[time-nuts] Off topic project sort of heart rate monitor NEED BEATS PRE MINUTE TO ANALOG VOLTAGE
eb at telight.com
Wed Feb 20 02:39:49 EST 2013
If you only need cardiac pulse rate, an optical pulse-oximeter type
interface - but without the oximetry part - would be much simpler than
an ECG system, and it doesn't need galvanic connection. If you need more
than that, then ECG methods should suffice.
Back in the 1970s, there was a lot of interest in biofeedback and TM
techniques, using ECG and EEG. Common feedback signals were sound and
light related to the detected physiological signals. A chart display is
a good visual feedback with dynamics too, and it records the events for
further study, so you can investigate the QRST details and whatever else
is interesting. Detecting and processing the signals is nearly trivial
now with modern electronics - it wasn't even that hard back then. If you
study what's transpired over the last forty years, you'll get a pretty
good idea of the whole history of the field, and the technologies
involved. Nowadays of course, the PC can take care of most of the
processing and feedback/indicator functions.
For a DIY, I'd recommend for each channel run the high-gain
instrumentation amplifier into a V-F or FM converter to translate the
signal into a workable frequency range like a few hundred Hz, then use a
sound card and SW to post-process. Copy front-end interface ideas from
the real stuff - professional medical equipment - to make sure it's safe
to hook up to your own hide. If you don't need absolute details, you can
AC-couple the physiological signals into the V-F process with
appropriate time constants, to avoid the drift, and average in SW.
I doubt that interest in this area has waned over the decades, so it's
likely there are all kinds of cooler, newer stuff available off-shelf,
so you may be able to find it ready to go - and even way beyond what you
had in mind.
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