Detect the heartbeat module KY-039

product description

This project uses bright infrared (IR) LED and phototransistor to detect the pulse of the finger, each pulse red LED flashes.
The working principle of the pulse display is as follows: LED is the light side of the finger, while the other side of the finger has a phototransistor, the phototransistor is used to obtain the emitted luminous flux. When the finger blood pressure pulsates, the resistance of the phototransistor will slightly change.
We chose a high-resistance resistor R1, because most of the fingers light is absorbed, so the phototransistor sensitivity enough. The resistance can be chosen experimentally to get the best result.
The most important thing is to shield the stray light in the phototransistor. For home lighting is particularly important, because most of the lighting at home is 50HZ or 60HZ fluctuations, so a weak heart will increase the considerable noise.