Cast a Shadow, Play a Note

Looking for a way to entertain friends and family this holiday season? Look no further than the Arduino-powered Photocell Piano. [Asahillis] has posted this Instructable for building a 6-note musical command center.

The piano uses photoresistors to turn each note on when the player runs their hand over it. Notes can be tuned independently using potentiometers on the front of the box. The hack uses two circuits: one to generate the tones, and a second to mix them. [Asahillis] adapted [Forest Mims III]’s timeless schematics for the 555 Tone Maker and the 741 Audio Mixer to create his Photocell Piano.

When the instrument is powered on, the code takes a 5-second reading of the ambient light, and sets a threshold based on its findings. Afterward, the first note will sound, indicating the piano is ready to be played. Each note has its own if-else statement that tells it to sound when its corresponding  photoresistor reaches a value below the set threshold (when the player casts a shadow). There’s a demo video included in the guide but we couldn’t embed it here.  Check out the demo video after the break.

If you prefer to rock out with your lights out, there’s always this impressive laser harp.

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Piano Repurposed as a Resonant Synth Speaker


[Richard] recently rediscovered some files from a hack he did back in 2004. He was experimenting with exciting piano strings via electromagnetic fields. The idea shares some elements with the self tuning piano we saw back in 2012. Piano strings, much like guitar strings, are made of steel alloys. This means they create electricity when vibrated in a magnetic field. This is the basic principle upon which electric guitar pickups are built. The idea also works in reverse. The strings will vibrate in response to a modulated electromagnetic field. Anyone who has seen an E-bow knows how this can be applied to the guitar. What about the piano?

[Richard] started with the Casio CZ-101, a classic synth in its own right. The Casio’s output was run through a Peavy 100 watt amplifier. The amplified output was then used to drive custom coils mounted on a piano. The coils had to be custom wound to ensure they would be compatible with the 4 – 8 ohm impedance expected by the amplifier. [Richard] ended up winding the coils to 28 ohms. Six of these coils in parallel put him just over the 4 ohm mark. The coils effectively turned the piano into a giant speaker for the synth. In [Richard’s] write-up (word doc link) he mentions that the strings basically act as a giant comb filter, each resonating strongly in response to frequencies in its harmonic series.

The results are rather interesting. The slow attack of the magnetic fields coupled with the synth’s patch results in a surprising variety of sound. The three examples on [Richard’s] blog vary from sounding like a power chord on a guitar to something we’d expect to find in an early horror movie. We would love to see this idea expanded upon. More efficient coils, and more coils in general would add to the effect. The coils on various string groups could also be switched in and out of the system using MIDI control, allowing for even more flexibility. Continue reading “Piano Repurposed as a Resonant Synth Speaker”

Time-lapse synthesizer build will blow your mind

[themonkeybars] recently uploaded a time-lapse video of his DIY synthesizer build. First off the video itself is a pretty neat hack. An iPhone time-lapse app was used to capture one frame every 5 seconds. By the time the build was complete, approximately 46,000 frames had been snapped. This boiled down to over 43 minutes of youtube footage. [themonkeybars] didn’t work full time on the project, so the video covers about a year’s worth of work which we think makes it even cooler. The synth is also featured in much of the video’s soundtrack.

The synthesizer itself would be classified as an analog modular synth, a type we’ve seen before. Modular synthesizers are one of the earlier forms of electronic music. The synthesizer is composed of discrete modules such as oscillators, modulators, and filters. The modules may be housed in the same box, but they are not internally connected. All connections are made via front panel patch cables. This is where the term “Patch” came from. Continue reading “Time-lapse synthesizer build will blow your mind”

Mario plays piano with a little help from Raspberry Pi


[David] has created his own live robot band to play live versions of the music and sound effects of NES games. Most of us who grew up in the 80’s and 90’s have the music of Nintendo games burned into our brains. While there have been some amazing remixes created over the years, [David] has managed to do something truly unique. Armed with an emulator, some software prowess, and a pair of Raspberry Pis, [Dave] created a system that plays game music and sound effects on analog instruments. A Yamaha Disklavier player piano handles most of the work through a connection to a Raspberry Pi. Percussion is handled by a second Pi.  Snare drum, wood block, and tambourine are all actuated by a custom solenoid setup.

The conversion process all happens on the fly as the game is played. [Dave] says the process has about ½ second of lag when played live, but we’re sure that could be fixed with some software tweaks. Continue reading “Mario plays piano with a little help from Raspberry Pi”

Completely analog electronic music box

For the Ottawa Mini-Maker Faire this year, [Steven Dufresne] created an electronic take on the classic mechanical music box.

A typical music box uses a sequence of bumps on a rotating drum to pluck the tuned teeth (called lamellae) of a metal comb. Steven ditched the drum and comb and replaced them with a strip of paper and a single 555 timer.  The timer is configured as an astable oscillator with a fixed capacitor and charging resistor.  The discharge resistor is selected via a series of 13 shaped wires that drag along the strip of paper.  When a wire drags over a hole, it is connected to a copper pad below that is soldered to a specific resistor.  This completes the circuit and generates a tone specific to the resistor selected.

While the electrical aspects of the project are fairly simple (not even requiring a circuit board), the mechanical parts are much more sophisticated.  Steven had problems getting the dragging wires to make good contact and keeping the paper roll pulled tight.  He outlines all of these challenges and how he solved them in his very thorough video summary (embedded after the break).  With all of his incremental improvements to the design, the finished music box stood up to a whole 14 hours of abuse at the Faire.

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Making a Propane Tank Hank Drum


A [Hank Drum], as explained here, is a steel drum-type instrument made out of a propane tank. The name comes from the [Hang] or [Hang Drum] which is significantly more expensive than that $40 or so an empty propane tank costs. Of course, you’ll have to do some work to get it to play beautiful music, which can be seen in a time-lapse construction video after the break.

The details of how this instrument was made can be found here, including how to lay everything out and cut out eight relatively neat “tongues” for producing different tones. I used a Dremel tool, but this can also be done using saber saw for a curved top. This method is explained here with a template, but the results may not be as neat.

If you want to try this yourself, make sure to use an empty, unused propane tank. This is extremely important. For another entirely different homemade instrument, why not check out the [Whamola] that we made a year or so ago? Continue reading “Making a Propane Tank Hank Drum”

Music challenge has you flapping your wrist to make sounds


This glove controller let you play a musical game. The challenge is to perform the correct wrist motions at the right tempo to play the intro to the song Where is my Mind by the Pixies. This is demonstrated in the video clip after the break.

We often see flex sensors used on the fingers of glove projects, but this one does it all with an accelerometer. That module, along with the Piezo buzzer used for playback are affixed to the small breadboard on the back side of his hand. Rubber bands connect the Arduino to his third and forth fingers. The tempo and rhythm are pre-programmed but the tone generated is based on the gravity reading at the start of each note. If you don’t have your hand positioned correctly the wrong tone will be played.

The code was published in link at the top. It would be fun to see this altered as a hacked Simon Says game.

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