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1、温度控制系统的设计摘要：研究了基于AT89S 51单片机温度控制系统的原理和功能，温度测量单元由单总线数字温度传感器DS18B 20构成。该系统可进行温度设定，时间显示和保存监测数据。如果温度超过任意设置的上限和下限值，系统将报警并可以和自动控制的实现，从而达到温度监测智能一定范围内。基于系统的原理，很容易使其他各种非线性控制系统，只要软件设计合理的改变。该系统已被证明是准确的，可靠和满意通过现场实践。关键词：单片机；温度；温度I. 导言 温度是在人类生活中非常重要的参数。在现代社会中，温度控制（TC）不仅用于工业生产，还广泛应用于其它领域。随着生活质量的提高，我们可以发现在酒店，工厂和家庭，
2、以及比赛设备。而比赛的趋势将更好地服务于整个社会，因此它具有十分重要的意义测量和控制温度。 在AT89S51单片机和温度传感器DS18B20的基础上，系统环境温度智能控制。温度可设定在一定范围内动任意。该系统可以显示在液晶显示屏的时间，并保存监测数据，并自动地控制温度，当环境温度超过上限和下限的值。这样做是为了保持温度不变。该系统具有很高的抗干扰能力，控制精度高，灵活的设计，它也非常适合这个恶劣的环境。它主要应用于人们的生活，改善工作和生活质量。这也是通用的，因此它可以方便地扩大使用该系统。因此，设计具有深刻的重要性。一般的设计，硬件设计和软件系统的设计都包括在内。II. 系统总体设计 该系统
3、硬件包括微控制器，温度检测电路，键盘控制电路，时钟电路，显示，报警，驱动电路和外部RAM。基于AT89S51单片机，DS18B20的将温度信号传送到数字信号的检测。和信号发送到微控制器进行处理。最后，温度值显示在液晶12232F。这些步骤是用来实现温度检测。使用键盘接口芯片HD7279在设定温度值，使用微控制器保持一定的温度，并使用液晶显示的温度控制设定值。此外，时钟芯片DS1302用于显示时间和外部RAM6264是用来保存监测数据。报警将给予及时蜂鸣器如果温度超过了上限和下限温度值。III. 硬件设计A. 微控制器 在AT89S51单片机是一种低功耗，高性能CMOS 8位4K的系统内可编程闪
4、存字节微控制器。该设备是采用Atmel的高密度非易失性内存技术，并与业界标准的80C51指令集和引脚兼容。片上闪存程序存储器可以编程就可以在系统或由传统的非易失性存储器编程。通过结合在系统灵活的8位CPU集成在一个芯片可编程闪存，Atmel的单片机AT89S51是一个功能强大的微控制器提供了一个高度灵活的和具有成本效益的解决方案很多嵌入式控制应用。为了节省监测数据，6264是用来作为外部RAM。它是一个静态RAM芯片，低功耗具有8K字节的内存。B. 温度检测电路 温度传感器是该系统的关键部分。达拉斯DS18B20的使用，它支持1 - Wire总线接口，板上专利是在内部使用。所有的传感器部分和转
5、换电路集成在一个晶体管集成电路像1。其测量范围为-55125，在-1085精度为0.52，3。由DS18B20的温度采集传输在1 - Wire总线的方式，这种高度提高了系统的抗干扰，使之适合在恶劣的环境现场温度测量4。有两个电源DS18B20的供应方式。首先是外部电源供给：DS18B20的第一脚连接到地面，第二引脚用作信号线，三是连接到电源。第二种方式是寄生电源5。由于寄生电源会导致硬件电路，软件控制的难度和芯片的性能下降等，但DS18B20的（s）的复杂性，可以连接到I/ O端口的单片机在外部电源供电方式，它更受欢迎。因此，外部电源供应使用，而第二个接脚连接到引脚P1.3可单片机AT89S5
6、1。其实，如果多有被检测，DS18B20的（S）可以连接到1 - Wire总线。但是，当数超过8，有一个向驾驶和更复杂的软件设计，以及1 - Wire总线长度的关注。一般而言，这是不超过50米。为了实现远程控制，该系统可在一个无线之一，旨在打破了1 - Wire总线长度的限制6。C. LCD显示器电路 液晶显示12232F使用，这可以用来显示字符，温度值和时间，并提供一个友好的显示界面。该12232F是一个具有819212832像素的汉字数据库和128个16 8像素的ASCII字符集图形液晶显示。它主要由行驱动器/列驱动器和128 32点阵的充分显示图形，以及7.5 2个汉字功能的液晶显示器。
7、它是在并行或串行方式连接到外部CPU7。为了节约硬件资源，12232F应以串行方式连接到单片机AT89S51，只有4个输出使用的端口。液晶显示屏灰度可以通过调整可变电阻连接的液晶VLCD的PIN码。CLK是用于传输串行通信时钟。SID是用于传输串行数据。CS是用来使能控制，液晶显示。L+是用来控制LCD背光电源。D. 时钟电路 达拉斯DS1302的使用，这是一种高性能，低功耗和实时时钟芯片与RAM。在DS1302的服务于带有日历时钟系统，用于监测的时间。读取数据的时间由AT89S51单片机，再由液晶显示处理。另外的时间可以调整键盘。在DS1302的晶体振荡器设定为32768Hz的，建议的补偿电
8、容是6pF。振荡器的频率较低，所以有可能不连接的电容器，这不会有很大的不同的时间精度。备用电源可以连接到3.6V的可充电电池。E. 键盘控制电路 系统中的键盘接口HD7279A的驱动下，它有一个+5 V单电源，这是连接，无需使用任何有源设备的键盘和显示。根据基本要求和系统功能，只有6个按钮是必要的。该系统的功能是由输入的数据接收单片机AT89S51。为了节省外部电阻器，1 6使用键盘和键盘代码定义为：07h的，0FH，17H条，1FH，27H款，2Fh的。该命令可以读出通过阅读代码指令。 HD7279A是连接到单片机AT89S51的串行模式，只有4个端口的需要。DIG0DIG5和DP分别列线和
9、六个键是实现键盘监控，解码和识别关键代码行线端口。F. 报警电路 为了简化电路，调试方便，是一个5V的蜂鸣器自动报警电路中的应用8。这使得软件编程简化。它是由9012 PNP晶体管的基连接到AT89S51单片机的引脚P2.5。当温度超过上限和下限的值，P2.5输出低电平使晶体管上，然后由一个报警蜂鸣器定。G. 驱动电路 一个步进电机作为驱动装置来控制温度。四相和八打脉冲分配模式是用来驱动电机和简单的延时程序是用来处理脉冲之间的时间间隔，获得不同的转速。有两个步进电机的输出状态。一：当温度超过上限值时，电机反向旋转（以低的温度），而当低于下限值时，电机旋转正常（提高温度），除了不等于预设值。二：
10、当温度在两者之间的某处结束，等于设定值时，电机停止。这些步骤是用来实现温度控制。此外，电机的转速也可以调整相对按钮。代码数据是通过港口答11A8的输入（P2.3P2.0的是）的逆变器74LS04由AT89S51单片机和反向输出。最后，它被放大功放2803A权力电机。IV. 软件设计 按照一般设计要求，该系统的硬件电路原理，以及该程序的可读性，可移植性和改进的调试方便，软件设计模块化。系统流程主要包括以下8个步骤：POST（加电自检），系统启动，温度检测，报警处理，温度控制，时钟芯片DS1302的操作，液晶显示和键盘操作。给一点分析，上述8个任务，很容易地发现，过去五年任务需要实时操作。但对温度
11、的检测，可与TIMER0计时1秒，即出现温度检测达到每秒。系统启动包括全局变量的定义，内存启动，启动特殊功能寄存器和外围设备的启动。全局变量的定义，主要完成对外部接口连接到单片机AT89S51芯片，内存单位和一些特殊的定义的接口定义。开始主要是指RAM的内存处理。例如，当系统通电时间码将在内部单位地址或闪烁标志存储的信息将被清除。特殊功能寄存器包括加载启动定时器初值的开放中断。例如，当系统通电定时器初始化。外围设备的启动，是指设置外围设备的初始值。例如，当系统通电后，LCD应该被初始化，启动显示器应该叫，温度转换命令时，必须先发出的时钟芯片DS1302也要被初始化。报警处理主要是降低和温度的提
12、高使温度保持在预设范围。当温度之间的上限和下限的值，这是不言而喻的温度控制处理，即需要的温度升高或降低根据预设值。这样做的条件温度等于设定值，从而达到温度的目标。V. 结论 温度控制系统具有友好的人机交互界面，硬件简单，成本低，温度控制精度高（误差在1范围内误差），便利性和多功能性等，它可广泛的场合使用的优点与-55至125范围内，且有一定的实用价值。Design of the Temperature Control System Based on AT89S51ABSTRACT The principle and functions of the temperature control sy
13、stem based on microcontroller AT89S51 are studied, and the temperature measurement unit consists of the 1-Wire bus digital temperature sensor DS18B20. The system can be expected to detect the preset temperature, display time and save monitoring data. An alarm will be given by system if the temperatu
14、re exceeds the upper and lower limit value of the temperature which can be set discretionarily and then automatic control is achieved, thus the temperature is achieved monitoring intelligently within a certain range. Basing on principle of the system, it is easy to make a variety of other non-linear
15、 control systems so long as the software design is reasonably changed. The system has been proved to be accurate, reliable and satisfied through field practice. KEYWORDS: AT89S51; microcontroller; DS18B20; temperatureI. INTRODUCTION Temperature is a very important parameter in human life. In the mod
16、ern society, temperature control (TC) is not only used in industrial production, but also widely used in other fields. With the improvement of the life quality, we can find the TC appliance in hotels, factories and home as well. And the trend that TC will better serve the whole society, so it is of
17、great significance to measure and control the temperature. Based on the AT89S51 and temperature sensor DS18B20, this system controls the condition temperature intelligently. The temperature can be set discretionarily within a certain range. The system can show the time on LCD, and save monitoring da
18、ta; and automatically control the temperature when the condition temperature exceeds the upper and lower limit value. By doing so it is to keep the temperature unchanged. The system is of high anti-jamming, high control precision and flexible design; it also fits the rugged environment. It is mainly
19、 used in peoples 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
20、 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 d
21、etected 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 microcontrol
22、ler to keep a certain temperature, and using the LCD to show the preset value for controlling the temperature. In addition, the clock chip DS1302 is used to show time and the external RAM 6264 is used to save the monitoring data. An alarm will be given by buzzer in time if the temperature exceeds th
23、e upper and lower limit value of the temperature. III. HARDWARE DESIGN A. Microcontroller The AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller with 4K bytes of in-system programmable Flash memory. The device is manufactured using Atmels high-density nonvolatile memory technology a
24、nd is compatible with the industry-standard 80C51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the At
25、mel AT89S51 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications. Minimum system of the microcontroller is shown in Fig. 2. In order to save monitoring data, the 6264 is used as an external RAM. It is a static RAM chip, low-
26、power with 8K bytes memory. B. Temperature Detection Circuit The temperature sensor is the key part in the system. The Dallas DS18B20 is used, which supports the 1-Wire bus interface, and the ON-BOARD Patented is used internally. All the sensor parts and the converting circuit are integrated in inte
27、grated circuit like a transistor 1. Its measure range is -55 125 , and the precision between -10 85 is 0.5 2 ,3. The temperature collected by the DS18B20 is transmitted in the 1-Wire bus way, and this highly raises the system anti-jamming and makes it fit in situ temperature measurement of the rugge
28、d environment 4.There are two power supply ways for the DS18B20. The first is external power supply: the first pin of the DS18B20 is connected to the ground; the second pin serves as signal wire and the third is connected to the power. The second way is parasite power supply 5. As the parasite power
29、 supply will lead to the complexity of the hardware circuit, the difficulty of the software control and the performance degradation of the chip, etc. But the DS18B20(s) can be connected to the I/O port of the microcontroller in the external power supply way and it is more popular. Therefore the exte
30、rnal power supply is used and the second pin is connected to the pin P1.3 of the AT89S51. Actually, if there are multipoint to be detected, the DS18B20(s) can be connected to the 1-Wire bus. But when the number is over 8, there is a concern to the driving and the more complex software design as well
31、 as the length of the 1-Wire 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 1-Wire bus 6. C. LCD Circuit The LCD 12232F is used, which can be used to show characters, temperature value and time, and s
32、upply 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 7.52 Chinese characte
33、rs. 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 t
34、he LCD. CLK is used to transmit serial communication 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, low-power and real-time clock chip with RAM.
35、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 recommended compensation capac
36、itance 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 3.6V rechargeable battery. E. Keyboard Control Circuit The keyboard interface in the s
37、ystem is driven by the HD7279A which has a +5V single power supply and which is connected to the keyboard and display without using any active-device. According to the basic requirements and functions of the system, only 6 buttons are needed. The systems functions are set by the AT89S51 receiving th
38、e entered data. In order to save the external resistor, the 16 keyboard is used, and the keyboard codes are defined as: 07H, 0FH, 17H, 1FH, 27H, 2FH. The order can be read out by reading the code instruction. HD7279A is connected to the AT89S51 in serial mode and only 4 ports are need. As shown in F
39、ig. 6, DIG0DIG5 and DP are respectively the column lines and row line ports of the six keys which achieve keyboard monitoring, decoding and key codes identification. F. Alarm Circuit In order to simplify the circuit and convenient debugging, a 5V automatic buzzer is used in the alarm circuit 8. And
40、this make the software programming simplified. As shown in Fig. 7, it is controlled by the PNP transistor 9012 whose base is connected to the pin P2.5 of the AT89S51. When the temperature exceeds the upper and lower limit value, the P2.5 output low level which makes the transistor be on and then an
41、alarm is given by the buzzer. G. Drive Circuit A step motor is used as the drive device to control the temperature. The four-phase and eight-beat pulse distribution mode is used to drive motor and the simple delay program is used to handle the time interval between the pulses to obtain different rot
42、ational speed. There are two output states for the step motor. One: when the temperature is over the upper value, the motor rotates reversely (to low the temperature), while when lower than the lower limit value, the motor rotates normally (to raise the temperature); besides not equals the preset va
43、lue. Two: when the temperature is at somewhere between the two ends and equals the preset value, the motor stops. These steps are used to achieve the temperature control. In addition, the motor speed can also be adjusted by relative buttons. As shown in Fig. 8, the code data is input through ports A
44、11A8 (be P2.3P2.0) of the AT89S51 and inverted output by the inverter 74LS04. Finally it is amplified by the power amplifier 2803A to power the motor.IV. SOFTWARE DESIGN According to the general design requirement and hardware circuit principle of the system, as well as the improvement of the progra
45、m readability, transferability and the convenient debugging, the software design is modularized. The system flow mainly includes the following 8 steps: POST (Power-on self-test), system initiation, temperature detection, alarm handling, temperature control, clock chip DS1302 operation, LCD and keybo
46、ard operation. The main program flow is shown in Fig. 9. Give a little analysis to the above 8 tasks, it is easy to find out that the last five tasks require the real time operation. But to the temperature detection it can be achieved with timer0 timing 1 second, that is to say temperature detection
47、 occurs per second. The system initiation includes global variable definition, RAM initiation, special function register initiation and peripheral equipment initiation. Global variable definition mainly finishes the interface definition of external interface chip connected to the AT89S51, and specia
48、l definition of some memory units. RAM initiation mainly refers to RAM processing. For example when the system is electrified the time code will be stored in the internal unit address or the scintillation flag will be cleared. The special function register initiation includes loading the initial val
49、ue of timer and opening the interrupt. For example, when the system is electrified the timer is initialized. The peripheral equipment initiation refers to set the initial value of peripheral equipment. For example, when the system is electrified, the LCD should be initialized, the start-up display should be called,