The Design Of Enviroment Monitor Based On MSP430

Temperature, humidity and illumination are indispensable parameters of calibrating environment, it has lots of meaning to accurately measure them.This paper designes an environment monitor which is used in the interior, it uses the ultra-low power MCU MSP430F449 as the core.System consists of two parts:the first part is the measurement of environmental parameters; the other one is data capture and processing.The measurement of parameters section consists of three basic elements:temperature measurement, humidity measurement and illumination measurement.Temperature measurement uses digital temperature transducer DS18B20, the temperature datas are send to the MCU by single-output 12-bit digital bus, after processing, the data will be displayed. Humidity measurement part uses humidity transducer HS1101 and a multivibrator circuit which is composed of 555 timer, it measures the output frequency, according to the relation between frequency and humidity to calculate the humidity. Illumination measurement part uses photocell transducer BPW34, output signal is amplified and send into the ADC12, it can get the measurements after data processing.MCU data acapture and processing section include the minimum system and the peripheral interface circuits. Peripheral interface circuit include five basic components:the keyboard part, display part, calendar part, serial communication part, USB interface part.The keyboard is used to adjust the time parameters.The display part uses LCD JM12864M-2, the function is display the environmental parameters and the time which is measured in real time. Calendar part uses clock chip DS12C887 which can produce the information of time.The serial communication part uses RS485 bus and communicates with PC, the system expands the external USB interface module it can store the measurement results into the U disk.The software of this monitor is written by C language,it consists of four parts, the first part is circulating measurement of temperature, humidity and illumination, the second is time display, the third is keyboard, the last is about U disk storage.The range of temperature measurement is -40℃～+120℃,the accuracy is±0.5℃; the range of humidity measurement is 10%-90%RH, the accuracy is±5%RH; the range of illumination measurement is 10-4000lux, the accuracy is±5lux.The system is small, portable, low power, high reliability and maintenance-free., it can communicate with PC for a long distance and the measurement results can be saved.its engineering cost and human resources cost are low, it is very suitable for monitoring the parameters of indoor environment and has the good prospect.