With the popularization of greenhouse technology,the amount of the greenhouse is larger and larger. However, the temperature control of the greenhouse is becoming a difficult problem. Currently, the temperature control system of greenhouse is mostly using a transfers system which consists of analog temperature sensors,multiplexing analog switches, A/D conversion units and SCM. This kind of temperature collection system needs a lot of cables which is laid to make the signal 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, what is transferred in the system is analog signals which are easily interfered and have more wastage. It is hard for the controller to make a decision in time according to the change of temperature because the measure error is bigger. So under this circumstance,it is necessary to develop a real time and precise temperature control system which is in a position to deal with temperature information of many nods.
This paper gives a greenhouse temperature control project which is based upon the SCM 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 into the A/D conversion units .At last the real time 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 which is preestablished, the SCM will give an alarm and autocontrol the temperature in the greenhouse. This project can make real time patrol checking to the different nod’s temperature in the greenhouse, and every separate checking unit can finish its task independently. This temperature control system whose stabilization and maintainability is good doesn’t need any fixed network to support and is easily fixed.
Keywords SCM;temperature sensor;greenhouse;measuring &controlling system
目 录
摘 要 i
Abstract ii
第一章 绪论 1
1.1选题的背景 1
1.2选题的现实意义 2
第二章 设计任务 3
2.1设计题目 3
2.2设计目标与要求 3
2.3设计方案 3
2.3.1方案一 3
2.3.2方案二 4
2.3.3方案比较 4
第三章 系统硬件电路的设计 5
3.1系统硬件电路构成 5
3.2温度传感器 6
3.2.1 DS18B20简介 7
3.2.2 DS18B20的性能特点 8
3.2.3 DS18B20的管脚排列 9
3.2.4 DS18B20的内部结构 9
3.2.5 DS18B20的控制方法 13
3.2.6 DS18B20的测温原理 14
3.2.7 DS18B20的时序 14
3.2.8 DS18B20的注意事项 16
3.3 单片机的选择 17
3.3.1 单片机的概述 17