Reflective infrared heart rate detector circuit diagram

Single chip microcomputer STM32L151CCU6

0805 red light, 0805 red, luminous tube, LED lamp bead, patch led

1206 red anti-stick

A design scheme of a reflective infrared heart rate detector based on uPSD3234. The program uses the single-chip uPSD3234 as the core component of the system, and uses the digital signal processing method such as matching filtering to obtain the heart rate data. The microelectronic technology and the biomedical engineering technology are closely combined to meet the requirements of the scheme design and realize the heart rate of the human body. measuring. The pulse wave originates from the heart beat and travels from the heart to the peripheral artery. Its comprehensive information on morphology, intensity, rate and rhythm largely reflects the blood characteristics of many physiological and pathological processes in the human cardiovascular system. Heart rate is an important physiological indicator. It refers to the number of heart beats per unit time and is a physiological indicator for clinical routine diagnosis. In order to measure the heart rate signal, there are many techniques that can be applied, such as blood measurement, heart sound measurement, ECG measurement, and the like. In this paper, we use the high opacity of blood and the great difference between tissue and blood translucency. The pulse signal is obtained by photoelectric pulse sensor. After analog-to-digital conversion (A/D), the sampled data is digitally analyzed and processed to achieve Measurement of the human heart rate.
Heart rate signal acquisition preprocessing circuit Pulse signal acquisition preprocessing circuit is mainly to convert pulse wave into electrical signal and perform preliminary high frequency filtering preprocessing. The key part is the photoelectric pulse sensor. Photoelectric pulse sensors can be divided into transmissive and reflective according to the way of receiving light. Reflective not only can accurately measure the change of blood vessel volume, but in practical applications, the reflection only needs to touch the sensor to any part of the body. When the blood flow of the irradiated part changes with the heartbeat, the infrared receiving probe receives the heart. The arterial pulse pulse signal is periodically contracted and dilated, thereby acquiring a heart beat signal.

This design uses a reflective infrared sensor. The photoelectric pulse sensor uses infrared pair tubes KP-2012F3C and KP-2012P3C, which are arranged in reflection. KP-2012F3C has good skin illumination, the current is generally set at 20mA, and the brightness is controlled by software through PWM current, which enables the infrared LED to work in a saturated region and emit light with stable light intensity. The KP-2012P3C transistor uses an AC-coupled structure to enhance amplification of weak signals. The signal detected by the transistor is divided into two paths when sampling. All the way is the DC signal line. It is the transistor output and the A/D conversion channel port 0 of the input MCU, which can be used to detect whether the transistor is in the active working state; the other is the AC signal line. It is input to the two-stage filter shaping circuit via an emitter follower and then input to the A/D conversion channel 1 of the microcontroller. The filter circuit is a two-stage band-pass filter circuit. Since the spectrum of the pulse wave contains rich pathological information, especially in the interval of 5 to 40 Hz, the spectrum carries a large amount of information related to coronary heart disease, so considering the expansion of functions in the future, The upper and lower limits of the pre-processing circuit are designed to be 48 Hz and 0.86 Hz.
The main infrared device of the reflective infrared heart rate detector designed by this scheme is the core component of the system. The digital signal processing method such as matched filtering is used to obtain the heart rate data, and the microelectronic technology and biomedical engineering technology are closely combined to achieve the solution. Design requirements. Moreover, the program has been successfully applied to treadmills for fitness products, which has certain innovation and practical application value, and has good marketing value.