1. What is an LED Resistor Calculator?

Definition: This calculator determines the appropriate resistor value needed for an LED circuit based on power supply voltage, LED characteristics, and desired current.

Purpose: It helps electronics hobbyists and engineers properly limit current through LEDs to prevent damage and ensure proper operation.

2. How Does the Calculator Work?

The calculator uses Ohm's Law formula:

Where:

• \( R \) — Resistance needed (ohms)
• \( V_s \) — Supply voltage (volts)
• \( V_{led} \) — LED forward voltage (volts)
• \( I_{led} \) — Desired LED current (amperes)

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 LED Current Limiting

Details: LEDs require precise current control. Too much current can burn out the LED, while too little results in dim operation.

4. Using the Calculator

Tips: Enter the supply voltage (must be higher than LED voltage), LED forward voltage (default 2.1V), and desired current (default 20mA = 0.02A).

5. Frequently Asked Questions (FAQ)

Q1: What's a typical LED forward voltage?
A: Red LEDs ~1.8V, Green ~2.1V, Blue/White ~3.3V. Check your LED's datasheet for exact values.

Q2: What current should I use for standard LEDs?
A: Common LEDs typically use 20mA (0.02A), but high-power LEDs may require more.

Q3: What if my supply voltage equals the LED voltage?
A: The calculator will show 0Ω, which means you need a current regulator instead of a simple resistor.

Q4: How do I choose the resistor wattage?
A: Calculate power (P = I²R) and choose a resistor with at least twice the calculated wattage.

Q5: Can I use this for multiple LEDs?
A: For series LEDs, sum their forward voltages. For parallel, calculate each branch separately.