With the improvement of people's living standards, more and more people hope to understand the basic condition of the body in a simple way. Therefore, human physiological monitors have begun to appear and are on the rise, and have evolved from the past single testers to the current multi-parameter monitors.
In actual life, physiological parameter monitors are mostly based on multi-parameter measurement of PC platform, expensive, bulky, and inconvenient to move. At present, most physiological parameter monitors cannot accurately measure the physiological parameters of human body movement in real time, which causes some people, especially the elderly, to exercise too much, causing greater damage to the body. However, because the coaches can't accurately grasp the changes of physiological parameters during the athlete's exercise, they can't "teaching students according to their aptitudes" and develop training programs in a targeted manner. Therefore, the training methods for athletes are popular training. In summary, it is of great significance to develop a portable physiological parameter monitor based on embedded system with small size and low price.
1 Portable Physiological Parameter Monitor System Solution
This system uses C8051F330 as the single chip of the system. The overall hardware circuit of the system includes power supply circuit, pulse sensor circuit, temperature sensor circuit, counting circuit, sound and light alarm circuit and LED digital tube display circuit, as shown in Figure 1.
The pulse sensor adopts HK-2000A, supplemented by the level pull-up circuit to make the output pulse signal meet the input high and low level requirements of the I/O port of the MCU, and the count is interrupted by the external interrupt of the MCU. The temperature sensor uses the DS18B20 and the sensor is powered by Vcc. The step counter module uses HA35DE, the sensor is powered by Vcc, and the step count is calculated by the external interrupt of the MCU, the distance, calories, etc. are calculated by the formula. The LED digital tube adopts a 4-digit common cathode serial digital tube, and the digital tube driver chip adopts ZLG7289B of Zhou Ligong; the system power supply adopts a single power supply of 3.3 V.
2 Hardware design of portable physiological parameter monitor system
2.1 Pulse and temperature measurement circuit design
The system uses the pressure-type integrated pulse sensor HK-2000 to measure the pulse of the human body, and directly converts the pulse signal into a digital pulse signal output. The hardware circuit is shown in Figure 2(a). The pulse signal output pulse signal has a high level of Vcc=-1.5 V, which is not enough for the MCU to recognize as a logic high level. A voltage-divided voltage boost circuit is used to generate a pulse signal that can be recognized by the MCU.
This system uses DS18B20 digital temperature sensor, the measurement result is 2 Byte digital signal, the measurement resolution is 0.1 °C. The temperature measurement hardware circuit is shown in Figure 2(b). The DS1-8B20 is powered by Vcc=3.3 V, so there is no need to enhance pull-up on the I/O line, allowing other data exchanges on the single-wire bus during conversion.
2.2 Step measurement circuit design
The system uses the non-electricity electrical measurement method to realize the number of detection steps. When the person walks, the foot, the leg, the waist and the arm will generate corresponding acceleration. The detection of the number of steps is most accurate by the acceleration of the foot. This design requires easy carrying, so the waist movement is selected to detect the number of steps. The human body motion is shown in Figure 3. During the walking process, the acceleration of each step is selected by the vertical motion of the upper and lower waist, and the number of steps is obtained by detecting the peak value of the acceleration.
The system uses 3D accelerometer as the core to sense human motion, and uses HA35DE step counter module to measure the number of human motion steps. The circuit of step counting measurement is shown in Figure 4. The HA35DE is powered by Vcc=3.3 V, and the 2-pin step signal output is a single-step pulse signal, which is connected to the external interrupt port of the MCU.
3 portable physiological parameter monitor system software design
3.1 Overall software structure
The system uses C8051F020 single-chip microcomputer for processing and analysis, sets the corresponding physiological parameter threshold value and displays the collected signal in real time, and can also alarm the over-standard signal. The overall software flow chart of the system is shown in Figure 5.
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