Building a hard drive scratch controller


If you’re reading this blog then chances are you have a dead hard drive hanging out somewhere in your house. Here’s a weekend project that will put it back into use. [Andreas] took on the popular project which combines a hard drive and optical mouse to build a scratch controller.

The gist of the build is that you use an optical mouse sensor to track the movement of the platter. But [Andreas] made things harder on himself by not using the USB capability of the mouse and mapping it in software for his needs. Instead he plucked the sensor from the mouse, reading it using an Arduino. After much trial and error with the best way to coat the underside of the platter to play nicely with the sensor he managed to get it up and running. The controller issues commands using the MIDI protocol, forming a strong foundation for future upgrades which could lead to a full-blown DJ console hack.

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Reading Sensors with Scratch

Scratch, a graphical programming language developed by MIT’s Media Lab, is an excellent tool for teaching programming. [Daniel] created an Arduino Sensor Shield to interface with Scratch, allowing for real-world input to the language.

This board is a derivative of the Picoboard, which is designed for use with Scratch. Fortunately, the communication protocol was well documented, and [Daniel] used the same protocol to talk to the graphical programming environment. The shield includes resistance sensing, a light sensor, a sound sensor, and a sliding potentiometer.

The main goal was to create a board that could easily be built by DIY etching. This meant a one sided board with as few jumpers as possible. The final design, which can be downloaded and etched at home, is single sided and uses only one jumper. Detailed steps on testing the board are provided, which is very helpful for anyone trying to build their own.

This board is perfect for educational purposes, and thanks to [Daniel]’s optimizations, it can be built and tested at at home.

Building sensors for the Scratch programming language

[Kevin Osborn] is making it a bit easier for young programmers to write programs that interact with the physical world. The device he’s holding in the picture is an Arduino based accelerometer and distance sensor meant for the Scratch language.

Scratch is a programming language developed at MIT. It has kids in mind, and focuses on graphical building blocks. This can make it quite a bit easier to introduce youngsters to programming concepts without the roadblocks and gotchas that come with learning syntax.

As you can see in the clip after the break, [Kevin’s] Arduino sketch includes hooks that automatically pull the accelerometer and distance data into the Scratch environment. We figure his example provides everything you need to get just about any type of sensor up and running, be it a magnetometer or LDR (both of which would make a nice burglar-alarm type project). Give it a try with your own hardware and see what you can accomplish.

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Machining an SLR camera from scratch

It took us a while to stop drooling long enough to write about this amazing machining project. [Denis MO] made a single-lens reflex camera from scratch. The banner image above is not the finished product, but just one step in the production chain. [Denis] has been thinking about doing this project for 25 years and finally took the plunge. From the start, the only parts he planned on NOT making himself were the screws, ball bearings, shutter, curtain fabric, and interchangeable lenses. Everything else is his own creation based off of his own design. Spend some time looking over his project. There’s plenty of information and images of both the machining process, and the drawings he mocked up in the design process. We’ve also included a pic of the finished camera and the contact sheet from his test roll of film after the break.

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Virtual Theremin

[Mojo] has taken a lot of the complex circuitry out of the mix by creating a virtual Theremin. A Theremin is an electronic instrument, usually with two antennas, that senses the proximity of the player’s hands to the instrument and responds accordingly.

This design, called the AirDeck, uses a Wii remote as an IR sensor and two gloves with IR LEDs in them. Data from the Wii remote is processed by a custom Java app that converts it into sound. [Mojo’s] interface also includes some alternative options such as a turn-table scratch interface.

In the end this is still just a synthesizer/midi controller and cannot stand up to the real thing. However if you’re not an accomplished player you’ll probably never notice the difference.

Destroying optical media

We got a tip about a USB CD destroyer. We found its methods amusing as it just scratches the CD as seen above on the left. If you really have data security issues, perhaps something more than scratched plastic should be used. There are a lot of paper shredders that can also shred CDs, what about taking that shredder with the burnt out motor and turning it into a hand-cranked shredder that doubles as a CD killer?

Got a lot of optical media that needs to go? These folks developed the chain-gun of CD shredding with an automatic feed. This consists of a CD shredder and a slew of discs connected with packing tape. As seen in the video after the break, the shredder advances and the next disk is pulled into its jaws.

Microwave has been a popular bringer of death for disc media. The light show and resulting chaotic art (above on the right and after the break) are what make this interesting, but it’s pretty hard on the much-loved kitchen appliance. What we’re really looking for is a way to force a CD/DVD writer to overwrite data. The fact that burnt discs, rather than factory pressed versions, are what normally need to be disposed of makes this a hack waiting to happen. Why isn’t this a standard hardware feature of all drives, and can it be implemented in software?

There’s always the low-tech snap, scratch, or mangle methods. We usually just scratch the foil off the top of the disc.

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[denha] has assembled a noise box he calls the XR-NOISE using an XR-2206 multi-waveform function generator. The output has an impressive number of controllable settings, and uses a set of LEDs to indicate sound level and rate. The XR-NOISE uses 1/4″ jacks for both in and out, and can also be controlled by the tap-sensitive mic located on the front of the box. Unfortunately, there doesn’t seem to be any further documentation or schematics to provide context, but it seems that this function generator chip has also been used for other audio hack projects as well, including a scratch-synth using resistive pressure sensors.

[via MatrixSynth]