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

[David]

The most straightforward method these days would be a small
microcontroller implementing a pulse width modulation digital to
analog converter.

The analog route is pretty easy though.  A traditional charge or
current pump can operate down to 30 Hz but will have an output ripple
versus settling time trade off.  That can be solved with a sample and
hold.

Charge balancing frequency to voltage converter on page 11:

http://cds.linear.com/docs/en/application-note/an03f.pdf

Current pump frequency to voltage converter with sample and hold
inside the feedback loop on page 4:

http://www.ti.com/lit/an/sbva005/sbva005.pdf

Given the low frequencies involved, a resetable ramp generator with
sample and hold would work great.  The fixed reset time would be so
short compared to the minimum input period that accuracy would not
significantly suffer.

On Tue, 19 Feb 2013 16:58:04 -0800 (PST), Paul Cianciolo
<paulc at snet.net> 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.
> 
>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.\\
> 
>Thank you for reading this and for any suggestions you folks might offer.
> 
>PaulC
>W1VLF