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溫度控制系統(tǒng)的設(shè)計外文翻譯中文-其他專業(yè)-文庫吧資料

2025-01-27 03:43本頁面
  

【正文】 t is more popular. Therefore the external power supply is used and the second pin is connected to the pin of the AT89S51. Actually, if there are multipoint to be detected, the DS18B20(s) can be connected to the 1Wire bus. But when the number is over 8, there is a concern to the driving and the more plex software design as well as the length of the 1Wire bus. Normally it is no more than 50m. To achieve distant control, the system can be designed in to a wireless one to break the length limit of the 1Wire bus [6]. C. LCD Circuit The LCD 12232F is used, which can be used to show characters, temperature value and time, and supply a friendly display interface. The 12232F is a LCD with 8192 12832 pixels Chinese character database and 128 168 pixels ASCII character set graphics. It mainly consists of row drive/column drive and 12832 full lattice LCD with the function of displaying graphics as well as 2 Chinese characters. It is in a parallel or serial mode to connect to external CPU [7]. In order to economize the hardware resource, the 12232F should be connected to the AT89S51 in serial mode with only 4 output ports used. The LCD grayscale can be changed by adjusting the variable resistor connected the pin Vlcd of the LCD. CLK is used to transmit serial munication clock. SID is used to transmit serial data. CS is used to enable control the LCD. L+ is used to control the LCD backlight power. D. Clock Circuit The Dallas DS1302 is used, which is a high performance, lowpower and realtime clock chip with RAM. The DS1302 serves in the system with calendar clock and is used to monitor the time. The time data is read and processed by the AT89S51 and then displayed by the LCD. Also the time can be adjusted by the keyboard. The DS1302 crystal oscillator is set at 32768Hz, and the remended pensation capacitance is 6pF. The oscillator frequency is lower, so it might be possible not to connect the capacitor, and this would not make a big difference to the time precision. The backup power supply can be connected to a rechargeable battery. E. Keyboard Control Circuit The keyboard interface in the system is driven by the HD7279A which has a +5V single power supply and which is connected to the keyboard and display without using any activedevice. According to the basic requirements and functions of the system, only 6 buttons are needed. The system39。s life to improve the quality of the work and life. It is also versatile, so that it can be convenient to extend the use of the system. So the design is of profound importance. The general design, hardware design and software design of the system are covered. II. SYSTEM GENERAL DESIGN The hardware block diagram of the TC is shown in Fig. 1. The system hardware includes the microcontroller, temperature detection circuit, keyboard control circuit, clock circuit, Display, alarm, drive circuit and external RAM. Based on the AT89S51, the DS18B20 will transfer the temperature signal detected to digital signal. And the signal is sent to the microcontroller for processing. At last the temperature value is showed on the LCD 12232F. These steps are used to achieve the temperature detection. Using the keyboard interface chip HD7279 to set the temperature value, using the microcontroller to keep a certain temp
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