KY-039 Finger Detection Heartbeat Module

The project uses bright infrared (IR) LEDs and a phototransistor to detect finger pulses,
each with a red LED flashing.

The working principle of the pulse monitor is as follows: LED is the light side of the finger, and the
phototransistor is on the other side of the finger. When the resistance of the phototransistor changes slightly,
the phototransistor is used to obtain the flux emitted when the blood pressure pulse passes through the finger.

We chose a resistor R1 with a very high resistance value, because most of the light is absorbed through the
fingers. We hope that the phototransistor is sensitive enough. Resistance can be selected experimentally for
best results.

The most important thing is to keep the shielding stray light in the phototransistor. It is particularly important
for home lighting, because most of the lights in the home fluctuate on the basis of 50HZ or 60HZ, so a weak
heartbeat will increase the obvious noise.