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 select the correct current-limiting resistor for LED circuits.

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 for LEDs

Details: LEDs require precise current control. Without proper current limiting, LEDs can burn out quickly or have reduced lifespan.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What if my calculated resistor value isn't a standard value?
A: Use the next higher standard resistor value to ensure safe current levels.

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

Q3: How do I find my LED's voltage drop?
A: Check the LED's datasheet or use typical values: red=1.8-2.2V, blue/white=3.0-3.4V, green/yellow=2.0-2.4V.

Q4: What if my supply voltage equals the LED voltage?
A: No resistor is needed (result will be 0Ω), but ensure exact voltage matching to prevent overcurrent.

Q5: How do I calculate resistor power rating?
A: Power = I²R. Choose a resistor with at least double the calculated power dissipation.