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

Jim Lux jimlux at earthlink.net
Tue Feb 19 23:02:02 EST 2013

On 2/19/13 4:58 PM, Paul Cianciolo wrote:
> Hello Folks,
> 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.

Interestingly, I've been doing the opposite... given a rate, generate a 
realistic pattern of beats.

> 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.
> 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  1 Hz applications,
> Then I thought maybe one of the frequecy counters could be configured
> as a rate meter and output a proportional voltage I need. No luck
> here either. Te latter components seem tobe somewhat time relatedand
> that is why I posted here.\\

A small microprocessor is your friend. Run your signal into an Arduino, 
PIC, teensy (my current favorite) or whatever..

That way it can set the threshold dynamically, count time between zero 
crossings, integrate over several beats, ignore skipped or extra beats, etc.

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