Pulse Necklace 05Aug2009
 Pulse Choker Hacking, Aug 5th, 2009
 Optical Circuit
The optical circuit is not working anymore? Chris spent a bunch of time trying to debug it, and found a disconnected cap, but the circuit still doesn't work. He also replaced the sensor with the backup, and discovered that the circuit has some "memory" - it will respond once when you touch it the first time, but then not respond again if you remove and retouch it.
 Thin Paint Traces
We tried to paint traces with 1mm spacing, but this proved to be impossible. Paint bleeds between the two traces and so it would short. We figure that ~3mm spacing is really required to be safe.
After running some calculations, we have to give up on 7 control lines, and retreat to 5 control lines plus a power, because otherwise the total width of the circuit becomes huge. BUT, we did a test and it is possible to get multiple LEDs on each control line. You must be very careful during the soldering of the first LED in the row though because the solder tends to "suck in" the silver paint, which can result in break in the trace, making the second LED not work.
The surface mount LEDs have about 2mm between the pads, and we know that headers have center-to-center spacing of 2.54mm. So the present idea is that if we skip every other header pin, we can have 2.54mm traces with 2.54mm gaps, and this should hopefully be convenient for both the LED soldering and the connection into a PCB. With 5+1 = 6 traces, the total width would be (6+5)*2.54 = 27.94mm, which is just barely over an inch. The around neck distance between farthest LEDs should be 12cm (based on current armature, which is 13.5cm and big enough), and the distance down to pendant about 6cm, but make the stencil 10cm so that we can cut it and have extra if need be. We're actually going to try 2mm traces with 3.08mm gaps.
We reworked the connection of the beta armature to the wires again, because the wires were causing the armature to twist all up, and the connections were breaking. We glued the armature to a piece of stiff paper using hot glue, and then soldered in the wires, and put a knot in the three wires for strain relief / to hold them in a constant position with respect to the armature. This seems to be working great so far. We plan to not need wires for the final product, but this is good stuff anyway.
We installed the Arduino software unto Chung-Hay's laptop, and the FTDI drivers, and we successfully flashed the ATMEGA from her computer.
Eric is gonna go buy the acrylic polymer base emulsion, and make sure that the ECG circuit gets in. Meredith has said that we can borrow her powdered graphite (which is on her shelf) since she has lots.
Chung-Hay is going to try to use illustrator to make a stencil design.