基于单片机控制的数字气压计设计外文文献

Design of Liquid Crystal Digital Voltmeter Based on Single Chip Microcomputer

Wang Hui-feng 1 Liu Xiao-hua2

1 Hubei Institute of Technology, Xianning, China,

2 Jiaozuo Teachers College,Jiaozuo,China

AbstractüThe design is based on Atmel51 microcontroller development platform and automatic control based on the principle of a digital voltage meter systemˊThe system uses Atmel89C52 microcontroller as the control core, ADC0832 for the sampled data system, The use of a zener diode for over voltage protection, and through the realization of analog switch achieves the input range automatic conversion, character liquid crystal display shows the measured voltage.

Key words- Digital voltmeter;Atmel89C52; A/D converter;

I.T HE OVERALL SYSTEM DESIGN SCHEME

This system realize the function mainly through the hardware design and software programming. First, according to the design requirements to produce complete the design of circuit diagram. The hardware circuit uses ATMEL's AT89C52 as the main processor, the system is mainly composed of signal acquisition, A/D conversion, data processing and output, drive and display modules. Second, according to the circuit diagram of program control chip, the program design use assembly language programming, the compilation and simulation using Keil software. The SCM control A/D converter analog to digital conversion, and display the corresponding voltage value on the LED.

Figure 1. System block diagram The measured DC voltage is collected and quantified by

A/D conversion unit, then the results of the A/D conversion are

scale transformatied by microcontroller to get the value of

measured voltage.SCM average logarithmicly over the results

of all transformation, then output the average value through the

SPI serial data interface to the display driving unit, the unit

complete the decoding, and drive the digital display.

II.T HE HARDWARE DESIGN AND THE CIRCUIT CHART

A.Power Supply Circuit

Three terminal regulator composed by some triode and resistor is a kind of integrated circuit element.when analyzing circuit, we can think it is a element adjusting the resistance automatically.when load current is large, resistance of three terminal regulator automatically becomes small, and when the load current is smaller, the resistance of the three terminal regulator change automatically, so we can maintain the output voltage constant.

Wanting to output the voltageof 5V,we so the selecte 7805. The letter in front of 7805 may be different due to manufacturers. the maximum output current of LM7805 is 1A, there is current limit short circuit protection in it,so a short period of time, such as a few seconds, short circuit of output to ground (2 feet) will not make 7805 burned out. Three terminal regulator followed by a 104 capacitor, the capacitor has the effect of wave filtering and damping.

Figure 2. Ower Supply Circuit

B.The A/D Conversion Module

Due to the type of analog conversion circuit, based on the precision, the conversion speed and stability, this design uses the ADC0832 conversion chip. The ADC0832 connected whith Single chip microcomputer through 3 wire interface is a serial interface of 8 bit A/D converter produced by National Semiconductor Corporation Ns. Bing of low power consumption, high cost performance, the ADC0832 is suitable to be used in intelligent instruments in the pocket. The ADC0832 is 8 bits resolution A/D conversion chip, the highest resolution can reach 256 level, can meet the general requirements for conversion of analog quantity. Double data output of the chip can be used as data verification, to reduce the error,besides,fast switching speed and stronger stability, independent of the chip make multiple devices connection and