voltmeter using pic 16f877a problem

jayanth.devarayanadurga · Sep 17, 2013

What is the max current you want to measure? 10 A? Show your circuit for measuring 10 A.

paulfjujo · Sep 17, 2013

hello,

If you want to do progress
split the problems.

Is your Mikroc an official versus (not cra..ed) or limited versus 2Kmax ?

is it ADC problems or display problems.
Try to put a constant into your code
v=512; // middle scale of voltage
i=256; // a quota of the scale for Amps
and see what result you get on LCD.

if OK , check ADC part
use a potentiometer connected betwwen +5V and 0V , cursor on ADC input
reactivate ADC reading ( instead of constant)
and check if you get 0 to Max scale...

if OK probleme is on divider voltage circuit..
You measure AMPS , is this circuit isolated from de other part PIC16F877
show us your exact drawing

madogas · Sep 17, 2013

this one is for measure from 0 to 30 volt and from 0 to 10A i did it in test board i have a driving kit for the pic. i want to measure any value of volt ant current in the past ranges

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when i measure the volt across the 20K it give me the value of volt that i connected to test the project but it displays a wrong value

paulfjujo · Sep 17, 2013

hello,

some remarks on hardware:
for voltage divider
the source voltage for ADC must be as low as possible of impedance
so reduce resistor divider value for voltage measurement
R1=10K R2=1,5K
idem for Amps measurement
R3=100k is to much , use 1K up to 4,7 maxi

Add 470µF in parralele with 100nF accross the battery 5V
Add a RC reset circuit on MCLR , not direct to 5V

madogas · Sep 17, 2013

this is the power for pic

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this is the power for pic

paulfjujo · Sep 17, 2013

hardware seems OK
so +5V is comming from a 5V regulator powered by 12V.

Do the tests on previous post and post results...

madogas · Sep 17, 2013

no Chang the same as wrong values i connect 9v as input the result is 30.88v and 5.6 A

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check the code

Code:

                              // LCD module connections
sbit LCD_RS at RB5_bit;
sbit LCD_EN at RB7_bit;
sbit LCD_D4 at RC4_bit;
sbit LCD_D5 at RC5_bit;
sbit LCD_D6 at RC6_bit;
sbit LCD_D7 at RC7_bit;

sbit LCD_RS_Direction at TRISB5_bit;
sbit LCD_EN_Direction at TRISB7_bit;
sbit LCD_D4_Direction at TRISC4_bit;
sbit LCD_D5_Direction at TRISC5_bit;
sbit LCD_D6_Direction at TRISC6_bit;
sbit LCD_D7_Direction at TRISC7_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,vp,ip,i;
  char *volt = "00.0";
  char *current = "0.00";
  TRISA  = 0xFF;
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  Lcd_Cmd(_LCD_CURSOR_OFF);

  do
  {

       ADCON1 = 0x00;
       v = ADC_Read(2);
       i = ADC_Read(3);
       i = (i*4.8828)/0.47;
       v = ((v*4.8828)/2)*12;
       if(v!=vp || i!=ip )
          Lcd_Cmd(_LCD_CLEAR);
       vp = v;
       ip = i;
       volt[0] = look(v/10000);
       volt[1] = look((v/1000)%10);
       volt[3] = look((v/100)%10);
       Lcd_Out(1,1,"Voltage = ");
       Lcd_Out(1,11,volt);
       Lcd_Out(1,16,"V");

       current[0] = look(i/1000);
       current[2] = look((i/100)%10);
       current[3] = look((i/10)%10);
       Lcd_Out(2,1,"Current = ");
       Lcd_Out(2,11,current);
       Lcd_Out(2,16,"A");
       Delay_ms(250);
  } while(1);
}

jayanth.devarayanadurga · Sep 17, 2013

What PIC are you using? 877A or 877? Why don't you use the code I posted? What does your switch case statement do? It doesn't have break;.

Add

Code C - [expand]
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TRISB = 0x00;
TRISC = 0x00;
PORTB = 0x00;
PORTC = 0x00;

madogas · Sep 17, 2013

finally i fix the problem thank you

the code is

Code:

                              // LCD module connections
sbit LCD_RS at RB5_bit;
sbit LCD_EN at RB7_bit;
sbit LCD_D4 at RC4_bit;
sbit LCD_D5 at RC5_bit;
sbit LCD_D6 at RC6_bit;
sbit LCD_D7 at RC7_bit;

sbit LCD_RS_Direction at TRISB5_bit;
sbit LCD_EN_Direction at TRISB7_bit;
sbit LCD_D4_Direction at TRISC4_bit;
sbit LCD_D5_Direction at TRISC5_bit;
sbit LCD_D6_Direction at TRISC6_bit;
sbit LCD_D7_Direction at TRISC7_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,vp,ip,i;
  char *volt = "00.0";
  char *current = "0.00";
  TRISA  = 0xFF;
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  Lcd_Cmd(_LCD_CURSOR_OFF);

  do
  {

       ADCON1 = 0x00;
       v = ADC_Read(2);
       i = ADC_Read(3);
       i = (i*4.89)/0.47;
       v = ((v*4.89)/1)*4.5;
       if(v!=vp || i!=ip )
          Lcd_Cmd(_LCD_CLEAR);
       vp = v;
       ip = i;
       volt[0] = look(v/10000);
       volt[1] = look((v/1000)%10);
       volt[3] = look((v/100)%10);
       Lcd_Out(1,1,"Voltage = ");
       Lcd_Out(1,11,volt);
       Lcd_Out(1,16,"V");

       current[0] = look(i/1000);
       current[2] = look((i/100)%10);
       current[3] = look((i/10)%10);
       Lcd_Out(2,1,"Current = ");
       Lcd_Out(2,11,current);
       Lcd_Out(2,16,"A");
       Delay_ms(250);
  } while(1);
}

the correct voltage divider

jayanth.devarayanadurga · Sep 17, 2013

Don't waste others time. You said you needed a range of 0 - 30V and you will measure 12V and now you are using another circuit whose range is 0 to 20V.

Try these changes.

Code C - [expand]
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char *volt = "00.0";
char *current = "00.0";
 
//v and i should be float type
 
v = v * 30.0 / 1023.0;
i = v * 10.0 / 1023.0;
 
volt[0] = (v / 10) + 48;
volt[1] = (v % 10) + 48;
volt[3] = ((v * 10) % 10) + 48;
 
 
current[0] = (i / 10) + 48;
current[1] = (i % 10) + 48;
current[3] = ((i * 10) % 10) + 48;

madogas · Sep 17, 2013

thank you jayanth.devarayanadurga , paulfjujo for your help i did it by your way now it is working thank you . if i want to use this project to control a relay connected with charger when the volt is less than 12 volt the relay switch the charger on other wise switch it off ???

jayanth.devarayanadurga · Sep 17, 2013

Code C - [expand]
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#define RELAY PORTD.F0      //RD0 is Relay pin.
 
 
if(v < 12.0){
    RELAY = 1;
}
else if(v >= 12.0){
 
    RELAY = 0;
}

madogas · Sep 17, 2013

thanks i do this can u correct it

Code:

                              // LCD module connections
sbit LCD_RS at RB5_bit;
sbit LCD_EN at RB7_bit;
sbit LCD_D4 at RC4_bit;
sbit LCD_D5 at RC5_bit;
sbit LCD_D6 at RC6_bit;
sbit LCD_D7 at RC7_bit;

sbit LCD_RS_Direction at TRISB5_bit;
sbit LCD_EN_Direction at TRISB7_bit;
sbit LCD_D4_Direction at TRISC4_bit;
sbit LCD_D5_Direction at TRISC5_bit;
sbit LCD_D6_Direction at TRISC6_bit;
sbit LCD_D7_Direction at TRISC7_bit;
// End LCD module connections
sbit rel at trisb.b1;

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,vp,ip,i;
  char *volt = "00.0";
  char *current = "0.00";
  TRISA  = 0xFF;
  TRISB = 0x00;
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  Lcd_Cmd(_LCD_CURSOR_OFF);

  do
  {

       ADCON1 = 0x00;
       v = ADC_Read(2);
       i = ADC_Read(3);
       i = (i*4.89)/0.47;
       v = ((v*4.89)/1)*4.5;
       if(v!=vp || i!=ip )
          Lcd_Cmd(_LCD_CLEAR);
       vp = v;
       ip = i;
       volt[0] = look(v/10000);
       volt[1] = look((v/1000)%10);
       volt[3] = look((v/100)%10);
       Lcd_Out(1,1,"Voltage = ");
       Lcd_Out(1,11,volt);
       Lcd_Out(1,16,"V");

       current[0] = look(i/1000);
       current[2] = look((i/100)%10);
       current[3] = look((i/10)%10);
       Lcd_Out(2,1,"Current = ");
       Lcd_Out(2,11,current);
       Lcd_Out(2,16,"A");

       Delay_ms(250);
         if(v=13.7,i=6.51)
       rel=0;
       else if(v<13.7,i<6.51)
       rel=1;
  } while(1);
}

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thanks i do this can u correct it iam using mickro c pro

Code:

                              // LCD module connections
sbit LCD_RS at RB5_bit;
sbit LCD_EN at RB7_bit;
sbit LCD_D4 at RC4_bit;
sbit LCD_D5 at RC5_bit;
sbit LCD_D6 at RC6_bit;
sbit LCD_D7 at RC7_bit;

sbit LCD_RS_Direction at TRISB5_bit;
sbit LCD_EN_Direction at TRISB7_bit;
sbit LCD_D4_Direction at TRISC4_bit;
sbit LCD_D5_Direction at TRISC5_bit;
sbit LCD_D6_Direction at TRISC6_bit;
sbit LCD_D7_Direction at TRISC7_bit;
// End LCD module connections
sbit rel at trisb.b1;

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,vp,ip,i;
  char *volt = "00.0";
  char *current = "0.00";
  TRISA  = 0xFF;
  TRISB = 0x00;
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  Lcd_Cmd(_LCD_CURSOR_OFF);

  do
  {

       ADCON1 = 0x00;
       v = ADC_Read(2);
       i = ADC_Read(3);
       i = (i*4.89)/0.47;
       v = ((v*4.89)/1)*4.5;
       if(v!=vp || i!=ip )
          Lcd_Cmd(_LCD_CLEAR);
       vp = v;
       ip = i;
       volt[0] = look(v/10000);
       volt[1] = look((v/1000)%10);
       volt[3] = look((v/100)%10);
       Lcd_Out(1,1,"Voltage = ");
       Lcd_Out(1,11,volt);
       Lcd_Out(1,16,"V");

       current[0] = look(i/1000);
       current[2] = look((i/100)%10);
       current[3] = look((i/10)%10);
       Lcd_Out(2,1,"Current = ");
       Lcd_Out(2,11,current);
       Lcd_Out(2,16,"A");

       Delay_ms(250);
         if(v=13.7,i=6.51)
       rel=0;
       else if(v<13.7,i<6.51)
       rel=1;
  } while(1);
}

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thanks can u correct this code

Code:

                              // LCD module connections
sbit LCD_RS at RB5_bit;
sbit LCD_EN at RB7_bit;
sbit LCD_D4 at RC4_bit;
sbit LCD_D5 at RC5_bit;
sbit LCD_D6 at RC6_bit;
sbit LCD_D7 at RC7_bit;

sbit LCD_RS_Direction at TRISB5_bit;
sbit LCD_EN_Direction at TRISB7_bit;
sbit LCD_D4_Direction at TRISC4_bit;
sbit LCD_D5_Direction at TRISC5_bit;
sbit LCD_D6_Direction at TRISC6_bit;
sbit LCD_D7_Direction at TRISC7_bit;
// End LCD module connections
sbit rel at trisb.b1;

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,vp,ip,i;
  char *volt = "00.0";
  char *current = "0.00";
  TRISA  = 0xFF;
  TRISB = 0x00;
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  Lcd_Cmd(_LCD_CURSOR_OFF);

  do
  {

       ADCON1 = 0x00;
       v = ADC_Read(2);
       i = ADC_Read(3);
       i = (i*4.89)/0.47;
       v = ((v*4.89)/1)*4.5;
       if(v!=vp || i!=ip )
          Lcd_Cmd(_LCD_CLEAR);
       vp = v;
       ip = i;
       volt[0] = look(v/10000);
       volt[1] = look((v/1000)%10);
       volt[3] = look((v/100)%10);
       Lcd_Out(1,1,"Voltage = ");
       Lcd_Out(1,11,volt);
       Lcd_Out(1,16,"V");

       current[0] = look(i/1000);
       current[2] = look((i/100)%10);
       current[3] = look((i/10)%10);
       Lcd_Out(2,1,"Current = ");
       Lcd_Out(2,11,current);
       Lcd_Out(2,16,"A");

       Delay_ms(250);
         if(v=13.7,i=6.51)
       rel=0;
       else if(v<13.7,i<6.51)
       rel=1;
  } while(1);
}

jayanth.devarayanadurga · Sep 17, 2013

Code C - [expand]
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if((v >= 13.7) && (i >=6.51))
       rel=0;
else if((v < 13.7) && (i < 6.51))
       rel=1;

madogas · Sep 17, 2013

thank you i will try it and till you the result

paulfjujo · Sep 17, 2013

I think you will have to add some hysteris value (example +-0.1) to avoid vibrate relais... or sharp situation
because of bit varation in ADC measure..
and also some spike due to the (solenoide) relais itself or in the contact if a big current pass trough.

Antiwheel diode accross relais solenoide + capacitor accross the contact

if((v >= 13.8) && (i >=6.6))
rel=0;
else if((v < 13.6) && (i < 6.4))
rel=1;

Are you sure to act on relay with the 2 conditions together ?
or if only one is over ... test with && or || function.

jayanth.devarayanadurga · Sep 17, 2013

Do as paulfjujo mentioned. It is better to check for any one parameter. Use Free wheeling diode and Snubber network for relay.

madogas · Sep 18, 2013

thanks for this useful things i will try it all and thank you all for help and iam sorry for your wasting time

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