>> > Does anyone know an easy way to convert heartbeats to pulses that a PIC
>> > could read?  I'm not interested in the amplitude but just the time between
>> > beats.  I would like to have a PIC log the times between beats to tell
>> > when they become irregular, especially when I'm asleep.
>>
>>   The oxygen saturation and pulse rate sensors I've seen all TOO much of
>> when Robin's in hospital, have a red LED and a photosensor, perhaps an
>> IR pair as well, in something rather like a large plastic clothespin (I
>> know what they look like but didn't feel like disassembling them while
>> there <G>)
>>
>>   You clamp it onto a finger and watch the light conductance waveform
>> for pulse rate, I know I've read before how they determine O2 saturation
>> but don't remember just now.  Basically, the blood pressure changes
>> change the light transmission through the skin <G>  I imagine you could
>> use this on a wristband or whatever as well, sort of a "back-scattering"
>> mode of the same thing.

>Check out patent #5,243,992. A sensor SRI developed and patented is
>described there.

You could also take a look at http://www.masimo.com

The have a bit information on the technology used in pulse oximeters.

They claim to have developed a better system than
the conventional "red over infrared" approach. They call it SET.

But you can take a look at their website for more details.

Regards,
-Oyvind