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 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 forward voltage drop (volts)
• \( I \) — Desired current through LED (amperes)

Explanation: The formula calculates the resistor needed to drop the excess voltage (supply minus LED voltage) at the desired current.

3. Importance of Proper Resistor Selection

Details: Using the correct resistor prevents LED damage from excessive current and ensures proper brightness and longevity.

4. Using the Calculator

Tips: Enter the supply voltage, LED voltage (default 2.1V for typical red LED), and desired current (default 20mA). 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, most LEDs will draw excessive current and burn out almost instantly.

Q2: What's a typical LED forward voltage?
A: Varies by color: ~1.8V (red), ~2.1V (yellow/green), ~3.3V (blue/white). Check your LED's datasheet.

Q3: What current should I use for my LED?
A: Standard LEDs typically use 20mA, but check your specific LED's maximum rating. High-power LEDs may need more.

Q4: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value to ensure current doesn't exceed your target.

Q5: How do I calculate resistor power rating?
A: Power = I² × R. Choose a resistor with wattage rating higher than this calculated value.