For this module, I designed, built, programmed, and tested a microcontroller-based photoelectric heart rate monitor. This type of heart rate monitors are attached to a patients’ finger to measure their heart rate in beats-per-minute (BPM). The device I built is based on a non-invasive photo transmitter/receiver pair sensor which detects small variations of blood flow in the fingers due to the heart pumping action. After filtering and amplifying such variations, a microcontroller useable signal can be generated. By measuring the period or frequency of such signal, the heart rate of the person using the sensor can be determined