Load Cells

I have 4 load cells, trying to figure out how to wire them correctly.

I have seen many pictures and watched a few you tube video's, but I want to make sure I am doing this correctly.

As the picture shows, I have 2 load cells with B-G-R wires, and 2 with B-W-R

I believe the 4 reds will be E- S- E+ S+

LC1 Green to LC2 Green
LC1 Black to LC3 Black
LC3 White to LC4 White
LC3 Black to LC2 Black

Does that look correct?

The idea is to make a full wheatstone bridge.
If two identical cells are used to form the bridge, you must swap Ucc / gnd for one of them.
(this way the ouput voltage will increase on one and decrease on the other)
This difference-voltage is fed to an intrument amp (HX711 is suitable)

If this is a scale with cell in each corner, you can parallel cells diagonally

It will be a scale with one cell in 4 corners. - Using HX711.

In that case, how to I parallel them diagonally?

What colours go together, and which 4 do I attach to the HX711?

To work out what the wires are, you need to measure the resistance between all combinations of them - this should give you three resistance values. On my 50kg load cells, two pairs give a reading of 990ohms (red - black and red - white) and one pair gives a reading of 1900ohms (black - white). The common wire in the pairs that have the same reading is the centre and the other two are the positive and negative. On mine, the red is the centre, the black is positive and the white is negative.

If you don't have one already, this load cell combinator simplifies the wiring of the Wheatstone bridge for you and is nicely matched to their hx711 breakout (the pins all line up if you put them together).

If you use the combinator, it is labelled for each cell (lower left, lower right, upper left, upper right).

If you get negative readings when you add more weight, you have the positive and negative wires around the wrong way on the load cells.

I worked all this out with the help of this guide.


If identical cells:
The idea is that two of them make a full bridge. To get the output_voltage correct, one of them is fed power with +/- swapped.

In your case, where wires indicates they are not identical, it may be so a pair is made from two different cells - then fed power as cable-color indicates.

The two are placed diagonally.

Make an identilcal pair of the other cells. The two full-bridges can be connected parallel, so two wires only goes to HX711 (A or B -different ampl-factor)