Skip to main content

Digital Voltmeter using PIC Microcontroller





This is a simple voltmeter which measures 0-5V at a precision of 4.8 mV. This is a simple design using inbuilt ADC of PIC 16F877A. PIC 16F877A have 8 channel 10bit ADC.  Measured voltage is displayed on 16x2 LCD display.
Using one of the most popular 8 bit PIC 16f877A, for instance, reading the datasheet, we'll find that the ADC modules (10 bit) are controlled by four different registers. The first two, ADCON0 and ADCON1, are used to set and start the ADC module. When high level language is used, the programmer doesn't need to care a lot of the register connected to the results because they are normally stored in a variable by a routine of the language itself (adc_read, for instance, using mikroc).
The ADCON0
As we can see this registers are 8 bit registers where.
- bit6 and bit 7 are used to set the frequency of the conversions.
- bits 3, 4 and 5 are used to select the pins of the microcontroller enabled to theadc conversions.
- bit 2 represents the status of the conversion procedure.
- bit 0 starts the conversion.


Regarding the second register, ADCON1, it must be set for two reasons: to select the format of the result value (bit 7), to select (bit0...bit3) the reference voltage and to set the port configuration control bits according to the following table




This circuit uses AN0 channel of ADC. The voltage conversion is employed in a logic, 16F877A have 10 bit ADC. That is, it can have 1024 levels. Reference voltage is fixed at
0 – 5 V Analog I/P is mapped to one of the 1024 levels (0-1023 Digital Count)
Resolution = 5/(1024)   (as it is 10 bit ADC)
= 5/1024
= 4.8828 mV   It  means that for a change in 4.8828mV, the binary output changes by 1.

For More Details See
PC Based Digital Voltmeter Using PIC 16F877A

ADC module of PIC Microcontroller converts the Signals on its analog pin to 10 bit binary data and it has software selectable high and low voltage reference input to some combination of VDD, VSS, RA2 and RA3. The analog input to PIC is limited to 0 to 5.The converted value is in mV. It is then converted to volts and displayed on LCD.


 Circuit



Digital Voltmeter using PIC Microcontroller 

 Code


/**********************************************/
/*
  
 http://www.facebook.com/EmbeddedProjects

 http://microcontrollerprojects00.blogspot.in/

 Author: Vishal K M

 uC:16F877A
 Compiler: mikroC
 Crystal freq: 4MHz


                                              */
/**********************************************/
// LCD module connections
sbit LCD_RS at RC0_bit;
sbit LCD_EN at RC2_bit;
sbit LCD_D4 at RD4_bit;
sbit LCD_D5 at RD5_bit;
sbit LCD_D6 at RD6_bit;
sbit LCD_D7 at RD7_bit;

sbit LCD_RS_Direction at TRISC0_bit;
sbit LCD_EN_Direction at TRISC2_bit;
sbit LCD_D4_Direction at TRISD4_bit;
sbit LCD_D5_Direction at TRISD5_bit;
sbit LCD_D6_Direction at TRISD6_bit;
sbit LCD_D7_Direction at TRISD7_bit;
// End LCD module connections






unsigned long temp;
unsigned int i;
char digit[]="0.000 VOLTS";

void main() {


TRISA=0xFF;


ADCON0=0x01;
ADCON1=0x0E;

 

     Lcd_Init();                        // Initialize LCD

  Lcd_Cmd(_LCD_CLEAR);               // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off
  LCD_Out(1,1,"EMBEDDED");
   LCD_Out(2,1,"PROJECTS BLOG");
   Delay_ms(1000);

  do {
    temp = ADC_Read(0);   // Get 10-bit results of AD conversion
    temp=temp*5000/1023;   //Convert ADC value to mV
   
   

    digit[0]=(temp/1000)+48;
    digit[2]=((temp%1000)/100)+48;
    digit[3]=(((temp%1000)%100)/10)+48;
    digit[4]=(((temp%1000)%100)%10)+48;
   
    LCD_Cmd(_LCD_CLEAR);
    LCD_Out(1,1,digit);

      //Carriage Return
    Delay_ms(500);

  } while(1);
}


Download Project Files

Popular posts from this blog

PIC Microcontroller Based Electronic Lock

Circuit Diagram

Security is a prime concern in our day-today life. Everyone wants to be as much secure as possible. An access control for doors forms a vital link in a security chain. The microcontroller based digital lock for Doors is an access control system that allows only authorized persons to access a restricted area. An electronic lock or digital lock is a device which has an electronic control assembly attached to it. They are provided with an access control system. This system allows the user to unlock the device with a password. The password is entered by making use of a keypad. The user can also set his password to ensure better protection. The major components include a Keypad, LCD and the controller PIC16F877A. This article describes the making of an electronic code lock using the 16F877A microcontroller.
The system is fully controlled by the 8 bit microcontroller 16F877A which has a 8Kbytes of ROM for the program memory. The password is stored in the EPROM so that we …

PIC Serial Communication Tutorial (UART)

First, a quick history of RS232. What is RS232? It's just a name for a standard that has propagated from generation to generation of computers. The first computers had serial ports that used RS232, and even current computers have serial ports (or at least USB ports that act like RS232 ports). Back in the day, serial information needed to be passed from devices like printers, joysticks, scanners, etc to the computer. The simplest way to do this was to pass a series of 1s and 0s to the computer. Both the computer and the device agreed on a speed of information - 'bits per second'. A computer would pass image data to a printer at 9600 bits per second and the printer would listen for this stream of 1s and 0s expecting a new bit every 1/9600 = 104us (104 micro-seconds, 0.000104 seconds). As long as the computer output bits at the pre-determined speed, the printer could listen.
Zoom forward to today. Electronics have changed a bit. Before they were relatively high power, high …