Fluctuation value at loadcell 10000kg + hx711

Using Arduino Sensors
1

I'm currently working with a Load Cell S-Type. I'm planning to measure weight with an Arduino Due,
With loadcell specifications input voltage from 5-12V, has 4 wires, 2 for source and 2 for output voltage. With rated output 2.000 ± 0.001 mV/V, maximum load capacity of 10 tons (10000Kg)

I'm using hx711 with sparkfun's green and hx711 board, and it works, but it is a bit unstable.

I have some questions hope you dont mind :slight_smile:

  • Is there any influence with the bits on hx711 (24bit) being too large resulting in too sensitive a value?
  • We are trying to looking for solution to make it more stable, and curious about SparkFun Qwiic Scale - NAU7802, maybe anyone has tried it?
  • Previously I saw the video on youtube sparkfun HX711 LOAD CELL demo - YouTube
    the output from loadcell is very good, almost no fluctuation value, is it because loadcell capacity is small? Or is there a limit capacity of load cell which can be read by those boards ?

On another experiment, I used a capacitor on the loadcell and used minimal noise power, but it didn't have a big impact.

May you could provide us some information or alternative solutions that can help us to solve this problem.
Any help would be appreciated, thank you for your time

Have a good day and Happy New Year

2

All sensors and electronics generate noise. You haven't given examples of what you mean by "unstable", but there are various techniques to deal with noise, depending on whether there is external environmental noise in addition to intrinsic sensor and amplifier noise.

Post the details of your setup, including some clear pictures.

You may need electrical shielding on sensors and input leads, you may need good grounding, and you certainly need to average many individual measurements to obtain representative "stable" values.

3

This is the 3000 kg load test that I did, at one point sometimes it goes down and sometimes the load value goes up again. Is this normal?

for the wiring I have adjusted the color order in hx711. However, because it uses a jumper cable as a connector, the color is different.

If I averaged the data out too slowly, is there another technique that could be smoother.

#include "HX711.h"

#define DOUT  12
#define CLK  13


const int VCC =  11;
const int VDD =  10;

HX711 scale;

float calibration_factor = -400.0; 

void setup() {
  Serial.begin(9600);
  pinMode(VCC,OUTPUT);
  pinMode(VDD,OUTPUT);
  digitalWrite(VCC,HIGH);
  digitalWrite(VDD,HIGH); 
  
  
  scale.begin(DOUT, CLK);
  scale.set_scale();
  delay(1000);
  scale.tare(); 
  
  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);
}

void loop() { 
  
  float w=0;
  scale.set_scale(calibration_factor); 

  w = scale.get_units();
  Serial.print("Reading: ");
  Serial.print(w,1);
  Serial.print(" kg"); 
  Serial.print(" calibration_factor: ");
  Serial.print(calibration_factor);
  Serial.println();
  delay(1);
  
  if(Serial.available())
  {
    char temp = Serial.read();
    if(temp == '+' || temp == 'a')
      calibration_factor += 100;
    else if(temp == '-' || temp == 'z')
      calibration_factor -= 100;
     else if(temp == 't')
     scale.tare();
  }
}

Arduino.png
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Data.png
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Arduino.png
Arduino.png1168×773 800 KB

Data.png
Data.png752×626 485 KB

4

The HX711 module uses a 4.25volt supply for the load cell's excitation voltage.
That can only work (stable) if you power the analogue part of the module with 5volt (the VCC pin).

The digital part of the chip (the VDD pin) must be powered with 3.3volt if you use a 3.3volt processor (the Due)
It is generally speaking NOT ok to use an output pin to power modules.
Leo..

5

Is this normal?

Yes, but first correct your wiring. Stable power supplies with the correct voltage are required.

6

OK, I'll try to use a stable, low noise power supply, and the shortest possible wiring.

Thank you for your attention and information

7

ianhade:
OK, I'll try to use a stable, low noise power supply, and the shortest possible wiring.

How are you going to do that...
USB could be 'cleaner' than a good supply on the DC socket or V-in.
Don't forget that the Due uses a (noisy) switching converter for those two.

Just connect the analogue supply of the HX711 module to the 5volt pin, and the digital supply to the 3.3volt pin.
Leo..