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 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 Proper LED Resistor Calculation

Details: Using the correct resistor prevents LED damage from excessive current and ensures optimal brightness and longevity.

4. Using the Calculator

Tips: Enter the supply voltage, LED voltage drop (typically 1.8-3.3V), and desired LED current (typically 0.01-0.03A for standard LEDs). All values must be > 0 and supply voltage must exceed LED voltage.

5. Frequently Asked Questions (FAQ)

Q1: What if my supply voltage equals the LED voltage?
A: The formula requires supply voltage to be higher than LED voltage. If equal, no resistor is needed (but not recommended as current can't be limited).

Q2: What's a typical LED current?
A: Standard LEDs typically use 20mA (0.02A), but check your LED's datasheet for exact specifications.

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

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: Does this work for multiple LEDs?
A: For series connections, sum the LED voltages. For parallel, calculate resistors separately for each LED.