Re: how to detect heart rate

Dear Yuki

If you manage to measure the heart rate electrically what you have got is 
really an electrocardiogram.

Did you look up ECG on the web? You will have seen that there are different 
waves present - differing shapes and some dipping down as well as some rising 
up. So if you ONLY want to count, which ones do you want to count?

If you press your finger to squeeze an artery against a bone (for example 
immediately in front of the top of your ear canal), you can FEEL a pulse. So a 
microphone (or stethoscope - which ought to be called a heart-rate-phone) could 
be fed to an electronic pulse counter (Bi-stable flip flop; operational 
amplifier with hysteresis in its positive feedback loop).

If that is what you want to do, look up those words in Google, print it out 
and get a teacher or parent to go through it with you. Or if you write back to 
us with a new question saying what help we can be, we will do our best!

But really the best way is to do the counting yourself (by touch) using a 
stopwatch for 60 seconds. I hope this helps with your question.

David