Specific realization function
This system is composed of STC89C51/52 single-chip microcomputer + LCD1602 display module + 5mm infrared receiver tube + LM358 operational amplifier circuit + button module and so on.
Specific functions:
(1) Put your finger in the infrared pair tube and read the heart rate within 2 seconds;
(2) LCD1602 LCD displays the current heart rate (heart rate/min);
(3) Press the button to set the upper and lower limit heart rate of the alarm. When the measured heart rate exceeds the alarm value, an alarm will be issued.
design background
With the development of science and technology, pulse measurement technology has become more and more advanced, and the accuracy of pulse measurement has become higher and higher. Different types of pulse measurement instruments have been developed at home and abroad, and the key is the research on pulse sensors. At first, the pulse test used for sports measurement focused on the research of contact sensors. Measuring instruments such as finger pulse and ear pulse developed by such sensors have their own advantages and disadvantages. Finger pulse measurement is more convenient and simple, but because there are many sweat glands on the finger, the finger clip is used all the year round, and pollution may reduce the measurement sensitivity: ear pulse measurement is relatively clean, the sensor uses less environmental pollution, and is easy to maintain. However, because the ear pulse is weak, especially when the season changes, the measured signal is significantly affected by the ambient temperature, resulting in inaccurate measurement results. In the past, the daily monitoring instruments that appeared in hospital clinical monitoring and daily middle-aged and elderly health care, such as portable electronic sphygmomanometers, can complete pulse measurement, but this portable electronic sphygmomanometer uses a miniature air pump to pressurize a rubber air bag, and each measurement requires one The process of pressurization and decompression has disadvantages such as large volume, discomfort during the process of pressurization and decompression, and low accuracy of pulse detection.
In recent years, domestic and foreign efforts have been devoted to the development of non-invasive and non-contact sensors. The important feature of this type of sensor is that the detection part of the measurement does not invade the body, does not cause body trauma, can automatically eliminate the error of the instrument's own system, and has high measurement accuracy, usually outside the body. , Especially the indirect measurement of the body's physiological and biochemical parameters on the body surface.
Among them, the photoelectric pulse sensor is a pulse sensor made according to the photovolume method, which indirectly detects the pulse signal by monitoring the light transmittance of the end of the finger. It has the advantages of simple structure, no damage, high precision, and reusability. The pulse measuring instrument developed by the photoelectric pulse sensor has been applied to various aspects of clinical medicine and has received ideal results.
hardware design
The overall design of the system consists of STC89C52, buttons, LCD1602, photoelectric sensor, clock module, operational amplifier, etc. The system has four buttons, which can set the upper and lower pulse rate. When the range is exceeded, the single-chip microcomputer will drive the buzzer to sound and the pulse When measuring, people need to gently press their hands on the photoelectric sensor. When the pulse of the human body is beating, the light transmittance of the blood will cause the signal strength of the receiver to be different, which indirectly transmits the human pulse signal. Then, it is amplified and reshaped by the op amp, and then connected to the IO port of the single-chip microcomputer. The single-chip uses an external interrupt to count it, and finally converts the number of pulses of an adult in one minute, and finally displays it on the LCD screen.
software design
After the single-chip microcomputer is powered on, it is initialized to clear the initial values of some parameters, and then wait for the user to press the corresponding button and enter the corresponding function. When the user presses the measurement button, the single-chip microcomputer measures the pulse number of the human body through a timed 15s, and then The corresponding real pulse frequency is converted and displayed on the LCD screen. When the user presses the set pulse range setting button, the single-chip microcomputer increases or decreases the range according to the button pressed by the user.
Schematic diagram
The system schematic design adopts Altium Designer19, as shown in the figure.
program
This design uses KEIL5 software to realize the program design, as shown in the figure.
Simulation implementation
This design uses protues8.7 software to realize the simulation design, as shown in the figure.
All information
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