Raspberry Pi Remote Audio Link

April 17, 2014 by Eric Evenchick 7 Comments

In broadcast, lots of people are still using dedicated analog lines to connect remote sites. These operate like old telephone systems: you call up the operator and request to be patched through to a specific site. They’re also rather expensive.

For a hospital radio station, [Marc] wanted to replace the old system with something less costly. The result is his Raspberry Pi STL in a Box. Inside the box is a Raspberry Pi, PiFace display, a pair of meters, and some analog hardware for the audio.

On the software side, the system uses LiquidSoap to manage the stream. LiquidSoap uses a language to configure streams, and [Marc] has a write-up on how to configure LiquidSoap for this application. On the hardware side, SSM2142 ICs convert the signal from single-ended to balanced. The meters use the LM3915 bar drivers to control the meters.

The Python script that controls the box is provided, and could be helpful for anyone needing to build their own low-cost audio link.

Interactive Gloves Turn Gestures Into Music

April 17, 2014 by James Hobson 11 Comments

Imogen Heap wearing her Mi.Mu gloves

[Imogen Heap] is a UK-based musician who is trying to change the way we think about making music. She’s been working on a pair of gloves called the Mi.Mu, and they’re getting close to production.

In the included interview she explains that while computers and technology have brought many new advances to music, twiddling dials and pushing random buttons “is not very exciting for me, or the audience”. With these gloves, the artist becomes one with the music and interaction.

The current iteration of gloves use flex sensors along each finger to determine the movement (along with motion sensors for other gestures). She’s been through many designs and hopes to integrate e-materials into the next — using the actual glove as the sensor (not physical flex sensors).

She’s been working with both developers and musicians mapping the various motions of the gloves to music which makes sense in an intuitive way, and it’s very unique to see in action.

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The Persistence Of Jumping Rope

April 17, 2014 by James Hobson 4 Comments

[Antonio Ospite] recently took up jump rope to increase his cardio, and also being a hacker decided to have some extra fun with it. He’s created the JMP-Rope — the Programmable Jump Rope.

He’s using the same principle as a normal POV (Persistence of Vision) display, but with a cool twist. He’s managed to put the microcontroller (a Trinket) and battery into the handle of the jump rope. Using a slip ring system, the RGB signal gets passed to the rope, which contains the LEDs. It’s a pretty slick setup, and he’s written another post all about how he did the hardware.

To create the images for his JMP-Rope, he’s outlined the steps to a successful POV image on his blog. These include re-sizing the image to a circle (duh), reducing the color palette, and then performing pixel mapping using a discrete conversion (from polar to Cartesian coordinates). After that it’s just a matter of representing your new-found pixel map in a 1D animation, played column by column. [Antonio] stores these frames on the micro-controller as an RLE (run length encoded) indexed bitmap.

Stick around to see how he made it, and some other cool examples of what it can do!

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Interactive 3D Projection Is Foggy At Best

April 17, 2014 by James Hobson 14 Comments

fog proj

Have a projector and a smoke machine handy? You might want to give this fog projection thing a shot! It’s called the MisTable and it’s a three-dimensional playground for interactive manipulation of images.

It’s a project by Bristol Interaction and Graphics group of the University of Bristol, and it’s an interesting twist on 3D projection. They’ve created what they call the MisTable which features a smoke machine, “smoke screens”, and three projectors. What it results in is an interactive table for two people. The tabletop surface is a display, as is the see through fog in front of each person (the “fog screens”).

While it is fairly easy to understand and explain, there’s a handy diagram after the following break showing how the system works. Our question is, when are one of you guys or gals going to try making one?

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Using Non-Crappy Software With The Da Vinci Printer

April 17, 2014 by Brian Benchoff 107 Comments

The Da Vinci printer from XYZprinting is turning out to be one of the best buys in the world of cheap, consumer printers. Sure, it uses chipped filament, but that’s an easy fix for anyone who knows what a .hex file is. And yes, the Da Vinci host software is a mess of proprietary garbage with limited functionality, but [Mark] has figured out a way around that.

When [Mark] received his Da Vinci, he immediately started snooping around inside the printer’s guts, like any good tinkerer should. He found an SD card holding all the sample prints that ship with the printer, all in a convenient Gcode format. Inside these sample .STL files were all the calls you would expect – setting the temperature, changing the layer height, and all the other good stuff you’d find in any other RepRap.

With a little bit of modification to .STL files generated by any slicing program, [Mark] isn’t limited any more by the terrible host software that ships with the Da Vinci. Combine this with the ability to reset the chip inside the filament cartridge, and [Mark] has a printer at least as functional as any open hardware model.

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Measuring Frequency Response With An RTL-SDR Dongle And A Diode

April 17, 2014 by Mathieu Stephan 17 Comments

[Hans] wanted to see the frequency response of a bandpass filter but didn’t have a lot of test equipment. Using an RTL-SDR dongle, some software and a quickly made noise generator, he still managed to get a rough idea of the filter’s characteristics.

How did he do it? He ‘simply’ measured his noise generator frequency characteristics with and without the bandpass filter connected to its output and then subtracted one curve with the other. As you can see in the diagram above, the noise generator is based around a zener diode operating at the reverse breakdown voltage. DC blocking is then done with a simple capacitor.

Given that a standard RTL-SDR dongle can only sample a 2-3MHz wide spectrum gap at a time, [Hans] used rtlsdr-scanner to sweep his region of interest. In his write-up, he also did a great job at describing the limitations of such an approach: for example, the dynamic range of the ADC is only 48dB.

Lego Robot Plays Games For You As You Sleep

April 17, 2014 by James Hobson 19 Comments

robot

[Uli Kilian] — best known for solving 100 Rubik’s cubes during the 2011 London Marathon — got addicted to a free iPad game called Jurassic Park builder. Being the efficient man he is, he soon realized the game could be automated — after all, you just have to tap on dinosaurs every few minutes to earn in-game currency…

He’s using a Lego Technic set with an old iPad, and an Arduino connected to a Windows laptop. Wheels roll the iPad back and forth as the robot plays the game. The “finger” of the robot is wrapped in tin-foil and connected to a ground pin to simulate a human finger for the iPad. The article doesn’t explain how it works, but by looking at the robot it appears to just randomly tap away back and forth across the screen — which we guess works for this game?

He hasn’t played with Lego since he was 8, and only just learned about the Arduino a few weeks prior to building this. As a 3D artist he was intrigued to do something in the real-world — nice!

[Thanks Aurelio and William!]