Electromagnetic harp with home made Ebows

Fresh from the Arduino subreddit comes [dataplex]’s 26 string electromagnetic harp. It’s a very cool, ambient instrument that sounds simply phenomenal through the Space Echo and Fender Twin rig [dataplex] has.

There’s not much in the way of build details, but judging from this post [dataplex] made several months ago the instrument works on the same principles as an Ebow. There’s a great prototype video showing the hardware and software. One small voice coil reads each string. A tiny op-amp sends this to another voice coil and back into the string. There’s tons of feedback, but it’s great for an ethereal ambiance.

The prototype is controlled by an Arduino via a computer, but for the final build [dataplex] moved on to a copper/zinc touch interface on the front of the harp.

It’s a very, very cool instrument and we’re waiting patiently for the build details to be released. You can check out the videos of [dataplex]’s work after the break.

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Music visualization generator with a Propeller

The folks over at Gadget Gangster have been working on a music visualization system using a Parallax Propeller. The visualizations are awesome in their early-90s demoscene way, and of course we love anything using the oft under-appreciated Propeller.

The project is called Video Beats and it generates music visualizations in the style of a blocky but very complex Atari 2600 game. There’s really not much to the build – just two RCA jacks for the audio input and video output along with a couple of resistors – but we do appreciate how nicely this project would fit in at a chiptunes show.

The Gadget Gangster team says the input isn’t limited to just audio – a potentiometer, accelerometer, or even a light sensor can be added to the build for a more dynamic output. After the break, you can see the demo of Video Beats, and a [Family Sohn] music video that used an early version of this circuit.

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Robotic light painting in 3D

For the last few months, [Ben] has been building a 3D light painting robot. Instead of a couple Arduino-controlled LEDs that a person moves around the Lightplot, as [Ben] calls it, uses a robotic arm to move a LED in 3D space.

The build started with [Ben] testing his idea by putting a laser pointer on an altitude and azimuth mount made out of LEGO. Eventually [Ben] decided to build a 3D plotter rig for a more impressive show. The 3D plotter sits in on a tripod with three axes of motion – up and down, clockwise and counterclockwise, and ‘in’ and ‘out’. A small RGB LED at the end of the robotic arm is controlled along with the servos and motors, making it possible to plot vector lines in 3D space.

There are a whole bunch of demo videos after the break. They look fantastic, but we’d really like to see the Lightplot be used outside on a dark, starry night.

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Hackaday Links May 9th 2012

Homecut – CNC Cutting Directory

homecut

So you have a CNC machine that you use as a hobby, but would like to do some actual work on the side? Or maybe you have an idea you’d like made. Homecut is a map directory where you can maybe hook up with the right person.

The Curta Mechanical Calculator

curta calculator

As [leehart] mentioned in our comments section, the Curta mechanical calculator is a truly ingenious piece of engineering. A quick Google search should find all kinds of information on it, but this article could be a good place to start for some mechanical hacking inspiration!

Luxman Amplifier DAC Upgrade

nand-dac

[R. Barrios] wasn’t happy with using the sound card for his HTPC setup, so decided to add a DAC module onto his reciever. The resulting audio quality was very good, and the build came out quite clean.  Check it out if you’re thinking of a hack-upgrade to your stereo equipment.

3D Printable Tilt-Shift Adapter

tilt-shift-lens

A tilt-shift lens a neat piece of equipment that is used to make a large scene look like they were miniatures. It’s a cool effect, but professional lenses to do this can cost thousands of dollars. This Instructable tells you how to go about printing your own. For more info on the technique itself, check out this Wikipedia article.

New 3D Printer on the Block

3d-printer

If you would like to take the plunge into 3D printing, but are looking for somewhere to get a parts kit, the [ORD Bot Hadron 3D Printer] may be worth a look.  The build quality looks great, and the price for the mechanical components is quite reasonable at $399. You’ll need to provide the electronics and extruder. Thanks [comptechgeek]!

An excellent introduction to transmission lines

[Bertho] sent in a great tutorial on terminating transmission lines. If you’ve ever tried to send a high frequency signal a long way down a wire, you know the problems that can crop up due to electronic strangeness. Luckily [Bertho]’s tutorial explains just about everything, from where and when to terminate a cable and why signals get screwed up in long wires.

[Bertho] begins his lesson by taking two oscilloscopes and 20 m of CAT5 cable with the twisted pairs wired in series to make an 80 meter long transmission line. A ~100kHz square wave was sent down the cable after being displayed on the first oscilloscope, and picked up on the other end by the second oscilloscope. It’s a great way to show the changes in a signal over a long cable run, and how small changes in the circuit (just adding a simple resistor) can affect the signal coming out of a cable.

It’s a great post that demystifies the strange electrical gremlins that pop up when you’re running a length of wire. Great job, [Bertho].

Metal detection using an inductor instead of a clock crystal.

This project from a few years back is an interesting take on a metal detector. Instead of building a detection circuit, [Bruno Gavand] replaced the external clock crystal with an inductor. Here you can see the inductor coil next to the PIC 12F683. You can see two components jumping from one breadboard to the other. These are smoothing capacitors on the inductor lines.

The watchdog timer for the chip is run by the internal RC oscillator. When the external crystal receives a pulse due to metal inducing a current in the coil, the value of the watchdog timer is compared to it. This data is filtered and if the proper parameters are present the green LED blinks. This is bicolor LED. If the inductor circuit is functioning properly it will blink red at power up. [Bruno] says that results will vary based on that inductor so you may need to try a few to get the calibration light to blink.

We’re thinking this would make a simple stud finder (by detecting where the nails/screws are in the wall). Check out the demo after the break, then let us know what you would use this for by leaving a comment.

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