Arduino Weighing Machine using Load Cell HX711 Module

Arduino Weighing Machine using Load Cell HX711 (Last Updated On: December 30, 2018)


In this project we will be “interfacing HX711 Load cell amplifier with Arduino” and 16*2 LCD for designing Arduino Weighing Machine using Load Cell HX711 Module. This is a simple “Arduino Weight Measurement project”.

Electronic weighing machine uses load cell to measure the weight produced by the load, here most load cells are follows the method of strain gauge, Which converts the pressure (force) into an electrical signal, these load cells have four strain gauges that are hooked up in a Wheatstone bridge formation.

Components Required:

For designing Arduino Weighing Machine using Load Cell & HX711 Module we use the following components. Each and every components are described below further.

1. Arduino UNO Board
2. HX711 Module - (Buy Online from Amazon)
3. Load Cell (Any type like 3 kg, 6 kg, 10 kg, 40 kg) - (Buy Online from Amazon)
4. 16*2 LCD (example JHD162)
5. Tact Switch (Reset Switch)
6. Breadboard
7. Connecting Wires
8. Mounting surface for Load Cell (Nuts, Bolts, Frame, Base)
9. Standard Weight blocks (100 gm)

Components Description

What is Load Cell?

Arduino Weighing Machine using Load Cell HX711

A load cell is a transducer that is used to create an electrical signal whose magnitude is directly proportional to the force being measured. It is basically a device that measures strain and then converts force into electric energy which serves as measurement for scientists and workers. The strain measurement by load cells helps in maintaining integrity of the unit under pressure and protects people and equipment nearby.

HX711 Load Cell Amplifier

The Load Cell Amplifier is a small breakout board for the HX711 IC that allows you to easily read load cells to measure weight. By connecting the amplifier to your microcontroller you will be able to read the changes in the resistance of the load cell, and with some calibration you’ll be able to get very accurate weight measurements.

The HX711 uses a two-wire interface (Clock and Data) for communication. Any microcontroller’s GPIO pins should work, and numerous libraries have been written, making it easy to read data from the HX711. Check the hookup guide below for more information. Load cells use a four-wire Wheatstone bridge configuration to connect to the HX711. These are commonly colored RED, BLK, WHT, GRN and YLW. Each color corresponds to the conventional color coding of load cells:

Arduino Weighing Machine using Load Cell HX711

Red (Excitation+ or VCC)
Black (Excitation- or GND)
White (Amplifier+, Signal+ or Output+)
Green (A-, S- or O-)
Yellow (Shield)

Arduino Weighing Machine using Load Cell HX711 Module

Load Cell & HX711 Connection:

Arduino Weighing Machine using Load Cell HX711

- RED Wire is connected to E+
- BLACK Wire is connected to E-
- WHITE Wire is connected to A-
- GREEN Wire is connected to A+

Load Cell Assembly on Base:

A base is also required to fix the load cell over it by using nuts and bolts. Here we have used a hard plyboard for the frame for placing things over it and a light wooden board as Base. This is required as load cell bends slightly when some weight is placed over it.

Arduino Weighing Machine using Load Cell HX711

Arduino Weighing Machine using Load Cell HX711

Circuit Diagram: Interfacing HX711 Load Cell with Arduino

Assemble the circuit as shown in the figure for designing “Arduino Weighing Machine using Load Cell HX711 Module” or simply “Interfacing HX711 Load Cell with Arduino“.
Arduino Weighing Machine using Load Cell HX711

Working Explanation:

Before making the whole circuit to work it is necessary to “calibrate load cell HX711 with Arduino“. For “calibrating Load Cell HX711 with Arduino” we need to put 100g weight at starting when the LCD displays put 100g weight. Once 100gm weight is kept over the load cell, calibration is done. Now simply you can put any weight for measuring with 99.9% accuracy.

Load cell which is an amplifier senses the weight and supplies a electrical analog voltage to HX711 Load Amplifier Module. Then this amplified value is fed to the Arduino where the output of HX711 is converted into the weight values in grams. The output result is displayed on 16*2 LCD.

Source Code for Interfacing HX711 Load Cell with Arduino:

Simply copy this code and upload to the Arduino board. Make sure to have the same connection as indicated above in the circuit diagram of Arduino Weighing Machine using Load Cell HX711 Module.

Video Preview & Explanation:

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    1. Boa noite! Eu sou técnico de balanças…
      Acredito que não precisará mudar o código, pois você irá utilizar as 4 células de carga em paralelo e para uni-las, deverá utilizar uma caixa de junção com 4 trimpots, para ajustar os cantos da balança.

  1. hello mr.. my name is pramono.. im from indonesia..
    i have a project use load cell..
    im doing project same with you,, but i have a problem,, when calibrating in 100 gr the program work very well, but if i change the mass up to 200 gr the measurement cant accurately

    sorry i cant speak english fluently
    i hope you can answer my question..

    1. For calibration the program is set in such a way that only 100 gm will calibrate the circuit. do not use any other weights for calibration, it won’t work

  2. hello sir i am doing same project but i want to measure weight 0 to 1000k. tell me components names please, i mean can we use hx711 amplifier for 1000kg weight too?? i am waiting for reply

    1. with larger weights the calibration for low weights will distort and may changes +/-10%. But for higher weights you can use the same Hx711 but load cell requires of 1000Kg

      1. Sir, I have 3 questions.
        1. want to use a 100 kg load cell. so for this also the hx711 and Arduino Uno 3 remains same or should I make any changes?
        2. Should I have to connect it to the computer all the time?
        3. Is calibration required whenever I turn it on?
        please answer it, sir. THANK YOU.

        1. 1. Yes you can use 100 kg load cell for measuring weight upto 100 kg. And yes the circuits remains same.

          2. You don’t need to connect to PC all the time. Rather 5 voly batter or 5 volt power supply adapter can be used instead of PC. PC is used for the first time for uploading code to Arduino.

          3. And yes calibration is required everytime you turn ON the machine.

  3. hi sir.. i am doing project on cantilever beam deflections using Arduino board and stain gauges..the problem is Arduino code..I was unable to write the code for it… i followed your “Arduino Weighing Machine using Load Cell HX711 Module” understand the code simply through me into great confusion. would you help me…please

    1. Please modify this same code using mathematical expression by multiplying with some factor using the formula for strain gauge, it should work.

  4. Hi sir. I’m newbie for this project, I’m just tested as same as yours,but there is a problem where the lcd cannot display the weight, and I don’t know where is the mistake. :”(

    1. Check the connection once again.The LCD id not didplaying anything bcoz of connection issue only, follow the diagram. Then Upload the code.

  5. tnx for the project also i used your code it works for me but i want to use your code and to print the out put on my computer so i want your help to edit the code to a serial print code please help me

  6. tnx for comment it works but i want to use 200kg load cell and the 100g calibrating is not working so please help me on the code or where to change the code?
    thank you

  7. hello Alex Newton i need your help i am doing same project but i want to measure water or liquid or measure scale can you please tell me whats the coding can i use your coding or procedure
    or may b change any thing in coding please help me

  8. hello Alex Newton sir i am doing same project but i want to measure water, liquid or fuel or petrol like this scale weight, but in litters not kg please tell me procedure or components i am waiting for reply

    1. sir sorry please explain briefly i m new for understand this can you help me more where i can change g to ml section in your coding
      can i add density code for measuring fuel or liquid ?????

  9. I am doing same project same as with you. I am using 3kg load cell from LWBMT, hx711, arduino mega, adapter for supply and LCD to display. I have tried some code like your code, HX711 bodge library, and try to edit both oh them. But, my best resolution is unstable +- 2g. I wanna get stable at least 1g without fluctuation. Can you give me advise what should i do?

  10. Hi Alex,I built up your project by using a 20kg Load cell and an I2-LCDisplay and it works fine until it gets to calibration.
    Display asks for that 100g weight,but nothing happens after putting the weight on it.
    Do you have an idea whats going wrong?
    Thanks so far!

    1. Check HX711 connection with load cell or arduino. One of the guy was facing the same issue. Later he found he hasn’t soldered one wire. Red colored HX711 and green color hx711 both has different pins.

  11. Hi! In getting the actual weight in grams, can you please explain this formula?

  12. Hello sir, I’m trying to make this project using 1kg load cell and I’ve done all the connections as per your circuit diagram. But still the LCD isn’t showing anything after “Put 100g & wait”. It’s not showing anything new after that even after I put 100g weight for a long time. The “Put 100g & wait” line is not going away either. I’m using the green HX711. Can you help me out?
    One more thing, in some previous comments you said that the system needs calibration every time it’s turned on. Is there any way to calibrate it for a long time, or until I want to calibrate it again?

    1. There are two versions of HX711, i.e Red & Green coloured. For green coloured circuit is same. But for red color 1 more extra connection is needed. You might be using red one and missing the connection. Connect vcc and vdd pins together.

      1. Actually I’m using the green one. Do I need to install the HX711 library? And can you help me with the permanent calibration? I mean I don’t want the system to be calibrated every time it’s turned on.

  13. Sir, The display shows waiting for calibration and load 100g for only a fraction of a second and it automatically shows weight as 0g irrespective of whether I place any weight or not.

    1. This means either your load cell is damaged.
      Or your load cell is shaking and not fixed properly.(maximum chance)
      Or you have shorted some of the terminals

  14. Sir, the project is working fine but it needs to calibrate every time it’s turned on. Is there any way of permanent calibration? Is it possible to store some value using EEPROM.write(address,value) in any address in the arduino which can be used (using to measure the weights instead of calibration when the next time the system is turned on?

    1. This can be done by modifying code and using eprom function to store value initially for calibration. You may try.

  15. Sir when i put 100gm weight, the weight in display keep changing between 95-107. It doesn’t not show a fixed value.

  16. Sir after putting 100gm weight, the LCD is showing various weight 95-107gm continuosly. What might be the issue?

    1. This happens if card board is not properly fixed on load cell or if it is not moving or if it has movable parts.
      Next thing don’t use the load cell in a room with fan or any other force bcoz fan air effects the mass.

  17. I have a problem in my program is giving continuous error message LCD problem
    please publish Hex code on this page

  18. hello sir..i have a problem..When it says to put 100g & wait I put 100g on but nothing happens, it doesnt go forward to calibration..can you please help me?

  19. hello sir..i have a problem..when it say to put on 100g % wait i put 100g on but nothing happens, it doesnt go forward to calibrating …can you please help me

    1. hello sir..i have a problem..When it says to put 100g & wait I put 100g on but nothing happens, it doesnot go forward to calibration..can you please help me?

  20. I want to knowed when I put 100g weight on load cell on. it showed -1g on lcd. What happen

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