Table of Contents
Choosing the correct resistor value is essential for safe and effective LED projects with Arduino. Proper resistor selection prevents damage to the LED and ensures optimal brightness. This guide provides a clear, step-by-step process to calculate the appropriate resistor value for your project.
Understanding the Basics
LEDs require a specific current to operate safely. Typically, a standard LED runs at about 20 milliamps (mA). The resistor limits the current flowing through the LED, protecting it from excess current that could cause damage.
Calculating the Resistor Value
The main formula used is:
Resistor (Ω) = (Supply Voltage – LED Forward Voltage) / Desired Current
Where:
- Supply Voltage: The voltage from the Arduino pin, typically 5V or 3.3V.
- LED Forward Voltage: Usually around 2V for red LEDs, varies by color.
- Desired Current: Usually 0.02A (20mA).
Example Calculation
Suppose you have a 5V supply, a red LED with a forward voltage of 2V, and a desired current of 20mA.
Resistor value = (5V – 2V) / 0.02A = 3V / 0.02A = 150Ω
Choosing the Resistor
Use the calculated value as a starting point. Standard resistor values may vary slightly, so choose the closest standard value, such as 150Ω or 160Ω, to ensure safety and performance.