How to Use HX711: Examples, Pinouts, and Specs

The HX711 is a precision 24-bit analog-to-digital converter (ADC) designed for applications requiring high accuracy and stability, such as weigh scales and industrial control systems. Manufactured by Soldered, the Soldered HX711 Breakout provides an easy-to-use interface for measuring small changes in voltage, making it ideal for load cells and other sensors.

• Digital weigh scales
• Industrial process control
• Force measurement systems
• Strain gauge sensors
• IoT-based weight monitoring systems

The HX711 is particularly popular in DIY projects and prototyping due to its simplicity and compatibility with microcontrollers like the Arduino.

The Soldered HX711 Breakout has the following pin layout:

1. Power the HX711: Connect the VCC pin to a 3.3V or 5V power source and the GND pin to the ground.
2. Connect the Load Cell:
   • Attach the load cell's excitation wires to the E+ and E- pins.
   • Connect the load cell's signal wires to the A+ and A- pins (or B+ and B- for Channel B).
3. Connect to a Microcontroller:
   • Connect the DT pin to a digital input pin on the microcontroller.
   • Connect the SCK pin to a digital output pin on the microcontroller.
4. Install a Library (if using Arduino):
   • Use the "HX711" library available in the Arduino IDE Library Manager for simplified communication.
5. Write Code: Use the library to read data from the HX711 and convert it into meaningful weight or force values.

• Power Supply: Ensure a stable power supply to avoid noise in the ADC readings.
• Load Cell Calibration: Calibrate the load cell to ensure accurate measurements.
• Shielding: Use shielded cables for the load cell to minimize interference.
• Data Rate: Choose the appropriate data rate (10 Hz for higher accuracy, 80 Hz for faster response).
• Pull-up Resistors: The DT and SCK lines may require pull-up resistors depending on the microcontroller.

Below is an example of how to use the HX711 with an Arduino UNO:

#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

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

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

  Serial.println("Calibrating... Place a known weight on the scale.");
  scale.set_scale(); // Set the scale to default (no calibration factor)
  scale.tare();      // Reset the scale to 0
  delay(5000);       // Wait for user to place a weight
  long known_weight = 100; // Replace with the known weight in grams
  scale.set_scale(scale.get_units() / known_weight); // Calibrate the scale
  Serial.println("Calibration complete.");
}

void loop() {
  // Read and print the weight
  float weight = scale.get_units(); // Get the weight in calibrated units
  Serial.print("Weight: ");
  Serial.print(weight);
  Serial.println(" g");
  delay(500); // Wait 500ms before the next reading
}

1. No Data Output:

   • Ensure the DT and SCK pins are correctly connected to the microcontroller.
   • Verify that the HX711 is powered (check VCC and GND connections).

2. Unstable Readings:

   • Use a stable power supply to reduce noise.
   • Shield the load cell wires to minimize electromagnetic interference.
   • Check for loose connections in the circuit.

3. Incorrect Weight Measurements:

   • Calibrate the load cell properly using a known weight.
   • Verify that the load cell is not overloaded or damaged.

4. Slow Response Time:

   • Increase the data rate to 80 Hz by adjusting the SCK pin timing in the code.

Q: Can I use the HX711 with a 3.3V microcontroller?
A: Yes, the HX711 operates at 2.6V–5.5V, making it compatible with both 3.3V and 5V systems.

Q: How do I connect multiple load cells to the HX711?
A: The HX711 supports two channels (A and B). You can connect one load cell to each channel, but note that Channel B has a lower gain (32x) compared to Channel A (128x).

Q: What is the maximum weight the HX711 can measure?
A: The maximum weight depends on the load cell used. The HX711 itself does not impose a weight limit but converts the load cell's output into digital data.

Q: Can I use the HX711 for non-weight-related applications?
A: Yes, the HX711 can measure small voltage changes, making it suitable for other sensors like strain gauges or pressure sensors.

This concludes the documentation for the Soldered HX711 Breakout.