Common HX711 Errors and Their Fixes

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Common HX711 Errors and Their Fixes

The HX711 is a popular analog-to-digital converter (ADC) used primarily for weighing scales and load cells. Despite its simplicity, it can face several errors that affect its functionality. Below, we will explore common issues users encounter with the HX711, why they occur, and step-by-step solutions to fix them.

1. No Output or Inconsistent Readings

Cause: This error is one of the most common and can arise from several factors, such as:

Loose or improper connections between the HX711 and the load cell. Insufficient Power supply or unstable voltage. Incorrect wiring or misconfigured software settings. The load cell itself being faulty or not connected properly.

Solution: Here’s how to solve this issue:

Check Wiring: Ensure that the connections are secure and correct. For a standard 4-wire load cell, the connections should be as follows: Red wire (Excitation+) to HX711 pin “E+.” Black wire (Excitation-) to HX711 pin “E-.” White wire (Signal+) to HX711 pin “A+.” Green wire (Signal-) to HX711 pin “A-.”

Power Supply: Ensure that the HX711 is receiving a stable 5V power supply. If there’s a fluctuation in voltage, the readings can become inconsistent.

Load Cell Check: Test the load cell separately with another working HX711 or a different system to confirm whether the load cell is functional.

Software Check: Ensure that you have the correct software libraries for HX711 in your code. Incorrect calibration or delay in the software loop can cause reading issues.

2. Overloaded or Negative Readings

Cause: This happens when the load cell experiences a force or weight beyond its capacity, or if the HX711 input pins are short-circuited.

Solution:

Inspect the Load Cell Capacity: Ensure that you are using a load cell that is suitable for the weight range you're measuring. If you try to measure too much weight, the load cell will generate over-range signals, which the HX711 can’t process.

Check for Shorts: Inspect the wires for any shorts or poor connections that might cause the signal to become negative or overloaded.

Perform a Reset: Power off the system and reset it by disconnecting and reconnecting the power supply to the HX711 module . This clears any erroneous readings.

Adjust Calibration: If negative readings persist, adjust the offset or zero scale in your code. This ensures the system starts at a known, zero weight when no load is applied.

3. Intermittent or Flickering Output

Cause: This issue is typically caused by:

Electrical noise or interference. Insufficient grounding. Long wires or poor quality connections.

Solution: To resolve flickering or inconsistent outputs:

Minimize Electrical Noise: Use shielded wires for the load cell and HX711 connections. Additionally, ensure that the power source is clean and stable.

Grounding: Proper grounding is essential for stable operation. Ensure that the ground (GND) of the HX711, the load cell, and the microcontroller are all connected properly.

Shorten Wires: If possible, shorten the wires between the load cell and HX711. Long wires can introduce noise into the signal, leading to flickering outputs.

Decoupling capacitor s: Add a 100nF ceramic capacitor between the VCC and GND pins of the HX711 to filter out high-frequency noise.

4. “Drifting” or Changing Readings Over Time

Cause: Drifting readings can occur due to environmental factors, such as:

Temperature changes affecting the load cell or HX711. Power supply fluctuations. Poor stability in the calibration process.

Solution:

Calibration: Recalibrate the HX711 properly. Ensure the scale is zeroed out before taking readings and use a known weight to set the correct scale factor.

Allow for Stabilization: After powering up the system, wait for a few moments to allow the HX711 to stabilize before taking measurements. Sudden temperature changes can cause the system to "drift."

Stable Power Supply: Use a stable power source. Power supply fluctuations, especially in battery-powered systems, can cause the readings to drift.

Temperature Compensation: Some HX711-based systems may have built-in temperature compensation, but if not, you can manually adjust readings for temperature changes if you are working in a highly variable environment.

5. “Busy” Signal or Timeout Error

Cause: The “busy” signal occurs when the HX711 is not able to process the data from the load cell because it’s waiting for new data from the previous conversion, or the system isn’t correctly synced.

Solution:

Check Code Timing : Make sure your code properly handles the timing for data collection from the HX711. Avoid calling the read function too frequently, as the HX711 needs time to perform the analog-to-digital conversion.

Increase Delay: Increase the delay between data readings in your code to give the HX711 sufficient time to process and clear previous data.

Verify Connections: Ensure that the clock pin and data pin are securely connected to the correct pins on your microcontroller. Loose connections could cause communication errors between the HX711 and the microcontroller.

Conclusion

By following these steps, you can identify and fix the most common HX711 errors effectively. Always check your wiring, power supply, and calibration first, as these are the most likely causes of issues. If the problem persists, it might be a hardware issue, such as a defective HX711 or load cell. Regular maintenance, correct setup, and environmental considerations will ensure the HX711 module works reliably for your weighing scale or load measurement projects.