How to Use HX711: Examples, Pinouts, and Specs

The HX711 is a precision 24-bit analog-to-digital converter (ADC) designed for high-accuracy weight measurement and industrial control applications. Manufactured by Arduino under the part ID HX711-Module, this component integrates a low-noise programmable gain amplifier (PGA) to interface directly with load cells, making it ideal for building digital weighing scales. Its compact design and high resolution make it a popular choice for applications requiring precise weight measurements.

• Digital weighing scales
• Industrial process control systems
• Force measurement systems
• IoT-based weight monitoring
• Laboratory equipment

The HX711 is optimized for high precision and low noise, making it suitable for sensitive measurements. Below are its key technical details:

The HX711 module has a total of 4 pins for power and communication. Below is the pinout:

The HX711 is straightforward to use with microcontrollers like the Arduino UNO. Below are the steps to integrate it into a circuit and use it effectively:

1. Power Supply: Connect the VCC pin of the HX711 module to the 5V pin of the Arduino and the GND pin to the Arduino's GND.
2. Data and Clock Pins: Connect the DT pin to a digital input pin (e.g., D3) and the SCK pin to a digital output pin (e.g., D2) on the Arduino.
3. Load Cell Connection: Connect the load cell's wires to the HX711 module's input terminals (E+, E-, A+, A-, or B+ depending on the channel used).

Below is an example Arduino sketch to read data from the HX711 module using the popular HX711 library:

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

// Define HX711 pins
#define DT_PIN 3  // Data pin connected to Arduino digital pin 3
#define SCK_PIN 2 // Clock pin connected to Arduino digital pin 2

// Create an HX711 object
HX711 scale;

void setup() {
  Serial.begin(9600); // Initialize serial communication
  scale.begin(DT_PIN, SCK_PIN); // Initialize the HX711 with the defined pins

  // Wait for the scale to stabilize
  Serial.println("Initializing scale...");
  delay(2000);

  // Set the scale to zero
  scale.set_scale(); // You can set a calibration factor here if known
  scale.tare();      // Reset the scale to zero
  Serial.println("Scale initialized.");
}

void loop() {
  // Read weight from the HX711
  if (scale.is_ready()) {
    float weight = scale.get_units(10); // Average 10 readings for stability
    Serial.print("Weight: ");
    Serial.print(weight);
    Serial.println(" grams");
  } else {
    Serial.println("HX711 not ready. Check connections.");
  }

  delay(500); // Wait 500ms before the next reading
}

• Calibration: The HX711 requires calibration to provide accurate weight readings. Use a known weight to determine the calibration factor.
• Noise Reduction: Minimize electrical noise by using short wires and proper grounding.
• Power Supply: Ensure a stable power supply to avoid fluctuations in readings.
• Data Rate: The HX711 supports two data rates (10Hz and 80Hz). Use the slower rate for higher accuracy.

1. Can the HX711 measure negative weights?
   Yes, the HX711 can measure negative weights if the load cell is configured to detect both tension and compression.

2. What is the maximum weight the HX711 can measure?
   The maximum weight depends on the load cell used. The HX711 itself supports an input voltage range of ±40mV at a gain of 128.

3. Can I use the HX711 with a 3.3V microcontroller?
   Yes, the HX711 operates at 2.6V to 5.5V, making it compatible with 3.3V systems. Ensure the load cell is also compatible with 3.3V operation.

4. How do I change the data rate?
   The data rate can be changed by connecting a resistor to the RATE pin on the HX711 IC. Most modules are preconfigured for 10Hz.

By following this documentation, you can effectively integrate the HX711 into your projects for precise weight measurement.