--- In "Charles" <> wrote:
>
> --- In "j.chitte" <j.chitte@> wrote:
> >
> > --- In "imthemoonman" <imthemoonman@> wrote:
> > >
> > > Any suggestions/reassurance is greatly appreciated.
> > >
> >
> > You will get a hell of a lot of spurious high frequency data and a lot of
> > d.p. to do to extract something useful from a sound recording of your heart.
> >
> > It may be better to look at another analogue proxy of blood flow or at
> > least some simple buffer/filter op amp cct on the mike.
> >
> > Some simple heart rate monitors use a light on your finger tip (like a
> > torch makes you finger glow red). The light tranmitted varies with the
> > blood flow and you can pick up a clean slow moving signal with an opto
> > sensor. this may be more use than trying to detect the envelop of an audio
> > frequency AC input.
>
> http://www.circuitcellar.com/library/print/1204/Bachiochi173/index.htm
> Pulse-ox and HR project.
>
> regards ......... Charlie
>
> > If you are talking about the std ADC on the TS boards be very careful not
> > to exeed 3V. These inputs on-chip inputs of the EP9203 . If you get too
> > careless you could blow the whole thing. At the very least it's easy to
> > take out the input permanently.
> >
> > Keep us posted, I thought of doing this myself at one time.
> >
> > HTH
> >
>
Yeah, don't see the interest in the frequency output there but the light
absorption curves are useful.
Thinking about it, I'd use a photo transistor, op amp comparator with a pot to
set threshold then feed a clean rectangular pulse wave into a DIO line and
count it. Don't see any sense in ADC here.
There's more robust ways but that's about the simplest I can see if you're just
messing about.
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