HX711 is not working

Hi everyone
Recently I bought a scale with 200 kg load Cell , this scale is a commercial one that is usually connected to a cheap commercial 7 segment display , but I bought only the scale part with the load cell only
here a photo of the unit

its load cell has the ordinary 4 wires red black white and green,
and I connected them to HX711 breakout board which I connected to an Arduino Nano as you can see here

I used different sketches like this one here

#include "HX711.h"

// HX711 circuit wiring
#define LOADCELL_DOUT_PIN  3
#define LOADCELL_SCK_PIN  2


HX711 scale;

void setup() {
  Serial.begin(57600);
  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
}

void loop() {

  if (scale.is_ready()) {
    scale.set_scale();    
    Serial.println("Tare... remove any weights from the scale.");
    delay(50);
    scale.tare();
    Serial.println("Tare done...");
    Serial.print("Place a known weight on the scale...");
    delay(5000);
    long reading = scale.get_units(10);
    Serial.print("Result: ");
    Serial.println(reading);
  } 
  else {
    Serial.println("HX711 not found.");
  }
  delay(1000);
}

the problem I'm facing now is that the reading from the scale is always 0 with no difference if a load is mounted on the scale or not
I used the same HX711 with another load cell and It seems working and the scale itself gave accurate reading when it was connected to the original 7 segment display
I'm not really sure what is the problem ?

What schematics did You use? Please post it. Lots of possibilities to have "not working".

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There is related discussion in @drmina2023's other topic on the project:

@drmina2023,l it is OK to make separate forum topics for well defined discrete aspects of a project. However, there are some requirements for this to be done in a manner compliant with the rules of the forum and respectful of the people offering free help:

Avoid convergence

Even when the topics start out on discrete subjects, they have a tendency to converge to parallel discussion over time. Parallel discussions are harmful because they waste the time of the helpers who unknowingly duplicate the previous efforts from the other topic. For this reason, you must manage the scope of the discussion to prevent this from happening. If discussion starts to stray into the territory of the other topic, then redirect the participants over to the other to continue that discussion.

Cross-reference

The readers of one topic won't necessarily be aware of the content in the other. If information in one topic is relevant to the discussion in another, help your helpers by mentioning it there with a link.


So far, you created three different topics about this project, caused overlap between each of them, and didn't mention the previous discussion. Do better in the future.

@pert
Ok sure , I will do that

1 Like

@Railroader
here is the schematic
Notice that my HX711 has a yellow pin that is free as my load cell has only 4 wires red black white and green all are soldered to the corresponding pins on the HX711.

Thanks!

Usually text is written from the left to the right, not from top to down.... Picture editing turned the picture 90 degrees CCW.

I see nothing wrong but have no knowledge about the colouring of HX711 wires. Maybe another helper will see something.

Can you open the scale and follow the wiring to the load cell ?
Can you measure the 4 resistance values of the load cell ?

The sketch and the photo and your drawing, they all seem okay. The only unknown part is the scale.

It's a 'Load Call Amp' --
image

It's HX711 breakout board, I'm pretty sure.

The soldering looks bad. Check for short circuits and proper continuity.

Compare with a DMM the resistances across the wire pairs on the good and suspect faulty load cell.
Do this with the cells not connected to the 711 module.

Thanks.. Tom... :grinning: :+1: :coffee: :australia:

1 Like

@drmina2023
The connections you show in your schematic for CLK and DAT are reversed from what you have in your code
Change to this

#define LOADCELL_DOUT_PIN  2  // was 3
#define LOADCELL_SCK_PIN  3  // was 2

@Koepel
here are the resistances of the current load cell as I measured them before


red - black	0.294
red - white	0.291
red - green	0.356
black-red	0.289
black-green	0.289
black-white	0.405
green-black	0.289
green-red	0.352
green-white	0.289
white-black	0.402
white-red	0.289
white-green	0.289

I Did correct the sketch but with no effect the reading is always 0

#include "HX711.h"

// HX711 circuit wiring
#define LOADCELL_DOUT_PIN  3
#define LOADCELL_SCK_PIN 4
int CalibrationFactor;

HX711 scale;


void setup() {
  Serial.begin(57600);
  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
  scale.set_scale();
  scale.tare();		
  Serial.print("place a known weight");
  delay(1000);
  
  CalibrationFactor = (9930);
  Serial.print("Calibration factor   ");
  Serial.print(CalibrationFactor);
  scale.set_scale(CalibrationFactor);

}

void loop() {
  
  //scale.set_scale(CalibrationFactor);
  Serial.println("Readings: \t\t");
  Serial.println(scale.get_units(10), 1);
  delay(1000);
    
  }


Thanks, there is resistance in the wires, but it almost seems that the wire colors are not standard.

Normal load cells that are use by the HX711 have a resistance of 1kΩ. The load cells of your scale might not be compatible with the HX711.
I suppose that those values are Ohms, not kilo-Ohms.

@Koepel
So what are your suggestions now?

I don't know, sorry.

And yet you just did it again. I'm giving you a short forum suspension since it seems that asking nicely isn't getting your attention. On your return to the forum I hope you will be more respectful of our community.

Please Accept my apology.

1 Like

I Asked the vendor of my scale unit for the data Sheet and he gave me the manual that came with the scale.
here it's



Would this offer any clue to the problem .