Hackaday Links: July 24, 2011

July 24, 2011 by 15 Comments

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!

Desktop Email Notification Bell

July 24, 2011 by 17 Comments

email_notification_bell

Instructables user [meseta] wanted an audible notification whenever he received an email, but must have thought that his computer’s built-in sounds were lacking in some regard. To get the perfect sound that he desired, he built himself a USB-powered notification bell.

Using an off the shelf “front desk bell” and a hand made electromagnet, he constructed a bell that could be triggered whenever a message showed up in his desktop email client. The electromagnet can be triggered by a quick pulse from a microcontroller, and in [meseta’s] case, he used a Forebrain dev board. He created a filter in his email client that runs an executable each time a message is received. This executable in turn sends a message to his microcontroller via USB, triggering the bell.

While we think that the notifier could have been put together using a far less powerful microcontroller, it’s a neat idea regardless. People seem to love alternative notification systems, so we’re pretty sure this bell will appeal to many in that crowd.

Keep reading to see a short video demonstration of his email notifier in action.

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Guitar Becomes An Improved Color Organ

July 24, 2011 by 12 Comments

[Charles] wanted to put some LEDs in his guitar. He also wanted individual notes to output certain colors, but he couldn’t find any projects with tone-based algorithms to convert sound into colors. After about a year of work, his ColorChord guitar was born.

Unlike every other color organ build we’ve seen, the color of a note does not relate to the absolute pitch of the note. Instead, the colors are mapped within a musical key. A I chord will always be Yellow, a IV chord will always be purple, and a V chord will always be blue. Playing in the key of C will have the LEDs output yellow, purple, and blue for a C, F and G chord, respectively.

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All About Accelerometers

July 24, 2011 by 6 Comments

If you’ve ever wondered about the use of or theory behind or the use of accelerometers, this tutorial by Love Electronics is a very good resource. In this article, Love takes one through how to hook up an ADXL345 accelerometer and use it with a Netduino processor. Before the subject of hooking everything up is broached, a very good discussion is given on the general theory and operation of accelerometers.

Information is given about installing all the required software and libraries. Additionally, a mini tutorial about writing a “hello” application using the .NET framework is given. Finally, the application gives the [Windows Presentation Foundation] tools necessary to visualize the raw data that the Netduino produces.

One could really start using this processor and accelerometer from scratch with this tutorial and some basic electronics knowledge.  This could add a great new feature to your next robot or allow measurement that couldn’t be done with simpler sensors.

Using An Arduino To Measure Inductance

July 24, 2011 by 24 Comments

Measuring an inductor is not something that most multi-meters can do. You usually need a high precision resistor (1% or better) in series with the inductor, a function generator to put a signal through the circuit, and an oscilloscope to measure the result. But what can you do if you don’t have these tools on hand? [Andrew Moser] has a method that lets you pull it off with an Arduino and an LM339 quad comparator.

The circuit works by feeding a signal in from the Arduino. This waveform is affected by the LC circuit, filtered by the comparator chip, then read back out the other side by the Arduino. That resulting signal is a square wave, which is an easy target for the Arduino to measure. That timing measured from the square wave can then be used to calculate the inductor’s value.

This is quite handy if you’re winding your own inductors. Now you can precisely tune that Joule Thief you’ve been working on.

[via Dangerous Prototypes and Adafruit]

Creating Music From GPU Noise

July 24, 2011 by 27 Comments

Yep, that’s a picture of a Laptop rocking out on an electric guitar. In what can only be described as a truly bizarre hack [CNLohr] discovered that the RF noise from the computer can be used to play music through the guitar’s pickup.

Check out the clip after the break to hear an annoying, but very discernible rendition of Jingle Bells. Once [CNLohr] stumbled onto the fact that changes in what the graphic processing unit is doing was affecting the pitch detected by the pickup he started writing some code. Now he’s got a program that automatically calculates the size of the window, and produces a white square on a black background to dial in the GPU at the right frequencies.

He mentions in the notes accompanying his video that he had to turn off Vsync to get this to work right. We don’t understand why but we’d love to hear what you think in the comments.

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Cypherbot Uses Older UC And Retro-controller

July 23, 2011 by 8 Comments

[PJ Allen] has been working on a little robot which he calls Cypherbot. The control circuitry is quite familiar; a Board of Education which features the Basic Stamp 2 microcontroller. This is an older and slower microprocessor, but it works quite well for this application since there’s no need for speed or heavy number crunching. The wheels of the bot are made out of plastic lids (we’re thinking peanut butter jars) with rubber bands for traction that are each driven by a servo motor. The third wheel is tiny and swivels as needed.

The front of the bot has a PING ultrasonic sensor mounted on a servo motor which lets the bot scan back and forth for a wider obstacle avoidance angle. In addition to the autonomous mode there’s an Xbee remote control. [PJ] picked up an Atari keyboard and is using that as the user input. Check out the little guy driving around the house in the video after the break.

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