RE: Pulse Hunter

genebren — Sat, 15 Dec 2018 18:41:05 GMT

Very nice blog! Just a couple of things that I noticed that I was not too sure about.

1) There is a buzzer that is connected direct to the 5V supply input. Is the buzzer intended to alert whenever the unit is on? Not sure why you want to do that.

2) In the isolated power supply, I noticed that there was no flyback diode to suppress the voltage that is generated when the primary of the transformer is shut off. You might want to look into this to help prevent any damage to your switching circuit.

Otherwise pretty cool. I have worked with a few engineers that came out of groups developing commercial pulse oximetry instruments. They were doing some pretty aggressive filtering of their signals (>10 tap filters) to clean up their signals. The load of these filters on a microprocessor where pretty heavy, up to the point that there was little to no background time available (of course they were using 8051 derivative).

Gene

RE: Pulse Hunter

jw0752 — Sat, 15 Dec 2018 16:52:06 GMT

This is a very interesting project and you have done an excellent job of explaining the circuitry and the physiology behind the effect. I look forward to your followup posts.

John