In order to deal with the shortcomings of a photoelectric mode cardiotachometer, such as wasting energy and slowly refreshing results, this study mainly focuses on a real-time displayed, portable, low-cost, and energy-saving cardiotachometer. The design is based on the Mbed, which is the core microprocessor, controlled and dispatched by the built-in function. Before filtering and amplifying the electronic signal, the pulse signal is collected by the photoelectronic sensor at the beginning of

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... whole process of the cardiotachometer. The energy-saving function can be achieved through audio p-type metal oxide semiconductor to switch on and off the light-emitting diode (LED) which is in the sensor. Eventually, the real-time ratio of the heartbeats and the waveforms can be displayed on the two 8 × 8 LED modules at the same time with overall energy-saving of about 50%. This design can be applied in many fields focusing on long battery life and portable, especially as a part of a wearable device.