Editing Pulse Necklace

==Design Thoughts==

<blockquote>"An electrocardiogram is obtained by measuring electrical potential between various points of the body using a biomedical instrumentation amplifier. A lead records the electrical signals of the heart from a particular combination of recording electrodes which are placed at specific points on the patient's body."

</blockquote>

However, for this project I think the best solution may be optical.  There is apparently a small change in the optical properties of your skin with your blood pressure, meaning that pulse can be observed by an optical sensor pressed against your skin.  I have a working "pulse watch" which uses this principle.

Display: Initially, only to people other than the wearer, via a string of LEDs inside the choker.  I imagine the pulsing centered on the LED in the center, and going out to all, then coming back in, similar to how some star trek (?) lights worked when the computer talked.  There may also be a lone vibrator, which could be used to signal to the wearer a variety of things (like pulse, but also time or low battery etc).  Although this is really stretching the definition of "display", the device might also log data for later retrieval via USB.  

Armature: Choker, plus it is likely that it will have to have a pendant hanging from it, which would contain the circuit and battery.  The vibrator might also be in the pendant.  The hard part of the armature will be how to wire the LEDs in a "soft" way (no ribbon cables around our necks!).  Also, the optical sensor will have to be held against the neck even while the neck moves, you breathe, etc - that might be tricky.  We have experimented with conductive thread with crimp beads, but they are very difficult to use, and end up being more fragile than is really acceptable.  We are presently investigating silk-screening conductive paint, and flexible PCBs are possible armature ideas.