learning the ropes

Taking a look back at the breadboarded circuit always turns up something I’ve neglected on the schematic: in this case, it’s the vibrating motor.

I’m also a little concerned; I haven’t heard the amplified sound from the MP3 player through a circuit we had on another breadboard.

Work continues on the schematic for Dust. I have spent hours in Eagle drawing this thing.

Design Questions:

• Current design will require two USB ports (Arduino + MP3 player). Will it be necessary to include both of them on the PCB?
• How much current does the circuitry require?
• What type of battery will we use to power the circuitry?

I also started creating a PCB design. I want to print it out this afternoon to see the physical size and see if this corresponds with the size we want to make the wearable item.

For the past two days I’ve been building up the Dust prototype circuit.

So far I’ve gotten away with entirely found parts… This is fine for the breadboard, but for our final wearable version, we’ll need to reduce the size significantly.

• Relays are Omron G5A and an OEG 105D. These are much too big. I would prefer Omron G6H (high density)
• TIP-120 Darlington transistors could be replaced by 2N3904 transistors (or maybe there are SMD transistors). I originally wanted to avoid using relays to drive the MP3 player, but our tests with transistor-only circuits were unsuccessful.
• The Coby MP3 player is small, but the Sakura (from the designer of the MAKE DaisyMp3) is smaller — and open source.

Remaining tasks:

• Writing the Arduino code
• Testing the LM386-based amplifier

I’m working with Shinyoung on a project called “Dust” for Wearables.

“Dust” is a discrete, wearable character who offers spoken affirmation and support in response to “deflated” gestures.

Initially we tried sensing a sigh in order to trigger Dust’s affirmations. We planned to mount a stretch sensor inside a waist-belt and sense the expansion and contraction of the wearer’s diaphragm. Preliminary experiments with the stretch sensor did not yield favorable results. The stretch sensor seems to be optimized for applications involving greater ranges of motion.

We decided to try a different approach. It may be possible to use pleated material with conductive thread or fabric between the pleats to sense the sigh. In the pictures below, I am pleating a section of fabric to create a prototype of the gesture sensing mechanism.

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.

Kelly taught me the basics of machine sewing this afternoon. Thanks for your patience, dear… I wasn’t the most model student. We discussed properly squaring up the fabric, threading the machine, and guiding the fabric.

I’m trying to create wearable audio cables which are a component of final project.

The result of my first experiment was not so successful. The machine seemed to choke on the conductive thread, even though I was feeding it from the bobbin (sp?).

• Can’t solder to conductive thread. It is best to create wire rings and loop the conductive thread around it many times to ensure a good connection
• Hot glue can be used as a strain relief for wires attached to the circuit. I used hot glue to relieve the strain on the piezo sensor solder joints
• Hot glue can be used as strain relief on snaps, too
• To sew very short stitches, push the point of the needle slightly into the fabric, then push your finger against it to make the needle point exit the fabric again
• When sewing on snaps and sewing conductive thread out from the snap (as opposed to terminating a conductive thread trace at a snap), tack one side of the snap down with non-conductive thread. Tie a knot in the end of the conductive thread and sew the conductive thread in the middle of the spot where the snap is being sewn. The messy knot should be on the outside of the garment. This is useful because it allows more control over the frayed ends of the conductive thread. It keeps them underneath the snap on the outer surface of the garment rather than exposed on the inside.

I found this lovely little item at the Family Dollar for $5. Coupled with a pair of pants for $3.75, I think I have the makings of a pair of percussion pants.