Arduino Scale With 5kg Load Cell and HX711 Amplifier
Intro: Arduino Scale With 5kg Load Cell and HX711 Amplifier
This Instructable describes how to make a small weighing scale using readily available off the shelf parts.
Materials needed:
1. Arduino - this design uses a standard Arduino Uno, other Arduino versions or clones should work also
2. HX711 on breakout board - This microchip is specially made for amplifying the signals from load cells and reporting them to another mircocontroller. The load cells plug into this board, and this board tells the Arduino what the load cells measure.
3. 5kg load cell - Load cells are specially shaped metal parts that have strain gauges glue to them. The strain gauges are resistors that change their resitance when they are bent. When the metal part bends, the resistance of the load cell changes (the HX711 measures this small change in resistance accurately). You can buy both the HX711 and load cell here: https://www.amazon.com/Degraw-Load-Cell-HX711-Combo/dp/B075317R45/
If you do purchase the kit please leave a review! It is really helpful for future buyers.
4. Sturdy flat mounting surface (x2) - a stiff piece of hardwood or metal is ideal.
5. Wires in various colors for connecting all the parts
6. Power supply for Arduino
STEP 1: Mount the Load Cell
First we are going to mount the load cell. Your mount will be unique, but here are the guidelines you need to follow:
1. The aluminum load cell should have 4 tapped holes and a label showing the direction of force.Mount the side without the label to the fixed surface and mount the side with the label to the moving surface. The arrow on the labeled side should point down in the direction the platform will move when a load is applied.
2. The mounting plate and the moving plate should both be as rigid as possible
3. Make sure to put some form of rigid spacers between the mounting plates and the load cell. Standoffs or washers both work well. The goal is that any force applied to the moving plate causes the load cell to bend and twist. Without spacers, load would be transferred directly from the moving plate to the fixed plate without affecting the load cell.
STEP 2: Wire the Load Cells and HX711
See the wiring diagram for how to connect the load cells, HX711, and Arduino.
On aluminum load cells, multiple strain gauges are already wired together to for a Wheatstone bridge. All you need to do is connect the wires to the HX711 board in the correct orientation.
STEP 3: Add HX711 Library to Your Arduino IDE
The HX711 library is available here: https://github.com/bogde/HX711
See this link on the Arduino website for instructions on how to add the library to your Arduino IDE: https://www.arduino.cc/en/Guide/Libraries
STEP 4: Calibrate and Weigh!
Sparkfun has great Arduino programs to run the scale. The most up to date versions are available on GitHub and reprinted below: https://github.com/sparkfun/HX711-Load-Cell-Amplifier
The first software step is to determine calibration factors for the scale. To do this, run this code:
/* Example using the SparkFun HX711 breakout board with a scale By: Nathan Seidle SparkFun Electronics Date: November 19th, 2014 License: This code is public domain but you buy me a beer if you use this and we meet someday (Beerware license). This is the calibration sketch. Use it to determine the calibration_factor that the main example uses. It also outputs the zero_factor useful for projects that have a permanent mass on the scale in between power cycles. Setup your scale and start the sketch WITHOUT a weight on the scale Once readings are displayed place the weight on the scale Press +/- or a/z to adjust the calibration_factor until the output readings match the known weight Use this calibration_factor on the example sketch This example assumes pounds (lbs). If you prefer kilograms, change the Serial.print(" lbs"); line to kg. The calibration factor will be significantly different but it will be linearly related to lbs (1 lbs = 0.453592 kg). Your calibration factor may be very positive or very negative. It all depends on the setup of your scale system and the direction the sensors deflect from zero state This example code uses bogde's excellent library:"https://github.com/bogde/HX711" bogde's library is released under a GNU GENERAL PUBLIC LICENSE Arduino pin 2 -> HX711 CLK 3 -> DOUT 5V -> VCC GND -> GND Most any pin on the Arduino Uno will be compatible with DOUT/CLK. The HX711 board can be powered from 2.7V to 5V so the Arduino 5V power should be fine. */ #include "HX711.h" #define LOADCELL_DOUT_PIN 3 #define LOADCELL_SCK_PIN 2 HX711 scale; float calibration_factor = -7050; //-7050 worked for my 440lb max scale setup void setup() { Serial.begin(9600); Serial.println("HX711 calibration sketch"); Serial.println("Remove all weight from scale"); Serial.println("After readings begin, place known weight on scale"); Serial.println("Press + or a to increase calibration factor"); Serial.println("Press - or z to decrease calibration factor"); scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN); scale.set_scale(); scale.tare(); //Reset the scale to 0 long zero_factor = scale.read_average(); //Get a baseline reading Serial.print("Zero factor: "); //This can be used to remove the need to tare the scale. Useful in permanent scale projects. Serial.println(zero_factor); } void loop() { scale.set_scale(calibration_factor); //Adjust to this calibration factor Serial.print("Reading: "); Serial.print(scale.get_units(), 1); Serial.print(" lbs"); //Change this to kg and re-adjust the calibration factor if you follow SI units like a sane person Serial.print(" calibration_factor: "); Serial.print(calibration_factor); Serial.println(); if(Serial.available()) { char temp = Serial.read(); if(temp == '+' || temp == 'a') calibration_factor += 10; else if(temp == '-' || temp == 'z') calibration_factor -= 10; } }
After calibrating the scale, you can run this sample program, then hack it up for your own purposes:
/* Example using the SparkFun HX711 breakout board with a scale By: Nathan Seidle SparkFun Electronics Date: November 19th, 2014 License: This code is public domain but you buy me a beer if you use this and we meet someday (Beerware license). This example demonstrates basic scale output. See the calibration sketch to get the calibration_factor for your specific load cell setup. This example code uses bogde's excellent library:"https://github.com/bogde/HX711" bogde's library is released under a GNU GENERAL PUBLIC LICENSE The HX711 does one thing well: read load cells. The breakout board is compatible with any wheat-stone bridge based load cell which should allow a user to measure everything from a few grams to tens of tons. Arduino pin 2 -> HX711 CLK 3 -> DAT 5V -> VCC GND -> GND The HX711 board can be powered from 2.7V to 5V so the Arduino 5V power should be fine. */ #include "HX711.h" #define calibration_factor -7050.0 //This value is obtained using the SparkFun_HX711_Calibration sketch #define LOADCELL_DOUT_PIN 3 #define LOADCELL_SCK_PIN 2 HX711 scale; void setup() { Serial.begin(9600); Serial.println("HX711 scale demo"); scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN); 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 Serial.println("Readings:"); } void loop() { Serial.print("Reading: "); Serial.print(scale.get_units(), 1); //scale.get_units() returns a float Serial.print(" lbs"); //You can change this to kg but you'll need to refactor the calibration_factor Serial.println(); }
37 Comments
sarfaraz_sa 1 year ago
I am new on Arduino
nipunachamara 2 years ago
I have a question regarding continuous monitoring using loadcells.
In my application, I have to measure the weight of the object continuously for around 1 month period. I have used this setup to measure the weight of an object. The mass of the object is constant. When I ran the program continuously and measure I found the value continuously decreasing. I have tried this for two different types of loadcells and the result is the same. As an example, the initial weight recorded by the system of a standard 500 g was 500 g. But after one day value is 482.5g. Any suggestions on how to remove this. Also, note that this is not a noise. A very smooth change over time.
cmouse42 2 years ago
My question is, the Wheatstone bridge is powered by the existing controller. Can I just use the other two sensor wires to read off a value? Do I need to common ground their controller and the HX711? Is this at all possible?
TommasoD 3 years ago
Thank you in advance
Michelin25 4 years ago
And my question is what is the 1 at the end for.
Michal
Kees_B 4 years ago
michal.demeter.tvrdon 4 years ago
sannalasrinadhreddy19 4 years ago
we need s-beam load cell with hx711 and arduino code, please anyone send me the code.
ojsemler 4 years ago
WastedRhino 4 years ago
Carlos AndrésB1 4 years ago
Are those load cells reliable? The amazon reviews are not very encouraging but there are only 3, so it is hard to judge by that.
JackG129 4 years ago
Arduino: error: HX711.h: No such file or directory
compilation terminated.
exit status 1
HX711.h: No such file or directory
anybody know how to fix this?
wumiaoshun 4 years ago
ramongayovazquez 4 years ago
sonaiguru.ei17 4 years ago
SudeB1 4 years ago
KennethM124 5 years ago
I am currently trying to get my load cell to work for my project. Unfortunately it appears there is some kind of error, and I cannot see why. I try running the calibration sketch, but I keep getting an error for the HX711 scale(DOUT, CLK) saying "no matching function for call to 'HX711::HX711(int,int)'" I have reviewed everything, I have the correct library installed, and am becoming a little frustrated. anybody else have this issue and was able to solve it? It appears to not like the HX711 part of the code.
jleona19 5 years ago
themosfet 5 years ago
DegrawSt 5 years ago
The code in the Instructables is now updated.