1. What is a 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 prevent LED damage by limiting current flow through the LED.

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 resistor value is calculated by subtracting the LED's voltage drop from the supply voltage, then dividing by the desired current.

3. Importance of Proper Resistor Calculation

Details: Using the correct resistor prevents LED burnout (too little resistance) or dim operation (too much resistance).

4. Using the Calculator

Tips: Enter the supply voltage (e.g., 5V for USB, 12V for car), LED voltage (typically 1.8-3.3V), and desired current (usually 0.01-0.03A). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What happens if I don't use a resistor?
A: Without current limiting, most LEDs will draw excessive current and burn out almost instantly.

Q2: What's a typical LED forward voltage?
A: Red LEDs ~1.8V, green ~2.0V, blue/white ~3.0-3.3V. Check your LED's datasheet for exact values.

Q3: How much current should I use?
A: Standard LEDs: 20mA (0.02A), high-power LEDs may need more (check specifications).

Q4: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value for safety.

Q5: How do I calculate resistor power rating?
A: \( P = I^2 \times R \). For most small LEDs, a 1/4W resistor is sufficient.