Digital Voltmeter using 8051 Microcontroller: Electronics Projects

A voltmeter is a voltage measuring instrument. We can measure the potential difference between any two points in an electrical network using a voltmeter. Let us design and make a simple voltmeter using 8051 microcontrollers which you can use as a mini-project in your college.

There are two types of voltmeter as analog voltmeter and digital voltmeter. Analog voltmeter moves the pointer on a scale but it has some limitations like the accuracy of few percent of full scale.

Digital Voltmeter using 8051 Microcontroller

In this section, we are going to make a digital voltmeter using 8051 microcontrollers. A digital voltmeter can display the numerical value of the voltage on a display by use of analog to digital converter (ADC). All the data processing and manipulating are in digital form, so it is essential to use ADC. We have used ADC0804 analog-to-digital converter IC. The range of input voltage is 0-15V. Here the input voltage should be DC voltage so as to get the steady output on the LCD display. If you give the AC voltage as an input, it will display continuously running numbers as the nature of AC voltage.

Components required for Digital Voltmeter using 8051 Microcontroller:

Microcontroller, AT89C51

Analog-to-Digital Converter, ADC0804

16x1 LCD

Oscillator circuit for the microcontroller
1. 12MHz Crystal Capacitor
2. 33pF Capacitors

Voltage divider circuit/ Input terminals
1. 200k, 100k Resistors
2. 100nF Capacitor

ADC Clock Circuit 100k Potentiometer (to adjust the back-light of the LCD)
1. 10k Resistor
2. 150pF Capacitor

100k Potentiometer (to adjust the back-light of the LCD)

Circuit Diagram of Digital Voltmeter using 8051 Microcontroller:

[caption id="" align="aligncenter" width="490"] Digital voltmeter using 8051 microcontroller[/caption]

Pin description of 16×1 LCD Display

[caption id="" align="aligncenter" width="300"] LCD pin diagram[/caption]

Pin No	Name	Description
1	Vss	Ground
2	Vdd	+5V
3	Vee	Contrast Adjustment -2V to -5V
4	RS	Register Select
5	RW	1 -Read, 0- Write
6	E	Enable Strobe
7	D0	Data Line
8	D1	Data Line
9	D2	Data Line
10	D3	Data Line
11	D4	Data Line
12	D5	Data Line
13	D6	Data Line
14	D7	Data Line
15	LED+	Backlit LED +V Vdd (Optional signal)
16	LED-	Backlit LED –V Vss (Optional signal)

C program for digital voltmeter using 8051 microcontroller:

#include <REGX51.H>
#include "lcd.h"
#define adc_port P1              //ADC Port
#define rd P3_7                  //Read signal P3.7
#define wr P3_6                  //Write signal P3.6
#define cs P3_5                  //Chip Select P3.5
#define intr P3_4                //INTR signal P3.4
void conv();                     //Start of conversion function
void read();                     //Read ADC function
unsigned int adc_avg,adc;
void main(){
char i;
LCD_INI();
while(1){                                                              //Forever loop
adc_avg = 0;
for(i=0;i<10;i++){
conv();                  //Start conversion
read();                  //Read ADC
adc_avg += adc;
}
adc_avg = adc_avg/10;
wrt_cmd(0x80);
wrt_string("V(DC): ");
adc = adc_avg * 59;
hex2lcd((unsigned char)(adc/1000));
wrt_data('.');
adc = adc%1000;
hex2lcd((unsigned char)(adc/10));
wrt_data('V');
}
}
void conv(){
cs = 0;                                    //Make CS low
wr = 0;                                  //Make WR low
wr = 1;                                  //Make WR high
cs = 1;                                    //Make CS high
while(intr);         //Wait for INTR to go low
}
void read(){
cs = 0;                                    //Make CS low
rd = 0;                                   //Make RD low
adc = adc_port; //Read ADC port
rd = 1;                                   //Make RD high
cs = 1;                                  //Make CS high
}

C Program:

Click here to download the C program, Hex file and project report of digital voltmeter using 8051 microcontrollers.

http://www.youtube.com/watch?v=MlDrj8A9D7w

Digital Voltmeter using 8051 Microcontroller: Electronics Projects