Design of Simple Digital Voltage Meter Based on Single Chip Microcomputer

With the single-chip microcomputer as the core device, a simple DC digital voltmeter is constructed. 

(1) Using 1 analog input, it can measure the DC voltage value between 0-5V. 

(2) The voltage can be displayed using a 4-digit LED digital tube, which can display at least two decimal places. 

The production of a simple digital voltmeter mainly involves knowledge of data (voltage) measurement, A/D conversion, and control display. 

(1) A/D conversion is implemented using ADC0808 and 0809. 

(2) The voltage display uses a 4-digit LED digital tube. 

(3) MCU selected is AT89C51

Preliminary system design 

The A/D converter is a device that realizes the conversion from analog quantity to digital quantity. According to the conversion principle, it can be divided into four types: counting A/D converter, dual-integral A/D converter, successive approximation A/D converter and parallel A/D converter.

The most commonly used A/D converters at present are dual-integral A/D converters and successive approximation A/D converters. The main advantages of the former are high conversion accuracy, good anti-interference performance, and low price, but the conversion speed is slow and is generally used in occasions where speed requirements are not high. The latter is a faster and more accurate converter with a conversion time of approximately a few microseconds to hundreds of microseconds.

ADC0809 is an 8-bit 8-channel successive approximation AD converter. 

The simulation diagram is as follows: 

The specific implementation of the code is as follows:

#include

#include

sbit OE=P1^0; // output enable control bit

sbit EOC=P1^1; //Conversion end status signal

sbit ST=P1^2; //Conversion start signal

sbit CLK=P1^3; // Clock signal

sbit C3=P1^4; // 

sbit C2=P1^5; //

sbit C1=P1^6; //

unsigned int temp;

unsigned char show[]={0XC0,0XF9,0XA4,0XB0,0X99,0X92,0X82,0XF8,0X80,0X90}; // 0-9

void delay(int n)

{

    int i,j;

    for(i=0;i    {

        for(j=0;j<200;j++);

    }

}

void display() // Digital tube display

{

    P3=0X80;

    P0=show[temp/1000]&0X7F;

    delay(5);   

    P3=0X40;

    P0=show[temp/100%10];

    delay(5);

    P3=0X20;

    P0=show[temp%100/10];

    delay(5);

    P3=0X10;

    P0=show[temp%10];

    delay(5);

}

unsigned int ADC0809()

{

    unsigned int dat;

    ST=0;

    ST=1;

    _nop_();

    ST=0;

    _nop_();

    _nop_();

    _nop_();

    _nop_();

    _nop_();

    EOC=1;

    while(EOC==0);

    OE=1;

    P2=0XFF; //Set P2 port as input port

    dat=P2;

    OE=0;

    return dat;

}

void main()

{

    ET0=1;

    EA=1;   

    TMOD=0X00; //Set the timer working mode to 0

    //11111111 11110

    TH0=0XFF;

    TL0=0X0;

    TR0=1;

    CLK=1;

    ST=0;

    OE=0;

    C1=0;C2=0;C3=0;

    while(1)

    {

        temp=ADC0809()*19.53125; //19.53125=5/256*1000 5/256 is the precision. Multiply by 1000 for the convenience of digital display.

        display();

    }

}

void inex_T0() interrupt 1

{

    TH0=0XFF;

    TL0=0X0;

    CLK=!CLK;   

}

Note: The collected data needs to be converted into data that can be reasonably output on the digital tube, so everyone needs to pay attention.

Effect simulation diagram: