How to Calculate Load Current in Arduino Projects Using Shunt Resistors

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Measuring current in Arduino projects is essential for monitoring power consumption and ensuring safety. Using shunt resistors provides a simple and effective method to measure load current accurately. This article explains how to calculate load current using shunt resistors in your Arduino projects.

Understanding Shunt Resistors

A shunt resistor is a low-value resistor placed in series with the load. When current flows through it, a small voltage drop occurs across the resistor. This voltage can be measured to determine the current using Ohm’s Law.

Calculating Load Current

The basic formula to calculate load current is:

I = V / R

Where I is the current in amperes, V is the voltage across the shunt resistor, and R is the resistance value.

Measuring Voltage with Arduino

The Arduino can measure the voltage drop across the shunt resistor using its analog input pins. Connect the resistor in series with the load, and connect the Arduino analog input across the resistor. Use the following steps:

  • Connect the shunt resistor in series with the load.
  • Connect the Arduino analog input to the resistor’s junction point.
  • Read the voltage using the Arduino’s analogRead() function.
  • Convert the analog reading to voltage: V = (analogRead() / 1023) * reference voltage.

Example Calculation

Suppose you use a 0.1Ω shunt resistor, and the Arduino reads a voltage of 0.05V across it. The load current is calculated as:

I = 0.05V / 0.1Ω = 0.5A