KY-039 Heartbeat Sensor

This module uses bright infrared (IR) LED and a phototransistor to detect the pulse of the finger, a red LED flashes with each heartbeat.
The heart rate sensor works as follows: the LED is on one side of the finger, and phototransistor on the other side of the finger, phototransistor used to obtain the flux emitted, when the hearbeat is detected in the finger, the resistance of the phototransistor will be slightly changed.
Chosing a very high resistance resistor R1, because most of the light through the finger is absorbed, the phototransistor is sensitive enough. The most important is to keep stray light away from the phototransistor to minimize interference. For home lighting that is particularly important because the lights at home mostly based 50HZ or 60HZ.

Specifications:

• Working voltage: 5V

• Weight: 2g