Basic digital voltmeter(0-5V) use PIC16F877A and Mickro C

In this tutorial we will learn how to make digital voltmeter use microcontroller. Here I am use PIC16F877A microcontroller and LM16x2 Lcd display. You can watch the video and read the written tutorial below.

PIC16F877A microcontroller has 8 channel ADC(Analog to Digital Converter) module. ADC module has software selectable high and low voltage reference input to some combination of VDD, VSS, RA2 and RA3. The ADC module recived analog signal and it convert 10 bit binary numbers. It can measure (0-5)V DC

.

Circuit Diagram

The A/D conversion of Analog input signal results in a corresponding 10 bit digital numbers.

0V → 00 0000 0000
2.5V → 00 1111 1111
5V → 11 1111 1111

Calculation :

Resulation = (5-0)/(1024-1)
= 0.00488758
=4.8875mV

Here,
ADC read = 0 V (Microcontroller read)
Actual Voltage = ADC read * Resulation
= 0 * 4.8875 mV
= 0V

Again,
ADC read = 5 V
Actual Voltage = ADC read * Resultion
= 1024 * (5/1023)
= 5.0048 V
= ~5 V

ADC Library

ADC (Analog to Digital Converter) module is available with a number of PIC MCU modules. ADC is an electronic circuit that converts continuous signals to discrete digital numbers. ADC Library provides you a comfortable work with the module.

Library Routine

ADC_Init
ADC_Init_Advanced
ADC_Read
ADC_Get_Sample

Mikro C code :

	// LCD module connections
	sbit LCD_RS at RB0_bit;
	sbit LCD_EN at RB1_bit;
	sbit LCD_D4 at RB2_bit;
	sbit LCD_D5 at RB3_bit;
	sbit LCD_D6 at RB4_bit;
	sbit LCD_D7 at RB5_bit;

	sbit LCD_RS_Direction at TRISB0_bit;
	sbit LCD_EN_Direction at TRISB1_bit;
	sbit LCD_D4_Direction at TRISB2_bit;
	sbit LCD_D5_Direction at TRISB3_bit;
	sbit LCD_D6_Direction at TRISB4_bit;
	sbit LCD_D7_Direction at TRISB5_bit;
	// End LCD module connections

	char look(int a)
	{
	switch(a)
	{
	case 0:
	return '0';
	case 1:
	return '1';
	case 2:
	return '2';
	case 3:
	return '3';
	case 4:
	return '4';
	case 5:
	return '5';
	case 6:
	return '6';
	case 7:
	return '7';
	case 8:
	return '8';
	case 9:
	return '9';
	default:
	return '.';
	}
	}

	void main()
	{
	unsigned int v;
	char *volt = "00.0";
	CMCON = 0x07;
	TRISA = 0xFF; // PORTA is Analog input
	PORTA = 0X00; // PORTA is clear
	ADCON1 = 0x00;
	Lcd_Init(); // Initialize lcd module
	ADC_Init(); // Initialize ADC module
	Lcd_Cmd(_LCD_CLEAR); // Clear Lcd display
	Lcd_Cmd(_LCD_CURSOR_OFF); // Cursor of the Lcd display
	Lcd_Out(1,1, "DEVELOPED BY"); // Lcd show "DEVELOPED BY"
	Lcd_Out(2,1, "MINA TECHNOLOGY"); // Lcd show "MINA TECHNOLOGY"
	delay_ms(2000); // 2 second delay
	Lcd_Cmd(_LCD_CLEAR); // Clear Lcd display

	do // loop start
	{
	v = ADC_Read(0); // RA0 is Analog input
	v = (v*4.89) ; // 4.89 is Voltage Resulation
	volt[0] = look(v/10000);
	volt[1] = look((v/1000)%10);
	volt[3] = look((v/100)%10);
	Lcd_Out(1,1,"Digital Voltmeter");
	Lcd_Out(2,1,"Voltage = ");
	Lcd_Out(2,11,volt);
	Lcd_Out(2,16,"V");

	Delay_ms(500) ; // 500ms delay

	} while(1); // loop end
	}