Weight Scale on ESP32-C3 on Liliygo T-Zigbee Board

[TinTin]

Hello,
i'm trying to build an weight scale with with the Liliygo T-Zigbee Board using an HX711 and 4x 50kg weight cells. I get different reading on every calibation and the reading dont really change as expeced on adding or removing weights on the cells and the measurement drifts.

I have rewired it multiple times already to make sure there are no mistakes there. I changed the the DT and SCK Pin connection to other GPIO-Pins without success.
I don't really know what else could be wrong. Could someone take a look and give me advice what i should change to get correct measurement and calibation.

The HX711 and the loadcells are wired like this

HX711 wiring.PNG (20.05 KiB) Viewed 2406 times

The HX711 is currently connected to the board as follows

GND -> GND
DT -> GPIO08
SCK -> GPIO06
VCC-> 3.3V

And The Pins on the board are like this

PINMAP.PNG (322.66 KiB) Viewed 2406 times

This is my current code

Code: Untitled.cpp Select all

#include <Arduino.h>

#include "HX711.h"

#include "soc/rtc.h"



HX711 scale;



uint8_t dataPin  = 8;

uint8_t clockPin = 6;



void setup()

{

  delay(2000);

  Serial.begin(115200);

  Serial.println();



    rtc_cpu_freq_config_t config;

    rtc_clk_cpu_freq_get_config(&config);

    rtc_clk_cpu_freq_mhz_to_config(80, &config);

    rtc_clk_cpu_freq_set_config_fast(&config);



  scale.begin(dataPin, clockPin);

delay(2000);

  Serial.print("UNITS: ");

  Serial.println(scale.get_units(10));



  Serial.println("\nEmpty the scale, press a key to continue");

  while(!Serial.available());

  while(Serial.available()) 

  Serial.read();

delay(5000);



  scale.tare();

  Serial.print("UNITS: ");

  Serial.println(scale.get_units(10));





  Serial.println("\nPut 1000 gram in the scale, press a key to continue");

  while(!Serial.available());

  while(Serial.available()) Serial.read();

delay(5000);

  scale.calibrate_scale(1000, 5);

  Serial.print("UNITS: ");

  Serial.println(scale.get_units(10));



  Serial.println("\nScale is calibrated, press a key to continue");

  Serial.print("Scale:");

   Serial.println(scale.get_scale());

   Serial.print("OFFSET:");

   Serial.println(scale.get_offset());

  while(!Serial.available());

  while(Serial.available()) Serial.read();

Serial.println("");

Serial.println("");

Serial.println("");

  Serial.print("UNIT");

  Serial.print("\t;");

  Serial.print("VALUE");

  Serial.print("\t;");

  Serial.println("READ");

  

}





void loop()

{

  long UNIT = scale.get_units(1);

  long VALUE = scale.get_value(1); 

  long READ = scale.read();

  Serial.print(UNIT);

  Serial.print("\t;");

  Serial.print(VALUE);

  Serial.print("\t;");

  Serial.println(READ);

 

}

The output and measurement i get while an 1000g wheight is on the scale is as follows

Code: Untitled.txt Select all

UNITS: -158241.80



Empty the scale, press a key to continue

UNITS: -111.80



Put 1000 gram in the scale, press a key to continue

UNITS: 13139.30



Scale is calibrated, press a key to continue

Scale:-0.01

OFFSET:-158227







UNIT    ;VALUE  ;READ

3610    ;-81    ;-158274

802     ;-62    ;-158252

-401    ;28     ;-158202

4312    ;-45    ;-158268

200     ;12     ;-158177

-4312   ;14     ;-158238

2607    ;-43    ;-158222

2908    ;-37    ;-158332

17953   ;-106   ;-158299

17151   ;-174   ;-158385

14242   ;-168   ;-158421

17351   ;-242   ;-158470

16750   ;-132   ;-158338

14142   ;-172   ;-158376

16449   ;-118   ;-158285

6018    ;-135   ;-158279

7622    ;-78    ;-158302

11033   ;-102   ;-158320

9929    ;-59    ;-158316

12236   ;-111   ;-158337

5416    ;-72    ;-158386

9227    ;-75    ;-158308

8625    ;-140   ;-158386

12938   ;-129   ;-158337

11534   ;-168   ;-158348

5616    ;-20    ;-158273

8425    ;-100   ;-158285

-200    ;18     ;-158138

-9929   ;101    ;-158131

-9628   ;143    ;-158042

-23269  ;201    ;-158004

-28886  ;216    ;-158027

-18856  ;138    ;-158130

-20260  ;240    ;-157978

-20461  ;182    ;-157996

-23169  ;203    ;-158000

-26579  ;218    ;-158048

-15145  ;143    ;-158126

-7422   ;55     ;-158172

-3510   ;27     ;-158168

-1705   ;14     ;-158158

-7923   ;23     ;-158220

-13640  ;196    ;-158122

-9829   ;139    ;-158056

-22868  ;208    ;-157940

-27983  ;300    ;-157925

-30290  ;324    ;-157839

-29989  ;312    ;-157896

-30992  ;344    ;-157852

-42326  ;429    ;-157781

-37512  ;428    ;-157762

-51052  ;572    ;-157584

-67401  ;648    ;-157559

-58575  ;615    ;-157517

-71413  ;753    ;-157297

-100199 ;1140   ;-156859

-143529 ;1442   ;-156896

-115345 ;1492   ;-156586

-174020 ;1796   ;-156508

-165795 ;1656   ;-156583

-168403 ;1603   ;-156698

-163087 ;1692   ;-156439

-191071 ;1813   ;-156463

-188664 ;1924   ;-156416

-186959 ;1918   ;-156285

-191974 ;1949   ;-156324

-196487 ;1967   ;-156212

-188664 ;1888   ;-156339

-189065 ;1716   ;-156582

-170911 ;1807   ;-156363

-188664 ;1764   ;-156469

-172917 ;1614   ;-156439

-177330 ;1786   ;-156329

-186758 ;1879   ;-156348

-181843 ;1852   ;-156272

-201903 ;2022   ;-156291

-186457 ;1906   ;-156305

-195384 ;1949   ;-156247

-205815 ;2055   ;-156194

-208022 ;2161   ;-156053

-216748 ;2162   ;-156046

-217751 ;2211   ;-156015

-215745 ;2114   ;-156146

-206517 ;2056   ;-156148

-210329 ;2051   ;-156154

-208924 ;2053   ;-156172

-211933 ;2099   ;-156065

-215444 ;2154   ;-156108

-212134 ;2121   ;-156080

-218453 ;2073   ;-156133

-212435 ;2153   ;-156141

-207119 ;2081   ;-156161

-206216 ;2008   ;-156190

-207420 ;2089   ;-156121

-225073 ;2337   ;-155858

-239115 ;2385   ;-155800

-244130 ;2417   ;-155906

-227179 ;2315   ;-155817

-240920 ;2365   ;-155895

-232796 ;2356   ;-155859

-245333 ;2447   ;-155844

-242525 ;2524   ;-155715

-249546 ;2452   ;-155820

-242324 ;2371   ;-155911

-228383 ;2198   ;-155964

-229386 ;2230   ;-155975

-229787 ;2317   ;-155926

-228182 ;2289   ;-155943

-233498 ;2297   ;-155943

-236407 ;2391   ;-155815

-244631 ;2395   ;-155768

-249747 ;2475   ;-155769

-246637 ;2490   ;-155770

-249646 ;2575   ;-155574

-264992 ;2593   ;-155646

-257169 ;2617   ;-155559

-272314 ;2711   ;-155452

-280037 ;2767   ;-155505

-279837 ;2751   ;-155475

-275624 ;2719   ;-155484

-276125 ;2690   ;-155560

-266798 ;2676   ;-155502

-267801 ;2660   ;-155514

-262485 ;2603   ;-155604

-263889 ;2623   ;-155573

-272414 ;2578   ;-155673

-257068 ;2616   ;-155580

-263287 ;2605   ;-155621

-261883 ;2625   ;-155646

-252354 ;2523   ;-155655

-250750 ;2469   ;-155783

-250148 ;2473   ;-155666

-262986 ;2624   ;-155693

-251251 ;2576   ;-155712

-246336 ;2485   ;-155752

-250649 ;2446   ;-155828

-246035 ;2438   ;-155906

-240720 ;2419   ;-155903

-233899 ;2383   ;-155881

-235103 ;2393   ;-155909

-237410 ;2412   ;-155823

-239215 ;2307   ;-155926

-240419 ;2341   ;-155843

-244732 ;2434   ;-155809

-245133 ;2529   ;-155696

-257670 ;2536   ;-155753

-251753 ;2531   ;-155716

-250850 ;2510   ;-155714

-257369 ;2543   ;-155731

-241221 ;2340   ;-155793

-250047 ;2439   ;-155792

[lbernstone]

You should read the HX711 datasheet. I don't think it works the way you are thinking- it is intended to be a differential reading between two poles on a strain sensor, and provide 2 such inputs. If you just want to read multiple analog inputs, the esp32 can do that directly, or you can get a device like ADS1115.
https://cdn.sparkfun.com/datasheets/Sen ... nglish.pdf

[TinTin]

Hello lbernstone,

yes i know that. Thats the reason the 4 halfbridge weight cells are forming a Wheatstone bridge so that on applying pressure on them the resistances change and the voltages on the inputs A+ and A- change accordingly. And the HX711 should amplify that input signal.

I took this as example for my setup
https://randomnerdtutorials.com/esp32-load-cell-hx711/
the difference to my setup there is that i use 4 halfbridge weight cells to form a full bridge weight cell and they use a different board. But it still uses an esp32 in that board.
And there are multiple setups there they use the same loadcells with the hx711 and the same wiring of the loadcells to the hx711 but instead with an arduino board and it works.

So i dont think I'm wrong in that part.
What i suspect is that maybe the internal ADC of the board trys to convert an alredy digital input. But that should not be it because i changed the pins to which the hx711 is connected to board.

Or its something i'm just to blind to see.

[eeseboi]

Any updates? I have the exact same issue. Most answers revolve around just using a full-bridge load cell vs the half-bridge + combinator.