Dust Prototype PCB Construction
May 04, 2007
May 03, 2007
Etchings in Dust
New Static Prototypes
Shinyoung made a mold and produced a total of 10 static models of Dust to display at the ITP Spring Show.
Headphone Jack Hacking
I also realized that we need a better way to connect the audio output of the Coby MP3 player to the Dust circuit board. For the breadboard, we connected a 1/8" mini phone plug from the output of the MP3 player into the input of the amplifier section.
I want to remove the headphone jack from the MP3 player for our smaller prototype in order to eliminate the bulky plug.
Time for surgery again.
After poking around for awhile with a multimeter to try to figure out how the jack was wired, I gave up and focused my efforts on freeing the SMD jack from the MP3 player's board. It was easier to diagnose the wiring of the jack once it was off the boad.
Since I was tired, I soldered the wires on the wrong side of the board at first (wasn't paying attention to the orientation of the USB pins I soldered on earlier in the day).
USB Connector Surgery
In order to reduce the size of the new Dust prototype, I am further hacking apart the Coby MP3 player. I bought an SMD mini USB connector from Digikey to attach to the printed circuit board. My plan is to replace the USB connector on the Coby unit with four male headers which will plug into the main Dust board. It was very confusing to make sense of the USB pinout. The mini connector has 5 pins, but the original large USB connector has four pins.
In the process of coaxing the original USB connector out, I damaged one of the vias and pads on the Coby board. I hope the damage isn't permanent. You can see the lifted pad right below the "B1" label (upside down)
I tried to repair the lifted trace and pulled out pad with a short section of wrapping wire.
Notice the wrapping wire soldered onto the end of a male header pin. The next trick is to solder the stripped end of the wrapping wire to the lifted circuit trace. I applied superglue to the bottom of the trace to hold it down and then scraped its surface to expose the copper.
I'll won't know if the repair was successful until I get the MP3 player attached to the main Dust circuit board. I'm still a little concerned that the USB wires going between the boards need to be shielded.
May 02, 2007
Dust PCB Design
I finished another revision of the Dust protoype schematic.
Changes from the last version include:
- Revised amplfier section. The breadboarded amplifier circuit didn't match the circuit in the physical computing textbook.
- Revised relays. I drew custom parts in the Eagle library for the Omron G6L-1F relays we ordered.
- Renamed parts on schematic so jumpers, transistors, and diodes have matching numbers (eg. Q2, R2, D2, J2). It was difficult to correlate them on the board layout view when their numbers were different.
- Changed motor diode to a SOT-23 package.
- Added landing spots ("Through Hole Pads" in EagleSpeak) for the qprox electrode and the electrode shield.
- Added USB connector
I also finished the first "real" version of the board layout.
It will be a double-sided board with handmade vias in several spots. There was a point yesterday evening when I just couldn't deal with the complexity of routing things on one side of the board only. I asked Rob Faludi to help me figure out how to add "vias" properly. The whole trick with the vias in Eagle is using the Ratsnest command, which redraws the screen and apparently recomputes connections.
Based on advice from a tutorial I found on Instructables, I drew registration marks on the top and bottom of the board layouts so I can align them perfectly before I iron the toner onto my copper clad board.
Next, I printed out the board to see how things would fit.
Next Steps
- Test amplifier circuit on breadboard
- Battery testing -- can we power with multiple watch batteries or do we need a 9-volt?
- Measure the pin spacing on power switch
- Add programming pins for connecting to the FTDI USB port (for upgrading Dust firmware)
- Fix resistor and capacitor package sizes on board design. Resistors are 0805 and there are two types of capacitors: 4x5.5mm and 6.3x8mm
- Etching
- Soldering
May 01, 2007
Updated Dust Schematic
This is the schematic for the version of Dust we showed at our final Wearables presentation. I'm still working on updates to shrink the size of the circuitry down.
April 20, 2007
Dust Surgery
The following is a record of an electronic surgery performed on 4/18/2007 in the Physical Computing Laboratory at ITP, wherein the patient "Dust" was brought to "life" in the manner of Frankenstein.
April 15, 2007
Dust Finite State Machine v2
We added more details to the state machine which defines Dust's behavior and started writing code to implement it.
April 14, 2007
Dust in the Oven
This reminds me of the story of the gingerbread man -- you know, he ran as fast as he could... but still ended up in the oven.
We started out with two halves joined together, but then realized that our presentation model should incorporate some of the circuitry. We cut out a door in the back to hold the speaker, LEDS, and vibrating motor.
Polymer clay (in this case SculpeyPremo) bakes for 25 minutes at 275° (or close to it).
After baking, the surface looks more matte.
April 12, 2007
Dust Prototype Circuit Pictures
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.
Dust Schematic and PCB Progress (2)
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.
April 11, 2007
Schematic and PCB Progress
April 02, 2007
Dust Prototype Circuit
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
February 28, 2007
Second Wearable Cable Attempt
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.
February 25, 2007
Sewing Lessons
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.
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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?).
February 14, 2007
Working with Conductive Thread
- 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.
February 11, 2007
Hacking a Toy
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.
February 07, 2007
Reaction to Steve Mann Reading
I found that Steve Mann's article responded to some of the issues raised in Frank Webster's Theories of the Information Society with regard to surveillance as an important information gathering tool of the "scientific management" mindset of our corporate and governmental systems. Mirroring Webster's desire to understand the impact of information technology (primarily in the form of information gathering) on the regulation of current society, Mann wants to question the claim that surveillance will lead to a "better future" (Mann 94).
What I found fascinating about the article was that Mann's experiments in "Reflectionism," relied upon his "clothing" and the identity he created with it. It seems that the experiments he undertook would not have been so directly provocative if he simply visited establishments wearing "normal" clothes and carrying a video camera. By using the personally expressive power of his clothing, he literally wore his attitude "on his sleeve." This was especially subversive in the context of our discussion of wearables because unlike a handheld technical accessory, his imaging and data transmission system was deeply embedded in the garments he was wearing. He mirrors the use of built-in video surveillance as a new "prosthetic territory" of architecture (Mann 95) by his total integration of the equiment into his identity, even going so far as to insist on his "self+prosethetic device" (Mann 101) identity on official documentation.
"'Reflectionism' and 'Diffusionism': New Tactics for Deconstructing the Video Surveillance Superhighway"
Steve Mann
Leonardo, Vol. 31 No. 2. (1998), pp.93-102
January 25, 2007
Reactions to "Fashion"
Fashion by Georg Simmel, The American Journal of Sociology, Vol 62, No. 6 (may, 1957), pp. 541-558
Georg Simmel explores at great length the dynamics of fashion, commenting on the affect of class distinction and economic progress on the transitory nature of the sociological phenomenon.
Quotes that stood out:
Thus fashion represents nothing more than one of the many forms of life by the aid of which we seek to combine in uniform spheres of activity the tendency towards social equalization with the desire for individual differentiation and change.
- I was struck by the consequence of this -- as well as the point Simmel makes later in his essay, which is that it is impossible to avoid the influence of fashion. Even by attempting to ignore fashion, I still participate in it in the negative.
[Fashion] has overstepped the bounds of its original domain, which comprised only personal externals, and has acquired an increasing influence over taste, over theoretical convictions, and even over the moral foundations of life.- I think this has increased beyond what Simmel observed in 1957. The television and more recently the internet have accelerated this consumeristic trend.
January 24, 2007
Create a Personal Object
We are asked to create a personal "Venus of Willendorf". The operative idea behind this is exploring the possibility of expression through a personal object.
I have chosen to "embody" myself in a small, pocket-sized ball which serves both as a Rosary and as a reminder of the committment Kelly and I share in our marriage. We are bound together by agreement, but more than that by the grace of God.
The two-toned ball has ten "flowers" on it which correspond to the ten beads on a Rosary. The juxtaposition of the Rosary with the reminder of our marital committment is also a reminder to continually pray for grace in our marriage.
 | I started with a simple ball of foil and covered it with Sculpey I (polymer clay). After baking the sphere for 25 minutes at 250 degrees, I mixed some Sculpey Premo colors together and applied them to the cooled sphere to create the two colored hemispheres. |
 | Using a metal stylus, I carved paths and "beads" into the sphere. There is a single continuous path which travels through all of the beads and joins the hemispheres. |
 | I baked the sphere again and after it cooled I sanded it with 400, 600, 800, then 1000 grit sandpaper to give it a smooth surface. I tried to polish the Rosary Ball with my Dremel using a muslin wheel, but the surface began to melt. I sanded away the burnt spots and enhanced the texture by rubbing drawing ink into the carvings. After the ink dried, I sanded it off with the 1000 grit sandpaper. |