Implementing the IoT Scale Tutorial (problem with the HX711 Load Cell Amp)

Sensors Force & Weight
1

This tutorial: https://learn.sparkfun.com/tutorials/io … ging-scale

I have bought all the same parts, including the same brand of scale, to try to keep the variables low in this part.

I’ve narrowed down my problem to communicating with the HX711 Load Cell Amp

Using the testing code from: https://github.com/olkal/HX711_ADC As suggested in the tutorial.

Using the testing code, it’s reporting a sampling rate way higher than I expected. I haven’t cut the trace, so I expected just 10. Not 1207, based on the .cpp file.

Start + tare is complete
Calibration Factor: 10000.00
HX711 measured conversion time ms: 0.83
HX711 measured sampling rate HZ: 1207.73
HX711 measured settlingtime ms: 15
Note that the settling time may increase significantly if you use delay() in your sketch!
!!Sampling rate is higher than specification, check MCU>HX711 wiring and pin designations

I’ve checked and double checked the wiring according to:

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I’m not sure I can provide good pictures of it, as it’s wired to go into the scale itself, not with pins and such, to avoid desoldering problems. I haven’t shorted VDD to VCC as mentioned in the documents for the Load Cell Amp, could that be the problem?

Thanks!

2

Turns out I just needed to short VDD and VCC to make it work. That’s in the datasheet for the Load Cell Amp, but not on the wiring diagram. Would be nice to have in the tutorial for noobs like me!

But it works! proof: https://youtu.be/fGraa08P2iA

Now I just need to calibrate it and finish it up!

3

Thanks for following up with this post. I had a feeling it was related to that since we have VCC and VDD netted together in the [Hookup Guide for the Load Cell Amplifier used in that tutorial. I’ll let our Tutorials team know about the wiring diagram error and we will get that fixed.

If you run into any other issues or have any other questions about this tutorial, let us know and we would be happy to help as much as we can.](https://learn.sparkfun.com/tutorials/load-cell-amplifier-hx711-breakout-hookup-guide#hardware-hookup-)

4

Sorry about that. We have updated the tutorial with the wire between VDD and VCC. I also included a battery in the image since the original author used an 850mAh LiPo. Thanks for letting us know! =)

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