesn’t have an aux input and you want to try something like this, the source code for the Arduino is available on the project page. Of course, if you don’t have a Volvo, there are many other ways to go about hacking an auxiliary input into various other devices, like an 80s boombox or the ribbon cable on a regular CD player. Things don’t always go smoothly, though, so there are a few nonstandard options as well.

Random Parcel Launches Steganographic Compulsion

A mysterious CD arrives in the mail with a weird handwritten code on it. What should you do? Put it in the computer and play the thing, of course!

Some might be screaming at their screens right now… this is how modern horror films start and before you know it the undead are lurking behind you waiting to strike. Seasonal thrills aside, this is turning into an involved community effort to solve the puzzle. [Johny] published the video and posted a thread on reddit.

We ran a similar augmented reality game to launch the 2014 Hackaday Prize solved by a dedicated group of hackers. It’s really hard to design puzzles that won’t be immediately solved but can eventually be solved with technology and a few mental leaps. When we come across one of these extremely clever puzzles, we take note.

This has all the hallmarks of a good time. The audio spectrogram shows hidden data embedded in the file — a technique known as steganography. There are some real contortions to make meaning from this. When you’re looking for a solution any little hit of a pattern feels like you’ve found something. But searching for the decrypted string yields a YouTube video with the same name; we wonder if they’ve tried to recover steganographic data from that source?

[Johny] mentions that this parcel was unsolicited and that people have suggested it’s a threat or something non-sensical in its entirety. We’re hoping it’s a publicity stunt and we’re all disappointed in the end, because solving the thing is the best part and publicity wouldn’t work if there was no solution.

The bright minds of the Hackaday community should be the ones who actually solve this. So get to work and let us know what you figure out!

CD Execution Chamber Sends old Discs off with a Bang

Welded steel safety cage? Check! Polycarbonate blast shield? Check! Vacuum cleaner motor wired to an inviting red button? Double check! Stack of CDs to dispose of as destructively as possible? [Firas Sirriyeh] has got you covered with his CD Terminator 1.0.

While [Firas’s] build log is a little short on descriptive text, there’s really no need for it. His pictures tell the tale. The combination media shredder and interactive performance art piece is a stoutly constructed affair, which you’d want anything capable of flinging razor-sharp plastic and Mylar shrapnel to be. [Firas] has displayed his CD execution chamber at the Jerusalem Mini Maker Fair 2015 (in Hebrew; English link) and the Musara Mix Festival where the must-see video after the break was shot (mildly NSFW language). Some CDs give up the ghost very quickly, but one held out for a remarkable long time before finally exploding; you can see it flexing and warping in a way that almost appears to be slow-motion.

For those who’d rather not fuss with all that bothersome safety, there’s always this automatic CD launcher to play with.

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Fully-Automatic CD Launcher Looks Dangerously Fun

When [JZSlenker] was challenged to find a creative way to destroy a bunch of compact discs that were burned incorrectly, he did not disappoint. He came up with a rather simple but fun contraption that launches the CD’s at high speeds and with a fast rate of fire. He doesn’t share many details about how this machine was built, but the 18 second video makes it pretty obvious how it works.

The CD gun is built mainly from a piece of plywood. This provides a flat base with which to mount the other components. A stack of compact discs is held in place by what appears to be a metal cage that was welded together. An inexpensive angle grinder is used as the propulsion mechanism. The grinding wheel is mounted just in front of the stack of CD’s in a vertical orientation. The wheel must be placed just high enough above the plywood base for a CD to fit in between the wheel and the base. This design is remarkably similar to the Sticker Gun which our own [Brian Benchoff] is building.

Some type of linear actuator is used as the firing mechanism. The actuator is hooked up to a thin piece of metal, cut into an L shape. It almost looks like a reaper tool. When a button is pressed, the actuator fires instantly. This pushes the metal hammer into the CD on the bottom of the stack. The CD is pressed forward into the grinder wheel which then shoots the CD into the air. Based on the below video, it looks like [JZSlenker] is able to fire at a rate of about three CD’s per second with this rig.

This has got to be a super-villain weapon for an upcoming movie, right? Maybe AOL-man?

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Measure Laser Wavelength with a CD and a Tape Measure

Obviously the wavelength of a laser can’t be measured with a scale as large as that of a carpenter’s tape measure. At least not directly and that’s where a Compact Disc comes in. [Styropyro] uses a CD as a diffraction grating which results in an optical pattern large enough to measure.

A diffraction grating splits a beam of light up into multiple beams whose position is determined by both the wavelength of the light and the properties of the grating. Since we don’t know the properties of the grating (the CD) to start, [Styropyro] uses a green laser as reference. This works for a couple of reasons; the green laser’s properties don’t change with heat and it’s wavelength is already known.

It’s all about the triangles. Well, really it’s all about the math and the math is all about the triangles. For those that don’t rock out on special characters [Styropyro] does a great job of not only explaining what each symbol stands for, but applying it (on camera in video below) to the control experiment. Measure the sides of the triangle, then use simple trigonometry to determine the slit distance of the CD. This was the one missing datum that he turns around and uses to measure and determine his unknown laser wavelength.

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Cutting a record… on a CD

Vinyl records are an amazingly simple technology, but surprisingly we haven’t seen many builds to capitalize on the ease of recording music onto a vinyl disk. [Seringson] made his own vinyl polycarbonate cutter to record his own records at home. The impressive thing is he did this with parts just lying around.

Just like the professional and obsolete record cutters of yore, [Seringson]’s build uses two speaker drivers mounted at a 45° angle to reproduce a stereo audio track. Each of these drivers reproduce the left and right audio track by carving them into the polycarbonate of a CD with an extremely sharp needle. From the video, the audio quality of [Seringson]’s record cutter is pretty good – more than enough to recreate the sound of a 1940’s 78 RPM record, but not quite up to the task of reproducing something produced and mastered recently.

We’re extremely impressed that [Seringson] was able to a record cutter out of scraps he had lying around. Now we’ll wait patiently until a combination record/CD is released.

Tip ‘o the billycock to [Gervais] for sending this one in.

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CD/DVD Polisher may save your backups someday

CD and DVD payers can often keep the music or movie going despite a small scratch. But occasionally you’ll have to skip to the next chapter/track or the player will just give up. But with data back-ups, a scratch can bork a whole set of files. We think that most of the time these headaches can be cured with this simple polisher.

[Wotboa’s] thrift store finds yielded almost all of the components needed to build the device. It’s made up of a couple of motors and a jig. One motor slowly rotates the upturned optical disc while the other spins the polishing pad. That pad is made from felt weather-stripping and is helped along with some plastic polishing compound. [Wotboa] asserts that five minutes in the noisy contraption will work wonders on any disc. You can get an idea of what it’s capable of by watching the video clip after the break.

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