digital voltmeter using 89c51 microcontroller
TRANSCRIPT
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DIGITAL VOLTMETER USING 89C51 MICROCONTROLLER
Guide,Prof. S. A. Karmude
By,Saylee S. Joshi
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INTRODUCTION• Voltmeter is a voltage measuring instrument. • We can measure the potential difference between any two
points in an electrical network using voltmeter. • There are two types of voltmeter as analog voltmeter and
digital voltmeter. • Analog voltmeter moves pointer on a scale but it has some
limitations like accuracy of few percent of full scale.• Digital voltmeter can display numerical value of voltage on a
display by use of analog to digital converter (ADC). • All the data processing and manipulating is in digital form, so
it is very essential to use ADC.
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Cont….
• 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.
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Block Diagram
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Components Required For Digital Voltmeter Using 89c51 Microcontroller• Microcontroller, AT89C51• Analog to Digital Converter, ADC0804‐ ‐• 16×1 LCD• Oscillator circuit for the microcontroller– 12MHz Crystal Capacitor– 33pF Capacitors
• Voltage divider circuit/ Input terminals– 200k, 100k Resistors– 100nF Capacitor
• ADC Clock Circuit 100k Potentiometer (to adjust the back light of the ‐ LCD)– 10k Resistor– 150pF Capacitor
• 100k Potentiometer (to adjust the back light of the LCD)‐
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Circuit Diagram Of Digital Voltmeter Using 89c51 Microcontroller
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Lcd Pin DiagramPin no. Name Description1 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)
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Components1. 8051 Based Controller: 12. ADC0804: 13. LCD 16x1: 14. Potentiometer 10K: 15. Resistor 10K: 26. Resistor 200K: 17. Resistor 100K: 18. Capacitor 33pF: 29. Capacitor 10uF: 110. Capacitor 150pF: 111. Capacitor 100nF: 112. Crystal 12Mhz: 1
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C Program For Digital Voltmeter Using 89c51 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 P3.4void conv(); //Start of conversion
functionvoid read(); //Read ADC functionunsigned 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 conversionread(); //Read ADCadc_avg += adc;}adc_avg = adc_avg/10;wrt_cmd(0x80);wrt_string("V(DC): ");adc = adc_avg * 59;hex2lcd((unsigned char)(adc/1000));
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Cont….wrt_data('.');adc = adc%1000;hex2lcd((unsigned char)(adc/10));wrt_data('V');}}void conv(){cs = 0; //Make CS lowwr = 0; //Make WR lowwr = 1; //Make WR highcs = 1; //Make CS high
while(intr); //Wait for INTR to go low
}void read(){cs = 0; //Make CS lowrd = 0; //Make RD lowadc = adc_port; //Read ADC portrd = 1; //Make RD highcs = 1; //Make CS high}
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Advantages
• This system is used to measure the voltage in low voltage applications.
• Used to measure the toy batteries.• We can measure the physical quantities like
temperature, humidity, gas etc. using this system with a little modification.
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disadvantages
• The input analog voltage range should be 0 to 5V.
• Using this system we can measure only one analog input value at a time.
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