In combination with an ultra-bright infrared light emitting diode and a phototransistor, this module detects the heartbeat by changing the resistance. As a result, an integrated red LED lights up at the rate of the heartbeat/pulse. Note Due to the frequency of indoor lighting (50 Hz/60 Hz), stray light needs to be avoided to obtain better results. https://elecena.pl/product/19541621/se049-developer-boards-finger-heartbeat-detection-sensor 2021-09-28 https://elecena.pl/product/19541621/se049-developer-boards-finger-heartbeat-detection-sensor 2022-11-07 https://elecena.pl/product/19541621/se049-developer-boards-finger-heartbeat-detection-sensor 2023-04-23 https://elecena.pl/product/19541621/se049-developer-boards-finger-heartbeat-detection-sensor 2023-10-01