Hello everyone,
So i'm doing a weighting scale project, and i hooked up a 5kg load cell to hx711, but i'm having a problem.
When there is no load on the scale i get fluctuation of the following results:
0,23
0,41
2,52
4,59
0,00
0,00
2,19
and so on. I've read many topics about this problem, but i cant seem to be able to figure it out and i need my scale to be a bit more accurate. I was looking for designing a low pass filter, but i'm puzzled how to do it exactly. Maybe filtering with capacitors as well, but i have no idea how to connect them as well.
I've twisted my load cell cables, check my pins voltage and which seems normal, i've put the scale on a sturdy platform, also powered up the arduino with 9V adapter and still the fluctuation persists.
So if anyone has any idea why this might be happening i would be very thankful.
So here is my code:
#include "HX711.h"
#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <MFRC522.h>
#include <SD.h> // for the SD card
#include <Wire.h>
#include "MegunoLink.h"
#include "Filter.h"
ExponentialFilter<long> ADCFilter(5, 0);
#define SS_PIN 10
#define RST_PIN 9
#define CS_SD 2
float average;
float calibration_factor = -402.46;
const int buttonPin = 6;
const int buttonPin2 = 7; // the number of the pushbutton pin
int buttonState = 0;
int lastButtonState = 0;
// Create a file to store the data
File myFile;
MFRC522 mfrc522(SS_PIN, RST_PIN);
HX711 scale;
float elements;
LiquidCrystal_I2C lcd(0x27,20,4);
String LCDLine1,LCDLine2;
int n;
float rounded;
void updateLCD () {
lcd.clear();
lcd.setCursor(0,0);
lcd.print(LCDLine1);
lcd.setCursor(0,1);
lcd.print(LCDLine2);
}
void setup() {
Serial.begin(9600);
SPI.begin(); // Initiate SPI bus
mfrc522.PCD_Init(); // Initiate MFRC522
pinMode (buttonPin, INPUT);
lcd.init();
lcd.backlight();
LCDLine1="Welcome";
LCDLine2="Scan your ID";
updateLCD();
if (SD.begin(CS_SD))
{
Serial.println("SD card is ready to use.");
} else
{
Serial.println("SD card initialization failed");
return;
}
while(true){
// Look for new cards02`11
if ( ! mfrc522.PICC_IsNewCardPresent())
{
continue;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial())
{
digitalWrite(CS_SD,LOW); // enables the cs pin
// If the file opened ok, write to it
if (myFile) {
Serial.println("Read:");
// Reading the whole file
while (myFile.available()) {
Serial.write(myFile.read());
}
myFile.close();
}
else {
Serial.println("error opening test.txt");
}
digitalWrite(CS_SD,HIGH);
}
break;
}
void(* resetFunc) (void) = 0;
while(true){
//Show UID on serial monitor
Serial.print("UID tag :");
String content= "";
byte letter;
for (byte i = 0; i < mfrc522.uid.size; i++)
{
Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
Serial.print(mfrc522.uid.uidByte[i], HEX);
content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
content.concat(String(mfrc522.uid.uidByte[i], HEX));
}
Serial.println();
Serial.print("Message : ");
content.toUpperCase();
if (content.substring(1) == "9E 7E 85 89") //change here the UID of the card/cards that you want to give access
{
Serial.println("Authorized access");
Serial.println();
delay(3000);
break;
}
else {
Serial.println(" Access denied");
delay(3000);
resetFunc();
}
}
Serial.println("HX711 Demo");
LCDLine1="Initializing ...";
LCDLine2="";
updateLCD();
// parameter "gain" is ommited; the default value 128 is used by the library
// HX711.DOUT - pin #A1
// HX711.PD_SCK - pin #A0
scale.begin(A1,A0);
scale.set_scale(); // this value is obtained by calibrating the scale with known weights; see the README for details
scale.tare(); // reset the scale to 0
// by the SCALE parameter set with set_scale
long zero_factor = scale.read_average(); //Get a baseline reading
Serial.print("Zero factor: "); //This can be used to remove the need to tare the scale. Useful in permanent scale projects.
Serial.println(zero_factor);
Serial.println("Readings:");
}
void itemweight()
{
elements = scale.get_units(10);
Serial.print(" \t| Weight \t");
Serial.print(elements);
LCDLine1=String(elements,1) + "g";
LCDLine2="";
updateLCD();
}
void Scale()
{
scale.set_scale(calibration_factor);
average = scale.get_units(),30;
ADCFilter.Filter(average);
if (average < 0)
{
average = 0.00;
}
float number = scale.get_units()/elements;//divide the average of 20 readings with the elements value to get the number of elements
n = round(number);
//n = (int)number; // convert float into int
Serial.print("\t| elements:\t");
Serial.print(n); //serial monitor
Serial.print("\t| average:\t");
Serial.println(average);
// lcd.clear();
//set cursor first row
LCDLine1=String(average)+" g"; //print on lcd average value from 10 raw readings 1 time
LCDLine2=String(n)+" pcs";
updateLCD();
// serial monitor -||-
//print PCS
scale.power_down(); // put the ADC in sleep mode
delay(1000);
scale.power_up();
updateLCD();
}
unsigned long getID(){
if ( ! mfrc522.PICC_ReadCardSerial()) { //Since a PICC placed get Serial and continue
return -1;
}
unsigned long hex_num;
hex_num = mfrc522.uid.uidByte[0] << 24;
hex_num += mfrc522.uid.uidByte[1] << 16;
hex_num += mfrc522.uid.uidByte[2] << 8;
hex_num += mfrc522.uid.uidByte[3];
mfrc522.PICC_HaltA(); // Stop reading
return hex_num;
}
void myFiles()
{
buttonState = digitalRead(buttonPin2);
if (buttonState == HIGH) {
myFile = SD.open("opit7.txt", FILE_WRITE);
myFile.println();
myFile.println("User ID:");
myFile.print(getID());
myFile.println();
if (myFile) {
Serial.print("Writing to test.txt...");
myFile.println("PCS:");
myFile.print(n);
myFile.println();
myFile.close();
}
else {
}
}
}
void loop() {
buttonState = digitalRead(buttonPin);
if (buttonState == HIGH) {
float average = scale.get_units(10);
LCDLine1="Place one item";
LCDLine2=String(average,1)+" g";
updateLCD();
itemweight();
}
else {
Scale();
myFiles();
updateLCD();
// saveandclose();
}
}
