We were motivated when considering a future society where a every person's heartbeat could be plainly sensed by other people and heartbeat data is constantly recorded.
We aim to create a wearable device that both transmits and records the wearers heartbeat and receives a heartbeat signal from another user.
While we wait for our pulse sensors and vibration motors to arrive we made this basic circuit: Each Arduino has an analog input and output (a pot and an led), and changing the analog input on one changes the output on the other. It was simple to build once we realized we had to equalize the grounds (by connecting the pins).
We 3D-printed our ear clip at Brown. The ABS material was just right in terms of flexibility, and the earpiece stayed firmly in place. We plan on making the piece curved so that the enclosure pints downward and presses flat against the wearer's head but we ran in to some issues with the sensors that will require changing the design (see next step!)
The pulse sensors arrived! Unfortunately, they're a bit finicky. They work optically, with a bright LED and photodiode that read the tiny brightness changes when capillaries fill with blood every heartbeat.
That means they only work where there is good bloodflow very close to the skin: the fingers (fingertips are best) and the earlobe. The places we can feel our pulse (wrist and neck) didn't work at all, and neither did our behind-the-ear plan.
We've realized we need to adapt our design to reach the earlobe. We can still wire the sensor and vibrate motor together, but our design needs to either be two separate halves (motor and sensor) or somehow adjustable/telescoping to accommodate different ear sizes.
We're brainstorming how best to improve the look of the earlobe clip. The included clip works fine but looks a little goofy, and we're trying to develop something more understated...
After testing our pulse sensors we learned that they only work when attached to the fingertip or earlobe. we changed our design to incorporate a sliding mount that will hold the pulse sensor up to the earlobe and can accommodate a variety of ear sizes.
New 3D-printed protype. We made it out of PLA filament in white. The properties of the material were slightly different than our last ABS model— the clip flexes differently, and the sliding piece doesn't fit as perfectly as before. But it's just as functional, and it'll work for the show.
We rewrote most of our Arduino sketch. A few changes:
(The sketch uses both files attached below).