This article presents a design approach for a reflective infrared heart rate sensor based on the uPSD3234 microcontroller. The system uses the uPSD3234 as its central component and applies digital signal processing techniques such as matched filtering to extract heart rate data. By integrating microelectronic and biomedical engineering technologies, this design meets the requirements of the system and successfully measures human heart rate.
The pulse wave originates from the heartbeat and travels through the arteries. It contains valuable information about the morphology, intensity, rate, and rhythm of blood flow, which reflects various physiological and pathological conditions in the cardiovascular system. Heart rate, defined as the number of heartbeats per unit time, is a crucial clinical indicator used for diagnosis.
To measure heart rate, several techniques can be employed, including blood pressure measurement, heart sound analysis, and ECG. In this design, we use the high opacity of blood and the difference in translucency between tissue and blood. A photoelectric pulse sensor captures the pulse signal, which is then converted into an electrical signal via analog-to-digital conversion (ADC) and processed digitally to determine the heart rate.
The pulse signal acquisition preprocessing circuit converts the pulse wave into an electrical signal and performs initial high-frequency filtering. The key component here is the photoelectric pulse sensor, which can be either transmissive or reflective. Reflective sensors are more practical as they only need contact with any part of the body. When the blood flow changes with each heartbeat, the infrared receiver detects the pulsating signal, allowing the system to capture the heart beat.
This design uses a reflective infrared sensor composed of KP-2012F3C and KP-2012P3C infrared pair tubes. The KP-2012F3C provides good skin illumination, and the current is typically set at 20mA, controlled by PWM through software to ensure stable light output. The KP-2012P3C transistor uses an AC-coupled structure to amplify weak signals effectively. The detected signal is split into two paths: one for DC monitoring and the other for AC signal processing through a two-stage filter circuit before being sent to the microcontroller’s ADC channel.
The band-pass filter is designed to cover a wide frequency range (0.86 Hz to 48 Hz), capturing rich pathological information related to coronary diseases. This design has been successfully implemented in fitness equipment like treadmills, demonstrating innovation and practical value in the market. Hydrogen Fuel Cell Energy Storage Inductor Hydrogen Fuel Cell Energy Storage Inductor,High Current Toroidal Power Inductor,High Current Power Toroidal Inductor,High Voltage Energy Storage Capacitor Huizhou Show-Grand Electronics Co., Ltd. , https://www.sgtransformer.com