论文总字数：17642字

摘 要

甲醛HCHO是一种无色易溶的刺激性气体，易挥发，所以在室内空气品质研究中，将其归为VOC，即挥发性有机化合物。其水溶液即“福尔马林”具有强烈刺激性气味，其毒性主要表现在神经系统及呼吸系统症状。

本系统采用51单片机作为控制核心模块，利用MQ-138甲醛传感器检测甲醛。实时监控室内甲醛浓度变化，并在数码管上进行显示。如果甲醛浓度过高或高于设定值时，系统的报警指示灯会常亮，且发出声音报警，提醒人们及时抢险，对危险情况进行处理。本系统适用于工业环境以及家庭。

单片机成本较低，控制功能比较强大，能较好的适应周边环境，运行过程比较稳定，故选单片机为控制核心元件。

MQ-138是一种二氧化锡半导体型甲醛气体传感器，对甲醛具有高的灵敏度和快速的响应性，适于便携式甲醛探测器，尤其适用于一般的家庭环境。

选用数码管作为甲醛实时监测数值的显示模块，以及LED灯作为报警信号灯。

本文叙述了基于单片机的有毒环境气体检测系统的设计过程，包括硬件电路、软件编程、软件仿真。

关键词：甲醛 单片机 检测 报警

Design based on microcontroller for monitoring gas under the poisonous environment

Abstract

HCHO is a kind of thrill gas, which has no color, can be easily dissolved and volatilized. So HCHO is classified as VOC, volatilize organic compounds, in the study of the quality of indoor air. The aqueous solution of HCHO, formalin, has an intense thrill smell, and the toxicity of HCHO mainly lies in the symptom of nervous system and respiratory system.

The system uses 51 microcontroller to do the core control module, and the MQ-138 HCHO transistor is used to detect HCHO. The concentration of indoor HCHO is monitored real-timely, which is showed in the digital tube. The indicator light for alarm will be on and the system will make an alarm sound when the concentration of HCHO is much high or over the set value to remind people rescuing the emergency and deal with the emergency. This system is suitable for the industrial environment and house.

The microcontroller is selected as the core control module for its low cost, strong ability of process, good adaptive of the surrounding environment, and the steady operation process.

MQ - 138 is a kind of tin oxide semiconductor type of formaldehyde gas sensors, and it has high sensitivity and fast respond to HCHO. MQ-138 is suitable for the portable HCHO detector, especially suitable for house.

This system selects the digital tube as the display module to display the HCHO value detected real-timely, and selects LED as the light of alarm signal.

This article narrates the design process of the toxic environment gas detection system based on single chip microcomputer, including hardware circuit, software programming, software simulation.

Keyword: HCHO, Microcontroller, Detection, Alarm

目录

摘要 II

Abstract III

目录 III

第一章 绪论 1

1.1课题研究背景及意义 1

1.2 研究现状 2

1.3 引言 3

第二章 硬件系统的设计 4

2.1 硬件的总体设计 4

2.2 单片机系统 5

2.2.1 单片机简介 6

2.2.2 时钟电路和复位电路 8

2.3显示电路 10

2.4 A/D转换电路 12

2.4.1 ADC0809简介 12

2.4.2 ADC0809内部结构 13

2.4.3 ADC0809引脚功能 13

2.4.4 ADC0809工作时序 14

2.5 甲醛传感器介绍 15

2.6 声音、灯光报警电路 17

2.7 本章小结 18

第三章 系统软件设计 19

3.1 总体软件设计思想 19

3.2 A/D转换函数 19

3.3 灯光、声音报警函数 21

3.4 显示函数 22

3.5 整体C语言函数 24

3.6 本章小结 24

第四章 实验过程 25

4.1 软件介绍 25

4.2绘制电路原理图 25

4.3编写程序 27

4.4软件仿真 29

4.5本章小结 32

结论 33

参考文献 34

致谢 35

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