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 Amplifier, this module integrates a low-noise amplifier, making it ideal for interfacing with load cells and other sensors requiring precise analog-to-digital conversion. Its compact design and ease of use make it a popular choice for projects involving weight scales, force measurement, and other applications requiring high-resolution data acquisition.

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

The HX711 module is designed to provide high precision and low noise for analog-to-digital conversion. Below are its key technical details:

The HX711 module has a total of 4 pins for interfacing with microcontrollers and power supply. Below is the pinout description:

The HX711 is straightforward to use in a circuit, especially for weight measurement applications. Below are the steps and best practices for using the module:

1. Power Supply: Connect the VCC pin to a 3.3V or 5V power source, depending on your microcontroller. Connect the GND pin to the ground.
2. Data and Clock Pins: Connect the DT pin to a digital input pin on the microcontroller and the SCK pin to another digital output pin.
3. Load Cell Connection: Connect the load cell to the HX711 module's input terminals (E+, E-, A+, A-, or B+ depending on the channel used).

Below is an example of connecting the HX711 to an Arduino UNO:

• VCC → 5V
• GND → GND
• DT → Digital Pin 3
• SCK → Digital Pin 2

The following Arduino code demonstrates how to interface the HX711 with an Arduino UNO to read weight data:

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

// Define pins for HX711
#define DT 3  // Data pin connected to Arduino pin 3
#define SCK 2 // Clock pin connected to Arduino 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("HX711 initialized. Place weight on the scale.");
}

void loop() {
  if (scale.is_ready()) { // Check if the HX711 is ready
    long reading = scale.get_units(); // Get the weight reading
    Serial.print("Weight: ");
    Serial.print(reading); // Print the weight value
    Serial.println(" units");
  } else {
    Serial.println("HX711 not ready. Check connections.");
  }
  delay(500); // Wait for 500ms before the next reading
}

• Power Supply Stability: Ensure a stable power supply to avoid noise in the readings.
• Load Cell Calibration: Calibrate the load cell before use to ensure accurate weight measurements.
• Data Rate Selection: The HX711 supports two data rates (10Hz and 80Hz). Use the appropriate rate for your application.
• Shielding: Use shielded cables for the load cell to minimize noise interference.

1. No Data Output

   • Cause: Incorrect wiring or loose connections.
   • Solution: Verify all connections, especially the DT and SCK pins.

2. Inconsistent Readings

   • Cause: Unstable power supply or noise interference.
   • Solution: Use a decoupling capacitor across the VCC and GND pins. Ensure proper shielding for the load cell wires.

3. HX711 Not Ready

   • Cause: Faulty module or incorrect initialization in code.
   • Solution: Check the module's power supply and ensure the scale.begin() function is called correctly in the code.

4. Weight Readings Are Incorrect

   • Cause: Load cell not calibrated or improperly connected.
   • Solution: Perform a proper calibration using known weights and verify the load cell wiring.

Q1: Can the HX711 work with a 3.3V microcontroller?
A1: Yes, the HX711 can operate with a supply voltage as low as 2.6V, making it compatible with 3.3V microcontrollers.

Q2: How do I calibrate the HX711?
A2: Use a known weight to determine the calibration factor. Adjust the factor in your code until the readings match the actual weight.

Q3: Can I use both channels (A and B) simultaneously?
A3: Yes, but note that Channel A has higher gain options (128 or 64) compared to Channel B (32).

Q4: What is the maximum weight the HX711 can measure?
A4: The maximum weight depends on the load cell used. The HX711 itself does not impose a weight limit but provides high-resolution readings for the connected load cell.

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