1. What is an LED Resistor Calculator?

Definition: This calculator determines the appropriate resistor value needed to safely operate an LED in a simple circuit.

Purpose: It helps electronics enthusiasts and engineers select the correct resistor to prevent LED burnout while achieving desired brightness.

2. How Does the Calculator Work?

The calculator uses Ohm's Law formula:

Where:

• \( R \) — Resistor value (ohms)
• \( V_{supply} \) — Power supply voltage (volts)
• \( V_{led} \) — LED forward voltage drop (volts)
• \( I_{led} \) — Desired LED current (amps)

Explanation: The resistor value is calculated by subtracting the LED's voltage drop from the supply voltage, then dividing by the desired current.

3. Importance of Proper Resistor Selection

Details: Using the correct resistor ensures the LED operates at optimal brightness without exceeding its current rating, preventing premature failure.

4. Using the Calculator

Tips: Enter the supply voltage (e.g., 5V for USB, 12V for car), LED voltage drop (typically 1.8-3.3V), and desired current (usually 10-30mA). All values must be > 0 and supply voltage > LED voltage.

5. Frequently Asked Questions (FAQ)

Q1: What happens if I don't use a resistor?
A: Without a current-limiting resistor, the LED will draw excessive current, potentially burning out immediately or having a shortened lifespan.

Q2: What's a typical LED voltage drop?
A: Red LEDs ~1.8-2.0V, blue/white ~3.0-3.3V. Check your LED's datasheet for exact values.

Q3: How do I choose the LED current?
A: Standard LEDs typically use 20mA, but high-efficiency LEDs may work well at 5-10mA. Never exceed the LED's maximum rating.

Q4: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value to ensure safe current levels.

Q5: How do I calculate resistor power rating?
A: Power = (V_supply - V_led) × I_led. Choose a resistor with at least twice this calculated power rating.