HX711 - Fluctuating values -optimization ideas?

HX711 unstable values

Hello everybody,
Iam currently modding a body scale with Wemos D1 Mini.
Everything would work well if the measured weight would be stable.

I read a lot of topics and Iam sure, the 4 loadcells are connected correctly in a wheatstone bridge.
Iam using a HX711 module with a shielding. I had an unshielded version before and replaced it, but it did not solve my problems.

I use the bodge HX711 Arduino library.
After figuring out a set_scale()-value, the output is roughly calibrated.
If I place a static weight on the scale, the values stays more or less stable, but I still have changes in the second decimal number.

When I stand on the scale and read out the average of 15 values (scale.get_units(15)), the difference between the measurements are more than +/-1kg.
I noticed that when I stand on the scale, it makes a big difference, if my center point is located to any side or if I try to stand directly in the middle.
This seems reasonable, but usual bodyscale also have to handle this issue, because one can not stand completely static on the scaleplate.

Is there anything I can do (hardware and software) to get more stable values?
Is there an influence regarding the power supply? Currently I have a small USB-Powerbank under the scale, which powers the Wemos D1 Mini.
Would it make any difference if I use 3,3V as power supply?
Also, the HX711 is powered with 3,3V, but it is able to use up to 5V for the loadcell-measurements. Will it influence the performance?

I would be very grateful for any hints or tips for optimizing the system.
Currently the scale is unusable, because the is so much fluctuation in the values.

Thank you very much
Chris

Many HX711 breakout boards use an on-board 4.3 v power supply for the load cell excitation voltage, so they need more than that - 5v is good - to work properly.

You could do like my bathroom scale does: waits for me to stop dancing around and then displays "the" weight, after which the number will not change until I step off.

You will probably still have a repeatability problem (getting different numbers each time you step on the scale).

What is full range of your scale? 100 kg? And you want a stable second digit...to 0.01 kg? That is, one part in 10,000?

If you use a 3.3volt processor then you need a HX711 module with separate analogue and digital supply pins.
Most boards have both supplies combined (can't use with Wemos/SP8266 without modding).
Post a link to the board you have if you're not sure.

Tha analogue part of the HX711 MUST be powered by 5volt for a stable excitation voltage, as DaveEvans already has explained.
Leo..

read out the average of 15 values (scale.get_units(15)), the difference between the measurements are more than +/-1kg.

That is expected noise, and averaging is the best you can do. The more points you average together, the less deviation from successive (averaged) measurements.