How to Use HX711 Load Cell (5kg): Examples, Pinouts, and Specs

The HX711 Load Cell (5kg) by SparkFun is a high-precision weight sensor designed to measure loads up to 5 kilograms. It operates by converting mechanical force into an electrical signal, which can then be amplified and processed by a microcontroller. This component is widely used in applications requiring accurate weight or force measurements, such as digital weighing scales, industrial automation, and DIY projects.

• Digital weighing scales
• Force measurement systems
• IoT-based weight monitoring
• Robotics and automation
• DIY projects requiring weight sensing

The HX711 Load Cell (5kg) is designed to work seamlessly with the HX711 ADC (Analog-to-Digital Converter) module, which amplifies and converts the small electrical signals from the load cell into a digital format readable by microcontrollers.

The HX711 Load Cell has four wires that connect to the HX711 ADC module. Below is the pin configuration:

The HX711 ADC module typically has the following pinout for connecting to a microcontroller:

1. Wiring the Load Cell to the HX711 ADC Module:

   • Connect the load cell wires to the HX711 module as follows:
     • Red wire to E+
     • Black wire to E-
     • White wire to S+
     • Green wire to S-
   • Ensure secure and proper connections to avoid signal noise.

2. Connecting the HX711 Module to an Arduino UNO:

   • Connect the HX711 module pins to the Arduino UNO as follows:
     • VCC to 5V
     • GND to GND
     • DT to digital pin 3
     • SCK to digital pin 2

3. Install the HX711 Library:

   • Use the Arduino IDE Library Manager to install the "HX711" library by Bogdan Necula or any compatible library.

4. Calibrate the Load Cell:

   • Calibration is essential to ensure accurate weight measurements. Use a known weight to determine the calibration factor.

Below is an example Arduino sketch to read data from the HX711 Load Cell:

#include "HX711.h" // Include the HX711 library

#define DT 3  // Data pin connected to digital pin 3
#define SCK 2 // Clock pin connected to digital pin 2

HX711 scale; // Create an instance of the HX711 class

void setup() {
  Serial.begin(9600); // Initialize serial communication
  scale.begin(DT, SCK); // Initialize the HX711 with DT and SCK pins

  Serial.println("Calibrating... Place a known weight on the scale.");
  delay(5000); // Wait for the user to place a weight
  scale.set_scale(); // Set the scale to default calibration factor
  scale.tare(); // Reset the scale to zero
  Serial.println("Calibration complete.");
}

void loop() {
  // Read the weight from the load cell
  float weight = scale.get_units(10); // Average 10 readings for stability
  Serial.print("Weight: ");
  Serial.print(weight);
  Serial.println(" kg");

  delay(1000); // Wait 1 second before the next reading
}

• Power Supply: Use a stable 5V power source to minimize noise and ensure accurate readings.
• Shielding: To reduce interference, use shielded cables or keep the load cell wires short.
• Mounting: Ensure the load cell is securely mounted and the load is applied evenly to avoid measurement errors.
• Calibration: Always calibrate the load cell before use to account for environmental factors and mechanical tolerances.

1. No Output or Incorrect Readings:

   • Check all connections between the load cell, HX711 module, and microcontroller.
   • Ensure the load cell wires are connected to the correct pins on the HX711 module.
   • Verify that the HX711 library is installed and correctly included in your code.

2. Fluctuating or Noisy Readings:

   • Use a stable power supply and avoid powering the HX711 from a noisy source.
   • Keep the load cell wires as short as possible and use shielded cables if necessary.
   • Ensure the load cell is not exposed to vibrations or sudden movements.

3. Calibration Issues:

   • Use a precise and known weight for calibration.
   • Ensure the load cell is properly tared (zeroed) before calibration.

4. Weight Readings Are Inaccurate:

   • Verify the calibration factor in your code. Adjust it based on the known weight.
   • Check for mechanical issues, such as uneven mounting or improper load application.

Q: Can I use the HX711 Load Cell with a 3.3V microcontroller?
A: Yes, the HX711 module operates within a voltage range of 2.6V to 5.5V, making it compatible with 3.3V microcontrollers like the ESP32 or Raspberry Pi Pico.

Q: How do I improve the accuracy of the load cell?
A: Use a stable power supply, shielded cables, and ensure proper calibration. Minimize environmental factors such as vibrations and temperature fluctuations.

Q: Can I measure weights above 5kg with this load cell?
A: No, exceeding the 5kg limit may damage the load cell and result in inaccurate readings. Use a load cell with a higher capacity for heavier loads.

Q: How do I reset the scale to zero?
A: Use the scale.tare() function in your code to reset the scale to zero before taking measurements.