Very strange variable behavior

Projects Programming
1

Hello everyone,
I am building an Energy meter with automatic price calculation, reset function and recovery whenever a power cut occurs.

Now, I am facing a very strange problem with my setup (a NANO (connected to a SD card reader) and IDE 2.3.2).
The local variable usage is massively increased if I add a line such as "cut = cut + 1;", hence making my sketch unusable.
I wonder if I just discovered a bug... (or maybe I am the bug in the whole story)
(for 2 days I am trying to modify my sketch, make it smaller, more compact... but nothing seems to change the result)

It would be fantastic if somebody could try to figure out what happens and maybe tell me how to resolve the issue,
Please see below my sketch.
I marked the interesting lines with "**"...

The first one without the line "cut = cut + 1;"
and
the second one with the line "cut = cut + 1;"... and this is where the massive memory increase occurs.

How to increase the "cut" of 1 without increasing the memory usage massively?

Another possibility would be to completely leave the variable "cut" and all its corresponding lines out of the sketch... but strange fully, without the variable "cut", the memory usage increases also...

#include <SD.h>
#include "LiquidCrystal_I2C.h"
LiquidCrystal_I2C lcd(0x27, 20, 4);
const int buttonPin = 8;
unsigned long startMillis[3];
unsigned long endMillis[3];
double calib[3] = { 0.8646, 1.3125, 1.16 };  //without Resistor 33 Ohm (25 June 2024)
double kilos[3];
float pay[3];
float payt = 0;
float RMSCurrent[3];
float RMSPower[3];
float kilot = 0;
float lt = 0;
float mt = 0;
float ht = 0;
int currentPins[3] = { 1, 2, 3 };
int buttonState = 0;
int low = 0;
int medium = 0;
int high = 0;
int count = 1;
**int cut = 0;  // problem: if cut = 0, and "line 164" is not present, then Global variables use 1584 bytes (77%) of dynamic memory, leaving 464 bytes for local variables. Maximum is 2048 bytes.**
int reset = 0;
byte one[8] = { 0x00, 0x00, 0x08, 0x18, 0x08, 0x08, 0x08, 0x00 };
byte two[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x10, 0x1C, 0x00 };
byte three[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x04, 0x18, 0x00 };
byte baht[8] = { 0x04, 0x1E, 0x15, 0x1E, 0x15, 0x15, 0x1E, 0x04 };
byte aleft[8] = { 0x00, 0x00, 0x00, 0x01, 0x12, 0x14, 0x18, 0x1E };
File myFile0;
File myFile1;
File myFile2;
void setup() {
  Serial.begin(115200);
  SD.begin(4);
  lcd.begin(20, 4);
  lcd.init();
  lcd.backlight();
  lcd.createChar(1, one);
  lcd.createChar(2, two);
  lcd.createChar(3, three);
  lcd.createChar(4, baht);
  lcd.createChar(5, aleft);
  pinMode(8, INPUT_PULLUP);
  lcd.clear();
  lcd.setCursor(6, 1);
  lcd.print("3 Phase");
  lcd.setCursor(4, 2);
  lcd.print("Energy Meter");
  lcd.setCursor(16, 3);
  lcd.print("v30a");
  delay(3000);
  lcd.clear();
  lcd.setCursor(4, 1);
  lcd.print("PLEASE  WAIT");
  delay(1000);
  lcd.setCursor(2, 2);
  lcd.print("Retrieving  Data");
  lcd.setCursor(0, 3);
  for (int i = 1; i <= 20; i++) {
    delay(200);
    lcd.print("x");
  }
  File myFile0;
  myFile0 = SD.open("L0.txt", FILE_READ);
  if (myFile0) {
    lt = myFile0.parseFloat();
  }
  myFile0.close();
  File myFile1;
  myFile1 = SD.open("L1.txt", FILE_READ);
  if (myFile1) {
    mt = myFile1.parseFloat();
  }
  myFile1.close();
  File myFile2;
  myFile2 = SD.open("L2.txt", FILE_READ);
  if (myFile2) {
    ht = myFile2.parseFloat();
  }
  myFile2.close();
  kilos[0] = lt;
  kilos[1] = mt;
  kilos[2] = ht;
  lt = 0;
  mt = 0;
  ht = 0;
  lcd.clear();
  lcd.setCursor(3, 0);
  lcd.print("DATA retrieved");
  lcd.setCursor(0, 1);
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h =L"
            "\1");
  lcd.setCursor(0, 2);
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h =L"
            "\2");
  lcd.setCursor(0, 3);
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h =L"
            "\3");
  delay(1000);
}
void readPhase()  //Method to read information from CTs
{
  for (int i = 0; i <= 2; i++) {
    float current = 0;
    float maxCurrent = 0;
    float minCurrent = 1000;
    for (int j = 0; j <= 200; j++) {
      delay(4);
      current = analogRead(currentPins[i]);
      if (current >= maxCurrent)
        maxCurrent = current;
      else if (current <= minCurrent)
        minCurrent = current;
    }
    if (maxCurrent <= 517) {
      maxCurrent = 516;
    }
    RMSCurrent[i] = ((maxCurrent - 516) * 0.707107) / calib[i];
    RMSPower[i] = 220 * RMSCurrent[i];
    endMillis[i] = millis();
    unsigned long time = (endMillis[i] - startMillis[i]);
    kilos[i] = kilos[i] + ((double)RMSPower[i] * ((double)time / 60 / 60 / 1000000));
    startMillis[i] = millis();
  }
}
void loop() {
  readPhase();
  DResetscreen();
  buttonState = digitalRead(buttonPin);
  if (buttonState == LOW) {
    reset = 1;
  }
  DKilowattHours();
  **if (cut == 1) {**
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  DRMSPower();
  **if (cut == 1) {**
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  DTotals();
  **if (cut == 1) {**
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  Dsavedata();
  //De();
  Resetnow();
}
void DResetscreen() {
  **if (cut == 1) {**
    lcd.clear();
    lcd.setCursor(4, 0);
    lcd.print("RESET ?   [v30a]");
    delay(400);
    lcd.setCursor(1, 1);
    lcd.print("press 'RED' button");
    lcd.setCursor(1, 2);
    lcd.print("and hold for 3 sec");
    delay(400);
    for (int i = 0; i <= 3; i++)
      lcd.setCursor(3, 3);
    lcd.print("\5"
              "--- NOW");
    delay(500);
    lcd.setCursor(3, 3);
    lcd.print("        ");
    delay(500);
  }
}
void DKilowattHours() {
  lcd.clear();
  lcd.setCursor(6, 0);
  lcd.print("Energy  [kW/h]");
  lcd.setCursor(0, 1);
  lcd.print("L"
            "\1"
            " ");
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 2);
  lcd.print("L"
            "\2"
            " ");
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 3);
  lcd.print("L"
            "\3"
            " ");
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h");
}
void DRMSPower() {
  lcd.clear();
  lcd.setCursor(7, 0);
  lcd.print("Power     [W]");
  lcd.setCursor(0, 1);
  lcd.print("L"
            "\1"
            " ");
  lcd.print(RMSPower[0], 3);
  lcd.print(" W");
  lcd.setCursor(0, 2);
  lcd.print("L"
            "\2"
            " ");
  lcd.print(RMSPower[1], 3);
  lcd.print(" W");
  lcd.setCursor(0, 3);
  lcd.print("L"
            "\3"
            " ");
  lcd.print(RMSPower[2], 3);
  lcd.print(" W");
}
void DTotals() {
  lcd.clear();
  kilot = kilos[0] + kilos[1] + kilos[2];
  for (int i = 0; i <= 2; i++) {
    if (kilos[i] < 150) {
      lt = kilos[i];
      low = 1;
      medium = 0;
      high = 0;
    }
    if (kilos[i] - 150 > 0) {
      lt = 150;
      mt = kilos[i] - 150;
      low = 1;
      medium = 1;
      high = 0;
    }
    if (kilos[i] - 400 > 0) {
      lt = 150;
      mt = 250;
      ht = kilos[i] - 400;
      low = 1;
      medium = 1;
      high = 1;
    }
    pay[i] = (lt * 3.2484 * low) + (mt * 4.2218 * medium) + (ht * 4.4217 * high);
    lt = 0;
    mt = 0;
    ht = 0;
    low = 0;
    medium = 0;
    high = 0;
  }
  payt = pay[0] + pay[1] + pay[2];
  lcd.setCursor(1, 0);
  lcd.print("Total consumption");
  lcd.setCursor(3, 1);
  lcd.print("\xF6"
            " (L"
            "\1"
            ", L"
            "\2"
            ", L"
            "\3)");
  lcd.setCursor(6, 2);
  lcd.print(kilot, 3);
  lcd.print(" kW/h");
  lcd.setCursor(3, 3);
  lcd.print("+/- ");
  lcd.print(payt, 2);
  lcd.print(" "
            "\4");
}
void Dsavedata() {
  count = count + 1;
  if (count == 100) {
    count = 1;
    File myfile0 = SD.open("L0.txt", FILE_WRITE | O_TRUNC);
    myFile0 = SD.open("L0.txt", FILE_WRITE);
    if (myFile0) {
      myFile0.print(kilos[0], 3);
    }
    myFile0.close();
    File myfile1 = SD.open("L1.txt", FILE_WRITE | O_TRUNC);
    myFile1 = SD.open("L1.txt", FILE_WRITE);
    if (myFile1) {
      myFile1.print(kilos[1], 3);
    }
    myFile1.close();
    File myfile2 = SD.open("L2.txt", FILE_WRITE | O_TRUNC);
    myFile2 = SD.open("L2.txt", FILE_WRITE);
    if (myFile2) {
      myFile2.print(kilos[2], 3);
    }
    myFile2.close();
    lcd.clear();
    lcd.setCursor(1, 1);
    lcd.print("Successfully saved");
    lcd.setCursor(4, 2);
    lcd.print("to 'SD' card");
    delay(600);
  }
}
void Resetnow() {
  if (reset == 1) {
    lcd.clear();
    lcd.setCursor(3, 0);
    lcd.print("!!! RESET !!!");
    reset = 0;
    for (int i = 0; i <= 2; i++) {
      kilos[i] = 0;
    }
    lcd.setCursor(1, 2);
    lcd.print("Counters all Reset");
  }
}


#include <SD.h>
#include "LiquidCrystal_I2C.h"
LiquidCrystal_I2C lcd(0x27, 20, 4);
const int buttonPin = 8;
unsigned long startMillis[3];
unsigned long endMillis[3];
double calib[3] = { 0.8646, 1.3125, 1.16 };  //without Resistor 33 Ohm (25 June 2024)
double kilos[3];
float pay[3];
float payt = 0;
float RMSCurrent[3];
float RMSPower[3];
float kilot = 0;
float lt = 0;
float mt = 0;
float ht = 0;
int currentPins[3] = { 1, 2, 3 };
int buttonState = 0;
int low = 0;
int medium = 0;
int high = 0;
int count = 1;
**int cut = 0;  // problem: if cut = 0, and "line 164" is not present, then Global variables use 1584 bytes (77%) of dynamic memory, leaving 464 bytes for local variables. Maximum is 2048 bytes.**
int reset = 0;
byte one[8] = { 0x00, 0x00, 0x08, 0x18, 0x08, 0x08, 0x08, 0x00 };
byte two[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x10, 0x1C, 0x00 };
byte three[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x04, 0x18, 0x00 };
byte baht[8] = { 0x04, 0x1E, 0x15, 0x1E, 0x15, 0x15, 0x1E, 0x04 };
byte aleft[8] = { 0x00, 0x00, 0x00, 0x01, 0x12, 0x14, 0x18, 0x1E };
File myFile0;
File myFile1;
File myFile2;
void setup() {
  Serial.begin(115200);
  SD.begin(4);
  lcd.begin(20, 4);
  lcd.init();
  lcd.backlight();
  lcd.createChar(1, one);
  lcd.createChar(2, two);
  lcd.createChar(3, three);
  lcd.createChar(4, baht);
  lcd.createChar(5, aleft);
  pinMode(8, INPUT_PULLUP);
  lcd.clear();
  lcd.setCursor(6, 1);
  lcd.print("3 Phase");
  lcd.setCursor(4, 2);
  lcd.print("Energy Meter");
  lcd.setCursor(16, 3);
  lcd.print("v30a");
  delay(3000);
  lcd.clear();
  lcd.setCursor(4, 1);
  lcd.print("PLEASE  WAIT");
  delay(1000);
  lcd.setCursor(2, 2);
  lcd.print("Retrieving  Data");
  lcd.setCursor(0, 3);
  for (int i = 1; i <= 20; i++) {
    delay(200);
    lcd.print("x");
  }
  File myFile0;
  myFile0 = SD.open("L0.txt", FILE_READ);
  if (myFile0) {
    lt = myFile0.parseFloat();
  }
  myFile0.close();
  File myFile1;
  myFile1 = SD.open("L1.txt", FILE_READ);
  if (myFile1) {
    mt = myFile1.parseFloat();
  }
  myFile1.close();
  File myFile2;
  myFile2 = SD.open("L2.txt", FILE_READ);
  if (myFile2) {
    ht = myFile2.parseFloat();
  }
  myFile2.close();
  kilos[0] = lt;
  kilos[1] = mt;
  kilos[2] = ht;
  lt = 0;
  mt = 0;
  ht = 0;
  lcd.clear();
  lcd.setCursor(3, 0);
  lcd.print("DATA retrieved");
  lcd.setCursor(0, 1);
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h =L"
            "\1");
  lcd.setCursor(0, 2);
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h =L"
            "\2");
  lcd.setCursor(0, 3);
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h =L"
            "\3");
  delay(1000);
}
void readPhase()  //Method to read information from CTs
{
  for (int i = 0; i <= 2; i++) {
    float current = 0;
    float maxCurrent = 0;
    float minCurrent = 1000;
    for (int j = 0; j <= 200; j++) {
      delay(4);
      current = analogRead(currentPins[i]);
      if (current >= maxCurrent)
        maxCurrent = current;
      else if (current <= minCurrent)
        minCurrent = current;
    }
    if (maxCurrent <= 517) {
      maxCurrent = 516;
    }
    RMSCurrent[i] = ((maxCurrent - 516) * 0.707107) / calib[i];
    RMSPower[i] = 220 * RMSCurrent[i];
    endMillis[i] = millis();
    unsigned long time = (endMillis[i] - startMillis[i]);
    kilos[i] = kilos[i] + ((double)RMSPower[i] * ((double)time / 60 / 60 / 1000000));
    startMillis[i] = millis();
  }
}
void loop() {
  readPhase();
  DResetscreen();
  buttonState = digitalRead(buttonPin);
  if (buttonState == LOW) {
    reset = 1;
  }
  DKilowattHours();
  **if (cut == 1) {**
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  DRMSPower();
  **if (cut == 1) {**
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  DTotals();
  **if (cut == 1) {**
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  Dsavedata();
  //De();
  Resetnow();
  **cut = cut + 1; // Problem: this line creates Global variables to use 1660 bytes or (81%) of dynamic memory, leaving 388 bytes for local variables. Maximum is 2048 bytes.**
}
void DResetscreen() {
 ** if (cut == 1) {**
    lcd.clear();
    lcd.setCursor(4, 0);
    lcd.print("RESET ?   [v30a]");
    delay(400);
    lcd.setCursor(1, 1);
    lcd.print("press 'RED' button");
    lcd.setCursor(1, 2);
    lcd.print("and hold for 3 sec");
    delay(400);
    for (int i = 0; i <= 3; i++)
      lcd.setCursor(3, 3);
    lcd.print("\5"
              "--- NOW");
    delay(500);
    lcd.setCursor(3, 3);
    lcd.print("        ");
    delay(500);
  }
}
void DKilowattHours() {
  lcd.clear();
  lcd.setCursor(6, 0);
  lcd.print("Energy  [kW/h]");
  lcd.setCursor(0, 1);
  lcd.print("L"
            "\1"
            " ");
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 2);
  lcd.print("L"
            "\2"
            " ");
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 3);
  lcd.print("L"
            "\3"
            " ");
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h");
}
void DRMSPower() {
  lcd.clear();
  lcd.setCursor(7, 0);
  lcd.print("Power     [W]");
  lcd.setCursor(0, 1);
  lcd.print("L"
            "\1"
            " ");
  lcd.print(RMSPower[0], 3);
  lcd.print(" W");
  lcd.setCursor(0, 2);
  lcd.print("L"
            "\2"
            " ");
  lcd.print(RMSPower[1], 3);
  lcd.print(" W");
  lcd.setCursor(0, 3);
  lcd.print("L"
            "\3"
            " ");
  lcd.print(RMSPower[2], 3);
  lcd.print(" W");
}
void DTotals() {
  lcd.clear();
  kilot = kilos[0] + kilos[1] + kilos[2];
  for (int i = 0; i <= 2; i++) {
    if (kilos[i] < 150) {
      lt = kilos[i];
      low = 1;
      medium = 0;
      high = 0;
    }
    if (kilos[i] - 150 > 0) {
      lt = 150;
      mt = kilos[i] - 150;
      low = 1;
      medium = 1;
      high = 0;
    }
    if (kilos[i] - 400 > 0) {
      lt = 150;
      mt = 250;
      ht = kilos[i] - 400;
      low = 1;
      medium = 1;
      high = 1;
    }
    pay[i] = (lt * 3.2484 * low) + (mt * 4.2218 * medium) + (ht * 4.4217 * high);
    lt = 0;
    mt = 0;
    ht = 0;
    low = 0;
    medium = 0;
    high = 0;
  }
  payt = pay[0] + pay[1] + pay[2];
  lcd.setCursor(1, 0);
  lcd.print("Total consumption");
  lcd.setCursor(3, 1);
  lcd.print("\xF6"
            " (L"
            "\1"
            ", L"
            "\2"
            ", L"
            "\3)");
  lcd.setCursor(6, 2);
  lcd.print(kilot, 3);
  lcd.print(" kW/h");
  lcd.setCursor(3, 3);
  lcd.print("+/- ");
  lcd.print(payt, 2);
  lcd.print(" "
            "\4");
}
void Dsavedata() {
  count = count + 1;
  if (count == 100) {
    count = 1;
    File myfile0 = SD.open("L0.txt", FILE_WRITE | O_TRUNC);
    myFile0 = SD.open("L0.txt", FILE_WRITE);
    if (myFile0) {
      myFile0.print(kilos[0], 3);
    }
    myFile0.close();
    File myfile1 = SD.open("L1.txt", FILE_WRITE | O_TRUNC);
    myFile1 = SD.open("L1.txt", FILE_WRITE);
    if (myFile1) {
      myFile1.print(kilos[1], 3);
    }
    myFile1.close();
    File myfile2 = SD.open("L2.txt", FILE_WRITE | O_TRUNC);
    myFile2 = SD.open("L2.txt", FILE_WRITE);
    if (myFile2) {
      myFile2.print(kilos[2], 3);
    }
    myFile2.close();
    lcd.clear();
    lcd.setCursor(1, 1);
    lcd.print("Successfully saved");
    lcd.setCursor(4, 2);
    lcd.print("to 'SD' card");
    delay(600);
  }
}
void Resetnow() {
  if (reset == 1) {
    lcd.clear();
    lcd.setCursor(3, 0);
    lcd.print("!!! RESET !!!");
    reset = 0;
    for (int i = 0; i <= 2; i++) {
      kilos[i] = 0;
    }
    lcd.setCursor(1, 2);
    lcd.print("Counters all Reset");
  }
}

By the way, I want also to thank all the authors of the sketch which I used to create mine.

2

you spare 24 bytes if use float

3

you marked this way a problem places. pls undo this and post normal sketch

4

Hello,

just tried the suggestion... it did not work... same as before

with "double"

Sketch uses 20082 bytes (65%) of program storage space. Maximum is 30720 bytes.
Global variables use 1660 bytes (81%) of dynamic memory, leaving 388 bytes for local variables. Maximum is 2048 bytes.

with "float"

Sketch uses 20082 bytes (65%) of program storage space. Maximum is 30720 bytes.
Global variables use 1660 bytes (81%) of dynamic memory, leaving 388 bytes for local variables. Maximum is 2048 bytes.

5

Ok, sketch without **

#include <SD.h>
#include "LiquidCrystal_I2C.h"
LiquidCrystal_I2C lcd(0x27, 20, 4);
const int buttonPin = 8;
unsigned long startMillis[3];
unsigned long endMillis[3];
double calib[3] = { 0.8646, 1.3125, 1.16 };  //without Resistor 33 Ohm (25 June 2024)
double kilos[3];
float pay[3];
float payt = 0;
float RMSCurrent[3];
float RMSPower[3];
float kilot = 0;
float lt = 0;
float mt = 0;
float ht = 0;
int currentPins[3] = { 1, 2, 3 };
int buttonState = 0;
int low = 0;
int medium = 0;
int high = 0;
int count = 1;
int cut = 0;  // problem: if cut = 0, and "line 164" is not present, then Global variables use 1584 bytes (77%) of dynamic memory, leaving 464 bytes for local variables. Maximum is 2048 bytes.
int reset = 0;
byte one[8] = { 0x00, 0x00, 0x08, 0x18, 0x08, 0x08, 0x08, 0x00 };
byte two[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x10, 0x1C, 0x00 };
byte three[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x04, 0x18, 0x00 };
byte baht[8] = { 0x04, 0x1E, 0x15, 0x1E, 0x15, 0x15, 0x1E, 0x04 };
byte aleft[8] = { 0x00, 0x00, 0x00, 0x01, 0x12, 0x14, 0x18, 0x1E };
File myFile0;
File myFile1;
File myFile2;
void setup() {
  Serial.begin(115200);
  SD.begin(4);
  lcd.begin(20, 4);
  lcd.init();
  lcd.backlight();
  lcd.createChar(1, one);
  lcd.createChar(2, two);
  lcd.createChar(3, three);
  lcd.createChar(4, baht);
  lcd.createChar(5, aleft);
  pinMode(8, INPUT_PULLUP);
  lcd.clear();
  lcd.setCursor(6, 1);
  lcd.print("3 Phase");
  lcd.setCursor(4, 2);
  lcd.print("Energy Meter");
  lcd.setCursor(16, 3);
  lcd.print("v30a");
  delay(3000);
  lcd.clear();
  lcd.setCursor(4, 1);
  lcd.print("PLEASE  WAIT");
  delay(1000);
  lcd.setCursor(2, 2);
  lcd.print("Retrieving  Data");
  lcd.setCursor(0, 3);
  for (int i = 1; i <= 20; i++) {
    delay(200);
    lcd.print("x");
  }
  File myFile0;
  myFile0 = SD.open("L0.txt", FILE_READ);
  if (myFile0) {
    lt = myFile0.parseFloat();
  }
  myFile0.close();
  File myFile1;
  myFile1 = SD.open("L1.txt", FILE_READ);
  if (myFile1) {
    mt = myFile1.parseFloat();
  }
  myFile1.close();
  File myFile2;
  myFile2 = SD.open("L2.txt", FILE_READ);
  if (myFile2) {
    ht = myFile2.parseFloat();
  }
  myFile2.close();
  kilos[0] = lt;
  kilos[1] = mt;
  kilos[2] = ht;
  lt = 0;
  mt = 0;
  ht = 0;
  lcd.clear();
  lcd.setCursor(3, 0);
  lcd.print("DATA retrieved");
  lcd.setCursor(0, 1);
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h =L"
            "\1");
  lcd.setCursor(0, 2);
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h =L"
            "\2");
  lcd.setCursor(0, 3);
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h =L"
            "\3");
  delay(1000);
}
void readPhase()  //Method to read information from CTs
{
  for (int i = 0; i <= 2; i++) {
    float current = 0;
    float maxCurrent = 0;
    float minCurrent = 1000;
    for (int j = 0; j <= 200; j++) {
      delay(4);
      current = analogRead(currentPins[i]);
      if (current >= maxCurrent)
        maxCurrent = current;
      else if (current <= minCurrent)
        minCurrent = current;
    }
    if (maxCurrent <= 517) {
      maxCurrent = 516;
    }
    RMSCurrent[i] = ((maxCurrent - 516) * 0.707107) / calib[i];
    RMSPower[i] = 220 * RMSCurrent[i];
    endMillis[i] = millis();
    unsigned long time = (endMillis[i] - startMillis[i]);
    kilos[i] = kilos[i] + ((double)RMSPower[i] * ((double)time / 60 / 60 / 1000000));
    startMillis[i] = millis();
  }
}
void loop() {
  readPhase();
  DResetscreen();
  buttonState = digitalRead(buttonPin);
  if (buttonState == LOW) {
    reset = 1;
  }
  DKilowattHours();
  if (cut == 1) {
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  DRMSPower();
  if (cut == 1) {
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  DTotals();
  if (cut == 1) {
    buttonState = digitalRead(buttonPin);
    if (buttonState == LOW) {
      reset = 1;
    }
  }
  delay(2300);
  Dsavedata();
  //De();
  Resetnow();
  cut = cut + 1; // Problem: this line creates Global variables to use 1660 bytes or (81%) of dynamic memory, leaving 388 bytes for local variables. Maximum is 2048 bytes.
}
void DResetscreen() {
  if (cut == 1) {
    lcd.clear();
    lcd.setCursor(4, 0);
    lcd.print("RESET ?   [v30a]");
    delay(400);
    lcd.setCursor(1, 1);
    lcd.print("press 'RED' button");
    lcd.setCursor(1, 2);
    lcd.print("and hold for 3 sec");
    delay(400);
    for (int i = 0; i <= 3; i++)
      lcd.setCursor(3, 3);
    lcd.print("\5"
              "--- NOW");
    delay(500);
    lcd.setCursor(3, 3);
    lcd.print("        ");
    delay(500);
  }
}
void DKilowattHours() {
  lcd.clear();
  lcd.setCursor(6, 0);
  lcd.print("Energy  [kW/h]");
  lcd.setCursor(0, 1);
  lcd.print("L"
            "\1"
            " ");
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 2);
  lcd.print("L"
            "\2"
            " ");
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 3);
  lcd.print("L"
            "\3"
            " ");
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h");
}
void DRMSPower() {
  lcd.clear();
  lcd.setCursor(7, 0);
  lcd.print("Power     [W]");
  lcd.setCursor(0, 1);
  lcd.print("L"
            "\1"
            " ");
  lcd.print(RMSPower[0], 3);
  lcd.print(" W");
  lcd.setCursor(0, 2);
  lcd.print("L"
            "\2"
            " ");
  lcd.print(RMSPower[1], 3);
  lcd.print(" W");
  lcd.setCursor(0, 3);
  lcd.print("L"
            "\3"
            " ");
  lcd.print(RMSPower[2], 3);
  lcd.print(" W");
}
void DTotals() {
  lcd.clear();
  kilot = kilos[0] + kilos[1] + kilos[2];
  for (int i = 0; i <= 2; i++) {
    if (kilos[i] < 150) {
      lt = kilos[i];
      low = 1;
      medium = 0;
      high = 0;
    }
    if (kilos[i] - 150 > 0) {
      lt = 150;
      mt = kilos[i] - 150;
      low = 1;
      medium = 1;
      high = 0;
    }
    if (kilos[i] - 400 > 0) {
      lt = 150;
      mt = 250;
      ht = kilos[i] - 400;
      low = 1;
      medium = 1;
      high = 1;
    }
    pay[i] = (lt * 3.2484 * low) + (mt * 4.2218 * medium) + (ht * 4.4217 * high);
    lt = 0;
    mt = 0;
    ht = 0;
    low = 0;
    medium = 0;
    high = 0;
  }
  payt = pay[0] + pay[1] + pay[2];
  lcd.setCursor(1, 0);
  lcd.print("Total consumption");
  lcd.setCursor(3, 1);
  lcd.print("\xF6"
            " (L"
            "\1"
            ", L"
            "\2"
            ", L"
            "\3)");
  lcd.setCursor(6, 2);
  lcd.print(kilot, 3);
  lcd.print(" kW/h");
  lcd.setCursor(3, 3);
  lcd.print("+/- ");
  lcd.print(payt, 2);
  lcd.print(" "
            "\4");
}
void Dsavedata() {
  count = count + 1;
  if (count == 100) {
    count = 1;
    File myfile0 = SD.open("L0.txt", FILE_WRITE | O_TRUNC);
    myFile0 = SD.open("L0.txt", FILE_WRITE);
    if (myFile0) {
      myFile0.print(kilos[0], 3);
    }
    myFile0.close();
    File myfile1 = SD.open("L1.txt", FILE_WRITE | O_TRUNC);
    myFile1 = SD.open("L1.txt", FILE_WRITE);
    if (myFile1) {
      myFile1.print(kilos[1], 3);
    }
    myFile1.close();
    File myfile2 = SD.open("L2.txt", FILE_WRITE | O_TRUNC);
    myFile2 = SD.open("L2.txt", FILE_WRITE);
    if (myFile2) {
      myFile2.print(kilos[2], 3);
    }
    myFile2.close();
    lcd.clear();
    lcd.setCursor(1, 1);
    lcd.print("Successfully saved");
    lcd.setCursor(4, 2);
    lcd.print("to 'SD' card");
    delay(600);
  }
}
void Resetnow() {
  if (reset == 1) {
    lcd.clear();
    lcd.setCursor(3, 0);
    lcd.print("!!! RESET !!!");
    reset = 0;
    for (int i = 0; i <= 2; i++) {
      kilos[i] = 0;
    }
    lcd.setCursor(1, 2);
    lcd.print("Counters all Reset");
  }
}
6

Not on a Nano (or other board with 8-bit processor); the compiler will happily treat doubles as floats.

7

If you just leave cut at the default value of 0, then all the code that only executes when cut equals 1 will be eliminated by the compiler, reducing the size of the code.

8

You declare a whole bunch of files that you don't use

File myFile0;
File myFile1;
File myFile2;

These can be removed, ok they are still empty but still.

Then you declare a different file object for every time you open a file, but there is no need, a single file object will suffice.

And if you use the F() macro for every string you write to the LCD you will find that you will be completely without issues. Just those 2 lines already reduced the variable use down to 1559 bytes (76%)

void Dsavedata() {
  count = count + 1;
  if (count == 100) {
    count = 1;
    //File myfile0 = SD.open("L0.txt", FILE_WRITE | O_TRUNC);
    File myFile0 = SD.open("L0.txt", FILE_WRITE);
    if (myFile0) {
      myFile0.print(kilos[0], 3);
    }
    myFile0.close();
    //File myfile1 = SD.open("L1.txt", FILE_WRITE | O_TRUNC);
    myFile0 = SD.open("L1.txt", FILE_WRITE);
    if (myFile0) {
      myFile0.print(kilos[1], 3);
    }
    myFile0.close();
    //File myfile2 = SD.open("L2.txt", FILE_WRITE | O_TRUNC);
    myFile0 = SD.open("L2.txt", FILE_WRITE);
    if (myFile0) {
      myFile0.print(kilos[2], 3);
    }
    myFile0.close();
    lcd.clear();
    lcd.setCursor(1, 1);
    lcd.print(F("Successfully saved"));
    lcd.setCursor(4, 2);
    lcd.print(F("to 'SD' card"));
    delay(600);
  }
}

Now uless you modify these values, they may just as well reside in progmem.

The variable 'cut' that showed up as an issue, might just as well be static local to loop(), since all it really does in

void DResetscreen() {
  **if (cut == 1) {**

is determine whether the function should be executed.
instead

if (cut == 1) DResetscreen();

makes more sense. And so forth.

What is the point of the braces here actually ? I am not even sure you need double here anyway, but the braces really don't make sense unless you use integers, and then they are in the wrong place.
and i would feel better if this literal is at least

1000000UL

or the calculation is not going to work properly at all.

9

Wow, thank you a lot,
I will try to implement your suggestions...
For the moment it is 23h42 where I am...
Hence, zzz zzz zzz ...

But I will definitely give a feedback.

10

Using a file will dynamically allocate a 512 byte buffer that is not counted in the total above. You will then have random memory overwritten, which leads to "unpredictable results".

11 
Sketch uses 18080 bytes (58%) of program storage space. Maximum is 30720 bytes.
Global variables use 1502 bytes (73%) of dynamic memory, leaving 546 bytes for local variables. Maximum is 2048 bytes.

#include <SD.h>
#include "LiquidCrystal_I2C.h"
LiquidCrystal_I2C lcd(0x27, 20, 4);
const int buttonPin = 8;
unsigned long startMillis[3];
unsigned long endMillis[3];
const float calib[3] = { 0.8646, 1.3125, 1.16 };  //without Resistor 33 Ohm (25 June 2024)
float kilos[3];
float pay[3];
float payt = 0;
float RMSCurrent[3];
float RMSPower[3];
float kilot = 0;

const byte currentPins[3] = { A1, A2, A3 }; 

int cut = 0;  // problem: if cut = 0, and "line 164" is not present, then Global variables use 1584 bytes (77%) of dynamic memory, leaving 464 bytes for local variables. Maximum is 2048 bytes.
volatile bool reset = 0;
byte one[8] = { 0x00, 0x00, 0x08, 0x18, 0x08, 0x08, 0x08, 0x00 };
byte two[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x10, 0x1C, 0x00 };
byte three[8] = { 0x00, 0x00, 0x18, 0x04, 0x08, 0x04, 0x18, 0x00 };
byte baht[8] = { 0x04, 0x1E, 0x15, 0x1E, 0x15, 0x15, 0x1E, 0x04 };
byte aleft[8] = { 0x00, 0x00, 0x00, 0x01, 0x12, 0x14, 0x18, 0x1E };

ISR (PCINT0_vect){   
    if(!(PINB&1))reset = true;
}

void setup() {
  Serial.begin(115200);
  pinMode(8, INPUT_PULLUP);
  SD.begin(4);
  lcd.init();
  lcd.backlight();
  lcd.createChar(1, one);
  lcd.createChar(2, two);
  lcd.createChar(3, three);
  lcd.createChar(4, baht);
  lcd.createChar(5, aleft);
  PCICR = (1 << PCIE0);  // enable PCINT interrupts
  PCMSK0 = (1 << PCINT0); // D8 = PCINT0
  lcd.clear();
  lcd.setCursor(6, 1);
  lcd.print("3 Phase");
  lcd.setCursor(4, 2);
  lcd.print("Energy Meter");
  lcd.setCursor(16, 3);
  lcd.print("v30a");
  delay(3000);
  File myFile;
  myFile = SD.open("L.txt", FILE_READ);
  if (myFile) {
    kilos[0] = myFile.parseFloat();
    while (myFile.peek() == '\n' || myFile.peek() == '\r') myFile.read();
    kilos[1] = myFile.parseFloat();
    while (myFile.peek() == '\n' || myFile.peek() == '\r') myFile.read();
    kilos[2] = myFile.parseFloat();
  }
  lcd.clear();
  lcd.setCursor(3, 0);
  lcd.print("DATA retrieved");
  lcd.setCursor(0, 1);
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h =L\1");
  lcd.setCursor(0, 2);
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h =L\2");
  lcd.setCursor(0, 3);
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h =L\3");
  delay(1000);
}

void readPhase(){  //Method to read information from CTs
  for (int i = 0; i <= 2; i++) {
    int current = 0;
    int maxCurrent = 0;
    for (int j = 0; j <= 200; j++) {
      delay(4);
      current = analogRead(currentPins[i]);
      if (current > maxCurrent)maxCurrent = current;
    }
    if (maxCurrent <= 517)maxCurrent = 516;

    RMSCurrent[i] = (float(maxCurrent - 516) * 0.707107) / calib[i];
    RMSPower[i] = 220 * RMSCurrent[i];
    endMillis[i] = millis();
    unsigned long Time = (endMillis[i] - startMillis[i]);
    kilos[i] = kilos[i] + (double)RMSPower[i] * (double)Time / 3600000000UL;
    startMillis[i] = millis();
  }
}

void loop() {
  if(!reset){readPhase();  delay(2300);}
  if(!reset){DResetscreen();  delay(2300);}
  if(!reset){DKilowattHours();  delay(2300);}
  if(!reset){DRMSPower();  delay(2300);}
  if(!reset){DTotals();  delay(2300);}
  if(!reset){Dsavedata();  delay(2300);}
  Resetnow();
  cut = cut + 1; // Problem: this line creates Global variables to use 1660 bytes or (81%) of dynamic memory, leaving 388 bytes for local variables. Maximum is 2048 bytes.
}

void DResetscreen() {
  if (cut == 1) {
    lcd.clear();
    lcd.setCursor(4, 0);
    lcd.print("RESET ?   [v30a]");
    delay(400);
    lcd.setCursor(1, 1);
    lcd.print("press 'RED' button");
    lcd.setCursor(1, 2);
    lcd.print("and hold for 3 sec");
    delay(400);
    lcd.setCursor(3, 3);
    lcd.print("\5--- NOW");
    delay(500);
    lcd.setCursor(3, 3);
    lcd.print("        ");
    delay(500);
  }
}
void DKilowattHours() {
  lcd.clear();
  lcd.setCursor(6, 0);
  lcd.print("Energy  [kW/h]");
  lcd.setCursor(0, 1);
  lcd.print("L\1 ");
  lcd.print(kilos[0], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 2);
  lcd.print("L\2 ");
  lcd.print(kilos[1], 3);
  lcd.print(" kW/h");
  lcd.setCursor(0, 3);
  lcd.print("L\3 ");
  lcd.print(kilos[2], 3);
  lcd.print(" kW/h");
}
void DRMSPower() {
  lcd.clear();
  lcd.setCursor(7, 0);
  lcd.print("Power     [W]");
  lcd.setCursor(0, 1);
  lcd.print("L\1 ");
  lcd.print(RMSPower[0], 3);
  lcd.print(" W");
  lcd.setCursor(0, 2);
  lcd.print("L\2 ");
  lcd.print(RMSPower[1], 3);
  lcd.print(" W");
  lcd.setCursor(0, 3);
  lcd.print("L\3 ");
  lcd.print(RMSPower[2], 3);
  lcd.print(" W");
}
void DTotals() {
  lcd.clear();
  kilot = kilos[0] + kilos[1] + kilos[2];
  for (int i = 0; i <= 2; i++) {
    byte lt = 0;
    byte mt = 0;
    float ht = 0;
    byte low = 0;
    byte medium = 0;
    byte high = 0;
    if (kilos[i] < 150) {
      lt = kilos[i];
      low = 1;
      medium = 0;
      high = 0;
    }
    if (kilos[i] - 150 > 0) {
      lt = 150;
      mt = kilos[i] - 150;
      low = 1;
      medium = 1;
      high = 0;
    }
    if (kilos[i] - 400 > 0) {
      lt = 150;
      mt = 250;
      ht = kilos[i] - 400;
      low = 1;
      medium = 1;
      high = 1;
    }
    pay[i] = (lt * 3.2484 * low) + (mt * 4.2218 * medium) + (ht * 4.4217 * high);
  }
  payt = pay[0] + pay[1] + pay[2];
  lcd.setCursor(1, 0);
  lcd.print("Total consumption");
  lcd.setCursor(3, 1);
  lcd.print("\xF6 (L\1, L\2, L\3)");
  lcd.setCursor(6, 2);
  lcd.print(kilot, 3);
  lcd.print(" kW/h");
  lcd.setCursor(3, 3);
  lcd.print("+/- ");
  lcd.print(payt, 2);
  lcd.print(" \4");
}
void Dsavedata() {
  static byte count = 1;
  count = count + 1;
  if (count > 100) {
    count = 1;
    File myFile = SD.open("L.txt", FILE_WRITE);
    if (myFile) {
      myFile.println(kilos[0], 3);
      myFile.println(kilos[1], 3);
      myFile.print(kilos[2], 3);
    }
    myFile.close();
    lcd.clear();
    lcd.setCursor(1, 1);
    lcd.print("Successfully saved");
    lcd.setCursor(4, 2);
    lcd.print("to 'SD' card");
    delay(600);
  }
}
void Resetnow() {
  if (reset == 1) {
    lcd.clear();
    lcd.setCursor(6, 0);
    lcd.print("RESET");
    reset = 0;
    for (int i = 0; i <= 2; i++) {
      kilos[i] = 0;
    }
    lcd.setCursor(1, 2);
    lcd.print("Counters all Reset");
  }
}
12

Hello World...

Thanks a lot, to all who contributed to sort out my problem.
There were many things I did not know (such as the use of "UL" (cf Deva_Rishi), david_2018, the 512-buffer allocation for using files (cf oldcurmudgeon), the clarification regarding doubles and floats on a NANO (cf sterretje) and obviousely the wonderful job done by kolaha.

While reviewing the proposed solutions, I learned many new things and it will keep me busy experimenting during the weeks to come (if my wife does not find anything else for me to do, just to get me off Arduino stuff).

I implemented the presented sketch and it worked instantly.

Now I wait for the next electricity bill in order to check if the results are the same.

See below pictures of the screens showing info about the current electricity consumption.
29038
29035
29034
29033
29037
29036

29044
290441854×1214 143 KB

29043
29043600×600 128 KB

And for those interested in building the same counter, I used 3 Split-Core AC current sensor as the following picture (for each phase 1 current sensor).
Obviously the coding will have to be adapted to what you pay for the kw/h in your country.
1983_1
1983_1579×510 58.9 KB

Note that one screen is missing... for it to appear, I need to wait a certain amount of time...
The reset button is also working fine but there, I had to adjust a few things... (just to say that I did something on my own... ha ha ha)

Again, thanks to all... and greetings from Chiang Mai (Thailand).