For PyroCardium to respond to people’s heartbeats, we need a way to electronically measure their heartbeat.   Since PyroCardium started life as a VU meter for music, the obvious way to do that was to hook up a stethoscope to a microphone.  Today I tried to do just that.

I had some cheap electret mikes leftover from an earlier project idea (a music responsive EL-wire cape that never made it off the drawing board), so I decided to do the obvious thing and jam one into the stethoscope tubing.  I then built a simple amplifier with a gain of about 100.

Hooking it up to the oscilloscope, I could see the trace move when I put the stethoscope on my chest, but I had no idea what it was responding to - if it was really my heartbeat, or if it was just noise.  It took me a while to come up with a way to figure out what was going on, but eventually I realized that I could hook it up to my stereo.  A few alligator clips later, I could hear my heartbeat booming out over my speakers.

I think our stethoscope amplifier is solved.

This entry was posted on Friday, March 28th, 2008 at 8:59 pm and is filed under Workshop.