This paper presents a design for a reflective infrared heart rate detector based on the uPSD3234 microcontroller. The system is centered around this single-chip processor and employs digital signal processing techniques like matched filtering to extract accurate heart rate data. By integrating microelectronic and biomedical engineering principles, the design effectively meets the requirements of heart rate measurement, offering a reliable and efficient solution for real-time health monitoring.
The pulse wave, which originates from the heartbeat and travels through the arteries, contains valuable information about the cardiovascular system, including morphology, intensity, rhythm, and frequency. Heart rate, as a key physiological parameter, is widely used in clinical settings for diagnosing various conditions. To measure this, several methods exist, such as blood pressure monitoring, heart sound analysis, and ECG. In this design, a photoelectric pulse sensor is used, taking advantage of the high opacity of blood and the difference in light transmission between tissue and blood.
The pulse signal is captured using a reflective infrared sensor, which only needs to make contact with the skin. As the heart beats, the blood flow changes, causing variations in the reflected infrared light. This change is detected by the sensor and converted into an electrical signal. The signal then undergoes analog-to-digital conversion (A/D) and is processed digitally to determine the heart rate.
The core components of the sensor are the infrared LEDs KP-2012F3C and the phototransistor KP-2012P3C, arranged in a reflective configuration. The LED is driven at a current of 20mA, controlled via PWM to ensure stable light output. The phototransistor uses an AC-coupled structure to amplify weak signals. The detected signal is split into two paths: one for DC signal detection and another for AC signal processing. The AC signal passes through a two-stage band-pass filter, designed to capture frequencies between 0.86 Hz and 48 Hz—frequencies that contain critical information about cardiovascular health.
This design has been successfully implemented in fitness equipment such as treadmills, proving its practical value and innovation. It offers a cost-effective and user-friendly method for measuring heart rate, making it suitable for both consumer and medical applications. With further enhancements, it could be expanded to support more advanced health monitoring features in the future. Iutput Com-M Inductor,Custom Potting Solenoid Valves,Ferrite Core Inductor,Differential Mode Chokes Huizhou Show-Grand Electronics Co., Ltd. , https://www.sgtransformer.com