learning the ropes

Shlomit and I made some progress on our audio art final. We decided to build a sonic field of springs.

Strategies for sensing movement:

• Flex sensor
• Magnetic pickup (like electric guitar)
• 2-axis potentiometer (joystick)

After brainstorming more about producing sound and sensing movement, we built a tiny prototype, using the technique I discovered while building a prototype for Designing for Constraints.

I’m working on a personal art project for my final in Designing for Constraints. The following is my first prototype. I feel pulled in many directions simultaneously — with ITP pulling the hardest. The inner sphere represents me. The springs tug at me in all directions.

I developed this prototype from a simple sketch:

I built the prototype out of materials I already had in my studio:

CD jewel case covers	Old guitar strings and 24 gauge wire spun into springs
	26 gauge wire wrapped around a still central armature

Class feedback:
- Walls of the piece could deform under pressure.
- Piece seems performative — it may require my performance of the object to get its point across. A video might help with this.
- Stretch the box to its limits and videotape it as it breaks

Last night, in preparation for building a perf board, I drew a first draft of the schematic for the Secret Tree.

There are several things to do yet to properly document the project’s electronics:

• Add the clock crystal and other required components for the ATMEGA-8
• Draw a system block diagram
• Draw the finite state machines (although this may be overly complicated

Anyone have suggestions on how to simplify this schematic?

Ai-Chen and I did a bit of rewiring on the Secret Tree circuit board. One of the problems we had last week was that all of the ground wires for the LEDs on the trees were connected to two PCB terminals. I didn’t purchase enough terminal at RadioShack so that every pair could have a ground of its own. This not only made things messy, but it also made the connections suspect.

The other major discovery I made which explained much of the circuit’s random (unintended) behavior was that the two AD5206 chips interfered with one another. I plugged a single LED into each of the twelve outputs (across the two chips) and found that a simple test program didn’t operate properly when both chips were running. As soon as I disconnected the three data lines (CLK, SDI, and CS) from the second chip, the first chip would work properly. I wondered if there might be some sort of “floating” condition when the two chips were used together. Since CLK and SDI were shared, I hypothesized that CS was likely the culprate. To test this, I added 10K pull-down resistors on the chip selects of both chips. It worked! The test program dimmed the lights in the proper sequence rather than skipping around randomly on the third and fourth outputs.

- Continued construction using the perfboard/shrink tubing sensor package and finished two shoe prototypes
- User Test – Patricia (using foamboard prototype + Korg synth module)
- Felt that more sensitivity was needed. She found it difficult to trigger the samples without stomping really hard
- Didn’t like bass drum on the heel; felt it would be more natural on the front
- Cannot tell where the sensor is — perception is that it is close to the center of the shoe
- Feels the system is more responsive with the 10k resistor than with the 2k
- Could play either sitting or standing
- Would like to play along with some other music

I took a short movie of Kelly walking across the kitchen, opening the door, and walking through it. The motion of her forearms created a 3-dimensional volume which I rendered in aluminum and brass tubing joined with aircraft cables.

On Thursday night I brought the structure home on the bus and found it to be quite the conversation starter. It was interesting to watch people watching me.

Design Process

Near completion

The Structure

When considering what to do for the creative part of my Physical Computing lab, I initially thought of some sort of mood-proclaiming piece of clothing.

Instead of using a flex or pressure sensor to light up the LEDs on a “luv-o-meter,” I wanted to prototype a display for a t-shirt that could display a short and partially encrypted message about the wearer’s stress level. I remember seeing a persistence of vision project on one of my first trips to ITP (perhaps it was the winter show?) and thought I might be able to make a single column of LEDs light up and scroll the message past.

Using only a slightly modified version of the circuit from my game of catch, I set about drafting some code to drive a vertical array of 5 LEDs.

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In addition to the adjustable LED level suggested in the lab notes, I decided to program the Arduino board to gradually fade the LED level down from the level set by the potentiometer. Last week when I was working on my game of catch I wanted to have the first LED gently fade in and out during the “wind-up” phase of the throw. This week, I figured out how to do it.

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Lisa Lurie commented that the shape of the photo collage I assembled was an interesting piece by itself. She also suggested that a black background might increase the sense of being in the room.

Somewhere in the back of my mind were memories of books from my childhood — the kind of books you cut shapes out of that become 3-dimensional objects. The form of the Living Room Composites I was created must have reminded me of the flattened out spheres from those books.

Originally, I was trying to assemble and distort the photos to represent the 3-dimensional space on the flat surface of the computer screen. With the second composite, I worried less about distoring the perspective of the photos and more about matching up each of the rows of shots I had taken. Taking the X-Acto in hand, I was able to transform the flat images back into 3-dimensional space by way of the curved lens through which the light in the room had reflected into the camera. After cutting between the “arms” of the image, I pulled them together into a hemisphere to match up the duplicated parts of the images.

The unknown is whether this satisfies the requirements of the assignment. I worked with thumbnails of the original 3 megapixel images in order to keep the “technology frustration” to a minimum — not having to worry so much about the time I had invested in the slow process of manipulating large images if the concept didn’t work out. As it stands, my “model” is about 4″ across and I’m not sure if it will be possible for people who are unfamiliar with my room to discern the objects in it.

I finished the first version of my catch game.

The schematic is pretty basic…

… and in fact it should be noted that I found a soldering problem on the little board I salvaged. Apparently when I rewired it, I knocked one of the circuit traces loose, which prevented the upper right switch from working. This caused me much consternation while trying to develop the catching algorithm. Thankfully Serial.println helped me figure things out.

I modified my program to use the upper left switch for both throwing and catching. Maybe it’s not so interactive anymore, but it’s done and I have other things like Spatial Design homework to do.

If you like to read source code, you can do so in the full entry.

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