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

[Bob Camp]

Hi

The first layer to the onion is that the ECG signal is a bit complex. There's also likely to be a bit of this and that on it. 

How about taking the output of the instrument amp into the A/D port on a cheap PIC? That would let you do some AGC and dynamic filtering. At even a modest sample rate (say 10 KHz) the heart rate could be worked out in software. I think I'd run a PWM out and drive an analog meter with it. 

The nice thing about keeping it simple is being able to run it off a 9 volt battery. That takes care of a *lot* of issues.

Bob

On Feb 19, 2013, at 7:58 PM, 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
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> 1Hxz
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