Load cells

Couple months back I ordered from AliExpress set of Load Cell sensors for our testing rig project .

Those arrived in a good shape and while being pretty interested into how those work, it took us a bit to get to them.

Sebi prepared a setup to give it a go. That aluminium thing is our load cell, it is connected to an amplifier, which is connected to some ArduinoNano and all that chain ends in Sebi’s laptop through USB. Each load cell comes with an arrow showing direction in which forces should be applied.

I’ve asked Sebi to describe it in his words.

Seeing that video, I noticed that that final plot is probably not visible properly, so I took a close picture. Interestingly you can see positive and also negative values, that may come pretty handy. Also while that load cell says that it is up to 1kg (9.80665N) we’ve been seeing even higher values (1.2kg).

If you would be interested in reproducing the same, Sebi shared with me his source code.

#include "HX711.h"

#define calibration_factor -21600 //This value is obtained using the SparkFun_HX711_Calibration sketch

#define LOADCELL_DOUT_PIN  3
#define LOADCELL_SCK_PIN  2

HX711 scale;

void setup() {
  Serial.begin(9600);
  Serial.println("HX711 scale demo");

  scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
  scale.set_scale(calibration_factor); //This value is obtained by using the SparkFun_HX711_Calibration sketch
  scale.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0

  Serial.println("Readings:");
}

void loop() {
  Serial.print("Reading: ");
  Serial.print(scale.get_units()*10, 1); //scale.get_units() returns a float
  Serial.print(" g"); //You can change this to kg but you'll need to refactor the calibration_factor
  Serial.println();
}

Now you probably wonder what it is for .. well here are few pictures to tune you up, but it is still work-in-progress so I’ll leave the rest for another article. 😉