Connecting a load cell to an Arduino Mega

Projects General Guidance
1

Greetings from S. Kor.

I am trying to connect a strain gauge load cell to the ARDUINO using INA125P amplifier to

excite the signal.

The problem is that the load cell has max. excitation voltage of 18V, and I am afraid that this

might fry my ARDUINO board.

So, here's my question.

  1. If the max voltage of the load cell is 18V, do I need a Vref of 18V as well?

  2. I am pretty sure that the 18V output will fry my board, do I need OP-Amp of some sort to

scale down the voltage?

  1. What's the resistance (Ohm) that I need to use to bridge the Rg of INA 125P?

Thanks a lot for all your supports.

Any help on the coding will also be appreciated! :grin:

ohm.PNG
ohm.PNG898×614 70.3 KB

2

P.S.

The code that I'm trying to use is similar to this one that I found in EDG, U of Chicago.

// Arduino with load cell

// Put two known loads on the sensor and take readings. Put those values
// here.
float aReading = 192.0;
float aLoad = 15.0; // lbs.
float bReading = 344.0;
float bLoad = 24.3; // lbs.

long time = 0;
int interval = 500; // Take a reading every 500 ms

void setup() {
Serial.begin(9600);
}

void loop() {
float newReading = analogRead(0);

// Calculate load based on A and B readings above
float load = ((bLoad - aLoad)/(bReading - aReading)) * (newReading - aReading) + aLoad;

// millis returns the number of milliseconds since the board started the current program
if(millis() > time + interval) {
Serial.print("Reading: ");
Serial.print(newReading,1); // 1 decimal place
Serial.print(" Load: ");
Serial.println(load,1); // 1 decimal place, println adds a carriage return
time = millis();
}
}

3

Hi,

Because the max rated is 18V, you don't have to use 18V.

In fact the calibration excitation voltage is 10V, so even that will work.

In fact if you use the "Search the Arduino Forum" function at the top of this page and look for load cell INA125P
you will find that what you are trying has been done before and will help.

Tom.... :slight_smile:

4

Thanks Tom I'll look it up right away :slight_smile: