University medical open report
University medical open report 1
Opening Report of Graduation Design (Thesis) of Beijing Union University
I. Task and purpose of the project
1. Work
This topic is the design of pulse wave extraction circuit based on single chip microcomputer. In this design, the digital-to-analog converter MAX 1240 chip is used to form an AD conversion circuit, a band-pass filter circuit and an amplifier circuit to collect voltage data, and then the collected pulse signal, that is, the analog voltage value, is converted into a 12-bit digital value and input to the single chip microcomputer. Then, the single-chip processor processes the data into two bytes, the lower byte is the lower 8 bits of the digital voltage value, and the upper 4 bits are the upper 4 bits. After the data is processed, it is sent out through the serial port.
2. The purpose of the project
Learn more about single chip microcomputer, master the circuit composition and design method of signal conditioning part, and the method of designing data signal acquisition circuit by single chip microcomputer.
Second, the survey data
At present, the pulse wave detection system has the following detection methods: photoelectric volume pulse wave method, liquid coupling cavity pulse sensor, piezoresistive pulse sensor and strain pulse sensor. In recent years, photoelectric detection technology has developed rapidly in clinical medical applications, because light energy can avoid strong electromagnetic interference, has high insulation and can detect various symptoms of patients non-invasively. Photoelectric extraction of fingertip pulse light information is the best method at present.
Digital design method of pulse wave detection system: extracting physiological and pathological information from pulse wave as the basis of clinical diagnosis and treatment has always been valued by Chinese and foreign medical circles. Almost all ethnic groups in the world have used it? Feel the pulse? As a means of diagnosing diseases. The comprehensive information of pulse wave in shape (waveform), intensity (amplitude), velocity (wave velocity) and rhythm (period) reflects many physiological and pathological blood flow characteristics of human cardiovascular system to a great extent, so it has high medical value and application prospect for the collection and processing of pulse wave. However, most biological signals of human body belong to low-frequency weak signals under strong noise background, and pulse wave signals belong to low-frequency weak non-electrophysiological signals, which must be amplified and post-filtered to meet the requirements of acquisition.
At present, the fingertip pulse detection system uses analog technology to complete filtering, amplification and integer processing, and then carries out analog-to-digital conversion and further processing. This method not only increases the complexity, power consumption and volume of hardware, but also increases the unreliability and instability of the system. With the rapid development of electronic measurement technology, modern electronic measuring instruments are developing towards digitalization and automation at an extremely fast speed.
On the waveform of pulse wave
Pulse wave is formed by the pulse (vibration) of the heart propagating around along arterial blood vessels and blood flow, so its propagation speed depends on the physical and geometric properties of the propagation medium-elasticity of artery, size of lumen, density and viscosity of blood, etc. Especially the elasticity, caliber and thickness of the arterial wall. It is found that the greater the elasticity of arterial blood vessels (that is, the greater the compliance), the smaller the propagation speed of pulse waves; The smaller the diameter of the artery, the greater the velocity. Therefore, pulse waves usually travel faster and faster along the aorta to the aorta and then to smaller arteries.
The characteristics of the landmark points in the pulse wave periodogram are closely related to their corresponding physiological factors, which has an important influence on the correct extraction of cardiovascular function parameters. As shown in figure 1, the starting point of B single wave (the opening point of the active pulse valve), the main peak of C (the highest aortic pressure), the peak of D pre-stroke (the first inflection point after the pressure drop at point C, caused by the elastic vibration of the aorta impacted by left ventricular ejection), the starting point of E relaxation, the trough of F re-stroke (the marking point when the atrioventricular valve begins to open and the left ventricle begins to fill), and the peak of G re-stroke (. Ps is systolic pressure, Pd is diastolic pressure, Pm 1 is mean systolic pressure, and Pm2 is mean diastolic pressure.
Figure 1 Specific characteristics of pulse wave
Main reference materials
[1]/ link? URL = 7Z9O5JW68XKWE0Nalz1GKDLKrCAFSWGIWKE988 _ YWVECZ-T _ X6NNOTOFY5OUYUOCDBJLWI-SK9GS0OnUEXAAOOYQQQQULGMALHKI (The design scheme of pulse wave extraction circuit based on single chip microcomputer is for others.
[2]/view/9b9e716f1eb9137f115cda.html (pulse wave feature monitoring)
[3] Organizing Committee of the National Electronic Design Competition for College Students. Selected Works of National Electronic Design Competition for College Students (2003). Beijing: beijing institute of technology press, 2003, First Edition.
[4] Zhou Runjing. Design, analysis and manufacture of single chip microcomputer circuit. Beijing: Machinery Industry Press, August 1, 20 1.
[5] Zhang/Huang Qinghua. Development technology and training of single chip microcomputer. Electronic industry press. In 2006, for the first time
[6] Lingyang Technology. Development example of Sunplus 16 single chip microcomputer. Beihang Press.
[7]:SGS- Thomson Microelectronics Application Notes. Application of Stone Bridge Divers [M]
[8]: Nordic VLSI ASA product specifications. Nrf40 1[M], a 433MHz single-chip RF transceiver. February. 2002
[9] Tan Haoqiang. C programming. Beijing: Tsinghua University Publishing House, 200 1.
Third, the preliminary design method and implementation plan
Fig. 2 overall system block diagram
The overall flow is as follows: firstly, the pulse wave is extracted by the HK2000B piezoelectric pulse sensor of the pulse wave signal extraction module, then it enters the pulse signal conditioning module for filtering and amplification, and then the conditioned digital wave is sent to the A/D conversion module, which is converted into an analog waveform by MAX 1240 and transmitted to the single chip microcomputer for processing. Finally, the waveform processed by single chip microcomputer is transmitted to PC through serial communication module.
1. Pulse signal extraction module
At present, the most commonly used pulse diagnosis method in TCM clinic is the method of taking an inch mouth alone, where the artery course is relatively fixed, the anatomical position is shallow and the adjacent tissues are relatively clear, which becomes a favorable position for pulse diagnosis. In this paper, HK2000B piezoelectric pulse sensor is used, which has low precision and high sensitivity, and its output is analog signal.
Attached with its factory technical indicators;
(1) power supply voltage: DC5? 6V；
(2) Pressure range: -50? +300 mmhg；
(3) Sensitivity: 2000? Volt/mmhg;
(4) Temperature coefficient of sensitivity: 0.000 1/? c；
(5) Accuracy:1.5%;
(6) Repeatability: 0.5%;
(7) hysteresis: 0.5%;
(8) Overload: 100 times.
2. Pulse signal conditioning module
(1) filter circuit
The main frequency band range of conventional pulse signal is 0. 1? 40 Hz. In order to prevent the pulse signal from being mixed with all kinds of noise in the interference environment, the passband frequency of 0. 1 is designed in this system. The 40Hz band-pass filter circuit separates the useful components of the pulse signal from the collected signal. In this paper, the band-pass filter will be composed of a 44Hz second-order low-pass filter and a 0. 1Hz second-order high-pass filter.
(2) Amplifier circuit
A transistor and a resistor form a reference multiple of 8? 10 times, the specific magnification can be tested in the simulation.
3. A/D conversion module
MAX 1240 is called analog-to-digital converter; Abbreviation? A/D converter? . Device for converting analog quantity into digital quantity. In the computer control system, it must be controlled by various detection devices, with continuously changing voltage or current as analog, and provide relevant parameters (such as speed, pressure, temperature, etc.). The control object of). The input of the computer must be digital, so an analog-to-digital converter is needed to achieve the purpose of control.
Main parameter
1.2.7V？ 3.6V single power supply.
2. The resolution is 12 bits.
3. The maximum sampling rate is 73K times per second.
4. Low power consumption, 37Mw(73Ksps), 5Uw (standby operation).
5. Sample/hold circuit is provided internally.
6. The conversion clock is provided internally.
Pin 3 (SHDN) is the control terminal, and the value is 0 in standby mode, 1 in normal mode, or it can be suspended. At this time, the internal power supply is invalid, and the reference power supply can be externally connected with 3 pins (Vref).
Figure 3 Schematic diagram of internal pins of Max1240
4. Single chip microcomputer module
This project adopts AT89S52 single chip microcomputer. Because MCS-5 1 series single-chip microcomputer has low cost, good universality and mature market application, AT89S52 has low power consumption and high performance, which is convenient for testing and debugging of various programs and is suitable for this design.
5. Serial communication module
Serial communication can be divided into asynchronous transmission and synchronous transmission. Asynchronous transmission is characterized by discontinuous data transmission on the line, but both parties must agree on the character format and baud rate of transmission in advance. The speed of synchronous transmission is higher than that of asynchronous transmission, but the hardware equipment is more complicated, and the phase consistency of synchronous clock signal is strict.
The following are some consistent concepts and standards of serial communication:
1) transmission rate: that is, baud rate in the range of 1 10? 9600。
2) RS232-C: The level conversion chip MAX3232 is needed for the conversion between EIA level and TTL level.
3)3.0? 5.5V power supply.
4)300? Low supply current.
5) directly add 0. 1? F capacitor.
6. Power pack
Pulse conditioning circuit needs -5, V+5V analog power supply, microcontroller needs 5V digital power supply, A/D converter and MAX3232 need 3.3V digital power supply, and digital power supply needs to be separated from analog power supply.
Four. Expected result
The pulse wave extraction circuit is completed, and the simulation is successful, so the recorded waveform can be tested. Hardware operation will go smoothly, conditions permit, and finally write a graduation design paper.
Verb (short for verb) scheduling
The first, second, third and fourth week: research data.
The fifth, sixth and seventh weeks: analyze and study the found materials.
Weeks 8, 9, 10 and 1 1: Start circuit design and simulation.
Week 12 and 13: debug the circuit and make the final modification.
Fourteenth and fifteenth weeks: writing graduation thesis.
Week 16: Complete graduation design, teacher's comments and graduation defense.
Open report of university medicine II
Graduation is coming. Have you finished your paper? The following is a model essay on the opening report of medicine. I hope you will gain something!
Topic: design of intelligent switch for patients to fall to the ground for help
(A) the background of the topic
With the rapid development of science and technology and the rapid improvement of living standards, people's requirements for health protection are getting higher and higher. When the patient highlights sudden diseases such as heart disease, cerebral hemorrhage, hypoglycemia and epilepsy, the life safety of the patient will largely depend on whether the patient can get effective assistance in the shortest time. This naturally promotes the development of first aid and the popularization of common first aid knowledge. In China, the whole first aid system is still in its infancy, and there are many hidden dangers, which may affect the first aid efficiency of patients after sudden illness. For example, what if a heart patient suddenly falls ill while walking on the roadside? Call? What if there is no public telephone nearby? Help? Once handled improperly by non-professionals, delaying treatment is likely to be self-defeating. Take a taxi to the hospital The data showed that brain cells began to die within 5- 10min after the patient's heartbeat stopped. That is to say, in this case, professional emergency personnel must be present as soon as possible to ensure the safety of patients. Thinking from this angle, I put forward an idea: Can a device be designed to simplify the process of patients falling to a doctor for treatment as soon as possible?
After consulting the relevant information in the Patent Office, we found that there is no design of this kind of product in China at present. A similar creative design is to set two metal contacts in a bottle and then pour some mercury into the bottle. When a person stands, mercury concentrates on a contact and the circuit is broken. When a person falls to the ground, the tilt of the bottle causes mercury to contact two contacts at the same time, the circuit is triggered, and the alarm built in the bottle gives an alarm and sends out a distress signal. This design is obviously rough.
(1) It only decides whether to call the police according to the angle of body inclination, not according to the real physiological condition, so it is bound to have a high false alarm rate.
(2) Only attracting the attention of others in the shortest time does not simplify the whole process, so it will not have a substantial impact on improving the rescue efficiency.
Combining your own ideas with the defects of existing facilities, I hope to make a set? Emergency system after falling to the ground? When the patient falls to the ground, the physiological conditions such as blood pressure and pulse of the patient are sensed by the monitoring device, and numerical analysis is carried out. Once it is determined that the patient is ill, it will send a radio signal to the nearest first-aid station, which will locate the patient's position through gps and dispatch emergency personnel as quickly as possible.
But after more than two months of discussion, there was almost no progress, and I almost came to the point of giving up. However, under the constant encouragement and inspiration of the teacher, one day, inspiration was lucky enough to visit my brain and seek the help of sound and light. Wired and wireless telephone alarm are both mature technologies. The key point is that there is no intelligent switch device to judge whether the patient falls or suddenly falls ill for other reasons.
Once the design can be realized, it will have great practical value and social value. First of all, it gives patients the greatest protection in the most critical link of first aid and greatly reduces the risk of sudden illness; Secondly, it will bring the new concept and new operation mode of the first aid industry, and also promote the popularization and promotion of related products (such as gps); In addition, it will enable many middle-aged and elderly people with sudden illness to face life with a relaxed and optimistic mood and participate in more social activities, resulting in considerable social effects.