Making A Phono Preamp For A First Electronics Project

October 27, 2012 by 34 Comments

Nearly everyone’s first electronic project is something that blinks a LED. There are a million ways to go about this ‘Hello World’ project of electronic design; 555 timers, microcontrollers, or maybe even discrete components if you’re really cool. When [miceuz] was asked by a friend to help with his first electronic project he eschewed the usual blinking LED project and taught him how to build something he actually needed: a phono preamp for an old turntable.

Back in the day when vinyl was king, albums needed to be mastered to play on a record player. The mastering process cuts some of the bass and increases the treble. When the record is played, this process needs to be reversed. It’s a preamp that does this job by attenuating the high frequency sounds and boosting the thumping bass.

[miceuz] found a nice DIY RIAA preamp  project and found a nice little op amp  somewhere in his parts bin. After laying out the circuit, [miceuz] etched a few boards and taught his friend how to solder SMD components.

Of course the project didn’t work the first time around, but after poking around with a meter and checking out the old turntable, the preamp came to life with the clang of chords from an old record. If you’d like to build your own, you can get the files from [miceuz]’s git.

OpenPLC, For Industrial Automation To Halloween Displays

October 27, 2012 by 27 Comments

Stepping out onto just about any factory floor you’ll find complex automatons building anything and everything imaginable. These machines need to be controlled somehow and before the age of computers these manufacturing robots were controlled with relays wired together to produce a multitude of actions. Relays, no matter how reliable and bulletproof the are, can’t be programmed without rewiring the entire machine. Now, factories have programmable logic controllers to take care of their automation tasks.

[Thiago] built his own programmable logic controller and released it as open hardware.Included in the OpenPLC are four 24V inputs, four 24V outputs (two with PWM), 0-10V analog inputs, and USB, SPI, and I2C for programming and expansion.

If you’re building anything from an industrial machine in your garage, or simply want really awesome Halloween (or Christmas) decorations, the OpenPLC can take care of driving all the solenoids, motors, and actuators needed. With the extendable I2C and SPI busses, it’s possible to add a plethora of sensors to bring a project to life.

The OpenPLC is based on an ATMega328 and is compatible with Arduino code. There are a few extension boards for digital and analog IO, as well as Ethernet.

Homebrew Guitar Tuner Also Includes MIDI Out

October 27, 2012 by 9 Comments

A few years ago, [Frédéric]’s brother in law wanted a guitar tuner for Christmas. Instead of going out and buying one, [Frédéric] broke out the soldering iron and built one from scratch.

[Frédéric]’s tuner is built around an ATMega168 uC on a Real Bare-Bones Board with an LM386 amplifier. The display is a standard 20×2 LCD character display, and the interface is torn from the pages of stomp box schematics with a very hefty foot switch.

Detecting the frequency of a note played into [Frédéric]’s tuner involves a fair bit of math. To measure the frequency, the Arduino samples the waveform coming from the input jack. This signal is delayed for a fraction of a second and the area underneath the real and delayed waveforms is measured. This delay slides across the original waveform until the area between the real and delayed samples are minimized. At that point, delayed wave form will be exactly one cycle behind the real signal, and the cycles per second can be calculated. It’s called the YIN algorithm, and you can read more about it here.

Since [Frédéric] already knew the exact frequency being played into the tuner, he figured it would be trivial to add a small analog audio to MIDI converter. This feature (as shown in the video after the break) turns the sounds from a guitar into MIDI notes. It’s monophonic and probably a little superfluous, but still very cool.

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Draw Your Own Vinyl Beats

October 26, 2012 by 13 Comments

 

The Dyskograf lets you make music with a magic marker. The musical installation looks much like a turntable for playing vinyl records. But instead of a spiraling groove containing the sounds, this uses marks on a paper disk to play sound samples.

You can see the light outline of several tracks on the paper disc shown above. By adding black marks the optical input of the Dyskograf knows when to start and end each sound. This is best illustrated in the video demonstration after the break.

The marker-based setup makes a lot of sense, and we think it would be perfect if the disc was a dry-erase board. It certainly makes it a lot easier to lay down new beats than this other optical turntable which required holes to be drilled in a vinyl record to play the sounds. While we’re on the topic you may also find this coin-based turntable sequencer of interest.

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Halloween Props: A Spooky Mirror

October 26, 2012 by 5 Comments

This mirror will spook your guests with a variety of static and animated images. It includes a proximity sensor so the images will not appear until someone comes close enough to see themselves in the looking glass.

The electronic parts are quite easy to put together. There is a 32×32 RGB LED matrix mounted on the back of the mirror. It is driven by an IOIO board with some custom firmware written by [Ytai], the creator of that board who happens to live next door to [Alinke]. Where this starts to get interesting is when [Alinke] was working on the mirror to make the LEDs visible from the front. He used a razor knife to put hundreds of scratches in the varnish on the back. This lets just enough light through to see the LEDs, but keeps the mirrored surface reflective. See for yourself in the clip after the break.

The images are fed to the IOIO board by an Android device. We think this could have a lot of use after Halloween as a weather display or news ticker. Perhaps you could even feed it from your diy Android thermostat.

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AM Chiptunes Played By A Modified Antenna Analyzer

October 26, 2012 by 5 Comments

Believe it or not, this VK5JST aerial analyzer kit is going to rickroll you. [Erich] wanted to see if he could use the device in a different way. His adventure led him to use it to feed different tones to an AM radio, producing the all too familiar [Rick Astley] offering.

There’s a fair bit of math that goes into getting the correct signals to generate a given pitch. But it basically boils down to patching into the hardware early in the RF generation. This way an audio signal can be rolled into the carrier frequency. Since this kit uses a PicAXE microcontroller with available source code it is rather easy to add audio input to tweak what the chip is putting out. But there is also some hardware tinkering to be done. Read more about that at the article linked above, and don’t forget to check out the bottom of that page to hear the final results.

DARPA Funded Robot Ninja Warrior?

October 26, 2012 by 23 Comments

Fans of the game show Ninja Warrior will immediately recognize the similarity of this test apparatus as the Spider Climb. Of course that’s not a human contestant, but a humanoid robot developed by Boston Dynamics. And it’s not actually clinging to the vertical walls as its only support. There are two narrow ledges to either side on which its feet gain purchase. Nonetheless this is some impressive work to keep itself upright and avoid slipping. Check out the video after the break to see how it does.

The sheer volume of amazing robot tech that this company spits out is remarkable. Just last month we saw the robotic cheetah which can run at almost 30 mph. We don’t expect to see either in the wild anytime soon, but especially this humanoid. you’ll notice the red rings positioned around the apparatus. We believe these are high-speed cameras set up to give the robot positional feedback and we’d wager it can’t perform without them. But that’s merely conjecture so judge for yourself.

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