learning the ropes

things I made at ITP and after: sketches, prototypes, and other documentation

Friday, May 4, 2007

Dust Prototype PCB Construction

Prototype Build 037 Prototype Build 038 Prototype Build 039 Prototype Build 040 Prototype Build 041 Prototype Build 042 Prototype Build 043 Prototype Build 044 Prototype Build 046 Prototype Build 047

posted by Michael at 11:10 pm  

Thursday, May 3, 2007

Etchings in Dust

Prototype Build 017 Prototype Build 019 Prototype Build 020 Prototype Build 021 Prototype Build 022 Prototype Build 023 Prototype Build 024 Prototype Build 025 Prototype Build 026 Prototype Build 027 Prototype Build 028 Prototype Build 029 Prototype Build 030 Prototype Build 031 Prototype Build 032

posted by Michael at 10:51 pm  

Thursday, May 3, 2007

New Static Prototypes

Dust Strip

Shinyoung made a mold and produced a total of 10 static models of Dust to display at the ITP Spring Show.

posted by Michael at 1:52 pm  

Thursday, May 3, 2007

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.

Headphone Jack Surgery-0

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).

Headphone Jack Surgery - annotated

posted by Michael at 12:32 pm  

Thursday, May 3, 2007

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.

USB Connector Surgery-0

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)

USB Connector Surgery-1

I tried to repair the lifted trace and pulled out pad with a short section of wrapping wire.

USB Connector Surgery-3

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.

USB Connector Surgery-4

USB Connector Surgery-5

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.

posted by Michael at 11:04 am  

Wednesday, May 2, 2007

Dust PCB Design

I finished another revision of the Dust protoype schematic.

Dust Prototype 7 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.

Dust Prototype 7 PCB

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.

IMG_6917

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: 4×5.5mm and 6.3x8mm
  • Etching
  • Soldering
posted by Michael at 6:25 pm  

Tuesday, May 1, 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.

Dust Schematic 2

posted by Michael at 1:22 pm  

Friday, 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.

Dust Surgery 003 Dust Surgery 001 Dust Surgery 002 Dust Surgery 005 Dust Surgery 004 Dust Surgery 006 Dust Surgery 007 Dust Surgery 008 Dust Surgery 009 Dust Surgery 012 Dust Surgery 010 Dust Surgery 011 Dust Surgery 013 Dust Surgery 014 Dust Surgery 016

posted by Michael at 1:01 am  

Sunday, April 15, 2007

Dust Finite State Machine v2

2007 04 14 Finite State Machine

We added more details to the state machine which defines Dust’s behavior and started writing code to implement it.

posted by Michael at 1:30 pm  

Saturday, 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).

Before Baking  Before Baking-1 

After baking, the surface looks more matte.

Baked Dust

posted by Michael at 11:48 pm  
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