MICRO explores the small universe that is our body and mind. It consists of an 8ft x 12 ft x 8ft structure that has 200 translucent balls hanging from the top of the structure, each ball containing a speaker. When a ball is bumped into it generates a unique sound, and lights up with one of 5 different colors. As people play with the balls they are engulfed by a symphony of lights and sounds surrounding them on all sides.


Each ball is independent from all the other balls, and contains a custom made circuit board inside. Since the installation needed to run for days (and later on for months), and we didn’t want to be changing batteries all the time, external power is run into each ball. MICRO also needed to stand up to the elements as it was to be shown outdoors originally. All of this proved to be quite the engineering problem. Here’s how we did it…

Inside a sphere


The circuit board contains a microcontroller, an audio amplifier, a flash storage chip for the audio file, a tilt switch, and a voltage regulator, as well as various transistors, capacitors and resistors. A high power LED plugs into the circuit board and floats above the board. The speaker attaches to the bottom of the circuit via velcro.


The first task was to figure out how the interaction would work. When someone touches a ball the goal, of course, was that the ball should light up and make sound. We originally considered using an accelerometer, but those are expensive and a little overkill for our intended use. I ended up finding a $.70 tilt switch which worked beautifully:

We didn’t want wind triggering the balls, but the tilt switch had its own solution to this. Inside the tilt switch there is a ball bearing that rests in a little cone. If the ball moves in a smooth arc, much like how it would move when the wind blows, due to centrifugal force the ball bearing stays at the bottom of the cone and the ball is not triggered:

For the microcontroller we went with a Trinket from Adafruit. It was cheap, and had the added feature that it could PWM an audio file. Adafruit has a wonderful tutorial about how to play audio with the Trinket here. In a nut shell, the trinket emits the audio as a square wave, then a low pass filter is used to smooth out the PWM into a listenable audio source.

Most of the circuit operates on 3.3V, but we found we needed 5V to really get the most out of the LED. 5V is fed to the circuit and the LED, then the voltage regulator brings the 5V down to 3.3V for everything else. One of the problems we discovered early on is that high power LED’s need constant current. This means that if the current starts getting too high it is brought down, if it gets too low it is brought up. Here’s a great instructable on building a constant current circuit with a few resistors and transistors. You can see the constant current circuit I designed in the lower right of the MICRO schematic. Its those two FET’s, one transistor, and two resistors. It worked great, no more blown LED’s:


Originally we showed MICRO at Burning Man and we needed to be sure it would withstand the elements. It can get quite hot on the playa, Eric Rosenthal (my mentor through many parts of this project) was encouraging me to throw the circuit in my oven. Hesitantly I did so, testing the circuit’s temperature with an infrared thermometer and hoping it would still work:

Moving outward

We used clear light fixtures for the balls, in three diameters: 6″, 9″ and 12″. We dipped them in rubber dip multiple times to get the texture and translucency we were looking for. We laser cut the bottoms for the spheres out of acrylic, and did the same rubber dip treatment to them.



We used a truss structure to suspend the spheres. This was great because it was easy to assemble, relatively light, and very strong. To keep the truss from blowing away in the high winds that often happen at Burning Man, we guy wired the top edges down to the ground. We lined LED strips on the guy wires so unsuspecting people on bikes and in art cars would not have an unpleasant (and possibly quite dangerous) surprise finding a guy wire where they didn’t expect one.


Power for 200 spheres was a problem. We needed to switch 120V AC down to 5V DC for 200 separate circuits, and make sure we had enough amperage for the LED’s and audio. We ended up using 11 of these switching power supplies that could deliver 30 amps each. These also have a watertight rating when hung in their included case vertically. They’ve proven quite reliable:

Without whom it would not of happened

One of the most wonderful parts of this project was meeting so many generous and amazing people who helped out along the way, I would be remiss to overlook all of you. You all have special places in our hearts and in the hearts of all those who have experienced MICRO. This doesn’t do you credit, but here you are:

Made possible with generous support from:
Burning Man Arts, Federation Square/Pause Fest, Cameron Arts Museum

A Purring Tiger collaboration:

Concept/Design/Creative Direction
Kiori Kawai

Concept/Music/Electrical Design
Aaron Sherwood

Andy Sigler, Lisa Park, Rosalie Yu, Laura Chen,
Wyna Liu, Scott Horton, Mark Hebert, Elise Knudson, Chris Hallvik, Angela Orofino,
Momo Nakayama, Logan Scharadin, Julia Montepagani, Chelsea Southard, Ni Cai

Betta Lambertini, Logan Scharadin, Julia Montepagani,
Matthew Hardy, Joshua batson, Kris Seto, Elise Knudson, Kiori Kawai

Roy Rochlin, Talya Stein, Momo Nakayama

Guardian Angel
Eric Rosenthal

Special thanks
The Generator Inc., Big Bang The, Camp Contact, River School Farm

Momo Nakayama, Kiori Kawai

Thank you all!


Patterns (maybe) & their emotional impact

Hundertwasser, ‘A New Way’ – concentric rings start large then become smaller and tighter adding tension until opening up into space at the center, and releasing tension. periodic breaks in the pattern add to the effect.

Chloroplast under a microscope – the energy is amped up on the left with a large burst and more stabilized on the right with three similar sized smaller bursts.

Sol Lewitt, ‘Wall Drawing # 232′  - visual tension increases with the addition of lines moving downward and to the right.

iOS Map Glitch – a smooth path through noisy terrain functions like light through dark clouds, but then becomes obscured by both the terrain and then the mesh glitch in the map. the tension is released when the path returns out of the glitch and is surrounded by the familiar terrain.

cotton candy under an electron microscope – starting from the left, the amount of spherical objects clumped together increase and their locations move upwards in the image. that movement then releases back down with the last sphere smeared out. the jungle of strands acts as a counterpoint to the spheres and a continual source of tension.

carina nebula as seen with visible light from the hubble space telescope – surrounded by a stable background of stars, the nebula acts as a literal large exclamation point in the image.


The Magnetophone is a sound sculpture with 14 guitar strings and 14 homemade electromagnets. Continuously generative, electromagnetic fields make the strings vibrate. Pictures available on the project’s main page.

Constructed out of aluminum and acrylic, the Magnetophone measures 3ft tall.



The circuitry sits atop the Magnetophone, with an Arduino Mega lowered down on a platform slightly below.


The Arduino sends out square waves to LM386 based amplifiers that power the electromagnets at the resonant frequencies of each of the strings. Its possible to sound overtones of the strings if upper partials of the harmonic series for an individual string are sent.


The circuit boards were acid etched, then treated with tinnit to keep them from oxidizing, thus the silver finish underneath. Each board has either 3 or 4 amplifier circuits, depending on which side of the Magnetophone it is being used for.



I made the electromagnets out of sewing machine bobbins wrapped with 32 gauge enamel covered magnet wire.


The electromagnets needed to have 8 ohms resistance to work properly with the amplifier circuits. After a lot of testing I found that 348 turns on the bobbin with the wire was the proper number. To help with the wrapping I used an Arduino, a photocell, and a drill. I put a strip of white tape on the chuck of the drill and every time it passed the photocell the level of light changed on the photocell and the Arduino counted for me. A light comes on when the right amount of turns is reached (thanks to Eric Rosenthal for the idea). Here is a sample video aiming for 10 turns:

When electricity passes through the coil a magnetic field is generated. Since I’m sending a square wave to the coil, the magnetic field is oscillating on and off at the frequency of the wave. I put a bolt through the hole of the bobbin, which becomes magnetized and vibrates with the magnetic field. The magnetic field from the bolt pulls and releases the string making it vibrate, which makes sound. On the back of the bolt I put a small rare earth magnet. One earth magnet strengthened the magnetic field nicely, anymore actually weakened it. Instead of sending a frequency to the coil, an input coil (50 ohms resistance) can be substituted. However, I found that the string vibrates more when it’s resonant frequency is sent rather than having an input coil.

To attach the coils I designed a complex insert and locking system, that would allow me to move the coils closer or further away from the strings:


But I needed to be able to move the coils side to side as well, and found that I couldn’t do it with this system. I ended up going a much simpler route, holding the coils down in place with one strip of material above them.


Here’s a test video vibrating a string:

Instrument Design

Acoustically, the strings vibrate the bridge, which vibrates the front plate, which pushes air molecules inside the resonance chamber back to bounce off the back wall. Plywood sheets are more resonant than 1/4″ acrylic, but the wood looked a little too much like a grandfather clock to me. Plus, I wanted it to look less like an instrument.


The strings spiral up around the sides of the piece. Different gauges of guitar string were used within each side to achieve variety on each side. They are tuned to an Ab major scale, but this was fairly arbitrary, the potentials for tuning being quite wide. The tone holes are also spaced so that no tone hole is facing another, my theory being that the air molecules should bounce back and forth against the sides inside the chamber.

Screen Shot 2013-12-02 at 12.13.27 AM


The Arduino is making some decisions about what to play, and will continually keep generating new music. It switches between two modes, sometimes choosing random strings to play, sometimes generating a pattern or sequence, then looping that melody for a bit.

Using the tone library (not the built in one), the Arduino Mega can play up to six tones at one time (it has six timers). In order to reuse the timers (not a standard function), shifting them to other pins for different strings, I had to modulo the tone pin count for the amount of timers I wanted to use. For example, if I wanted to use 4 of the Mega’s timers i would do this in the tone.cpp file:


Since I was using a Mega 2560 I also had to change everywhere in the .cpp file that said:

#if defined(__AVR_ATmega1280__)


#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)


Here is a schematic for one circuit, and an image of the three circuit board:

schematicMagnetophone 3ampsbrd


Thanks to Scott Garner for aiding me in my times of need, and to the Basic Analog Circuits class at ITP for etching a ton of PCB boards for me.

Special thanks to Danny Rozin, Eric Rosenthal, and Marina Zurkow for guidance, support, ideas, and bobbins.