The most important is to keep the shield stray light into the photo transistor. For home lighting that is particularly important because the lights at home mostly based 50HZ or 60HZ fluctuate, so faint heartbeat will add considerable noise.This module uses bright infrared (IR) LED and a photo transistor to detect the pulse of the finger, a red LED flashes with each pulse. Pulse monitor works as follows: The LED is the light side of the finger, and photo transistor on the other side of the finger, photo transistor used to obtain the flux emitted, when the blood pressure pulse by the finger when the resistance of the photo transistor will be slight changed.
We choose a very high resistance resistor R1, because most of the light through the finger is absorbed, it is desirable photo transistor sensitive enough. Resistance can be selected by experiment to get the best results.
The most important is to keep the shield stray light into the photo transistor. For home lighting that is particularly important because the lights at home mostly based 50HZ or 60HZ fluctuate, so faint heartbeat will add considerable noise.
Package Includes:
