The HX711 Load Cell Weight Pressure Sensor Module is a precision analog-to-digital converter (ADC) designed for weighing applications. It interfaces with load cells to measure weight or pressure, converting the analog signal from the load cell into a digital signal that can be read by microcontrollers such as Arduino or Raspberry Pi. The HX711 module is commonly used in digital weighing scales, pressure measurement systems, and other applications requiring precise load measurements.

Key Applications:

• Digital weighing scales
• Pressure measurement systems
• Force measurement
• Industrial and laboratory applications
• Load testing

Features:

• High Precision: Offers accurate weight and pressure measurements with high resolution.
• Low Noise: Designed to minimize noise and interference in measurements.
• Built-in Amplifier: Includes an integrated amplifier to boost the signal from the load cell.
• Easy Interface: Provides a simple interface for connecting to microcontrollers via a two-wire digital interface.
• Low Power Consumption: Suitable for battery-powered applications.

Specifications:

• ADC Resolution: 24-bit
• Interface: Digital (Two-wire communication: Data and Clock)
• Supply Voltage: Typically 2.7V to 5.5V
• Power Consumption: Low, typically around 1.5mA
• Load Cell Compatibility: Supports both single and dual load cell configurations
• Gain Settings: Configurable gain settings (e.g., 32, 64, 128) to adjust the amplification level
• Measurement Range: Depends on the load cell used
• Operating Temperature: -40°C to +85°C
• Package Type: Usually in a compact module format with connectors for load cell and power supply

Connection Pinout:

• VCC: Power supply pin (2.7V to 5.5V)
• GND: Ground pin
• DT: Data pin (Digital output from the HX711 to the microcontroller)
• SCK: Serial Clock pin (Clock signal from the microcontroller for data reading)

How to interface with an Arduino?

Interfacing a load cell with an Arduino involves connecting the load cell to an amplifier (such as the HX711), which then sends the signal to the Arduino. Here’s how you can interface 1Kg, 5Kg, 10Kg, and 20Kg load cells using Arduino:

Components Required:

• Load Cell (1Kg, 5Kg, 10Kg, or 20Kg)
• HX711 Load Cell Amplifier Module
• Arduino (UNO or any compatible board)
• Jumper Wires
• Breadboard
• Power Supply

Steps to Interface Load Cells with Arduino:

1. Wiring the Load Cell to the HX711 Amplifier:

Most load cells, regardless of their capacity (1Kg, 5Kg, 10Kg, or 20Kg), come with four wires:

• Red: +E (Excitation+)
• Black: -E (Excitation-)
• Green: +S (Signal+)
• White: -S (Signal-)

Wire the load cell to the HX711 module as follows:

• Red wire from the load cell to E+ on the HX711.
• Black wire from the load cell to E- on the HX711.
• Green wire from the load cell to A+ on the HX711.
• White wire from the load cell to A- on the HX711.

(Note: If you’re using a load cell with five wires, the extra wire (usually yellow) is for grounding or shielding and can be ignored.)

2. Wiring the HX711 to the Arduino:

Connect the HX711 module to the Arduino as follows:

• VCC on HX711 to 5V on Arduino.
• GND on HX711 to GND on Arduino.
• DT (Data) on HX711 to Pin 3 on Arduino.
• SCK (Clock) on HX711 to Pin 2 on Arduino.

3. Arduino Code:

You'll need the HX711 library to easily read data from the load cell. Install the library via Arduino IDE:

• Go to Sketch → Include Library → Manage Libraries, then search for "HX711" and install the HX711 library by "Bogdan Necula."

Here's a sample code for reading load cell data:

#include "HX711.h"

// HX711 circuit wiring
const int LOADCELL_DOUT_PIN = 3;
const int LOADCELL_SCK_PIN = 2;

HX711 scale;

void setup() {
  Serial.begin(9600);
  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
  Serial.println("Load Cell Setup Ready");
}

void loop() {
  if (scale.is_ready()) {
    long reading = scale.read();  // Read raw data from load cell
    Serial.print("Raw reading: ");
    Serial.println(reading);
    
    // You can add calibration here based on your specific load cell
  } else {
    Serial.println("HX711 not found.");
  }
  delay(1000); // Delay for easier viewing in the Serial Monitor
}

4. Calibrating the Load Cell:

To accurately measure weight, you need to calibrate the load cell. Place a known weight on the load cell, read the raw value, and determine the scaling factor. Modify the code to output the actual weight based on your load cell's calibration factor.

Here’s how you can calibrate:

// Add this part after setting up the load cell in the setup() function
long calibration_factor = 2280; // You will need to adjust this based on your specific load cell
scale.set_scale(calibration_factor); // Set the calibration factor
scale.tare(); // Tare the scale to 0

void loop() {
  Serial.print("Weight: ");
  Serial.print(scale.get_units(), 2); // Print the weight in KG
  Serial.println(" Kg");
  delay(1000);
}

5. Adjusting for Different Load Cells (1Kg, 5Kg, 10Kg, and 20Kg):

• The procedure is the same for different capacities of load cells. The only difference is the calibration factor.
• For each load cell (1Kg, 5Kg, 10Kg, 20Kg), you will need to calibrate using a known weight and adjust the calibration factor accordingly.
  • For example, for a 5Kg load cell, place a 5Kg weight, observe the raw reading, and calculate the calibration factor.

6. Calibration Factor Calculation Example:

• Place a known weight on the load cell, for example, 2Kg.

• Note down the raw reading displayed in the Serial Monitor.

• Use the following formula to calculate the calibration factor:

Calibration Factor = Raw Reading / Known Weight

• Replace calibration_factor in the code with your new value.