is this hx711 problem or the load cell?

[Wiraputra86]

this is the result of hx711 test

this is HX711 that I use

I cant get the sparkfun brand in Indonesia. the purple one is out of stock too.

can I use this hx711 or should I change it?

Thanks

[Wiraputra86]

Update. This is my setup to test it

[206cc]

This is actually the same HX711 board I originally used during development.
If the board is functioning properly, the drift should be around 0.8g.
However, in your photo, the drift reaches 30g, which makes it unusable in this project. You can try the following methods:

Suggestions:

1. Buy another one from a different seller
   Based on my past testing, only about 1 out of 5 boards have acceptable drift levels and are usable.

2. Reflow the solder joints using a hot air gun
   If you have a hot air gun, try reheating all solder joints on the board. After cooling, the drift issue is often significantly reduced.

Note:

This HX711 board has DATA and CLOCK pins reversed compared to the SparkFun HX711.
You cannot plug it directly into the PCB I designed – please use jumper wires to connect it correctly.

Advice:

Tension accuracy is extremely important in this project.
I strongly recommend solving the HX711 drift issue before proceeding to the next steps.

The pins on the Pico side are partially blocked in your photo.
Could you please take another clear photo showing the wiring?
I’d like to help check if the pin connections are correct.

[206cc]

I think the most challenging part of this project is finding a stable and reliable SparkFun HX711 module, along with a high-quality NJ5 YZC-133 load cell.

In addition, the quality of the 5V power supply can also affect the drift, though its impact is not as significant as the other two components.

If all these conditions are met, the system can run continuously for an entire day with a drift of less than 1g.

You might also consider checking other online stores for the SparkFun HX711 module.

Wish you all the best.

[206cc]

If possible, could you take a photo showing all the wiring between the Raspberry Pi Pico, the load cell, and the HX711? I can help check if anything is connected incorrectly.

[Wiraputra86]

Hi, sorry for MIA for someday. I have other things to do and waiting for the new HX711 arrive. the purple one. I short of fix the problem but not pass on all test on 60s drift test. its already 1,8G on 1 module and 1,58g on the other one. I only test 2 out of 4 the new HX711 that I bought.

the first module that I tested

the 2nd module that I tested

next question. is it good enough? or it need to be below 1G? at 60s drift test.

[Wiraputra86]

Uodated. I change the load cell to the better one. And i got all passed for 60s drift test.

My problem have been fixed.

Thanks for the advice....

[206cc]

Your test results seem fine.

In most cases, the issue lies with the HX711 and the load cell. That’s why I now only recommend using the SparkFun HX711 and the NJ5 YZC-133 load cell. While other models might work in some cases, the failure rate is just too high to be reliable.

You can proceed with the next steps of the build. Just make sure to carefully observe the tension test shown at the end of EP7 (YouTube link: 21:42 mark) — check whether there’s any noticeable drift when no force is applied, and confirm that the readings increase steadily as more tension is added.