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.

I tried again to make another cable prototype yesterday afternoon.

Signal “Wire” Layer

Applying the First Shield Layer

Applying the Second Shield Layer

My sewing was not entirely straight, so I’m not sure how well the prototype will carry audio signals. There may even be shorts between the layers. My next step is to test the “cable” with an audio signal. I want to try the wearable cable with a microphone to see how much noise my homemade cable produces. I also need to terminate the shield and signal wires with rings so I can solder wires or other connectors to them.

I’ve had another idea about how to make the cables: if I use wider strips of conductive fabric, I could make piping with a stitch of conductive thread down the middle. This would be easier to construct than my second prototype.

I’ve discovered that three layers of fabric and the associated stitching produce a fairly stiff package. I’m not sure if this will work well for creating curved “wire” paths in clothing.