IR Plethysmograph - Health-related HW

Tom Boonsiri tom.boonsiri at
Thu May 29 03:09:56 EDT 2008

The OLPC Goldenstate grassroots group has developed an alternative heart
rate monitor to add to the ECG Prototype.
A simple Plethysmograph circuit was implemented leveraging the built-in ADC
and a modified version of Arjun's Measure code. A Plethysmograph is an
infrared photoelectric sensor used to record changes in pulsatile blood flow
from the finger. The Plethysmograph operates by recording changes in blood
volume as the arterial pulse expands and contracts the microvasculature. A
simple beat detection method was implemented to capture heart rate.

Video link:
Original ECG Prototype link:

Tom Boonsiri
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