1. What is an LED Resistor Calculator?

Definition: This calculator determines the appropriate resistor value needed to safely operate an LED with a given power supply.

Purpose: It helps electronics hobbyists and engineers prevent LED burnout by calculating the correct current-limiting resistor.

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 voltage drop (volts)
• \( I_{led} \) — Desired LED current (amps)

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

3. Importance of Proper Resistor Calculation

Details: Using the correct resistor ensures the LED operates at optimal brightness without being damaged by excessive current.

4. Using the Calculator

Tips: Enter the supply voltage, LED voltage drop (default 2.1V for typical LEDs), and desired current (default 20mA). All values must be > 0 except LED voltage which can be 0.

5. Frequently Asked Questions (FAQ)

Q1: What happens if I don't use a resistor?
A: Without a current-limiting resistor, most LEDs will draw excessive current and burn out almost instantly.

Q2: What's a typical LED voltage drop?
A: Red LEDs typically drop 1.8-2.2V, white/blue 3.0-3.6V. Check your LED's datasheet for exact values.

Q3: What current should I use for my LED?
A: Standard LEDs typically use 20mA (0.02A), but high-power LEDs may require more. Always check specifications.

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 double this wattage for safety.