1. What is an LED Resistance Calculator?

Definition: This calculator determines the appropriate resistor value needed to safely operate an LED in an electronic circuit.

Purpose: It helps electronics hobbyists and engineers select the correct current-limiting resistor to prevent LED damage.

2. How Does the Calculator Work?

The calculator uses Ohm's Law formula:

Where:

• \( R \) — Required resistance (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 resistance, excessive current can damage the LED or cause premature failure.

4. Using the Calculator

Tips: Enter the supply voltage, LED voltage drop (typically 1.8-3.3V), and desired current (usually 10-30mA). All values must be > 0, and supply voltage must exceed LED voltage.

5. Frequently Asked Questions (FAQ)

Q1: Why do we subtract LED voltage from supply voltage?
A: The resistor must only drop the excess voltage not used by the LED itself.

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

Q3: What if my supply voltage equals LED voltage?
A: No resistor is needed, but you should use a constant current source instead.

Q4: How do I find my LED's voltage drop?
A: Check the datasheet or use 2.0V for red, 2.1V for amber/yellow, 3.3V for blue/white/green LEDs.

Q5: What resistor wattage should I use?
A: Calculate power (P = I²R) and choose a resistor with at least double the calculated wattage.