ABSTRACT
Environmental factors are closely related to our life, among which ambient temperature and
humidity are two vital factors. Recent years, with the explosion of technological products,
Microcontrollers is developed rapidly for its characteristics of low costs, high-performance, small
but high integration; ambient temperature and humidity monitoring alarm system that based on
Microcontrollers is one of the hot research areas. Using Temperature and humidity sensor, LCD
monitor, buzzer and independent keyboard and some other modules this paper designed
environmental monitoring system that based on Microcontrollers.
When it is necessary to monitor ambient temperature and humidity in some small and medium
industry or our normal life, it is often being ignored, because so far, environmental monitoring
system is mostly used by large industry or in environmental protection. The system designed here
can be widely used because of its high-performance, low-cost, simple operation, wide applicability.
The system using AT89S52 Microcontrollers with C51 kernel, the collection of ambient
temperature and humidity date is sensor DHT11 with an accuracy of ±2℃/±5%RH, the date is
showed on a 16*2 LCD monitor. Furthermore, the date can be limited through independent
keyboard, thus realizing auto-alarm when over-limit. It makes real-time monitoring of ambient
temperature and humidity and smart alarm function come true.
It uses AT89S52 that with 8-bit CPU and registers, flash Member with 8k which makes it
easy to use and easy to program and good enough to meet the need of high-performance, low-cost,
simple operation, wide applicability. Temperature and humidity sensor DHT11 can collect
ambient temperature and humidity at the same time and can realize analog-digital conversion and
data transmission by itself. it has the characteristics of high precision and real-time monitoring, it
has 2 lines, 16 characters on each line so it can show the data of both temperature and humidity on
one screen. It is an inexpensive and easy to use display device. Four independent keyboard can set
temperature and humidity alarm to the limits. The buzzer can alarm by itself when the data is over-
limited. By controlling different modules, Microcontrollers realized monitoring ambient
temperature and humidity. The design process is firstly to define Microcontroller’s foot, then
define function keyboard respectively. And software programing the module of the drive. This
system is designed for small industry and for daily use, so it is reliable, good real-time performance,
inexpensive and easy to operation.
This paper based on the design method of Microcontrollers, control theory of Microcon-
trollers and usage of peripheral module besides Microcontrollers writing driver of each component,
this system is simulated by Proteus. Eventually, download the system process to Microcontrollers.
It is proved that this system has well-functioned and has application value of simple operation,
low cost, simple circuit, reliable and perfect real-time monitor.
Keywords：AT89S52 Microcontroller; DHT11 sensor; LCD1602; buzzer
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