1. What is a Current Limiting Resistor for LED?

Definition: This calculator determines the appropriate resistor value to safely limit current through an LED when connected to a power supply.

Purpose: It helps electronics hobbyists and engineers prevent LED burnout by calculating the correct series 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 Current Limiting

Details: LEDs are current-driven devices that require proper current limiting to prevent overheating and premature failure.

4. Using the Calculator

Tips: Enter the supply voltage, LED voltage drop (default 2.1V for standard red LED), and desired current (default 20mA). All values must be > 0.

5. Frequently Asked Questions (FAQ)

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

Q2: What's a typical LED current?
A: Most standard LEDs operate at 20mA (0.02A), but high-power LEDs may require more current (check datasheet).

Q3: How do I find my LED's voltage drop?
A: Check the datasheet or use typical values: Red=1.8-2.1V, Blue/White=3.0-3.5V, Green/Yellow=2.0-2.4V.

Q4: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value for safety.

Q5: How do I calculate resistor power rating?
A: Power = I²R. For safety, choose a resistor rated for at least twice the calculated power.