Build a Precise Electronic Scale with Arduino UNO – Step-by-Step Guide, Parts, and Code

Apps and online services

Arduino IDE

About this project

I want to know about the electronic components weight. So I decided to do my own weighing machine :)

To do that you have to download some libraries which are listed below

LiquidCrystal_PCF8574

Wire

HX711

Connect all components as per the circuit diagram.

Programming part is critical

1. Calibration

In Calibration open the calibration sketch upload with out any load on the tray. Then put some known weight element then open serial port increment or decremented the calibration factor util you see the known value.

For example if you put 250gram weight, on first time it will give 400 gram or 1kg before calibration.. You use a, s, d, f or z, x, c, v keys to correct the calibration level until you get 250 grams from 400gram or 1kg. Then just note down the calibration factor.

2. Actual Sketch

Put the calibrated value xxxxxxx on this line and upload thats all....

scale.set_scale(xxxxxxx);

3. To reset the tare value I use one push button.

Code

• Code

CodeC/C++

/*
 * https://facebook/nissiembeddedlab
 * 2018 September 4
 * 3 Kg Load Cell HX711 Module Interface with Arduino to measure weight in Kgs
 Arduino  pin  2 -> HX711 CLK 3 -> DOUT 5V -> VCC GND -> GND
*/

#include "HX711.h"  
#define DOUT  3
#define CLK  2

HX711 scale(DOUT, CLK);
#include <Wire.h>
#include <LiquidCrystal_PCF8574.h>

LiquidCrystal_PCF8574 lcd(0x3F);
float calibration_factor = -96650;
const int SW = 7;
void setup() 
{
  Wire.begin();
  Wire.beginTransmission(0x3F);
  pinMode(SW, INPUT_PULLUP);
  lcd.setBacklight(255);
  lcd.begin(16, 2);
  lcd.setCursor(0,0);
  lcd.print("Nissi 3kgLoadCell");
  lcd.setCursor(0,1);
  lcd.print("Press Sw to tare");
  scale.set_scale(-849650); 
  scale.tare();           
}
void loop() 
{
  lcd.setCursor(0,1);
  lcd.print("W =  ");
  lcd.setCursor(6,1);
  lcd.print(scale.get_units(),3); 
  lcd.println(" kg   ");
  int x = digitalRead(SW);
  if(x == LOW)
  {
      scale.tare();  
  }
}

Schematics