Voltimetro AC V2

/* ==========================================================
    This sketch(code) was programmed by THE ELECTRO MENTOR
    and was downloaded from theelectromentor.com
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*/

#include<math.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#define I2C_ADDR    0x27
LiquidCrystal_I2C lcd(I2C_ADDR, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE );

int decimalPrecision = 2;           // decimal places for all values shown in LED Display & Serial Monitor
int VoltageAnalogInputPin = A0;     // Which pin to measure voltage Value (Pin A0 is reserved for button function)
float voltageSampleRead  = 0;       /* to read the value of a sample in analog including voltageOffset1 */
float voltageLastSample  = 0;       /* to count time for each sample. Technically 1 milli second 1 sample is taken */
float voltageSampleSum   = 0;       /* accumulation of sample readings */
float voltageSampleCount = 0;       /* to count number of sample. */
float voltageMean ;                 /* to calculate the average value from all samples, in analog values*/
float RMSVoltageMean ;              /* square roof of voltageMean without offset value, in analog value*/
float adjustRMSVoltageMean;
float FinalRMSVoltage;              /* final voltage value with offset value*/


/* 1.1- AC Voltage Offset */

float voltageOffset1 = 0.00 ;  // to Offset deviation and accuracy. Offset any fake current when no current operates.
// Offset will automatically callibrate when SELECT Button on the LCD Display Shield is pressed.
// If you do not have LCD Display Shield, look into serial monitor to add or minus the value manually and key in here.
// 26 means add 26 to all analog value measured.
float voltageOffset2 = 0.00;   // too offset value due to calculation error from squared and square root



void setup() {

  Serial.begin(9600);  /* In order to see value in serial monitor */
  lcd.begin(16, 4);
  //  pinMode(pin, INPUT);
}

void loop(){
  /* 1- AC Voltage Measurement */
  if (micros() >= voltageLastSample + 1000 )                                                                     /* every 0.2 milli second taking 1 reading */
  {
    voltageSampleRead = (analogRead(VoltageAnalogInputPin) - 512) + voltageOffset1;                           /* read the sample value including offset value*/
    voltageSampleSum = voltageSampleSum + sq(voltageSampleRead) ;                                             /* accumulate total analog values for each sample readings*/

    voltageSampleCount = voltageSampleCount + 1;                                                              /* to move on to the next following count */
    voltageLastSample = micros() ;                                                                            /* to reset the time again so that next cycle can start again*/
  }

  if (voltageSampleCount == 1000)                                                                               /* after 4000 count or 800 milli seconds (0.8 second), do the calculation and display value*/
  {
    voltageMean = voltageSampleSum / voltageSampleCount;                                                      /* calculate average value of all sample readings taken*/
    RMSVoltageMean = (sqrt(voltageMean)) * 1.5;                                                               // The value X 1.5 means the ratio towards the module amplification.
    adjustRMSVoltageMean = RMSVoltageMean + voltageOffset2;                                                   /* square root of the average value including offset value */                                                                                                                                                       /* square root of the average value*/
    FinalRMSVoltage = RMSVoltageMean + voltageOffset2;                                                        /* this is the final RMS voltage*/
    if (FinalRMSVoltage <= 2.5)                                                                               /* to eliminate any possible ghost value*/
    {
      FinalRMSVoltage = 0;
    }
    Serial.print (FinalRMSVoltage, decimalPrecision);
    Serial.print( "\n" );
    lcd.clear();
    lcd.setCursor ( 0, 0 );
    lcd.print("RMS");
    lcd.setCursor ( 0, 1);
    lcd.print("Voltaje  ");
    lcd.setCursor ( 0, 2);
    lcd.print(FinalRMSVoltage, decimalPrecision);
    lcd.print("V");

    voltageSampleSum = 0;                                                                                     /* to reset accumulate sample values for the next cycle */
    voltageSampleCount = 0;                                                                                   /* to reset number of sample for the next cycle */
  }
}