High Voltage DC Voltmeter with Arduino UNO and Op-Amp with Seven Segment display, (Measure 1500+ Volts!!!)

Published by MKDas on

Measuring over 1500V is not a safe work at all. But sometimes, we need to implement such a meter. Here in this article, we will make a high voltage DC voltmeter with Arduino UNO that can measure over 1500V. As assistive devices we’ll use Op-Amp and 4×1 seven segment display. Keep reading…

Disclaimer: Electricity is always dangerous. Skill required to work with electricity. Do work with your own risk. Author will not be responsible for any misuse or harmful act. This website contents is also copyright protected. Anything copied and directly posted in your website and claiming it as yours is prohibited and nonsensical. Author published all the articles as opensource to help you making your project and learning purpose only. Learn and make one for yourself. If need any help feel free to ask the author. Author will be helpful to you. Thanks.

High voltage measurement technique:

Measuring high voltage is not safe for anyone. But if it is need to be done, then we must find a safe way to do the job. We should not measure high voltages keeping one terminal connected with the measuring instrument. Connecting with common terminal increases risk of getting electric shock, burn or fire. That is why, an isolation is required. Sometimes this isolation is done through high valued resistors, sometimes with opto-couplers. But in DC circuit, we can use high valued resistors in series to form an isolation. Adding an Op-Amp circuit, the process become more sensitive and accurate.

Op-Amp based high voltage measurement circuit:

Op-Amp based high voltage measurement

Here in this circuit, we use an Op-Amp and several resistors to make a floating or isolated voltage measuring circuit. The circuit simply measuring the voltage difference between two points. This differential amplifier circuit can be used in many types of measuring circuit where we can measure voltage differences of two points. Simple configuration and simple calculation.

Here, Gain = R9/(R2+R6+R7+R8)

Voltmeter circuit diagram:

Utilizing the differential amplifier circuit we can draw our circuit diagram of the voltmeter.

Circuit diagram

Arduino Coding:

Before we start coding, I’m requesting you to check my other article about “DC voltage measurement with Arduino and Multiplexed 7Segment display“.

#include <TimerOne.h>
const char segment_pins[] = {13, 12, 11, 10, 9, 8, 7, 6}; //segments a to g
const char digit_pins[] = {5, 4, 3, 2}; // 4digits
const int digit_number = 4;//for 4 digit segment
byte dot_position;//set dot position from right side.
bool dot_point = false; // having dot or not, true = have dot, false = no dot.

const int segment_array[10][8] = // for common cathode segment only
{
  {HIGH, HIGH, HIGH, HIGH, HIGH, HIGH, LOW, LOW}, //0
  {LOW, HIGH, HIGH, LOW, LOW, LOW, LOW, LOW},     //1
  {HIGH, HIGH, LOW, HIGH, HIGH, LOW, HIGH, LOW},  //2
  {HIGH, HIGH, HIGH, HIGH, LOW, LOW, HIGH, LOW},  //3
  {LOW, HIGH, HIGH, LOW, LOW, HIGH, HIGH, LOW},   //4
  {HIGH, LOW, HIGH, HIGH, LOW, HIGH, HIGH, LOW},  //5
  {HIGH, LOW, HIGH, HIGH, HIGH, HIGH, HIGH, LOW}, //6
  {HIGH, HIGH, HIGH, LOW, LOW, LOW, LOW, LOW},    //7
  {HIGH, HIGH, HIGH, HIGH, HIGH, HIGH, HIGH, LOW},//8
  {HIGH, HIGH, HIGH, HIGH, LOW, HIGH, HIGH, LOW}, //9
};


void int_sev_segment()
{
  for (int k = 0; k < 8; k++)
  {
    pinMode(segment_pins[k], OUTPUT);//I/O settings
  }
  for (int k = 0; k < digit_number; k++)
  {
    pinMode(digit_pins[k], OUTPUT);//I/O settings
  }
  for (int k = 0; k < 8; k++)
  {
    digitalWrite(segment_pins[k], LOW);//keep low
  }
  for (int k = 0; k < digit_number; k++)
  {
    digitalWrite(digit_pins[k], HIGH);//keep high = disable segments (CC)
  }
  Timer1.initialize(5000);//5000us = 5ms
  Timer1.attachInterrupt(display_segment);
}


char digits[5];
void display_7segment(int number, byte dot)
{
  digits[3] = number / 1000u;//extract 1000th digit
  digits[2] = (number / 100u) % 10u;//extract 100th digit
  digits[1] = (number / 10u) % 10u;//extract 10th digit
  digits[0] = (number / 1u) % 10u;//extract 1st digit
  dot_position = dot;
}


int digit_position = 0;
void display_segment(void) // called periodically using timer interrupt
{
  for (int k = 0; k < digit_number; k++)
  {
    digitalWrite(digit_pins[k], HIGH);//reset digit pins
  }
  if (digit_position > 3)digit_position = 0;

  for (int k = 0; k < 8; k++) //print the a to g segment pins
  {
    digitalWrite(segment_pins[k], segment_array[digits[digit_position]][k]);
    if (digit_position == dot_position && dot_point == true)
    {
      digitalWrite(segment_pins[7], HIGH);//print dot point
    }
  }

  if (digit_position == 3)
  {
    digitalWrite(digit_pins[0], LOW);
    digitalWrite(digit_pins[1], HIGH);
    digitalWrite(digit_pins[2], HIGH);
    digitalWrite(digit_pins[3], HIGH);
  }
  else if (digit_position == 2)
  {
    digitalWrite(digit_pins[0], HIGH);
    digitalWrite(digit_pins[1], LOW);
    digitalWrite(digit_pins[2], HIGH);
    digitalWrite(digit_pins[3], HIGH);
  }
  else if (digit_position == 1)
  {
    digitalWrite(digit_pins[0], HIGH);
    digitalWrite(digit_pins[1], HIGH);
    digitalWrite(digit_pins[2], LOW);
    digitalWrite(digit_pins[3], HIGH);
  }
  else if (digit_position == 0)
  {
    digitalWrite(digit_pins[0], HIGH);
    digitalWrite(digit_pins[1], HIGH);
    digitalWrite(digit_pins[2], HIGH);
    digitalWrite(digit_pins[3], LOW);
  }
  digit_position++; 
}


long dc_voltage = 0;
void setup()
{
  int_sev_segment();//initialize seven segment program
}

void loop()
{
  dc_voltage = 0; //clear previous result
  for (int i = 0; i < 20; i++)
  {
    dc_voltage += analogRead(A0)*1.472; 
  }
  dc_voltage /= 20; //get average value

  display_7segment(dc_voltage, 0); //display value of cnt, dot in position 1 from right side

}

// end

Here all the codes are almost same as my previous articles. Only the constant 1.472 is calculated from different values.

Tips: In most of the circuits, calculations are linear. Here you can simply calculate the value of constant by maximizing the input range and then checking maximum ADC reading. Then simply calculate constant.

Const. = Maximum Input/ Maximum ADC reading.

Test result:

Test result

As you can see we can easily measure 1500V with our Arduino based DC voltmeter. If you need to measure higher voltage, you can add resistances in series in the input lines of op-amp.

But keep in mind that electricity is always dangerous. Do work on your own risk.

I hope you have learned how to make a high voltage DC voltmeter using Arduino UNO and Op-Amp circuitry. Now you can make one for yourself. If you need any help, just ask me. Thank you. Enjoy!


MKDas

Mithun K. Das; B.Sc. in EEE from KUET. Blog: https://labprojectsbd.com

2 Comments

djalltra · October 20, 2020 at 11:18 am

thanks a lot I’ll try to port the code using mikroc

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