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 864 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 864 times

This is my current code

Code: [Select all] [Expand/Collapse]

1. #include <Arduino.h>
2. #include "HX711.h"
3. #include "soc/rtc.h"
4.  
5. HX711 scale;
6.  
7. uint8_t dataPin  = 8;
8. uint8_t clockPin = 6;
9.  
10. void setup()
11. {
12.   delay(2000);
13.   Serial.begin(115200);
14.   Serial.println();
15.  
16.     rtc_cpu_freq_config_t config;
17.     rtc_clk_cpu_freq_get_config(&config);
18.     rtc_clk_cpu_freq_mhz_to_config(80, &config);
19.     rtc_clk_cpu_freq_set_config_fast(&config);
20.  
21.   scale.begin(dataPin, clockPin);
22. delay(2000);
23.   Serial.print("UNITS: ");
24.   Serial.println(scale.get_units(10));
25.  
26.   Serial.println("\nEmpty the scale, press a key to continue");
27.   while(!Serial.available());
28.   while(Serial.available())
29.   Serial.read();
30. delay(5000);
31.  
32.   scale.tare();
33.   Serial.print("UNITS: ");
34.   Serial.println(scale.get_units(10));
35.  
36.  
37.   Serial.println("\nPut 1000 gram in the scale, press a key to continue");
38.   while(!Serial.available());
39.   while(Serial.available()) Serial.read();
40. delay(5000);
41.   scale.calibrate_scale(1000, 5);
42.   Serial.print("UNITS: ");
43.   Serial.println(scale.get_units(10));
44.  
45.   Serial.println("\nScale is calibrated, press a key to continue");
46.   Serial.print("Scale:");
47.    Serial.println(scale.get_scale());
48.    Serial.print("OFFSET:");
49.    Serial.println(scale.get_offset());
50.   while(!Serial.available());
51.   while(Serial.available()) Serial.read();
52. Serial.println("");
53. Serial.println("");
54. Serial.println("");
55.   Serial.print("UNIT");
56.   Serial.print("\t;");
57.   Serial.print("VALUE");
58.   Serial.print("\t;");
59.   Serial.println("READ");
60.  
61. }
62.  
63.  
64. void loop()
65. {
66.   long UNIT = scale.get_units(1);
67.   long VALUE = scale.get_value(1);
68.   long READ = scale.read();
69.   Serial.print(UNIT);
70.   Serial.print("\t;");
71.   Serial.print(VALUE);
72.   Serial.print("\t;");
73.   Serial.println(READ);
74.  
75. }
76.  

GeSHi © Codebox Plus Extension

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

Code: [Select all] [Expand/Collapse]

1. UNITS: -158241.80
2.  
3. Empty the scale, press a key to continue
4. UNITS: -111.80
5.  
6. Put 1000 gram in the scale, press a key to continue
7. UNITS: 13139.30
8.  
9. Scale is calibrated, press a key to continue
10. Scale:-0.01
11. OFFSET:-158227
12.  
13.  
14.  
15. UNIT    ;VALUE  ;READ
16. 3610    ;-81    ;-158274
17. 802     ;-62    ;-158252
18. -401    ;28     ;-158202
19. 4312    ;-45    ;-158268
20. 200     ;12     ;-158177
21. -4312   ;14     ;-158238
22. 2607    ;-43    ;-158222
23. 2908    ;-37    ;-158332
24. 17953   ;-106   ;-158299
25. 17151   ;-174   ;-158385
26. 14242   ;-168   ;-158421
27. 17351   ;-242   ;-158470
28. 16750   ;-132   ;-158338
29. 14142   ;-172   ;-158376
30. 16449   ;-118   ;-158285
31. 6018    ;-135   ;-158279
32. 7622    ;-78    ;-158302
33. 11033   ;-102   ;-158320
34. 9929    ;-59    ;-158316
35. 12236   ;-111   ;-158337
36. 5416    ;-72    ;-158386
37. 9227    ;-75    ;-158308
38. 8625    ;-140   ;-158386
39. 12938   ;-129   ;-158337
40. 11534   ;-168   ;-158348
41. 5616    ;-20    ;-158273
42. 8425    ;-100   ;-158285
43. -200    ;18     ;-158138
44. -9929   ;101    ;-158131
45. -9628   ;143    ;-158042
46. -23269  ;201    ;-158004
47. -28886  ;216    ;-158027
48. -18856  ;138    ;-158130
49. -20260  ;240    ;-157978
50. -20461  ;182    ;-157996
51. -23169  ;203    ;-158000
52. -26579  ;218    ;-158048
53. -15145  ;143    ;-158126
54. -7422   ;55     ;-158172
55. -3510   ;27     ;-158168
56. -1705   ;14     ;-158158
57. -7923   ;23     ;-158220
58. -13640  ;196    ;-158122
59. -9829   ;139    ;-158056
60. -22868  ;208    ;-157940
61. -27983  ;300    ;-157925
62. -30290  ;324    ;-157839
63. -29989  ;312    ;-157896
64. -30992  ;344    ;-157852
65. -42326  ;429    ;-157781
66. -37512  ;428    ;-157762
67. -51052  ;572    ;-157584
68. -67401  ;648    ;-157559
69. -58575  ;615    ;-157517
70. -71413  ;753    ;-157297
71. -100199 ;1140   ;-156859
72. -143529 ;1442   ;-156896
73. -115345 ;1492   ;-156586
74. -174020 ;1796   ;-156508
75. -165795 ;1656   ;-156583
76. -168403 ;1603   ;-156698
77. -163087 ;1692   ;-156439
78. -191071 ;1813   ;-156463
79. -188664 ;1924   ;-156416
80. -186959 ;1918   ;-156285
81. -191974 ;1949   ;-156324
82. -196487 ;1967   ;-156212
83. -188664 ;1888   ;-156339
84. -189065 ;1716   ;-156582
85. -170911 ;1807   ;-156363
86. -188664 ;1764   ;-156469
87. -172917 ;1614   ;-156439
88. -177330 ;1786   ;-156329
89. -186758 ;1879   ;-156348
90. -181843 ;1852   ;-156272
91. -201903 ;2022   ;-156291
92. -186457 ;1906   ;-156305
93. -195384 ;1949   ;-156247
94. -205815 ;2055   ;-156194
95. -208022 ;2161   ;-156053
96. -216748 ;2162   ;-156046
97. -217751 ;2211   ;-156015
98. -215745 ;2114   ;-156146
99. -206517 ;2056   ;-156148
100. -210329 ;2051   ;-156154
101. -208924 ;2053   ;-156172
102. -211933 ;2099   ;-156065
103. -215444 ;2154   ;-156108
104. -212134 ;2121   ;-156080
105. -218453 ;2073   ;-156133
106. -212435 ;2153   ;-156141
107. -207119 ;2081   ;-156161
108. -206216 ;2008   ;-156190
109. -207420 ;2089   ;-156121
110. -225073 ;2337   ;-155858
111. -239115 ;2385   ;-155800
112. -244130 ;2417   ;-155906
113. -227179 ;2315   ;-155817
114. -240920 ;2365   ;-155895
115. -232796 ;2356   ;-155859
116. -245333 ;2447   ;-155844
117. -242525 ;2524   ;-155715
118. -249546 ;2452   ;-155820
119. -242324 ;2371   ;-155911
120. -228383 ;2198   ;-155964
121. -229386 ;2230   ;-155975
122. -229787 ;2317   ;-155926
123. -228182 ;2289   ;-155943
124. -233498 ;2297   ;-155943
125. -236407 ;2391   ;-155815
126. -244631 ;2395   ;-155768
127. -249747 ;2475   ;-155769
128. -246637 ;2490   ;-155770
129. -249646 ;2575   ;-155574
130. -264992 ;2593   ;-155646
131. -257169 ;2617   ;-155559
132. -272314 ;2711   ;-155452
133. -280037 ;2767   ;-155505
134. -279837 ;2751   ;-155475
135. -275624 ;2719   ;-155484
136. -276125 ;2690   ;-155560
137. -266798 ;2676   ;-155502
138. -267801 ;2660   ;-155514
139. -262485 ;2603   ;-155604
140. -263889 ;2623   ;-155573
141. -272414 ;2578   ;-155673
142. -257068 ;2616   ;-155580
143. -263287 ;2605   ;-155621
144. -261883 ;2625   ;-155646
145. -252354 ;2523   ;-155655
146. -250750 ;2469   ;-155783
147. -250148 ;2473   ;-155666
148. -262986 ;2624   ;-155693
149. -251251 ;2576   ;-155712
150. -246336 ;2485   ;-155752
151. -250649 ;2446   ;-155828
152. -246035 ;2438   ;-155906
153. -240720 ;2419   ;-155903
154. -233899 ;2383   ;-155881
155. -235103 ;2393   ;-155909
156. -237410 ;2412   ;-155823
157. -239215 ;2307   ;-155926
158. -240419 ;2341   ;-155843
159. -244732 ;2434   ;-155809
160. -245133 ;2529   ;-155696
161. -257670 ;2536   ;-155753
162. -251753 ;2531   ;-155716
163. -250850 ;2510   ;-155714
164. -257369 ;2543   ;-155731
165. -241221 ;2340   ;-155793
166. -250047 ;2439   ;-155792

GeSHi © Codebox Plus Extension

[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.