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 damage by limiting current flow through the circuit.

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 Proper Resistor Calculation

Details: Using the correct resistor prevents LED burnout, ensures proper brightness, and maximizes LED lifespan.

4. Using the Calculator

Tips: Enter the supply voltage, LED voltage drop (default 2.1V for typical LEDs), and desired current (default 20mA = 0.02A). All values must be > 0 except LED voltage which can be 0.

5. Frequently Asked Questions (FAQ)

Q1: Why do we subtract LED voltage from supply voltage?
A: The LED drops a fixed voltage, so the resistor only needs to handle the remaining voltage to limit current.

Q2: What's a typical LED current?
A: Most standard LEDs operate at 20mA (0.02A), but check your LED's datasheet for exact values.

Q3: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value to ensure you don't exceed the LED's current rating.

Q4: How do I find my LED's voltage drop?
A: Check the datasheet or use 2.1V for red, 3.3V for blue/white LEDs as general guidelines.

Q5: What resistor wattage should I use?
A: Calculate power with P = I²R and use a resistor rated for at least twice that value.