Pulse Necklace 01July2009
Pulse Choker Hack Notes, July 1st, 2009
We disassembled the pulse watch, and found the sensor part consists of a little LED + photo diode part, with 4 wires.
We tried to use the watch on our necks, and it did sometimes show a beat pattern, but it was irregular and the watch would not return a bpm reading. It didn't matter whether we had the clear "window" part or not.
We measured the voltages. The LED has a voltage drop of .6V, and V+ of 2.8V. The photo diode had a reading of 1.2V without finger, 1.073V with finger. Whatever the pulse signal is with finger, it's too small for the multimeter to read. Clearly we'll have to build an amplifier circuit.
Try using the conductive epoxy to attach conductive thread to a SM LED. It look a few attempts, but we did find a way to attach it that wasn't too much trouble. The epoxy takes a lot longer than 5 minutes to dry though - probably more like several hours. Method we used: "wet" the ends of the thread, and press them against the pads of the LED. Generalization: wet a whole bunch of thread ends in an array, press the LEDs down against them. Do it on wax paper or similar that the epoxy doesn't stick too.