learning the ropes

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.

- Modified MAX patch to playback samples instead of routing notes to a MIDI synthesizer
(full comments are found in 12/1 notes)

- 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

- Problem: Sensitivity Training. It is difficult to get the sensors to trigger samples consistently. We’re concerned after studying the FSR datasheet and application notes that we might be saturating the sensors and going outside of their useful operating range. We try replacing the 10k resistors in the sensors’ voltage dividers with 2k resistors. We are also trying to eliminate the opposite problem: standing still on the prototype triggers samples. Is the circuitry too sensitive?

- Problem: The MAX patch plays two notes simultaneously. We work to debug this issue by breaking the MAX patch into sections… first by printing the received note data, then watching this data as it propagates through successive objects in the patch.

- Breakthrough: Tried sandwiching sensors between layers of foamboard in the hopes of avoiding sensor wear and exposed wiring. Much of the discussion continues to focus around protecting the sensors.

- I ordered connector samples from Samtec: female headers so we could prototype the FSR strain relief packages and 6-position modular jack connectors in the event we want to build printed circuit boards for this project.

- Finished rewriting Arduino code to send sensor data to MAX/MSP as NoteOn/NoteOff messages. This patch takes the NoteOn message(s) sent from the shoes and can remap them to different note numbers so it is not necessary to modify the Arduino code every time we want to change the sounds.

- We’ve been destroying FSRs. The tiny staples which make contact with the conductive layer of the FSR fall off if too much heat or pressure is applied.

- Discussed strain relief for FSRs. Lisa is going to call Interlink to see if we can get replacements for free. (see 11/12 notes for picture of initial strain relief Prototype)

- Crimped modular connectors (RJ-11?) onto the ends of phone cable. We are planning to use these connectors and jacks to improve the reliability of our system. These will replace the stripped wires plugged directly into the breadboard.

(from Lisa)

We continue to work on the housing for the sensor. We explore other
options to the lucite house, as the machining of it really time
consuming. We go back to the lucite housing, and retest the sensor to
make sure it still works. Michael does some stomping. It still works.

The question is as to whether this housing will last long-term as
built. The area with the solder seems to be the new vulnerable spot.
(Before the “ vulnerable spot” was the connector.) Will our strain
relief stand the test of time?? Stay tuned patient viewers..

We decide to create 2 versions, one is as described above, the other
is heat shrinked.
We are almost ready for user testing! Woo-hoo.. We still need to
attach them to the shoes, and will be attaching one to the front left
and the other to the front right, and seeing which is the victor, in
the test of durability.