1. What is an LED Resistor Calculator?

Definition: This calculator determines the proper 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 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 drops the excess voltage (supply minus LED voltage) while limiting current to the desired value.

3. Importance of LED Current Limiting

Details: LEDs require precise current control. Without proper current limiting, LEDs can burn out instantly or degrade quickly.

4. Using the Calculator

Tips: Enter the power supply voltage, LED forward voltage (typically 1.8-3.3V), and desired current (typically 10-30mA). All values must be > 0 and supply voltage must exceed LED voltage.

5. Frequently Asked Questions (FAQ)

Q1: Why do we need a resistor for LEDs?
A: LEDs are current-driven devices that require current limiting to prevent damage from excessive current flow.

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

Q3: How do I find my LED's voltage drop?
A: Check the LED datasheet or use 2.1V for red, 3.3V for blue/white as typical values.

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: Why does the calculator show resistor power?
A: The resistor must be rated for the power it will dissipate (P = V × I). Standard 1/4W resistors work for most small LEDs.