Using Two Load Cells with a Single HX711 – Wiring and Calibration Issues

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1

Can anyone help me with using two load cells with a single HX711 sensor.

I am a beginner and trying to calibrate two load cells using a single HX711 module, but I am facing issues in the code. I have tested both high precision (Channel A) and low precision (Channel B) inputs. One load cell’s signal is connected to A+ and A-, while the second load cell’s signal is connected to B+ and B-. The excitation wires (red and black) of both load cells are shorted together and connected to E+ and E- of the HX711.

2

Seems legit so far.

Maybe try posting schematics, pics, code, and the issues you are having as per:

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3

Your topic does not seem to indicate a problem with IDE 2.x and therefore has been moved to a more suitable location on the forum.

4

Thanks for your response!
For calibration, I initially placed a known mass on each load cell and took around 30-40 raw readings. Then, using the formula:

Calibration Factor = Known Mass / Average Raw Reading,

I calculated the calibration factor for both load cells separately. However, when I switch between Channel A (high precision) and Channel B (low precision), the readings fluctuate too much. Even after calibration, I don’t get consistent results.

Any suggestions on improving the stability or a better approach for dual load cell calibration with one HX711?

5

Tare?

How much fluctuation is "too much"?

How much fluctutaion is OK?

How much fluctuation are you getting?

Data?

Pics?

Code?

What library are you using?

Do the library examples work acceptably with your current wiring and setup, but with the code adjusted to the default single-cell operation?

Schematic?

X-Y?

6

I just finished a scale project; these cells are very sensitive, so I used the slower but more accurate method to get the weight that involves a sort, I can't remember it and am too lazy to look it up.

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Thanks for sharing your experience! I understand that load cells are quite sensitive, and stability is an issue. Could you elaborate on the slower but more accurate method you used?I'd appreciate any insights on improving accuracy.

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Sure, I am using the HX711 library, and it has the following member function

coffeeScale.set_medavg_mode();

I set the sample size to 9 and that function throws away the top 1/4 and bottom 1/4 of the sorted values then does a simple average of the remaining 5.

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9

I can't remember it and am too lazy to look it up.

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