2016 International Conference on Advanced Manufacture Technology and Industrial Application (AMTIA 2016) ISBN: 978-1-60595-387-8 Design of Soybean Milk Machine Control System based on STC89C52 Ya-gang SUN, Yue ZHANG, Zhi-gang YANG, Rui-cheng ZHANG and Xiao-wei SHEN College of Electrical Engineering, North China University of Science and Technology, China Keywords: STC89C52 single ship, Soybean milk machine, Hardware design, Software design. Abstract. Aiming at making soybean milk machine efficiently, hardware circuit and software are designed. The design of soybean milk machine is based on STC89C52 single chip, using AD sampling to detect the water level, and temperature sensor to detect temperature. Hardware system consist six main modules: temperature detection module, water level detection module, LCD module, key module, heating and polishing module and alarming module. The paper presents electrical schematic and diagrams of printed circuit board. The design is practical. The product has great market potentials. Introduction Soybean milk is a good liquid nutrition for both the young and the old, which contains iron element as6 times as milk, so it is called the milk of the plants. People can make soybean into hot and delicious soybean milk. With the improvement of people's health, it is a big trend that people love to buy soybean milk machine to make it all by themselves to avoid buying soybean milk from unidentified source, so the machine has a huge market [1]. Due to on the complexity of soybean milk machine, a lot of problems existed in soybean milk machine haven t been solved efficiently. These problems not only affect the customers to use, but also limit the development of soybean milk machine [2]. This paper introduces a soybean milk machine control system design based on single chip microcomputer. When the system starts, it first initializes settings for working MCU module. When the MCU module initialization setting is completed, it begins to measure the temperature and water level, and then displays the information on the screen. User can then choose the working module, i.e., automatic mode, manual heating mode, manual crushing mode and stop mode. After that, the system will work according to the selected mode. System Structure This system adopts STC89C52 single-chip microcomputer as the core controller, because its price is relatively cheap and its function can also satisfy the design requirement. It uses LCD1602 as display, and use 18B20 sensor to measure temperature. It gets the current water level voltage by water level detection probe, then it can detect the state of high and low water level through ADC0832 AD sampling chip. After choosing a working mode, system will work according to the chosen mode. In automatic mode, the MCU will sample temperature and water level to make a decision to switch the state of alarming, crushing and heating. The system structure block diagram is shown as Figure 1 [3]. System Functions The main functions of the system are as follows. (1) Power on the whole system, which starts initializing of each modules (2) Measure the water level and current temperature, and display the information on the screen. If the current water level is not within the range of preset value, the system will alarm, pause the chosen working mode and display the water level abnormal situation on the screen. (3) Start regulate work mode, each key corresponds to the different work modes including automatic mode, manual heating mode, manual crushing mode and stop mode. After setting the work mode through the keys, the system will display the current work mode information on the screen, and
it will work according to the chosen work mode. (4) In the course of work, the system will detect the current state of water level and temperature. When the water level anomalies, the system will sound the alarm, and the system will be at stop mode. Water level detection prode Serial port downloader Control single Crushing and heating mode Download programs Analog voltage Main control system STC 89C52 Alarm single Sound and light alarm system Measure temperature Water level detection prode Digital voltage Temperature sensor Various paramenters LCD 1602 display Figure 1. System structure block diagram. Hardware Design Water Level Detection Module Circuit Design This module needs to detect upper and lower water levels in order to sound the alarm when the level is not within the preset range. The system only needs to sound the alarm when the water level is below or above set water level. So water level detection module only need to detect highest and lowest water level. Therefore, two water level probes are installed to detect the highest and lowest water level in this module circuit design. When the liquid surface contact the probe, the voltage of the probe will appear as different value that it is not contacted with water. The analog voltage of the probe can be converted to digital voltage by the modulus conversion chip ADC0832. The digital voltage will be sent to single chip microcomputer. With voltage information, water level can be determined by microcomputer, which completes the task of water level detection [4]. Temperature Detection Module Circuit Design This module needs to detect the temperature of the soybean milk, which is displayed on the screen later on. Temperature detection module can measure the current temperature of the soybean milk. After the MCU get the current temperature value of the soybean milk, it can display it on the screen. Then users can see the current temperature of the soybean milk and make the decision to stop the system or not. Temperature detection function of soybean milk machine control system is so important that we put its circuit design at an important position.ds18b20 chip is used as the temperature sensor of this system. The chip is single wire interface and needs only a line between MCU to communicate. The temperature range is -55 ~+125, which can satisfy the demand of the temperature detection. Its hardware structure is relatively simple and can reduce the space of hardware circuit. Heating and Pulping Module Circuit Design Crushing and heating modules are needed to crush and heat soybean milk. Dry mold heat pipes are used to simulate the heating process, the 12V power supply fan is used to simulate the pulping process. The two modules need 12V voltage and large current, so its power supply need to be separated. This two modules need 12V DC power supply, so 12V 2A power supply is selected as the power supply module. In this design, heating and crushing modules are controlled by microcomputer, relay control is used to realize the function of weak current controlling high voltage.
A Serial Port Communication Module Circuit Design After completing the design of hardware, Software should be designed, implemented, and downloaded to the MCU in the process of software debugging. Therefore, a serial port communication module is needed in the design of whole circuit. This design uses STC microcomputer downloader to download the software by using the principle of asynchronous communication. The RXD port of downloader (data receiver) is connected to P3.1 foot of MCU (MCU RXD port, data sender), the TXD port of downloader is connected to RXD foot of MCU. After completion of the hardware connection, software program can be burned to the MCU. Software Design The system software mainly contain six parts. There are temperature measurement module; water level measurement module; the key module; display module; crushing and heating module; alarm module. The system software flow control diagram is shown as Figure 2 [5-7]. Start LCD Initialization Information Display Motor Initialization Buzzer Initialization Get Temperature Level Information Choose Work Mode Automatic Mode Heat 15S Crush 15S, Continue 60S Stop Manual Mode Crush 15S or Heat 60S Stop Figure 2. Technologic diagram of system. Electrical Schematic Diagram Before design PCB circuit, schematic diagram should be designed first and each module circuit need be to electricallyconnected. The PCB design software is Altium Designer 10, which specilize inhardware design and is the mainstream hardware design software. It can meet the needs of most hardware design cases. Its operation is simple that it s very suitable as hardware circuit design software. The soybean milk machine electrical schematic diagram is shown as Figure 3. Printed Circuit Board After generating PCB diagram according to the schematic diagram, the following should be paid attention to finishing the electrical connection. (1) In the generated PCB diagram, put all components at the suitable position for the convenience of electrical connection. (2) The whole circuit board should avoid external disturbance. The best design method is that the power and ground circuit line should be more coarse than the signal lines. (3) The digital and analog circuits of the signal shouldinterfere with each other easily. So it s best to separate to place them. This is especially important in the large scale integrated circuit design. (4) In order to ensure integrity of the ground electrode so as to enhance its ability to withstand high current. It would be better to set the vacant position of the circuit board as ground electrode. (5) While designing the circuit, the binding pads should have the largest contact surface with the copper clad surface. And it will reduce the probability of virtual welding. (6) Circuit lines should be set at a reasonable density so that it can not only reduce
the size of the circuit board but also improve the performance. The soybean milk machine PCB board is shown as Figure 4. Test Results After finishing hardware circuit design, software design is then started. Each modules is designed individually according to modular programming described above. After debugging good modules of software, combine all the codes under a project. The soybean milk machine test results are shown as Figure 5. Figure 3. Soybean Milk Machine Electrical Schematic Diagram. Figure 4. Soybean milk machine PCB board.
Figure 5. Soybean milk machine test results. Summary This paper present the design of a soybean milk machine which is based on STC89C52 single chip. It can heat and polish the soybean milk automatically. The design study can solve some problems existed in conventional soybean milk machine, it s conducive to the market promotion of soybean milk machine and help people to drink delicious soybean milk. The subject research will bring about huge market demand and satisfy people s demand, so it s very meaningful to further research. Acknowledgements This work was financially supported by the Key Project of Sichuan Provincial Department of Education (13ZB0200), Tangshan Technology R & D Program (15110202a), Doctoral Scientific Research Foundation of North China University of Science and Technology, Research and Practice of Teaching Reform in Education of North China University of Science and Technology (QZ-1536-09), Hebei Provincial Natural Science Foundation (F2014209192) and Educational Commission of Hebei Province of China (ZD20131011) References [1] Hao Liu. Research and Practice of the automatic soymilk machine s improved design [D]. Wuhan University of Technology, 2011. [2] Wen-li Lei, Xin-Cheng Ren, Xin-Liang Cao. Full-Automatic Soymilk Machine Control System based on Z86E02 [J]. Journal of Yanan University (Natural Science Edition), 2015, Vol.34 (2):80-81. [3] Cheng-Zhong Hu, Jian Zhao, Dong-Sheng Zhang. The Design of Beanstalk Timing System Based on MCU [J]. Electronics Technology, 2013 (1): 21-23. [4] Xiang-feng Zhang, Qiang-Jun Zhang, Hong-Tao Ren. Development of Intelligent Soymilk Machine Control System [J]. Journal of Luoyang Institute of Technology, 2001, Vol. 22(4): 77-79. [5] Feng-guo Jiang, Peng Liu. Full-Automatic Soymilk Machine Control System based on AT89C52[J]. Journal of Yantai University (Natural Science and Engineering Edition), 2014, Vol.27 (1):75-78. [6] Sheng Liu, Jing-Li Yang. Full-Automatic Soymilk Machine Control System based on PIC16C54 [J]. Electronic Engineer, 2004, Vol.30 (7):77-79. [7] Fen Liu. Design of a Soymilk Grinder Based on SH69P42 Microcontroller [J]. Electronic Sci. & Tech., 2010, Vol.24(5): 62-64.