Using 8 half bridge load cells together

Question

In my arduino project, I want to combine 8 half bridge load cells (each has 3 wires, RED, BLACK & WHITE) because i will be weighing irregularly shaped objects and 4 points of contacts may not be enough. I am not planning to make a flat platform on top, just 8 individual load cells raised from floor and object will sit on as many load cells as it would.

I am having a hard time trying to figure out wiring 8 load cells. I understand I may need multiple HX711 load cell amplifiers and combinators. All the help I could find either discusses full bridge 4 wire load cells or combining 4 load cells to make a bathroom scale.

Answer 1

I'd do two separate 4-half-bridge load cells as in 3-wire load cells and wheatstone bridges from a bathroom scale and add their results in software or hardware.

The issue with combing 8 half-bridge load cells into a single wheatstone bridge is that the two strain gauges in each half cell complement each other and would cancel each other out if put on the same leg of the wheatstone bridge. If you try to wire up two wheatstone bridges in parallel directly, it will reduce the sensitivity.

You can sum the separate wheatstone bridge differences in circuit with a differential adder like "Can you sum and difference in a single op-amp?" so you could wire both separate bridges to the HX711 INA+/- through some attenuating/isolating resistors.