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Topic: hx711 load cell tare reset offset problem (Read 7680 times) previous topic - next topic

mhbalaman

hi,ı made a weight sensor project using with hx711 and  an load cell.ı using sparkfun tutorial below link "https://learn.sparkfun.com/tutorials/load-cell-amplifier-hx711-breakout-hookup-guide".ı determine my calibration factor and using below code;
Code: [Select]
#include "HX711.h"

#define calibration_factor 105.65 //This value is obtained using the SparkFun_HX711_Calibration sketch

#define DOUT  3
#define CLK  2

HX711 scale(DOUT, CLK);
void setup() {
  Serial.begin(9600);
  Serial.println("HX711 scale demo");

  scale.set_scale(calibration_factor); //This value is obtained by using the SparkFun_HX711_Calibration sketch
  scale.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
  }

void loop() {
//double  x=scale.get_units(40);
Serial.print("Reading:");
Serial.print(scale.get_units(40),3);
//Serial.print(3.829935739385924+0.9845073409025196*x-0.0005277155842050920*pow(x,2)+0.000002894159881057114*pow(x,3)-0.000000004539284963929932*pow(x,4));
Serial.print(" gr"); //Change this to kg and re-adjust the calibration factor if you follow SI units like a sane person
Serial.println();
}


in this code and hardware,sensor doesnt give  zero value when there is no weight on scale so scale.tare function doesnt work well. also every reset of arduino scale give different offset tare value.


Wawa

Post a link to the load cell.
Post a picture of how you have connected things.
Not all use the same colour code. Some have red as supply, some have red as output.
Measure the voltage on A+ and A-. Both should exactly the same, and half of what's on AVDD.
Leo..

mhbalaman

#2
Sep 16, 2015, 05:05 pm Last Edit: Sep 28, 2015, 09:05 am by mhbalaman
http://www.direnc.net/HX711-Cift-Kanal-Tarti-Sensoru-Modulu,PR-23369.html

http://www.direnc.net/UZUN-LOAD-AGIRLIK-SENSOR-0-500GR-,PR-15785.html

ı checked connections many times between hx711 and load cell.ı ensured that there isnt any problem between hx711 and load cell in  your opinion what type of error can be occured  in my system?
ı connected A+  green
                  A-. white
                  E+  red
                  E-   black

mhbalaman

ı connected A+  green
                  A-. white
                  E+  red
                  E-   black
as Wawa said,ı measure the voltage on A+ and A-,obtain same value. ı still dont solve reset problem.what can be other option or solution to handle this issue?

Wawa

How do you supply the Arduino.
USB, Vin, DC jack.
Battery?
What voltage.

What are the voltages on the load cell.

Does weight increase or decrease when you put something on the load cell.
Leo..

mhbalaman

ı supply the arduino from usb port.
weight increase  when you put something on the load cell.Also for example ı put no weight sensor give 2.2 gr then ı put 100gr give 99.8 .After reset arduino,ı put no weight sensor give 3.1 gr then ı put 100gr give 99 gr.ı think this problem occurs because of "tare" funvtion

mhbalaman

 A+  green    2.8v
 A-. white      2.8v
   E+  red   4.8v
   E-   black   0.8v

Wawa

Black should be 0.0volt...

Did you measure with the black/ground pin of the DMM to Arduino ground.

Did you connect ground of the HX711 to Arduino ground.

Check the ground wire between Arduino and HX711.
Leo..

mhbalaman

ı check wires between grounds. ı think there is no problem wires between grounds why this 0.8 volt can  be generate E- in hx711?

Wawa

E- is directly connected to ground.
There should be 0.00volt on E-

https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/SparkFun_HX711_Load_Cell_v10.pdf

Do you use a breadboard?
Maybe post a picture of your setup.
Leo..

mhbalaman

 picture of our setup attached below

Wawa

So how did you measure 0.8volt on E-
Where did you have your black meter lead.

As said, there should be 0.00volt on E-
That has to be solved first.
Leo..

mhbalaman

black meter lead on ardunio ground
red meter lead on hx711 e-

TomGeorge

Hi, try black lead to gnd on 711 board and E-.

Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

Wawa

Arduino ground, HX711 ground, and E- is all ground.

There should be no voltage between them.
Leo..

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