[time-nuts] Off topic project sort of heart rate monitor NEED BEATS PRE MINUTE TO ANALOG VOLTAGE

Herbert Poetzl herbert at 13thfloor.at
Tue Feb 19 20:21:50 EST 2013

On Tue, Feb 19, 2013 at 04:58:04PM -0800, Paul Cianciolo wrote:
> Hello Folks,

First, I cannot speak for the list, as I'm quite new here,
but in general 'Thread Hijacking' is frowned upon :)
(read: start your own thread :)

> I am working on a project intended to convert an analog ECG
> signal to a voltage proportional the heart rate, The actual
> electrodes instrumentation amp is pretty much working fine 
> so no worries there.

> The problem is, and here is where the relationship to time nut
> comes in. The signal output from the instrumentation amplifiers
> will be at a rate of approx 60 BPM or pulses, up to perhaps 90
> BPM.  

> The purpose of this apparatus is to print a rolling chart on
> the screen of a computer of heart BPM and then try different
> technicues of meditaion  and calming technicues to lower my
> heart rate for short periods of time.

That doesn't sound to me like you would actually need a
Voltage, i.e. some other Information from which you can
deduce the current BPM would be fine as well ...

> My first tthought was a frequency to voltage IC like the
> LM2907 or the 2917 but I get the impresiion from the data
> sheets that these chips will not work at these very low 1Hz
> applications,

> Then I thought maybe one of the frequecy counters could be
> configured as a rate meter and output a proportional voltage
> I need.

I wouldn't count the frequency directly, instead, I'd
simply count the intervals, with a counter running at
a known frequency, for example, with a 1kHz or maybe 1MHz
clock, which can be easily done with a $1 microprocessor
The 'counts' for each interval are inverse proportional
to the current BPM, with some averaging you should get
a reasonable result to display on screen.

> No luck here either. 
> Te latter components seem tobe somewhat time relatedand that
> is why I posted here.\\

> Thank you for reading this and for any suggestions you folks might offer.


> PaulC

> 1Hxz
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