0 Preface
Since 2013, smart watches, bracelets, and glasses have gradually entered the public's field of vision, becoming the object of "influx", and this year was recognized by the industry as "the first year of wearable devices." In simple terms, a wearable device is a portable device that can be worn directly on the body or integrated into the user's clothing or accessories. However, with the development of wireless sensor technology. A wide variety of wearable smart clothing is also gradually appearing in people's lives. Smart clothing is to embed small chips, electronic components, power supplies and other equipment into the clothing, which can realize specific functions, which is convenient for people. life. The ZigBee wireless module heart rate acquisition and monitoring module designed in this paper uses the most advanced photoelectric reflection sensor on the market. It is different from the conventional piezoelectric and film-type sensors and has high sensitivity. At the same time, this article specifically designed the pockets of clothing. By placing the pulse sensor, it is more convenient to collect and monitor the pulse of the human body in real time.
1 Photoelectric reflection sensor works
Pulsesensor is a photoelectric reflective analog sensor for pulse heart rate measurement. The signal is collected by the principle of the photoelectric volume method, and is worn on a finger or an earlobe, and the pulse is measured by utilizing the difference in light transmittance caused by the human tissue during the pulsation of the blood vessel. Since the pulse is a signal that periodically changes with the pulsation of the heart, the volume of the arterial vessel also periodically changes, so the period of the electrical signal change of the photoelectric transducer is the pulse frequency.
1.1 system function module division
The functional modules of the overall system of this paper are divided as shown in Figure 1. Including ZigBee wireless data acquisition module, micro processing module, wireless data transceiver ZigBee wireless module, liquid crystal display module and serial communication module.
Figure l system function module diagram
1.2 shaping circuit design
The shaping circuit of the system uses a four-voltage comparator LM339 and a plurality of resistors and capacitors to form a single-limit voltage comparison circuit. Figure 2 shows the circuit schematic of the shaping part. Since the pulse signal is shaped into a square wave signal with an amplitude of 2-3 V, it is appropriate to set the threshold voltage to 2.5 V. The whole circuit is +5. V DC voltage source power supply, after experimental determination. The best value for Ruler 2 is 10 kn. The shaping circuit can conveniently realize the statistics of the pulse number and provide conditions for the monitoring of the upper computer.
Figure 2 Schematic diagram of the shaping circuit
2 heart rate signal processing module design
In order to get the correct pulse rate, you can use the means of setting the interrupt to achieve the function. Set the I/O port P1.3 as an external interrupt port. The falling edge of the input signal can trigger an external interrupt to make the system enter the external interrupt service subroutine. Each time the service subroutine pulse counter is incremented by 1, the timer 1 timer user Custom time period. Once the timing is reached, the value in the counter is read, and after reading, the registers are cleared for the next count. FIG. 3 is a flow chart of a ZigBee wireless module of a pulse acquisition module of the system, and FIG. 4 is a flow chart of a heart rate ZigBee wireless data acquisition process.
Figure 3 Pulse acquisition module flow chart 4 heart rate acquisition flow chart
3 heart rate acquisition monitoring interface design
When the sensor collects the pulse value, the collected data is uploaded to the remote terminal through the ZigBee wireless module, and the heart rate of the tested person is displayed in real time, and the real-time line graph is drawn by programming to track and monitor the trend of heart rate change. When an abnormality occurs, an alarm will be triggered to facilitate rescue and minimize the risk. Figure 5 shows the monitoring curve of a tester when the heart rate is normal (basically stable at 84 times/min), and Figure 6 shows the alarm when another tester's heart rate is abnormal (such as 50 times/min), and the green light turns red and simultaneously sounds. Flute.
Figure 5 Monitor interface when the tester's heart rate is normal
Figure 6 Monitoring interface when there is a problem with heart rate
4 heart rate acquisition device test results on smart clothing
In this paper, the ZigBee wireless module and power module of the pulse acquisition device are packaged. At the same time, a special pocket is designed to fix and place the ZigBee wireless data acquisition module. Special holes are designed at the bottom of the pocket. It can be routed to expose the photoelectric sensor, as shown in Figure 7. In order to ensure the accuracy of the measured heart rate, the sensor is black shading treatment, which can be placed on the finger. As shown in Figure 8. Easy to measure.
Figure 7 Heart rate acquisition device on smart clothing Figure 8 Heart rate sensor shading collection
5 Conclusion
Wearable technology faces both opportunities and severe challenges. This paper designs a wearable pulse heart rate acquisition and monitoring device based on ZigBee wireless module using wireless sensor network technology. This device can not only realize real-time ZigBee wireless data acquisition of pulse. It can also be monitored in real time through a remote terminal. The era of big data and the intelligent and technological products of information technology will change people's lifestyles in the future. The wearable pulse monitoring system designed in this paper is another emerging product of the combination of clothing field and electronic communication field. Development has very important research significance and practical value.
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