KY-039 Heartbeat Sensor Module

The KY-039 heartbeat sensor is designed to detect a pulse while a human finger is place between the infrared diode and the photo transistor.  The pulse will be represented on the signal output pin.

This sensor works by using a photo transistor to detect the presence of light, in this case how much light is passing through a finger.  When blood moves, the amount of light changes and that change can be detected as a pulse.