Building A Contact Mic Using Homemade Piezo Crystals

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[Leafcutter] is big in to making music and has put together all sorts of musical instruments and tools over the years. Recently, he was inspired to make his own piezo crystals, and wrote in to share the results of his experiments with us.

[Leafcutter] is no stranger to messing around with piezo elements, and after seeing [Collin’s] tutorial on making your own piezo crystals at home, he knew he had to give it a try. He stopped by the grocery store to fetch all of the ingredients, then followed [Collin’s] instructions to the letter…well, almost. It seems that he might have cooled the solution too quickly, so he found himself with a jar full of tiny, barely usable piezo crystals instead of larger ones like [Collin] was able to produce.

Undeterred, he decided to see if the stuff was any good, and rigged up a makeshift contact microphone using some conductive foil and a clamp. He piped the output to his amplifier, and wouldn’t you know it…it worked!

He has a small sound clip of what the mic sounded like on his site, and it worked pretty darn well despite the crystal’s tiny size. He is going to give the whole process another go, so we hope to see more experiments with bigger crystals in the near future.

ChipKIT Sketch: Mini Polyphonic Sampling Synth

In our hands-on review of the Digilent chipKIT Uno32, we posed the question of what the lasting appeal might be for a 32-bit Arduino work-alike. We felt it needed some novel applications exploiting its special features…not just the same old Arduino sketches with MOAR BITS. After the fractal demo, we’ve hit upon something unique and fun…

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Easter Egg Hacking

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Spring is upon us and Instructables user [Mischka] decided it was a good idea to combine two flavors we never considered putting together: The Easter Bunny and the A-Team.

He decided to build the egg as an Easter gift for his brother, who is a huge fan of the A-Team. He found a slightly larger than normal plastic egg, and proceeded to paint the shell white, adding a printed picture of Mr. T once the paint had dried.

The guts of the egg are made up of a Picaxe 08M micro controller mounted on a Picaxe protoboard. Rather fond of buzzing, beeping audio, he decided to forgo a normal speaker and opted to use a piezo instead. To activate the music when the egg is shaken, a tilt switch was added to the board as well. He uploaded his software to the Picaxe, sealed up the egg, and called it a day.

We can imagine his brother will be pretty pleased with the creation – who wouldn’t be? We only wish that there was video of the egg in action.

MIDI Drum Interface Helps You Step Up Your Game

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[Dan] likes Rock Band, but playing it makes him feel as useful as a one-legged man in an ass-kicking a drumming contest. He says that even using his friend’s ION kit leaves him searching out excuses as to why he’s not as good as he should be on the drums.

Eventually, he decided that he would settle things once and for all. The final excuse he came up with was that it is too difficult to press the drum pedal rapidly without getting tired, as the Rock Band gear does not properly simulate real drum equipment. Bass pedals on professional kits are weighted and balanced to allow the drummer to exert the least amount of work for the most return, resulting in a less tiring experience.

To give him a leg up while playing the game, he decided to rig a trigger to his Yamaha MIDI bass pedal, which is properly weighted. He consulted the Rock Band forums, and after looking at a couple of different circuit diagrams, he designed his own. He etched a PCB, mounted his SMD components, and was well on his way to becoming a drum legend.

He says that the pedal interface works quite well, and despite a couple of tiny soldering setbacks, he has yet to see any errant hits register in-game.

Be sure to check out the video below of his drum trigger undergoing some tests.

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Transmitting Power And Data Through Thick Metal Enclosures

So let’s say you have a submarine, or a nuclear containment chamber which has walls made of thick metal. Now let’s say you want to transmit power or data through this wall. Obviously you’re not going to want to drill a hole since this wall is either keeping seawater out, or potential contamination in, but wireless signals aren’t going to travel well through dense metal. [Tristan Lawry’s] entry in the Lamelson-MIT Rensselaer Student Prize seeks to address this issue by using ultrasound waves to transmit data and power.

In the video after the break [Tristan] speaks briefly about his project, then demonstrates the transmission of power and digital audio simultaneously through a two-inch thick steel plate. This is accomplished with a set of piezo transducers attached to both the inside and outside of the plate. Communications originate by feeding electricity to one transducer, which sends ultrasonic vibrations through the material to be received by its counterpart on the other side. It’s easy for us to understand data transmission conducted in this manner, after all that’s how the knock block receives information. What we don’t understand is how it can “transfer large amounts of electrical power”. If you can explain it in layman’s terms please do so in the comments.

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Sound-sensitive Android Figure Speaks In Morse Code

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Instructables user [tanbata] recently got his hands on a Google Anroid figurine and thought that while it looked great, it served no real purpose. He decided to change that, and converted this once-useless hunk of plastic into a miniature robot that moves and responds to sound.

He pried of the head of the figure and got busy fitting a servo into the Android’s body to enable head movement. An ATiny was added to control the figure, along with a microphone to enable it to respond to sound. A piezo was inserted to relay Morse code messages, and a handful of LEDs were installed in the body cavity and eyes of the figure just for kicks.

When the bot is powered on and senses a loud enough sound, the eyes light, the head spins from side to side, and the robot spouts off a random message in Morse code as you can see in the video below.

It’s not the most advanced project out there, but with a few tweaks, it could make for a great USB-powered email or IM notification system for your PC. Better yet, it’s a great project to do with a child who is interested in electronics, since they get to make a cool robot toy they can keep.

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Multitool Alarm System

Here’s a way to make sure you don’t leave your Leatherman multitool somewhere. It’s an alarm system that will start a timer when the tool is removed from the holster. After five minutes the module beeps to remind you to put the tool back where it belongs. Annoying? Possibly, but if you’re not done with your work just press the reed leaf switch on the module to reset the timer. A PIC 12F683 handles the timing and generates the waveform for the piezo buzzer. Perhaps this could have been accomplished with a dual 555 chip like the LM556 (one timer for the countdown and another for the piezo waveform) but the PIC has power-down modes available that should make the button batteries last a long time.