Voltmeter and Ammeter using PIC Microcontroller

Voltmeter and Ammeter using PIC Microcontroller

Voltmeter and Ammeter can be easily made using PIC Microcontroller having ADC (Analog to Digital Converter). I am using PIC16F877A and the result is displayed on an LCD Display. PIC16F877A is enough if you do this project only for testing purposes. I suggest to use PIC with low pin numbers and multiplexed 7 segment display if you wish to use this as your measuring instrument.

Prerequisite

If you don’t know the basis of PIC ADC and LCD Interfacing please read the following articles.

ADC Calculation

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 VSS and VDD voltages (0 – 5V) of PIC.

This circuit is designed to measure 0 to 30V. So we will map 0 to 30V to 0 to 5V by using a voltage divider. Current through a circuit can be measured by introducing  a 1 ohm resistor and measuring the voltage across it. To minimize the path resistance we will use .47 ohm special resistor with fuse (shown in figure) and current is calculated. Voltage and Current Sampling circuit is shown below. When the Input voltage is 30V (max) the voltage across 20K ohm resistor becomes 5V which is feedback to the analog pin RA2 of the PIC Microcontroller.


The voltage across .47 ohm resistor is also feedback to the analog pin RA3 via 100K ohm resistor. 5.1V Zener Diode is added in parallel to these analog input pins to protect PIC from over voltages.0.47 ohm Resistor Fuse

The ADC module of PIC converts analog input to 10 bit digital number. We want to convert this digital to corresponding voltage in decimal.

  • 0v  =  0 0 0 0
  • 5v  =  1  1  1  1

Resolution = (Vref+ – Vref-)/(1024-1)   (as it is 10 bit ADC)

= 5/1023

= 4.887 mV

Thus it means that for a change in 4.887mV, the binary output changes by 1.

So voltage input to the analog pin of PIC can be calculated as follows…

v = ADC_Read(2);  // ADC value of channel 2 (voltage)
i = ADC_Read(3);  // ADC value of channel 3 (current)
V = v*4.89;       // Converting ADC value to mV
I = i*4.89;       // Converting ADC value to mV

By using values V and I we can calculate the Input Voltage and Current across the Load (Connected across Output terminals).

Voltage across 20K resistor = V

Current through 20K = V/20K

Input Voltage = Current through 20K * 120K  (Current flowing to PIC can be neglected)

Thus,

V = (V/20)*120;

Voltage across 0.47 ohm resistor = V

Current through Load = Current through 0.47 ohm resistor = V/0.47

Thus,

I = I/0.47;

To display the results in LCD Display we need to convert these readings into string, we use the user defined function look() for it. It converts each digit in the reading to corresponding character (see the source code).

Circuit Diagram

Note: VDD and VSS of the pic microcontroller is not shown in the circuit diagram. VDD should be connected to +5V and VSS to GND.

MikroC 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";
  CMCON = 0x07;
  TRISA = 0xFF;
  ADCON1 = 0x00;
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  Lcd_Cmd(_LCD_CURSOR_OFF);

  do
  {
    v = ADC_Read(2);
    i = ADC_Read(3);
    i = (i*4.89)/0.47;
    v = ((v*4.89)/20)*120;
    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);
}

You may also use IntToStr() to convert integer to string

Download Here

You can download the hex file, MikroC source code, Proteus files etc here…

 

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  • {
    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 ‘.’;
    }
    sir would you kindly clear me why above code is necessary for the project

  • Hi, i am using same circuit but amps is zero only, how i can increase or decrease amps,
    voltage is correctly showing 30V dc,
    i have also applied dc ammeter , it is also showing 0.00 value,

  • Hi Ligo sir,
    I am currently working with the wireless mobile charging. Will this idea work for changing Current and Voltages, and why did you used a 5 v battery for the Vpp input…???

  • Dear sir,could you please support me to know how select specific voltage to take a particular action thank you

  • Hello, Can you tell me a store where I find the resistor R4 0,47? What is the link to datasheet?

  • how can i run it plz ? how to do a simple simulation of this project , i’m new to this ! SOS

  • Hello Ligo, if i want to monitoring just the voltage can i delete the 0.47 resistor and 100k ?

    Cheers

  • Hello I’m a newbie in the world of PIC, and coding. I’m building a an ATS with vtage and current measurements. I have a simple diagram and when I try to implement the code all I see is a light on the LCD screen. I’m using Proteus 8, and mikroC. Please help me with any working diagram and code that is working.

  • Hi sir,
    can you explain to me what the R3 resistor is good for? Is it just for current flow reduction into the proc?
    Does it have any effect on the current measurement (along with 0.47R)?
    It seems to measure well, but…

    I changed the 0,47R resistor for 0.1R (with 3A load it would become quite hot (5W type) and I would like to reduce the heat). I have also changed the line “i = (i*4.89)/0.47” –> i = (i*4.89)/0.1. Proteus works fine, it shows correct numbers, but the hardware does not, unfortunately.
    With 12V and 100R resistor as a load it should show 0,12A (but it displays 0,09A), however, with 10R load it displays 1,35A (it should be 1,2A)… it seems the error grows with larger load and descends with lower load… ??? When I put 0,47R back, it works fine… Do you have any idea ? Thanks a lot… M.

  • Dear Mr. Mark,

    Sorry for the delay in reply. I will ready comments only when I get free time.

    Yes, I can help you regarding that. I have good knowledge in both hardware and software aspects of that project. You can write to me : [email protected]

  • Mr Ligo George can you help me

    Voltmeter and Ammeter using PIC Microcontroller but I am going to use online monitoring website to displayed the result instead LCD Display. Do you have any idea how create it? I am very thankful for your help

  • can i use a shunt of 200A/75mV in place of resistor of 0.47R and change the range of measure ? and how can implement this?

  • Today i worked on this project. First i want to thank you. I increased the amperes to 40 and it reads correctly in the proteus simulation. Used voltage divider on this circuit, setted the voltage formula x240, it is ok with 60 Volt. But when i use 1/3 divider and set the voltage formula to x 360, LCD shows me half of the real voltage.. So there is always half voltage at the screen after 60 V.

    i’m using cracked MikroC Pro.. May be because of it ?

  • HI you have an idea on ph metre using microcontroller pic16f877A

    and send to me program in mikroc

  • I am unable to multiply v & i because they in matrix form. Can u help me to multiply by converting them first to integer? I cant convert it to int. It gives me an error

  • Thank you Mr.Ligo

    could you please help me and edit the code to be able with using FloatToStr()

    I tried to much, but still NOT working , I really need your help.

    Thank you

  • hello sir, what is the result that displayed on ur lcd? i’ve got current = 0.00 and voltage = 00.0 . what should i do to change the value? hope for ur answer. tanks sir

  • Hello George,
    nice circuit you have built here 🙂 i’m trying to build one myself…still learning some details… can you tell me what is the maximum current intensity shown on the ldc?

  • You mean AC or DC ?
    If it is DC you may use proper voltage dividing resistors for that.. but it is recommended to use proper isolation as you are playing with HIGH voltages.

  • why you use :

    volt[0] = look(v/10000);
    volt[1] = look((v/1000)%10);
    volt[3] = look((v/100)%10);

    why %10 !!
    why in current you used [0] [2] [3] And in voltage you used [0[2][3]

  • hello i’ve built it(although i used a pic16f88) and it works like a charm and now i would like to send the results through parallel transmission to a second pic robot brain. my problem is that i have not enough pins can i use the pins that interface with the lcd to also be used in the parallel transmission?
    thanks a lot in advance

  • hi ligo can you help me. i’ve used your circuit and code above. the problem is when connected to the lcd display it only displays bar on the lcd thanks i hope you can help me

  • Hi,
    volt and amps meter you are using ic PIC16F877A , when i use pic16f73 . not working. showing wrong voltage..
    whats the problem?

    Code:

    // LCD module connections

    sbit LCD_RS at RB2_bit;
    sbit LCD_EN at RB3_bit;
    sbit LCD_D4 at RB4_bit;
    sbit LCD_D5 at RB5_bit;
    sbit LCD_D6 at RB6_bit;
    sbit LCD_D7 at RB7_bit;

    sbit LCD_RS_Direction at TRISB2_bit;
    sbit LCD_EN_Direction at TRISB3_bit;
    sbit LCD_D4_Direction at TRISB4_bit;
    sbit LCD_D5_Direction at TRISB5_bit;
    sbit LCD_D6_Direction at TRISB6_bit;
    sbit LCD_D7_Direction at TRISB7_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;
    TRISB = 0x00; // Battery charing on off port
    PORTB = 0x00;
    TRISC = 0x00; // Load OUTPUT
    PORTC = 0x00;
    Lcd_Init();

    Lcd_Cmd(_LCD_CLEAR);
    Lcd_Cmd(_LCD_CURSOR_OFF);

    do
    {

    ADCON1 = 0x00;

    v = ADC_Read(2);
    i = ADC_Read(3);
    s = ADC_Read(1);
    i = (i*4.89)/0.47;
    v = ((v*4.89)/20)*120;
    s = ((s*4.89)/20)*120;

    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);

    }

  • hmm
    How can i controls PORTD0 LED. 11V up PORTD0 Led off, 11v under PORTD0 LED ON.
    when amper 1 up PORDT0 LED ON. under PORTD0 LED off.

    how to write like this coding. can u help me?

  • Thank u for replay.

    // function 1 when volt 11 under i want PORTD0 LED on.

    when i remove code // function 2, this time // function 1 PORTD0 led is working,

    when add // function 2 this time //function 1 PORTD0 not working. but i don’t understand why not working.

  • 12F675 is an 8 pin ic right ?
    There will be 6 pins for I/O operations if we use internal oscillator and MCLR as IO..
    But you need those 6 pins for connecting LCD…
    Then how will you measure voltage/current ?

    You may use serial LCD to save pins.. but it is better to use a microcontroller having more pins..

  • hi ligo,

    i’ve read through most of your posts and their comments and i like how u respond to quenstions quickly in the comments section. it’s good for learning. keep it up.

    i’m building a power inverter and i think i can adapter this meter, with some modifications, to my project to display battery voltage, load current and power on 16×2 lcd.

    my doubt is the pic i want to use is 12F675, will it work?

  • Hello sir,

    i face problem this code. can u solve this problem

    function 2 is working But my problem is function 1 when 11v under PORTD0 led not on always off.
    why always off?

    // function 1
    if(v = 1)
    {
    PORTD.F0 = 1; // LED off
    PORTD.F5 = 1; // LED ON
    }
    else
    {

    PORTD.F0 = 0; // Load ON
    PORTD.F5 = 0; // Load ON
    }

  • mm, reading that, I think that degrades more with the offset voltage of the internal op-amp, argh. Thank you

  • Even if you are using 0.47 ohm resistor… it actual value may vary.. Values each component you are using may vary like this .. So calibrate your program with a standard multimeter by multiplying / adding with a constant… through a series of tests..

  • im sorry , i meant to say in series. I have used a 1watt .47ohm resistor,to measure the current .Do u think this might be the issue.

    im using 6 leds in series =19.8V 150mA(If=150mA for each led)

    the voltage and current is provided by the DC source 19.8V 150mA. When i connect the ammeter in series with the led strip it reads 160mA whereas on the LCD it reads .28 A . I tried to make changes in code.But nothing helps.Kindly help.

  • Hi, what if, for example, my Vref+ is 20mV and my Vref- is 10 mV and I use a 10 bits ADC, does the chip can read voltages in order of microvolts? I can’t find it in datasheet. Thanks for the help.

  • sir, is not working..

    code:

    if(v == 10)

    {

    PORTD.F0 = 1;

    }

    when i change like this led on but problem is always led on.

    if(v > 10)

    {

    PORTD.F0 = 1;

    Delay_ms(10);

    }

  • Current Across LED ??

    Current measurement should be done in series with LED..

    Just measure the actual current using ammeter … and let me know both values..

  • hi lijo, i have tried the same circuit in order to measure voltage and current across leds, the voltage is working perfect, wheras im facing issue while displaying current.The current value is always flickering and hardly shows the right current value, could you please suggest a fix.

  • hi lijo, i have tried the same circuit in order to measure voltage and current across leds, the voltage is working perfect, wheras im facing issue while displaying current.The current value is always flickering and hardly shows the right current value, could you please suggest a fix. im using in4007 instead if in4733A,is it ok?

  • hi lijo, i have tried the same circuit in order to measure voltage and current across leds, the voltage is working perfect, wheras im facing issue while displaying current.The current value is always flickering and hardly shows the right current value, could you please suggest a fix.

  • Hi logo

    you are using pic16f877a Voltmeter and Ammeter. when i use ic pic16C73B volt and ammeter not perfect working.
    what’s problem i don’t understand. i just change ic…

    I attach picture file.

  • HI, is not working led on off when 10 volt led on, 10 volt up led off here is code. can u tell me what the problem.

    // 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;

    TRISD.F0 = 0;

    PORTD.F0 = 0;

    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)/20)*120;

    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);

    //——led on off—————–

    if(v == 10)

    {

    PORTD.F0 = 1;

    }

    else if(v > 10)

    {

    PORTD.F0 = 0;

    }

    } while(1);

    }

  • Hi logo. I want add led in voltmeter . How write code . when voltmeter show 10 volt Led on. When 10volt up led off.

  • Hi,this line ( i = (i*4.89)/0.47; V = (V/20)*120; ) How to find for amps 0.47 this number , and for volt this number 20,120 . i don’t understand can u explain me.

  • Hello Mr Ligo

    I try to make a project and I have some difficulties…

    Here is my code..

    // LCD module

    sbit LCD_RS at RD2_bit;

    sbit LCD_EN at RD3_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;

    //End of LCD Module

    //LCD pin direction

    sbit LCD_RS_Direction at TRISD2_bit;

    sbit LCD_EN_Direction at TRISD3_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

    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,v1;

    int x,j ;

    char *volt = “00.0”;

    char *volt1 = “00.0”;

    TRISA = 0xFF; //PORTA is Input

    TRISE.F0 = 0xFF; //RE0 is Input

    TRISE.F1 = 0xFF; //RE1 is Input

    TRISB.F0 = 0; //RB0 is Output

    TRISB.F1 = 0; //RB1 is Output

    TRISC.F2 = 0; //RC2 is Output

    Lcd_Init();

    Lcd_Cmd(_LCD_CLEAR);

    Lcd_Cmd(_LCD_TURN_ON);

    Lcd_Cmd(_LCD_CURSOR_OFF);

    PWM1_Init(400); //PWM duty cycle 75%

    PWM1_Start();

    PWM1_Set_Duty(192);

    do

    {

    Lcd_out(1,1,”TASK No3″);

    if (PORTE.F1==1){

    Lcd_out(3,-3,”OVERFLOW”);

    }

    ADCON1 = 0x00;

    v = ADC_Read(2);

    v1 = ADC_Read(3);

    v1 = ((v1*4.89)/20)*120;

    v = ((v*4.89)/20)*120;

    volt[0] = look(v/10000);

    volt[1] = look((v/1000)%10);

    volt[3] = look((v/100)%10);

    Lcd_Out(3,-3,”Voltage = “);

    Lcd_Out(3,8,volt);

    Lcd_Out(3,12,”V”);

    volt1[0] = look(v1/10000);

    volt1[1] = look((v1/1000)%10);

    volt1[3] = look((v1/100)%10);

    Lcd_Out(4,-3,”Voltage1 = “);

    Lcd_Out(4,8,volt1);

    Lcd_Out(4,12,”V”);

    Delay_ms(250);

    PORTB = 0;

    Lcd_Out(2,1, “00011000”);

    delay_ms(200);

    PORTB = 1;

    Lcd_Out(2,1, “00100100”);

    delay_ms(200);

    PORTB = 2;

    Lcd_Out(2,1, “01000010”);

    delay_ms(200);

    PORTB = 3;

    Lcd_Out(2,1, “10000001”);

    delay_ms(200);

    PORTB = 2;

    Lcd_Out(2,1, “01000010”);

    delay_ms(200);

    PORTB = 1;

    Lcd_Out(2,1, “00100100”);

    delay_ms(1);

    } while(1);

    }

    I use PIC16F877A and proteus for simulation.

    My problem is in this point of my code:

    if (PORTE.F1==1){

    Lcd_out(3,-3,”OVERFLOW”);

    }

    My PIC do not write OVERFLOW and simply read the analog value…

    Also, when I put a motor with PWM technique the hole program became very slow

    PWM1_Init(400); //PWM duty cycle 75%

    PWM1_Start();

    PWM1_Set_Duty(192);

    Thanks for your time…!

  • Yes, you are right… but it will take some time to list all commonly used components and modules…. We need to buy all items before listing from wholesale dealers.. It needs time and money…
    Thanks… 🙂

  • 1n4733a ഒരിടത്തും ഇല്ല. tutorial പോസ്റ്റ്‌ ചെയ്യുന്നതോടൊപ്പം അതിനാവശ്യമായ എല്ലാ കംപോനെന്റ്സും സ്റ്റോറിൽ ഇട്ടാൽ വളരെ നന്നായിരിക്കും.

  • Can we use this circuit for continues(24*7) voltage measurement of a 12v lead acid battery?

  • Actually, I didn’t get what your are asking… I hope that 3 LEDs are connected in series so total voltage drop = 3.3 + 3.3 + 3.3 = 9.9V …. You can connect voltage divider (R1 + R2) parallel to these LEDs …
    Then you can measure the voltage as done in above project… … You can download the code above.

  • hi, im trying to measure voltage across an led ,by using 2 resistors in series like divider and feeding output to adc,each led takes 3.3v,now suppose i use 3 leds i need my lcd to display voltage as 9.9,could you please suggest me some solutions with respect to coding.,i am using adc, with an input of 9.9v,im getting drop of 1v acrsoss led,and adc value of 200,

  • Hi,George,

    Nice project ,and i am try to do this myself,but i have one doubt and two problem to resolve,hope you will help me.
    in your schematic you have grounded both end of the resistor 0.47 and serially connected a resistor 100k and put it to the microcontroller is it ok?

    because this configuration did not give me the current reading,but when i ungrounded the one end of the resistor 0.47 and one end of resistor 100k connected with positive terminal of input voltage it will show the current.

    next,voltage reading after decimal point are highly fluctuate how can i made it stable??

    next,I want to take this reading voltage as well as current into PC through serial port and plot a real time graph can you please help me out to do this,

    Thakns in advance. 🙂

  • Hi,George,

    Nice project ,and i am try to do this myself,but i have one doubt and two problem to resolve,hope you will help me.
    in your schematic you have grounded both end of the resistor 0.47 and serially connected a resistor 100k and put it to the microcontroller is it ok?

    because this configuration did not give me the current reading,but when i ungrounded the one end of the resistor 0.47 and one end of resistor 100k connected with positive terminal of input voltage it will show the current.

    next,voltage reading after decimal point are highly fluctuate how can i made it stable??

    next,I want to take this reading voltage as well as current into PC through serial port and plot a real time graph can you please help me out to do this,

    Thakns in advance. 🙂

  • Hi, this is an excellent example. I have a very newbie question though…I got the simulator running in Proteus but I don’t see any amps or volts on the LCD, it prints out 0.00 for both values. Now I read from all the comments that I need to add a load. So I have 2 questions how do I specify the voltage and the load on the existing circuit?

  • i couldn’t find pic16f877A i using pic16f877 20/p if i specify it in microC and proteus it should still work? the pin layout practically the same

  • hii,,

    I can t able to read 5 adc ports at the same time…..
    I can able to read the values of 3 adc ports and displayed in lcd perfecty….help….

  • hello sir, measuring voltage was very helpful.i am using 18f4550 and coding in mikroc. i would like to know if there is anyway that i can measure frequency using zcd or convert it to voltage. if there is anyway pls help me. thanks in advance.

  • Hello …
    i have a problem with my DVM, when i measure a voltage a cross battery , it give a half voltage of battery

    Note: i don’t use above circuit , My circuit is attached bellow

  • It will work perfectly without that resistor….
    It can be used to protect the microcontroller from over voltage/current…..
    If the input voltage is above 5.1V .. zener conducts… R3 will limit the current through the zener…
    Zener and R3 can be avoided if you are sure about input voltage and current range..

  • By blank I meant that the LCD is powering up , but is all blank , doen’t display anything.
    And yes , I did try adjusting the contrast using the Pot , it was working.
    According to the code , I should atleast be getting “Voltage = ” and “Current= ” on the LCD , but I get nothing. The LCD just powers up all blank green.

  • Sir,
    I am trying to program the PIC16F887A using an ICD 2 programmer by simply importing the .hex file in MPLAB IDE and then writing the file to the chip , but my LCD display stays all blank ( all connections made according to the schematic provided ).
    Could you suggest a solution?
    Would appreciate a ton 🙂

  • Import means?? You need to just open the .mcppi file with mikroc pro..
    If it is not working.. try creating a new project… and copy paste my code..don’t forget to set the microcontroller to 16F877A and clock frequency to 8MHz when you create a new project.

  • Hi once more… finally got it work !!! 🙂
    But I have one more question : I import the *.mpcii file into microC 8 Pro for Pic. I can see the C code. I do NO changes and I build the project. I get 4 warnings of: “search path does not exist (c:users…defs; c:users…usesp16; f:electronicsembeddedvoltmeter; and f:electronicspower supply” – the first 2 dirs ARE there, the 2nd two not – I dont have F drive !). But the build is compiled successfully.
    I have a new hex file and import the design into proteus 8 pro where the new hex is assigned to the PIC. But it doesn´t work – the display shows blinking letter V only (like Volts). I have many warnings of one kind repeatedly occurring – “PIC16CORE – PC=0x0421 Indirect write of 0x30 to address 0x0000 is itself an indirect write”.
    My hex is 70 bytes shorter and 35 words shorter than yours. Just mentioning once more – I do NO changes to your C code !!
    If I upload your hex, it works fine.
    What am I doing wrong ??? Any settings anywhere ???
    Thanks once more…:-)

  • Gregory
    Hi Sir. How would you eliminate the leading zero when the voltage or current displayed is less than 1? For example: 250mA as displayed 0.25A is changed to .25A or 450mV as displayed 0.45V is changed to to .45V

  • You should use low value resistor.. which is able to withstand 70 amps…. I haven’t any experience with such high current.. try searching on google…
    I thinks that it is better to use current transformer instead of resistor..

  • Hello Sir, thank you for all of your help! I would like to measure up to 70 amps, what kind of resistor would I need? Would anything else need
    to be changed in the circuit? Thanks!

  • Usually we can write hex file to pic… just by selecting the microcontroller in programmer software….
    Sorry, I have no idea about your programmer….. try searching on google..

  • Yep, I AM using 16F877A chip and it IS properly selected in my programmer [checked several times]. How about the fuses ? Do I have them set well ?
    Thanks anyway… 🙂

  • Sorry, I am not familiar with your programmer..
    Verify that you are using PIC 16F877A and it is selected properly in your programmer settings..
    Note that PIC 16F877 and PIC 16F877A are different microcontrollers..

  • Hi Sir,
    I’ve built this ammeter exactly as you show here on this website. However, after connecting it to Vdd [no voltage on input], the display shows no data. [I expected 0V at least. I also checked the trimmer for contrast but in vain].
    What fuses should be set when uploading the *.hef file into the chip ???

    After burning the PIC I have this error – Fuse Error : 0x2007, Good : 0x3F79, Bad : 0x3F7A.
    I am using the K150 chip programmer and the fuses are set like this : WDT-disabled, BODEN-enabled, CPD-disabled, Debug-disabled, Code Protect-disabled, PWRTE-disabled, LVP-disabled, WRT enable-enabled, Oscil-XT
    I can read the chip after burn and the code is inside, but verify goes wrong.
    ROM ends on line 538 with number 0008 [after it just 3FFF]
    Can you help me with this , pleeease ???
    Thanks a lot …

  • Download the above program… and go to mikroc project settings…
    Then change the device 16F877A to 16F883…. then rebuild the project..
    Then you will get the new hex file corresponding to your pic..

  • sir this download is not starting.i click download button my account is automatically logout. please solve thi problem

  • It is to convert the integer voltage to corresponding string… You can do it in many simpler ways…
    If V = 546000
    then volt[0] = ‘5’
    volt[1] = ‘4’
    volt[2] = ‘.’
    volt[3] = ‘6’
    so… volt = “54.6”

  • Sir, would u pls explain this lines

    volt[0] = look(v/10000);
    volt[1] = look((v/1000)%10);
    volt[3] = look((v/100)%10);

  • Sir,

    As you say I multiply current and voltage but the output gives weird.
    Would you pls check where I have done wrong I pest full code and output
    image here. I put i=10; as testing purpose.

    // 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,w;
    char *volt = “00.0”;
    char *current = “0.00”;
    char *watt = “00.0”;

    TRISA = 0xFF;
    Lcd_Init();
    Lcd_Cmd(_LCD_CLEAR);
    Lcd_Cmd(_LCD_CURSOR_OFF);

    do
    {

    ADCON1 = 0x00;
    v = ADC_Read(2);
    i =10;// ADC_Read(3);
    i = (i*4.89)/0.47;
    v = ((v*4.89)/20)*120;
    w = v*i;

    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(1,1,volt);
    Lcd_Out(1,6,”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(1,9,current);
    Lcd_Out(1,14,”A”);
    //Delay_ms(250);

    watt[0] = look(w/10000);
    watt[1] = look((w/1000)%10);
    watt[3] = look((w/100)%10);
    Lcd_Out(2,1,watt);
    Lcd_Out(2,5,”W”);

    } while(1);
    }

  • Sir,

    As you say I multiply current and voltage but the output gives weird. Would you pls check where I have done wrong I pest full code and output image here. I put i=10; as testing purpose.

    // 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,w;
    char *volt = “00.0”;
    char *current = “0.00”;
    char *watt = “00.0”;

    TRISA = 0xFF;
    Lcd_Init();
    Lcd_Cmd(_LCD_CLEAR);
    Lcd_Cmd(_LCD_CURSOR_OFF);

    do
    {

    ADCON1 = 0x00;
    v = ADC_Read(2);
    i =10;// ADC_Read(3);
    i = (i*4.89)/0.47;
    v = ((v*4.89)/20)*120;
    w = v*i;

    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(1,1,volt);
    Lcd_Out(1,6,”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(1,9,current);
    Lcd_Out(1,14,”A”);
    //Delay_ms(250);

    watt[0] = look(w/10000);
    watt[1] = look((w/1000)%10);
    watt[3] = look((w/100)%10);
    Lcd_Out(2,1,watt);
    Lcd_Out(2,5,”W”);

    } while(1);
    }

  • for a 10bit adc of reference voltages…. 0 and 5V..

    INput —- > ADC-Output

    0 —-> 0000000000

    4.887mV—-> 0000000001

    2.5 —-> 0000011111

    5V —-> 1111111111

    So ADC output is not voltage.. it is the corresponding 10 bit digital value……

    You can convert it to any format as per your requirement…… Here for convince .. it is converted to milli volt…..

    Read this article carefully..

    Try this too..

    http://www.electrosome.com/analog-to-digital-converter-pic/

  • do you have any website or link which could help me understand basic sampling from volttage drop to adc,,,if yes pls provide

  • is it mandate to always covert into millivolt,can i use the corresponding adc value read as my voltage value and convert it to current and use it….

  • V = v*4.89; // Converting ADC value to mV
    SO U MEAN TO SAY THAT 4.89 IS MULTIPLIED JUST TO CONVERT THE VOLTAGE DROP TO MILLIVOLT ???

  • 1. Adjust the potential divider network for the required voltage range..
    2. Yes.. for measuring AC.. .first convert it to dc.. the ac voltage = dc voltage/squrt(2)
    3. Max current depends on the series resistor…here it is 5V/0.47 …
    4. Yes you can measure both voltage and current…. In DC, you can measure power by just multiplying current and voltage..

  • Hello Sir,
    This is a wonderful project. But I have some question.
    1. If we want to measure voltage higher then 30V (like 300V) what to do?
    2. Can we measure both AC and DC volt with this module?
    3. What is the max current that can measure by this module?
    4. If we can measure both current and voltage, we can find energy by multiplying them and display in LCD. What should be the code for doing so?
    Pls discuss.

    Best Regards

  • My query is related to pwm- is it possible to switch voltage levels in ton of a same duty cycle i.e. in the on time i want to divide on time of the duty cycle into 3 samples,provide (assign) three different voltages into these 3 samples -is it possible? i am reading the voltage across resistor to adc pin of uC and displaying voltage on scope thru pwm pin.pls help.

  • To measure current through LED, put a 0.47 ohm fusible resistor (power rating depends of the current required for the LED…. give the voltage across that resistor to the ADC input of PIC… as given in the above circuit diagram… Note one thing, if you are using 2 power supplies, both of them should have a common ground.. as given above..

  • It is very simple to change the hex file…. you just edit the mikroc program by changing the constant andthen Build the project… The new hex file will be generated automatically..

  • Sir
    do I have to change even the hex code, if so can you help me with it also with the program. im such a bad programmer.

  • Sir

    do I hev to change even the hex code for a 0 to 10 V and 4 to 20 mA, if so can you help me with it also with the program. im such a bad programmer.

  • that’s working really good. but I would also want to know how to display only 0 to 10 V and 4 to 20 mA if you can help me with the program. Thanks in advance.

  • That code is not completely correct… I think you need to send voltage and current to second pic. .then why you are writing PORTB to UART…?? if so write voltage and current……

  • hello do you agree with this?
    MikroC Code

    Transmitter

    void main()

    {

    unsigned int v,vp,ip,i;
    TRISA = 0xFF;

    PORTB = 0;

    do

    {

    ADCON1 = 0x00;

    v = ADC_Read(2);

    i = ADC_Read(3);

    i = (i*4.89)/0.47;

    v = ((v*4.89)/20)*120;

    if(v!=vp || i!=ip )

    vp = v;

    ip = i;

    }

    while(1);

    UART1_Init(9600); // Initialize UART module at 9600bps

    Delay_ms(100); // Wait for UART module to stabilize

    while (1)

    { // Endless loop

    UART1_Write(PORTB); // and send data via UART

    Delay_ms(500);

    }

    }

    Receiver

    void main()

    {

    TRISB = 0;

    PORTB = 0;

    UART1_Init(9600); // Initialize UART module at 9600bps

    Delay_ms(100); // Wait for UART module to stabilize

    while (1)

    { // Endless loop

    if (UART1_Data_Ready())

    { // If data is received,

    PORTB = UART1_Read(); // read the received data,

    }

    }

    }

  • hi i have problem the voltmeter dose not give me right reading when the input is 9 the reading is 30.9 when i test it with avometer across 20k its reads 9 but the lcd reads 30.9 … help me

  • hello first of all nice work
    secondly can you help me with a project of mine?
    can i use pic16f88 instead of pic16f877? what changes would i have to make?
    how can i have a serial output? i want to send it to another pic16f628.

  • Nop, but you can convert it to Hi-Tech C by just by replacing ADC functions, lcd functions and some register assigning statements.. See our Hi-Tech C LCD and ADC tutorials..

  • Hi great projedt1 I just have one question..what is the max. amp’s. that this circuit can read in this program ?Thanks in advance.

  • The code with this report is not working. But in Proteus, Its work well. But I cant Burn the chips. But intime, I can burn other programme to the same chips. That means, the programmer and the chip are good….
    Hope your help soon..

  • Hi my friend.
    Thanks from software and hardware of VM-AM whit PIC16F877A.
    I have made it Voltage is shown up correct bt the amps on 12.00V is shown 160mA without load. What did I do wrong.
    Best Regards

  • Is it possible to measure Resistance by simply dividing measured voltage v by measured current i ? I guess the only problem is that the Resistance to be measured must have a voltage across it

  • hi if wont use this module to 230v i can use transformer and low down the voltage dc 5 but where should i change the programmer?
    do you have any tutorials about RF modules and compactors?
    thank you vary much

  • The hex file in the above zif folder is 100% working. Now I checked its working in Proteus ISIS. We don’t provide any wrong hex files in this website.

  • Hi, my friend L George.
    Thanks from replay. O yeah the pic is PIC16F877A and hex does not works. Crystal is 8MHz.
    My friend I am bad programmer and I do not know to make HEX file, but I am electronic engineer. I do not have any problem to make PCB and I made it. But hex file make me solid problem. Please would you like to send me one time again that hex file.
    Best Regards my friend L George and have a nice day.
    Vanja

  • Hi my friend.
    I have made this very nice VM-AM, but the HEX file is wrong.
    Please would you like to send me new hex file.
    Best Regards
    Vanja

  • Good evening Thanks very much the friend Ligo George , i tried use too MikroC PRO 5.8.0 but don’ works, if possible you help me i need ready 40V 30A , possible compiler for me , since already thanks very much one more time , have great hug from Brazil.

    Elionaldo.´.

  • // 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)/0.235;
    v = ((v*4.89)/20)*120;
    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);
    }

    error in compiling

    2:0 11 ‘;’ excepted but LCD_RS found
    2:0 12 Internal error
    I need help to on this file i used MikroC 8.2 , i try make it to read Current 20A , since already thanks very much.
    Elionaldo.´.

  • Hi , I have made this great meter but i have i small problem ow he is in my powersupply the suppl is 24 volt and 5 amp and when i have no load the current gives me 150ma the voltage is perfect what can i dot to change is to zero?
    I doint now how to change the software is there a way with a resistor or something?
    Thank and sorry for my bad english

  • Wonderfull project i want to make it thanks for it!

    I have 2 questions:

    a what kind of crystal you use
    and can i take the 5v from the same travo or do i use a second supply for the PIC ?
    Thanks

  • use 8Mhz oscillator… connect mclr to VDD…
    ignore other settings…

    For current you should connect a load in series with 0.47 ohm resistor…

  • HI there !

    when i connect a battery through a pot at the INPUT it shows Volts on the Lcd but not the amps ! so what i am doing wrong !

    and kindly tell me the configuration settings i.e

    Oscillator , MCLR, PWRT , WDT OFF.
    regards

  • Yes, this comes under the title PIC 16 analog inputs… as this project uses ADC of PIC 16F877A………. You can download proteus files at the bottom of the article..

  • thx for this but i have a question. I have a project titled “PIC 16 analog inputs”. That’s the title, i find it vague. So i was wondering if this fits for that category. We also have to use proteus isis 7 professional to simulate. It’s purely educational it doesn’t have to be actually created as hardware. Note : i am new to this domain but i’m a fast learner.

  • hello sir,
    i using dspic33 ,in .C language,and using mikroC debugger. i have coded it but appear error at ” ADC_READ undeclared identifier”..here my code,can u explain the error why the error.hope ur reply soon.
    ===============================================================
    // LCD module connections
    sbit LCD_RS at RB5_bit;
    sbit LCD_EN at RB6_bit;
    sbit LCD_D4 at RB0_bit;
    sbit LCD_D5 at RB1_bit;
    sbit LCD_D6 at RB2_bit;
    sbit LCD_D7 at RB3_bit;

    sbit LCD_RS_Direction at TRISB5_bit;
    sbit LCD_EN_Direction at TRISB6_bit;
    sbit LCD_D4_Direction at TRISB0_bit;
    sbit LCD_D5_Direction at TRISB1_bit;
    sbit LCD_D6_Direction at TRISB2_bit;
    sbit LCD_D7_Direction at TRISB3_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
    {

    AD1CON1 = 0x00;
    v = ADC_Read(2);
    i = ADC_Read(3);
    i = (i*4.89)/0.47;
    v = ((v*4.89)/20)*120;
    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);
    }

  • hello sir, in my Embedded course project,i must using this dspic33fj128gp802 PIC. so,which code in asm that i need to change..sorry,i’m newbie about this embedded system.hope u can help me figure i out..thanks for ur support

  • Nop, 0.47 ohm resistor is connected in series with load, so current through it depends on the load resistance…. and the voltage across the 0.47 resistor is given to an analog pin of pic microcontroller..

  • Hi! can you please explain in depth what resistors R3 and R4 do? For example, if the input voltage is 30volts on the .47ohm resistor, wouldnt that make the current 63 amps?! wouldnt that fry the micro controller?

  • hello sir, i can’t download the hex file, mikroC and proteus files cause i can’t register
    would you help me?

  • I mean to say the values display on LCD keep on fluctuating without connecting any measurement…so what could be the reason ?

  • Hello sir,

    i have made this great Digital Meter + Ammeter. But as soon as i finished programming it with my Pickit3 the values of current and voltage are dancing/fluctuating randomly and its not measuring any value… could u tell me what could be the reason ?

  • You can use 1/4 watt resistors for R1, R2, R3. Better to use resistors of tolerence 1%. After completing the project measure the value of R1 & R2 and change the program accordingly for accurate results..

  • hello
    I am French and would like to get into this project before but I want to know what tolerence in% and W for resistance R1, R2, R3
    1% 0,6 W?
    thank you

  • You may use a small value capacitor (0.001uF) parallel to reduce voltage fluctuations ……… Change the +Vref & -Vref according to voltage that to be converted to digital to increase the accuracy of the adc conversion.

  • I built this circuits and thanks. However, following are my observations:-
    1) For higher amp it reads data properly (e.g. higher than 500mA), but for values lower than 50mA it does not show the correct conversion/ reading
    2) Also ADC pin reading are not stable and changes upto +/-3 times, where as load/amp has not been changed
    3) I also found that PIC ADC cannot read value below 20 mV and if voltage at ADC pin is lower than it shows output 0 (Zero).
    4) also lower amp value shows slightly lower and higher amp values show slightly higher

    Thanks.

  • Using PIC microcontroller we will read the voltage across 20K resistor, then the current through it can be calculated by dividing it with 20K…………
    Then the input voltage can be calculated easily by multiplying current through 20K ohm resistor * 120K

  • ill just add you sir in your facebook and maybe ill send the schematic there because in email it fails. thank you sir!

  • sir this is my code in my digital ohmmeter. i hope you can help me with this….

    // LCD module connections sbit LCD_RS at RC4_bit; sbit LCD_EN at RC5_bit; sbit LCD_D4 at RC0_bit; sbit LCD_D5 at RC1_bit; sbit LCD_D6 at RC2_bit; sbit LCD_D7 at RC3_bit; sbit LCD_RS_Direction at TRISC4_bit; sbit LCD_EN_Direction at TRISC5_bit; sbit LCD_D4_Direction at TRISC0_bit; sbit LCD_D5_Direction at TRISC1_bit; sbit LCD_D6_Direction at TRISC2_bit; sbit LCD_D7_Direction at TRISC3_bit;// End LCD module connections// Define Messages

    void main() { char message1[] = “DIGITAL OHMMETER “; char *temp = “0000000”; unsigned int v,R1,R2,VCC;  TRISC = 0; // PORTC All Outputs  TRISA = 0b000011; // PORTA All Outputs, Except RA3 and RA2    Lcd_Init();                      // Initialize LCD  Lcd_Cmd(_LCD_CLEAR);             // CLEAR display  Lcd_Cmd(_LCD_CURSOR_OFF);        // Cursor off  Lcd_Out(1,1,message1);           // Write message1 in 1st row  do {  ADCON1 = 0x00;  VCC=5000;  R1=10000;  v = ADC_Read(1);  R2=((v*4.89*R1))/VCC-v*4.89;     temp[0] = (R2/1000000)+48; // Add 48 to get the ASCII character value   temp[1] = ((R2/100000)%10) + 48;   temp[2] = ((R2/10000)%10) + 48;   temp[3] = ((R2/1000)%10) + 48;   temp[4]=  ((R2/100)) %10+48;   temp[5] =  (R2%10)%10 + 48;   temp[6] =  R2%10 + 48;   Lcd_Out(2,7,temp);   Delay_ms(400);  } while(1); }

    we are encountering problems in displaying it in the LCD. because for example our. R1(fixed)=10000 ohms and our R2(to be measured)=5k ohms. in the display it shows only. less than the desired value..

    i will send our ckt diagram in your email sir. because we have problems in uploading the image here. thanks sir!

  • I use those steps for converting integer to string to be displayed in the LCD………….You needn’t bother about it use inbuilt functions of mikroC such as FloatToStr() , IntToStr()
    to convert numbers to corresponding string…

  • can you explain this part sir i get confused with this:

    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”);

  • Yes you can put that equation in mikroC…
    Note that actual voltage is adc value * 0.00489 …
    I used 4.89 to minimize the floating point calculations…..

    Declarations are similar to C…
    int variable_name;
    float var_name;
    short var_name;
    etc………

  • sir using this:

    VCC=5V
    R1=known resistance or(fixed R1)
    R2= unknown or to be measured
    v= adc value * 4.89

    from:

    v=(R2*VCC)/(R1+R2)

    i will find R2

    after rearranging the equation

    it will come up like this sir:

    R2=(v*R1)/(VCC-V)

    so sir. can i directly put this equation in mikroC compiler?

    how about the declaration in mikroC sir?. thank you sir!

  • Circuit is a problem………….

    Use a potential divider to find unknown resistance………..
    Connect unknown resistance in series with a known resistance………You may change the known resistance according to the range of Unknown resistance to be measured.

    Then by reading voltage across unknown resistance we can easily calculate unknown resistance………

    In MikroC you can use the same expressions as in C…….

  • sir we dont have a problem with our circuit, but our problem is coding, if you could please make a sample code for us it would be a big help.

  • I think it is better to use Wheatstone bridge to find unknown resistance. In this case you need’nt change the +Vref,,,,,,,,,,,,,,instead of you can change the known resistors in the Wheatstone bridge according to the range of resistances you want to measure…..

  • Please refer the datasheet of particular pic you are dealing with………….

    Go to Analog to Digital Converter section..

    Read it and set the ADCON1 register according to your needs…..

    When ADCON1 = 0x88

    Voltage at pin AN3 is the Vref+ and voltage at pin AN2 is the Vref-

  • so you mean to say i will use 5v lower ? 4v? 3.5v? sir can you help me how to declare it. or how can i deal with it in the complier(“mikroc”)?. thank you sir!

  • Yes .. of-course

    The min voltage PIC ADC can measure when -Vref = 0 and +Vref = 5 is (5-0)/1023 = 0.0049……

    When a 5V is applied to a 1M ohm resistor..
    current = 5/1M = 0.000005

    So we can’t measure this current because the voltage produced by this current is very less than the min voltage that PIC ADC can measure…

    So you must adjust +Vref to a lower value………

    Note: You can’t adjust +Vref above 5V…….

  • can i also use the Voltage Divider principle for that ? like in your circuit?. sir with your permission can i use your schematic diagram up there to build my digital ohmmeter?.

    how about changing the +Vref and -Vref?  instead of 5v i will change it to > or < 5v?. thank you sir!

  • Yes it is possible………Apply a known voltage to the unknown resistor and find the current through that resistor………..Then we can easily calculate the unknown resistor…………..

    For measuring currents up to 1M ohm, you may need to change the +Vref & -Vref of the PIC ADC………..

  •  is that possible for me to make also a digital ohmmeter? ranges from 30 ohms up to 1M ohm? iam hoping that you can help me. thanks!

  • current reading is not showing..
    do i have to connect load across the output terminal for it ?
    plz answer briefly..


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