Final Project Documentation – James Z.

The goal of this project was to create an array of LEDs embedded in ping pong balls, and the balls would be able to move and react independently to interaction. Each ball is attached to a series of metal wires, providing a physical output of motion when acted upon by a user. Each LED is also capable of dimming, providing a visual output of a change in light. This was made to create a simple, enjoyable experience that comes from being able to interact with these little balls of light. I wanted this to be  something that was fun to interact with, as well as beautiful to look at.

Note: photographing and recording LED light is very difficult. but if you look closely, the lights do dim, but they are dimming very very quickly. the side view is best for seeing that.

How It Works:


The motion of each ball comes from the metal wires supporting it, and the bolt attached directly below the ping-pong ball. All of these things are meant to keep the ball  in motion for as long as possible when acted upon. Also, the bolt functions to provide the ball with some weight so that a ball  in motion can collide with a stationary ball and cause a chain reaction.


Each LED is also capable of independently dimming, because on each metal support wire, there is a bending variable resistor. The current going to the LED passes through the resistor. When the metal wire is bent, the resistor bends with it,  increases resistance, and limits the current flowing to the LED. The LED dims as a result:

Please enlarge this picture!


The Base:

The base is made of MDF. the holes were drilled in a 3 x 12 pattern, making 36 holes. I used a 1/16in drill bit, because these holes have to be as small as possible. The whole wire assembly is inserted into the hole, and it is imperative that the hole and size of the music wire inserted into it are as close as possible. Then, I drilled a larger hole next to each of the smaller ones, for electrical wires to pass through to attach to the circuit underneath.

The Wire Assembly:

Each part of the wire assembly was chosen very methodically, and was a result of experimentation with various  materials. What I ended up choosing helped me achieve the motion that I had originally wanted when I was coming up with the concept. The wire assembly is comprised of the following components:

Music Wire: Provides the overall bend. It is very flexible yet strong, and consistently returns to an unbent state when the stress that is bending the wire is removed.

a Bolt: Provides the weight to keep the ball in motion for a longer period of time acting as as a sort of pendulum.

Steel Wire: To get the entire assembly to move in a consistent manner, this section needed to be completely stiff. It allows controllable oscillation to occur, because of the distance the bolt is away from the flexible music wire. if the entire wire assembly was flexible, the movement of the ping-pong ball would be inconsistent, and it would flop around rather than swing.

Brass Tube: Connects the steel and music wire.

LED: Wrapped in scotch tape, to diffuse the light even more.

All of these components were glued together with 5-Minute Epoxy.

I made 36 of these. Gluing it all together definitely was the most time consuming part. I used pliers to squeeze down on the brass tube once I had inserted the music and steel wires into either end, to help secure them in place while they were gluing. This additionally helped secure them even more once the glue had dried.

Note: You have to use heavy duty cutters to cut music wire. It is extremely strong wire and will damage all normal wire cutters, and even more rugged ones. That is why I suggest you buy linesman cutters, which I listed below under the materials section.

Please enlarge this picture!

The Bendable Resistors:

This video tutorial explains every step I went through to create the bendable resistors:

After cutting out all the resistors, I took two thin strips of .02 styrene, placed a piece of music wire along the back of the resistor, and glued the strips of styrene over the wire, so they would be secured to the resistor and wrapping over the wire:

the two strips of styrene on the top and bottom hold the resistor to the music wire. They were glued there using Plastruct Bondene

Once they were done drying, I pulled out the music wire I had used to shape the styrene strips (I couldnt use the actual music wire because it was still drying from having been glued into the wire assembly)


I took the resistors I had made (with the conductive thread attached) and slipped them onto the music wire end of the wire assembly.

I inserted  the wire assemblies into each of the 36 holes, gluing them in with 5-Minute epoxy,. Then I soldered on electrical wire to the prongs of the LEDs. This is what it looked like before and after I wired it all up.

I took the conductive thread at the top end of the resistor and wrapped it around the electrical wire that was attached to Positive side of the LED, and secured the two together with electrical tape.

I simply attached the LEDs in parallel. Underneath the MDF board, each row  of LEDs  has a designated Power and Ground wire that each LED in that row is attached to.  I took the conductive thread at the other end of the resistor, fed it through the larger hole i drilled, and wrapped it around the Power wire. I took the Ground electrical wire and soldered it to the designated Ground wire for the row. Then, all three Power and  three Ground wires are connected to the breadboard to the Power or Ground columns.


Schematic of Circuit

Bottom of wire assemblies with resistors attached


36 Ping Pong balls

36 LEDs (Super Bright, Low Voltage) [Electronic Goldmine]

.32 mm Music Wire [CMU Art Store]

1/8 inch Brass Tubing [CMU Art Store]

14 Gauge Galvanized Steel Wire [CMU Art Store]

Smaller Gauge Wire [CMU Art Store]

Utility Knife [CMU Art Store]

Heavy Duty Wire Cutter (Something like this)

Wire Stripper [Electronic Goldmine]

Black Electrical Tape [CMU Art Store]

Scotch Tape [CMU Art Store]

.5 inch Thick MDF [Home Depot]

Nails [Home Depot]

36 Bolts [Home Depot]

Electrical Wire [Sparkfun]

Soldering Iron [Radioshack]

Solder (Rosin Core)

5 Minute Epoxy [CMU Art Store]

Hot Glue Gun [CMU Art Store]

Drill (I drilled holes that were 1/16 in. and 5/32 in.

Staple Gun

.25 Acrylic Sheeting

Black Spray Paint [CMU Art Store]

3 AA Batteries


For the Resistors:

Conductive Thread

Graphite Powder

Rubber Cement [CMU Art Store]


Measuring Spoon [Giant Eagle]

.02 inch Styrene Plastic

Plastruct Bondene


~ by jzulkie on May 22, 2010.

One Response to “Final Project Documentation – James Z.”

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