Autobotix KY-039 Finger Detection Heartbeat Measuring Sensor Module

The KY-039 Finger Detection Heartbeat Measuring Sensor Module utilizes a bright infrared (IR) LED and a phototransistor to detect the pulse of the finger, indicated by a flashing red LED with each heartbeat.

The IR LED emits light on one side of the finger, while the phototransistor detects the light flux on the opposite side. When the finger experiences a blood pressure pulse, the resistance of the phototransistor undergoes slight changes.

To ensure sensitivity, a high resistance resistor (R1) is selected, as most of the light passing through the finger is absorbed. The resistance value can be adjusted through experimentation to optimize sensor performance. Shielding against stray light is crucial to prevent interference.

In home environments, this shielding is particularly important due to fluctuations in household lighting, typically at 50Hz or 60Hz. Without proper shielding, faint heartbeat signals may be obscured by significant noise.