05 Jun 2024

Building a Weight Sensor with Arduino: A Beginner’s Guide

Weight sensors are widely used in various applications, such as measuring the weight of objects in industrial settings, monitoring the weight of people in fitness equipment, and even in home automation systems. In this article, we will guide you through the process of building a weight sensor using an Arduino board, a load cell, and a HX711 amplifier.

Components Needed:
1. Arduino board (such as Arduino Uno)
2. Load cell (we recommend using a 20kg load cell)
3. HX711 amplifier module
4. Breadboard
5. Jumper wires
6. Resistors (10k ohms)
7. Potentiometer

Step 1: Connect the Load Cell to the HX711 Amplifier
The load cell has four wires – two red wires, a white wire, and a black wire. Connect one red wire to E+ (excitation positive) on the HX711 module and the other red wire to E- (excitation negative). Connect the white wire to A+ (signal positive) and the black wire to A- (signal negative).

Step 2: Connect the HX711 to the Arduino
Connect the VCC pin on the HX711 module to the 5V pin on the Arduino board. Connect the GND pin to the GND pin on the Arduino. Connect the DT (data) pin to digital pin 2 on the Arduino, and the SCK (clock) pin to digital pin 3.

Step 3: Program the Arduino
Download and install the HX711 library for Arduino. Open the Arduino IDE and write the following code:


#define DOUT 2
#define CLK 3

HX711 scale;
float calibration_factor = -7050.0;

void setup() {
scale.begin(DOUT, CLK);

void loop() {
Serial.print(“Weight: “);
Serial.print(scale.get_units(10), 1);
Serial.println(” kg”);

Upload the code to the Arduino board.

Step 4: Calibrate the Sensor
To calibrate the sensor, place a known weight on the load cell and adjust the calibration factor in the code until the reading matches the actual weight. You can do this by tweaking the value of the calibration_factor variable in the code.

Step 5: Test the Sensor
Connect the Arduino to your computer and open the Serial Monitor in the Arduino IDE. You should see the weight readings displayed in kilograms.

Congratulations! You have successfully built a weight sensor using an Arduino board, a load cell, and a HX711 amplifier. You can now use this sensor in various projects such as a smart scale, a luggage weight checker, or even in a home automation system to monitor the weight of objects. Have fun experimenting with different applications of your new weight sensor!


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