Finger Detection Heartbeat Measuring Sensor Module KY-039 uses bright infrared (IR) LED and a phototransistor to detect the pulse of the finger, a red LED flashes with each pulse. This component is ideally suited to adding heartbeat sensing to your project.

Pulse monitor works as follows: The LED is the light side of the finger, and phototransistor 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. This detection module combines a photo transistor and IR LED, which when a finger is placed between will provide a varying signal. Reading this analog signal you can interpret a change in signal as a heartbeat.

We chose a very high resistance resistor R1, because most of the light through the finger is absorbed,it is desirable phototransistor 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.

As a simple module it will suit use within a large range of projects based on microcontrollers such as Arduino boards and the Raspberry Pi. The module has a M2 mounting hole allowing for its easy attachment to a multitude of surfaces