Pulse Necklace 12Aug2009
 Pulse Choker Hack Notes Aug 12th, 2009
 2-lead Open ECG Circuit
We have received the tiny little red board, and wired it up on a bread board, put on some Red Dots, and it works! We were able to observe 1V signal spikes in time with hearts.
However, one of the electrodes really did have to be over the heart. Moving to the other side of the chest or up to pendant location still worked, but signal was about 1/4 the size. Neck and arm electrodes showed nothing. We did get clear, beautiful signals from heart beat just below the pect and eye blink just outside the eye though.
We had a long discussion about how to proceed next - whether to try optical stuff again, or to try to work forward on ECG, or what else we could do.
We looked at stethoscopes (they are cheap, like $5, at Amazon), and that made us think again of acoustic techniques. Could we have a differential acoustic solution, involving two microphones, one of which is like a stethoscope and picks up your internal noises, and the other is external and provides a "reference" that you subtract from the first signal in order to cancel out background noises? We'd need to tackle some signal processing, perhaps using triangulation to separate out external sounds from internally generated sounds like heart beat and vocalization. Need a good common-mode-rejection op-amp but placement might be really tricky, since even just having the sound waves out of phase would make it totally broken. Maybe active noise canceling stuff could be useful too? Eric will look into this idea.
Chung-Hay did some research into neck-positioned optical solutions, and didn't find much. She did find a paper in IEEE on a military helmet with an optical blood-oxygen sensor. They claimed that forehead was the best location (better than chin, jaw, nape of neck). Forehead still wasn't as good as finger, but it was close.
We took a hacking break for some conductive body paint awesomeness - Humanthesizer
Eric purchased a numetrex Fabric Chest Strap, which hopefully will allow us to use ECG without having to use those super painful Red Dots on chest hairs again ;-).