I’ve not tried using the 3 wire load cells yet but I believe you have the half bridge type.

To use the circuit in this article, you will need to convert your load cell to a full bridge. The links below point to discussions about converting a 3 wire half bridge load cell to a 4 wire full bridge load cell.

The software for the Arduino outputs grammes but the code can easily edited to output Kg instead, I can help with that when you are ready.

http://www.electro-tech-online.com/threads/3-wire-load-cell-question.32536/
https://forum.allaboutcircuits.com/showthread.php?t=84383

Mark

sir, I really don’t know much about,
I use the combination of 3 wires load cell (Red, White and Black wire) which give out 4 pin labelled as S+ S- E+ E-

I want these 4 pin into INA125P , as Vout from INA125P connect to arduino Uno to convert the value to kilograms as I want to calculate the people weight..

Kindly need your help sir…

Ammar

You could use any load cell I guess, the issue you will have is the final measuring resolution after calibration. 180KG load cell might have a resolution of around 200grams through an 10bit analogue microcontroller input such as on the Arduino UNO. The Teensy 3.1 microcontroller will provide better resolution; High Resolution Analog Inputs (13 bits usable, 16 bit hardware).

If you need better resolution than what can be provided by the microcontrollers, try the 24bit HX711 Dual-Channel Weighing Sensor Module. The reads will be much slower, but fast enough if you are just weighing stuff.

Mark

It looks like I have indeed made a mistake with the Arduino voltage reference configuration. I originally thought that the Aduino automatically switched to the external voltage reference when a voltage was applied to the AREF PIN. The Arduino was probably saved due to the internal voltage being the same as the external when shorted.

For this application, the Arduino internal voltage reference should be used and the Arduino AREF PIN should be disconnected. This decision is made due to the external voltage reference, applied from the INA125, measuring more than 5v (5.77v), possibly exceeding the Arduino AREF PIN voltage limit.

No changes to the code is necessary and the Schematic and circuit in this article will be updated with the AREF connection removed.

The INA125 PIN 12(VREFCOM) was left floating since there was enough voltage headroom to calibrate the load cell. I’ll have to investigate VREFCOM when I get a bit of time, but for this article, the circuit will work well enough without it. This article serves as a starting point for working with the IAN125 and it is likely that the more experienced will want to access more features of the chip, and that’s fine.

After some investigation I’ve decided to amend the breadboard circuit and schematic to include connecting the VREFCOM to ground. The resistance range for gain was much smaller than what would have been and kept within the limits of the 100R trimmer pot.

Mark

Mark

The purpose of the firmware is just to read the analogue values and convert them to grams with a bit of smoothing. Any requirements beyond that you will need to add your own code.
You could add an “else if” like in the following code snippet to point to your own subroutines.

if (calibrate) {// print test results
Serial.print(“Analog pin value: “);Serial.println(analogValue);
Serial.print(“Smoothed analog value: “);Serial.println(analogSamplesAverage);
Serial.print(“Scale load (grammes): “);Serial.println(loadGrams);
Serial.println(” “);
} else if (calibrate == 2) { // remember to change the calibrate variable to 2
// Your code here
} else { // Output to Processing as such
Serial.println(loadGrams);
}

To execute your “else if” block just change the calibrate variable to 2.
You will need to pass variables such as loadGrams, analogValue and analogSamplesAverage to your own subroutines if you plan to use the values they contain.