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
• Force measurement systems
• IoT-based weight monitoring
• Laboratory equipment for precision measurements

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

The HX711 module has a total of 4 pins for interfacing with microcontrollers and power supply. 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 to the 5V output of the Arduino UNO and the GND pin to the Arduino's GND.
2. Data and Clock Pins:
   • Connect the DT pin to a digital input pin on the Arduino (e.g., D3).
   • Connect the SCK pin to another digital pin on the Arduino (e.g., D2).
3. Load Cell Connection: Attach the load cell to the HX711 module's input terminals (E+, E-, A+, A-, B+ if applicable).

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

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

// Define the pins connected to the HX711 module
#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 for debugging
  scale.begin(DT_PIN, SCK_PIN); // Initialize the HX711 with the defined pins

  // Optional: Set the gain (default is 128)
  scale.set_gain(128);

  Serial.println("HX711 initialized. Place weight on the scale.");
}

void loop() {
  if (scale.is_ready()) { // Check if the HX711 is ready to send data
    long reading = scale.get_units(); // Get the weight reading
    Serial.print("Weight: ");
    Serial.print(reading);
    Serial.println(" units");
  } else {
    Serial.println("HX711 not ready. Check connections.");
  }

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

• Power Supply: Ensure a stable power supply to avoid noise in the readings. Use decoupling capacitors if necessary.
• Load Cell Calibration: Calibrate the load cell to convert raw ADC values into meaningful weight units (e.g., grams or kilograms).
• Shielding: Use shielded cables for the load cell to minimize interference in noisy environments.
• Gain Selection: Use the appropriate gain setting (32, 64, or 128) based on the load cell's sensitivity and the desired resolution.

1. No Data Output

   • Cause: Loose or incorrect connections.
   • Solution: Verify all connections, especially the DT and SCK pins. Ensure the load cell is properly connected.

2. Unstable or Noisy Readings

   • Cause: Electrical noise or unstable power supply.
   • Solution: Use a stable power source and add decoupling capacitors near the VCC and GND pins. Shield the load cell wires.

3. Incorrect Weight Readings

   • Cause: Load cell not calibrated.
   • Solution: Perform a proper calibration using known weights and adjust the scale factor in the code.

4. HX711 Not Ready

   • Cause: Faulty module or incorrect wiring.
   • Solution: Check the module's power supply and ensure the DT and SCK pins are correctly connected.

Q1: Can the HX711 be used with a 3.3V microcontroller?
Yes, the HX711 operates with a supply voltage as low as 2.6V, making it compatible with 3.3V systems.

Q2: How do I calibrate the HX711?
Use a known weight to determine the scale factor. Modify the code to divide the raw ADC value by this factor to get accurate weight readings.

Q3: Can I use both input channels (A and B) simultaneously?
Yes, but note that Channel A has a programmable gain (128 or 64), while Channel B has a fixed gain of 32. Channel A is typically used for higher precision measurements.

Q4: What is the maximum weight the HX711 can measure?
The maximum weight depends on the load cell used. The HX711 itself does not impose a weight limit but provides high-resolution ADC readings for the connected load cell.

By following this documentation, you can effectively integrate the HX711 into your projects and achieve precise weight measurements.