mPelectronic
Published © LGPL

High Precision Scale with Arduino

This is a very precise scale for any weight up to 1.5 kg!

IntermediateShowcase (no instructions)11,206
High Precision Scale with Arduino

Things used in this project

Hardware components

Arduino Nano R3
Arduino Nano R3
×1
Standard LCD - 16x2 White on Blue
Adafruit Standard LCD - 16x2 White on Blue
×1
HX 711 scale module
×1

Software apps and online services

Arduino IDE
Arduino IDE

Hand tools and fabrication machines

Saw
3D Printer (generic)
3D Printer (generic)

Story

Read more

Custom parts and enclosures

The 3d model, altough it is just a prototype.

Schematics

The connection of the HX711 module

HX711 Library

Code

The code

C/C++
This code might be not the best written one, but please remember that this was one of my very first projects!
#include <LiquidCrystal_I2C.h>
#include <HX711.h>

HX711 scale(A1, A0); 
LiquidCrystal_I2C lcd(0x3F,16,2);


// 
volatile float newWeight;
volatile float prevWeight;
volatile float money;
volatile float item;
volatile float change;
volatile float flag;
volatile int show = 1;
volatile float itemWeight;
volatile int amount;

int tara = 4;
unsigned long int lastTime;

int up = 2;
int down = 3;
volatile int pos = 1;


void setup() {
  lcd.init();                                         //   
  lcd.backlight();                                    //  
  scale.set_scale(-1537.34);                          //    (   )
  scale.tare();                                       //  
  prevWeight = 0;                                     //    
  scale.power_up();

  Serial.begin(9600);
  
  pinMode(tara, INPUT);
  pinMode(up, INPUT);
  attachInterrupt(0, dec, RISING);
  pinMode(down, INPUT);
  attachInterrupt(1, inc, RISING);

}

void myClear() {
    lcd.setCursor(0,0);
    lcd.print("                ");
    lcd.setCursor(0,1);
    lcd.print("                ");
    lcd.setCursor(0,0);
  }

void reload() {
  prevWeight = 0;
  newWeight = 0;
  money = 0;
  item = 0;
  change = 0;
  show = 1;
}

void dec() {
  reload();
  if (pos > 1) {
    pos -= 1; 
  }
  else {
    pos = 4;  
  }
}

void inc() {
  reload();
  if (pos < 4) {
    pos += 1;  
  }
  else {
    pos = 1;  
  }    
}

void analysis() {
  if (change > 1.00 && change < 2.40) {               // 1c           
    money += 1;
    flag = 1.25;
  }
  else if (change > 2.80 && change < 3.15) {          // 2c
    money += 2;
    flag = 2.50;
  }
  else if (change > 3.70 && change < 3.99) {          // 5c
    money += 5;
    flag = 3.80;
  }
  else if (change > 4.00 && change < 4.15) {          // 10c
    money += 10;
    flag = 4;
  }
  else if (change > 5.50 && change < 6.80) {          // 20c
    money += 20;
    flag = 6;
  }
  else if (change > 7.60 && change < 7.95) {          // 50c
    money += 50;
    flag = 7.80;
  }
  else if (change > 7.30 && change < 7.50) {          // 1E
    money += 100;
    flag = 7.40;
  }
  else if (change > 8.20 && change < 9.00) {          // 2E
    money += 200;
    flag = 8.50;
  }
}

//  :
void standard() {
  lcd.setCursor(0,0);
  lcd.print(" Standard mode! "); 
  lcd.setCursor(0,1);                                 //    1  2 !
  lcd.print("Weight: ");
  if (prevWeight != round(scale.get_units(10)) ) {     //   ,
    newWeight = scale.get_units(10);                   //     
  }
  lcd.setCursor(9,1);
  if (newWeight < 0) { scale.tare(); }
  else { lcd.print(newWeight); }
  prevWeight = newWeight;                             //    

}
///////////////////////////////////

void multiMoney() {
  lcd.setCursor(0,0);
  lcd.print("  Money multi!  ");
  lcd.setCursor(0,1);
  lcd.print("Euro: ");
  if (prevWeight != round(scale.get_units(10)) ) {    
    newWeight = scale.get_units(10);
    change = newWeight - prevWeight;
    analysis();
    lcd.setCursor(6,1);
    lcd.print(money / 100.00);
    prevWeight = newWeight;          
  }
}
//////////////////////////////////////////

void massMoney() {
  if (prevWeight != round(scale.get_units(20)) ) {    
    newWeight = scale.get_units(20); 
    change = newWeight - prevWeight;
    prevWeight = newWeight;
    if (change > 1) {
      lcd.setCursor(0,1);
      lcd.print("C:");
      lcd.setCursor(2,1);
      lcd.print(show);
      lcd.setCursor(7,1);
      lcd.print("A:");
      lcd.setCursor(10,1);
      lcd.print(show * money / 100);
      show = show + round(change / flag);  
    }
  }
}
//////////////////////////////////////

void itemsMass() {
  if (prevWeight != round(scale.get_units(10)) ) {    
    newWeight = scale.get_units(10);
    change = newWeight - prevWeight;
    amount = round(change / itemWeight);
    lcd.setCursor(0,1);
    lcd.print("Items: ");
    lcd.print(amount);
    lcd.setCursor(9,1);
    lcd.print("W:");
    lcd.print(newWeight);
  }
}
//////////////////////////////////////////


void loop() {
  if (millis() - lastTime > 100) {
    if (digitalRead(tara) == 1) {
      reload();
      scale.tare();
    }
    lastTime = millis();
  }
  
  if (pos == 1) {
    myClear();
    lcd.setCursor(4,0); 
    lcd.print("Standard");
    delay(1000);
    myClear();
    while (pos == 1) {
      standard();
    } 
  }

  else if (pos == 2) {
    myClear();
    lcd.setCursor(3,0);
    lcd.print("Money multi");
    delay(1000);
    myClear();
    while (pos == 2) {
      multiMoney();  
    }
  }

  else if (pos == 3) {
    myClear();
    lcd.setCursor(3,0);
    lcd.print("Money mass");
    delay(1000);
    myClear();
    lcd.print("Place ONE coin!"); 
    while (money == 0) {
      if (prevWeight != round(scale.get_units(10)) ) {    
        newWeight = scale.get_units(10);
        change = newWeight - prevWeight;
        analysis();
        lcd.setCursor(0,1);
        lcd.print(money / 100);
        prevWeight = newWeight;          
      }
    }
    myClear();
    lcd.print("Counting ");
    if (money < 100) {
      lcd.setCursor(10,0);
      lcd.print(money);
      lcd.print("c");
    }
    else {
      lcd.setCursor(10,0);
      if (money == 100) { lcd.print("1 Euro"); }
      else { lcd.print("2 Euro"); }
    }
    prevWeight = 0;
    newWeight = 0;
    change = 0;
    while (pos == 3) {
      massMoney();
    }
  }
  

  else if (pos == 4) {
    myClear();
    lcd.setCursor(3,0);
    lcd.print("Items mass");
    delay(1000);
    myClear();
    myClear();
    lcd.print("Place ONE item!");
    while (newWeight < 1) {
      if (prevWeight != round(scale.get_units(10)) ) {    
        newWeight = scale.get_units(10);
        itemWeight = newWeight - prevWeight;
      }
    }
    itemWeight = newWeight - prevWeight;
    lcd.setCursor(0,0);
    lcd.print("Item weight:");
    lcd.print(itemWeight);
    while (pos == 4) {
      itemsMass();
    }
  }
}

Credits

mPelectronic

mPelectronic

3 projects • 17 followers

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