Hi, in my project I use 3 wire load cell (like this (3wire 50kg) but mine are purchased from ebay) and HX711 for weighing.
My wiring is like this (but i use Arduino mini pro 3V3):
Apparently it should be a full-bridge circuit where the temperature is fully compensated and temperature changes are minimal. However, my last-day charts are like this (is loaded statically with 18kg).
The graphs show that the weight varies with temperature. Therefore, I put all temperatures and changes from the calibration value into a graph and from this came out this graph. Where the X-axis is the temperature and the Y-axis is the change from the known value (18KG).
This chart showed me that the weight is probably not ONLY dependent on temperature as the first charts might seem.

I'm really frustrated about it because I've tried everything, but the result is always the same, even though this wiring should compensate for itself.
Has anyone encountered anything like this?

Thank you for any advice!

 

hi Pedro,
Welcome to AAC.
Are you using two of the 3 wires load cells, or just one with bridge resistors.?
Is the project wired like this image.?
E

 

hi Pedro,
Welcome to AAC.
Are you using two of the 3 wires load cells, or just one with bridge resistors.?
Is the project wired like this image.?
E

Hi! Thank you for quick answer. No, i use 4 of them. All are connected to the hx711, which is powered from the arduino mini pro from the Vcc pin (3V3).

 

hi,
Please post a circuit diagram , showing how you have connected the 4 half bridge load cells.
E

 

hi,
Please post a circuit diagram , showing how you have connected the 4 half bridge load cells.
E

hi,
I created the wiring as I have it connected, the individual sensors are connected to each other in the same color (white-white, black-black). The load cell also has a total resistance of 2kohm and 1kohm between white-red or black-red.
Pedro

 

hi,
That is an usual way of connecting.
What is the resistance value of the R load cell elements.?

Where is the Signal out pair.? BK, BK. ?
E

 

hi,
For testing use just two Load Cells, connect as this diagram.
The two WH wires go to the HX711 input.
Repeat your earlier tests, let us know the result.
E

Note:
For a further test build a second bridge, same as the first and connect them in parallel.
On a common Base plate this will increase the maximum load to 100kG

 

hi,
For testing use just two Load Cells, connect as this diagram.
The two WH wires go to the HX711 input.
Repeat your earlier tests, let us know the result.
E

Note:
For a further test build a second bridge, same as the first and connect them in parallel.
On a common Base plate this will increase the maximum load to 100kG

Thank you for your advice! I'm going to try it and let you know.