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 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 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 supply voltage, LED voltage drop (typically 1.8-3.3V depending on color), and desired current (usually 10-30mA). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why do we need a resistor for LEDs?
A: LEDs have very low internal resistance and will draw excessive current without a limiting resistor, leading to failure.

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 datasheet or use these typical values: Red=1.8-2.2V, Blue/White=3.0-3.4V, Green/Yellow=2.0-2.4V.

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 to handle the power dissipation (P = I²R) without overheating.