Embedded Projects Blog: Digital Voltmeter using PIC Microcontroller

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

5 comments:

  1. May I know which software you used to draw circuit and simulation?

    ReplyDelete
  2. hy
    yar ye jo code likha hua hy is se 000.000 ki velu show krva dy aor ye program PIC16F676 ka ley compile krva dy
    main os ka bahot shukria ada kron ga main programming ko thora thora samjhta ho ap logo ki mehrbani ho gi
    reply is email par kr dain muqeemcsk@gmail.com

    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);
    }







    ReplyDelete
  3. @Muhammad
    I dont know Hindi well please write in English.
    If the reading shown is 0.000 make sure that the program enter in do-While Loop, make sure ADC config is correct, and make sure ADC read something.

    There is another version of it USing PC is published here check it also

    ReplyDelete
  4. Nice information.Generally in College final year projects, Digital Voltmeter is used to measure voltage. 8051 voltmeter and A/D converter are the main components of the digital voltmeter. The circuit diagram clearly depicts the concept of signal conversion through PIC Microcontroller.

    ReplyDelete