# hx711 load cell tare reset offset problem

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;

``````#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(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.

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..

http://www.direnc.net/HX711-Cift-Kanal-Tarti-Sensoru-Modulu,PR-23369.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

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?

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..

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

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

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..

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?

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

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

picture of our setup attached below

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..

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

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

Tom.... :)

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

There should be no voltage between them. Leo..

Hi,

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

Exactly, got to find where the 0.8V drop on E- is.

Then try between arduino ground and HX711 ground.

Tom... :)

arduino ground and hx711 ground between no voltage but e- give still 0.8

I had a closer look at the picture of the HX711 from your link. It seems there is a 220?ohm resistor in series with E- This is different from the Sparkfun board. Don't know why your board has that. Try connecting the E- wire of the load cell directly to ground, as in the HX711 datasheet.

I also see a heavy steel disc mounted on the 500gram load cell. Did you try without that plate. Leo..

ı try e- directly to ground,but sensor still give different offset tare value.

What is the weight of that metal disc on top of the load cell. Seems heavy for a 500gram load cell. Did you try without the metal plate. Leo..