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 forward voltage drop (volts)
• \( I_{led} \) — Desired LED current (amps)

Explanation: The resistor value is calculated by subtracting the LED voltage from the supply voltage, then dividing by 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 (typically 1.8-3.3V), and desired current (default 20mA). Supply voltage must be greater than 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 current?
A: Standard LEDs typically use 20mA (0.02A), but always check your LED's datasheet for exact specifications.

Q3: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value to ensure safe current levels.

Q4: How do I find my LED's voltage drop?
A: Check the datasheet or use 2.0V for red LEDs, 3.0V for blue/white LEDs as general estimates.

Q5: What about power rating for the resistor?
A: Calculate power as P = I²R. Standard 1/4W resistors work for most small LEDs.