How to get average readings from the load cell

Projects Programming
1

Hi, I am doing a project to measure the weight of an object by using ESP32 and load cell. The library that I am using is the HX711_ADC by Olav Kallhovd (can be installed by searching in Manage Library). The readings that I obtained is not that accurate so I want to get the average of 5 readings. The code to get one reading is shown below:

#include <HX711_ADC.h>
#if defined(ESP8266)|| defined(ESP32) || defined(AVR)
#include <EEPROM.h>
#endif

//pins:
const int HX711_dout = 19; //mcu > HX711 dout pin
const int HX711_sck = 21; //mcu > HX711 sck pin

//HX711 constructor:
HX711_ADC LoadCell(HX711_dout, HX711_sck);

float i;
float weight_limit = 10.0;
const int calVal_calVal_eepromAdress = 0;
unsigned long t = 0;

void setup() {
  Serial.begin(115200); 
  delay(10);
  Serial.println();
  Serial.println("Starting...");

  float calibrationValue; // calibration value
  calibrationValue = 696.0; // uncomment this if you want to set this value in the sketch
#if defined(ESP8266) || defined(ESP32)
  //EEPROM.begin(512); // uncomment this if you use ESP8266 and want to fetch this value from eeprom
#endif
  //EEPROM.get(calVal_eepromAdress, calibrationValue); // uncomment this if you want to fetch this value from eeprom

  LoadCell.begin();
  unsigned long stabilizingtime = 2000; // tare preciscion can be improved by adding a few seconds of stabilizing time
  boolean _tare = true; //set this to false if you don't want tare to be performed in the next step
  LoadCell.start(stabilizingtime, _tare);
  if (LoadCell.getTareTimeoutFlag()) {
    Serial.println("Timeout, check MCU>HX711 wiring and pin designations");
  }
  else {
    LoadCell.setCalFactor(calibrationValue); // set calibration factor (float)
    Serial.println("Startup is complete");
  }
  while (!LoadCell.update());
  Serial.print("Calibration value: ");
  Serial.println(LoadCell.getCalFactor());
  Serial.print("HX711 measured conversion time ms: ");
  Serial.println(LoadCell.getConversionTime());
  Serial.print("HX711 measured sampling rate HZ: ");
  Serial.println(LoadCell.getSPS());
  Serial.print("HX711 measured settlingtime ms: ");
  Serial.println(LoadCell.getSettlingTime());
  Serial.println("Note that the settling time may increase significantly if you use delay() in your sketch!");
  if (LoadCell.getSPS() < 7) {
    Serial.println("!!Sampling rate is lower than specification, check MCU>HX711 wiring and pin designations");
  }
  else if (LoadCell.getSPS() > 100) {
    Serial.println("!!Sampling rate is higher than specification, check MCU>HX711 wiring and pin designations");
  }
}

void loop() {
  static boolean newDataReady = 0;
  const int serialPrintInterval = 500; //increase value to slow down serial print activity

  // check for new data/start next conversion:
if (LoadCell.update()) newDataReady = true;

  // get smoothed value from the dataset:
  if (newDataReady) {
    if (millis() > t + serialPrintInterval) {
      i = LoadCell.getData();
      Serial.print("Load_cell output val: ");
      Serial.println(i);
      newDataReady = 0;
      t = millis();
    }
  }

  // receive command from serial terminal, send 't' to initiate tare operation:
  if (Serial.available() > 0) {
    char inByte = Serial.read();
    if (inByte == 't') LoadCell.tareNoDelay();
  }

  // check if last tare operation is complete:
  if (LoadCell.getTareStatus() == true) {
    Serial.println("Tare complete");
  }

}

I tried to use a for loop to get the average reading but the serial monitor will get spammed by showing 5 readings per iteration.

#include <HX711_ADC.h>
#if defined(ESP8266)|| defined(ESP32) || defined(AVR)
#include <EEPROM.h>
#endif

//pins:
const int HX711_dout = 19; //mcu > HX711 dout pin
const int HX711_sck = 21; //mcu > HX711 sck pin

//HX711 constructor:
HX711_ADC LoadCell(HX711_dout, HX711_sck);

float i;
float weight_limit = 10.0;
const int calVal_calVal_eepromAdress = 0;
unsigned long t = 0;

void setup() {
  Serial.begin(115200); 
  delay(10);
  Serial.println();
  Serial.println("Starting...");

  float calibrationValue; // calibration value
  calibrationValue = 696.0; // uncomment this if you want to set this value in the sketch
#if defined(ESP8266) || defined(ESP32)
  //EEPROM.begin(512); // uncomment this if you use ESP8266 and want to fetch this value from eeprom
#endif
  //EEPROM.get(calVal_eepromAdress, calibrationValue); // uncomment this if you want to fetch this value from eeprom

  LoadCell.begin();
  unsigned long stabilizingtime = 2000; // tare preciscion can be improved by adding a few seconds of stabilizing time
  boolean _tare = true; //set this to false if you don't want tare to be performed in the next step
  LoadCell.start(stabilizingtime, _tare);
  if (LoadCell.getTareTimeoutFlag()) {
    Serial.println("Timeout, check MCU>HX711 wiring and pin designations");
  }
  else {
    LoadCell.setCalFactor(calibrationValue); // set calibration factor (float)
    Serial.println("Startup is complete");
  }
  while (!LoadCell.update());
  Serial.print("Calibration value: ");
  Serial.println(LoadCell.getCalFactor());
  Serial.print("HX711 measured conversion time ms: ");
  Serial.println(LoadCell.getConversionTime());
  Serial.print("HX711 measured sampling rate HZ: ");
  Serial.println(LoadCell.getSPS());
  Serial.print("HX711 measured settlingtime ms: ");
  Serial.println(LoadCell.getSettlingTime());
  Serial.println("Note that the settling time may increase significantly if you use delay() in your sketch!");
  if (LoadCell.getSPS() < 7) {
    Serial.println("!!Sampling rate is lower than specification, check MCU>HX711 wiring and pin designations");
  }
  else if (LoadCell.getSPS() > 100) {
    Serial.println("!!Sampling rate is higher than specification, check MCU>HX711 wiring and pin designations");
  }
}

void loop() {
  static boolean newDataReady = 0;
  const int serialPrintInterval = 500; //increase value to slow down serial print activity

  // check for new data/start next conversion:
if (LoadCell.update()) newDataReady = true;

  // get smoothed value from the dataset:
  if (newDataReady) {
    for (int a=0; a<5; a++)
    {
    if (millis() > t + serialPrintInterval) 
      {
      i = LoadCell.getData();
      newDataReady = 0;
      t = millis();
      accumulated = accumulated + i;
      }
      averageweight = accumulated/5; 
     Serial.print("Load_cell output val: ");
     Serial.println(averageweight);
    }
  }

  // receive command from serial terminal, send 't' to initiate tare operation:
  if (Serial.available() > 0) {
    char inByte = Serial.read();
    if (inByte == 't') LoadCell.tareNoDelay();
  }

  // check if last tare operation is complete:
  if (LoadCell.getTareStatus() == true) {
    Serial.println("Tare complete");
  }

}

Can someone help out with the coding as I am not familiar with this library? Thank you

2 
...
    if (millis() > t + serialPrintInterval) {
...

If I had a nickle every time someone...

3

As far as I can tell the variable accumulated is never defined. This shouldn't even compile.

  if (newDataReady) {
    float accumulated = 0.0f; // <-- add this
    for (int a=0; a<5; a++)
4

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