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Interface Load cell with Arduino Uno

Load cell is a passive transducer or sensor which converts applied force into electrical signals.

  • They are also referred to as Load transducers.
  • There are many varieties of load cells, strain gauge based load cells are the most commonly used type.
  • Load cells use different operating principles.
    Load Cells based on fluid pressure.
    Load Cells based on elasticity.
    Load Cells based on magnetostriction effect or piezoelectric effect.
  • Load cell primarily consists of a spring material and strain gauge.
  • Spring material causes strain due to applied load and strain gauge changes its resistance in accordance with the change in strain.
  • A mechanical arrangement, the force being sensed deforms a strain gauge.
  • The strain gauge measures the strain as an electrical signal.
  • A load cell usually consists of four strain gauges in a Wheatstone bridge configuration.
  • Load cells of one strain gauge (quarter bridge) or two strain gauges (half bridge) are also available.
  • The electrical signal output is typically in the order of a few millivolts and requires amplification by an instrumentation amplifier before it can be used.
  • The output of the transducer can be scaled to calculate the force applied to the transducer.

Application

  • Weight Machine

Hardware Required

  • Load Cell.
  • Instrumentation Amplifier.
  • Arduino.

Circuit

Code

 float knowred1 = 160.0;
 float knowload1 = 25.0; // lbs.
 float knowred2 = 300.0;
 float knowload2 = 40.0; // lbs.
 long time = 0;
 int interval = 500; // Take a reading every 500 ms
 
 void setup()
 {
 Serial.begin(9600);
 }
 
 void loop()
 {
 float unknownread = analogRead(0);
 float unknownload = ((knowload2 - knowload1)/(knowred2 - knowred1)) * (unknownread - knowred1) + knowload1;
 if(millis() > time + interval)
 {
 Serial.print(" Load: ");
 Serial.println(unknownload,1);
 time = millis();
 }
 }

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