I am currently doing a project that involves making an infrared based heart rate meter. If anybody has done same thing then I would appreciate any info.

Specifically , I wanted to know abt suppose I have digital pulses(heart beats), then how do I count the heart rate. I know how to make a conventional frequency counter in which counting time is 1 sec, but here the counting time is 1 min, so if I do by that method then the problem is of generation of a pulse of less than 1 Hz freq.

 

There are essentially two ways of gating a frequency counter, either gating the incoming frequency for a fixed time (measuring the frequency), or using the incoming pulses to gate a fixed oscillator (measuring the pulse width).

You normally use the first for high frequencies, and the second for low frequencies - but for the second you have to convert it to give the required frequency or B.P.M. for heart rate.

It's easier to do it with a micro-controller, you might have a look at this PIC based version? http://www.web-ee.com/Schematics/HeMon/HeMon.htm.

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you need a hi freq counter with stop start feature and count time interval between heart beats