发布时间：2015-01-18 来源：人大经济论坛

自动化专业论文范文 目 录 摘 要I AbstractII 第1章 绪论1 1.1选题的背景及意义1 1.2课题研究的主要内容1 第2章 系统方案设计2 2. 1系统实现方案的比较2 2. 1.1传统方案2 2. 1.2本设计的方案2 2.2温度传感器的选择3 2.2.1 DS18B20简介4 2.2.2 DS18B20的性能特点5 2.2.3 DS18B20的管脚排列5 2.2.3 DS18B20的内部结构6 2.2.3 DS18B20的控制方法9 2.2.3 DS18B20的测温原理10 2.3单片机的选择11 2.3.1单片机概述11 2.3.2 AT89S51芯片的主要性能12 2.3.3 AT89C2051芯片的主要性能12 2.3.4 AT89C2051芯片的管脚说明13 2.4 串行通信15 2.4.1 串行接口标准15 2.4.2 RS-485的特点17 第3章 系统硬件电路设计19 3.1 下位机电路设计19 3.1.1温度采集电路20 3.1.2 输出控制电路20 3.2上位机电路设计20 3.2.1键盘电路21 3.2.2显示电路21 第4章 系统软件的设计23 4.1系统主程序23 4.1.1 下位机程序23 4.1.2 上位机程序24 4.2系统部分程序24 4.2.1 DS18B20初始化子程序25 4.2.2 DS18B20读子程序26 4.2.3 DS18B20写子程序27 4.2.4 DS18B20定时显示子程序28 4.2.5 DS18B20温度转换子程序29 第5章 课题的总结30 致谢31 主要参考文献：32 摘 要 随着温室技术的普及，温室数量不断增多，温室的温度控制成为一个难题。目前应用于温室的温度检测系统大多采用由模拟温度传感器、多路模拟开关、AD转换器及单片机等组成的传输系统。这种温度采集系统需要在温室内布置大量的测温电缆，才能把现场传感器的信号送到采集卡上，安装和拆卸繁杂，成本也高。同时线路上传送的是模拟信号，易受干扰和损耗，测量误差也比较大，不利于控制者根据温度变化及时做出决定。在这样的形式下，开发一种实时性高、精度高，能够综合处理多点温度信息的测控系统就很有必要。 本课题提出一种基于单片机的总线结构温度测控系统应用于温室的的设计方案，该方案是利用温度传感器将温室内温度的变化，变换成电流的变化，再转换为电压变化输入模数转换器，其值由单片机处理，最后由单片机去控制数字显示器，显示温室内的实际温度。一旦该温度值超过我们预先设定的上、下限，单片机便启动控制装置，进而对温室内温度进行控制。为了能够多通道数据采集和处理，系统采用了一台上位机和多个下位机的集总式结构。上位机采用AT89S51单片机，下位机采用AT89C2051单片机。上位机与下位机之问采用RS485总线通信。其中上位机系统配置液晶显示屏、按键。该测控系统安装简单方便，系统稳定可靠、可维护性好。 关键词: 单片机; RS485总线; 温度传感器; 温度监控; 温室 Abstract With the popularity of greenhouse technology, the amount of greenhouse is larger and lager. However, the temperature control of greenhouse is becoming a difficult problem. Currently,the temperature control system of greenhouse is mostly using a transfers system which consists of analog temperature sensor, multiplexing analog switches, AD conversion units and SCM. This kind of temperature collection system needs a lot of cables which is laid to make the single of the sensor be sent to the collection card in the greenhouse.Thus the work of fixing and take-down is miscellaneous,and the cost is high.What’s more,the transmission line is analog signal which are vulnerable to interference and loss, measurement error is relatively large, were not conducive to control temperature in a timely manner according to a decision. In this form, to develop a real-time, high precision, integrated approach to multi-point temperature measurement and control information system will be necessary. This issue gives a temperature control of greenhouse based on SCM and digital monobus technology. In this project，the change of temperature in the greenhouse is transformed into the change of electric current and then into the change of voltage by using the temperature sensors.The change of voltage is input inio the AD conversion units and the result is dealt with by SCM.At last the realtime temperature in the greenhouse is displayed on the monitor under the control of SCM.Once the value of the temperature in the greenhouse exceeds the minimum and maximum whieh is preestablished.SCM will start the control device, and thus to control the temperature inside the greenhouse. To be able to the multi-channel data acquisition and processing ,system is a mian machine and a number of lower machines structure. Main machine is AT89S51 , lower machine is AT89C2051. they communicate with each other by RS485 bus. And the main machine deploy LCD, keys. The control system easy to install, system is reliable and good maintainability.