HEART BEAT SENSOR

A Heart Beat Sensor is one of the common sensors used to detect the heartbeat per minute. It provides a digital output of the heartbeat when the finger is placed on it. This Heartbeat sensor comes with a bright infrared (IR) LED and a phototransistor to detect the pulse of the finger. The phototransistor in the sensor detects the presence of light, which means, how much light is passing through a finger.  When blood passes through the finger, the number of light changes and that change can be detected as a pulse.

A red onboard LED flashes with each pulse. The LED connected to the light side of the finger, and the phototransistor on the other side of the finger. The phototransistor is used to obtain the flux emitted when the blood pressure is pulse by the finger. As a result, the resistance of the phototransistor will be slightly changing.

R1 is chosen with a high resistance value, because most of the light through the finger is absorbed, so it is desirable phototransistor sensitive enough. The most important matter to take care of is to keep the shield stray light into the phototransistor. In the case of home lighting, it is essential because the lights at home are mostly based on 50HZ or 60HZ fluctuate, so a faint heartbeat will add considerable noise. This Heartbeat sensor can be easily interfaced with any micro-controllers such as Arduino boards and the Raspberry Pi. The module has an M2 mounting hole allowing easy installation of the sensor to a multitude of surfaces.