1. What is an LED Diode Resistor Calculator?

Definition: This calculator determines the appropriate resistor value needed to safely operate an LED from 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)
• \( V_{diode} \) — LED forward voltage drop (volts)
• \( I \) — 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 Resistor Calculation

Details: Correct resistor selection prevents LED damage from excessive current, ensures proper brightness, and maintains circuit reliability.

4. Using the Calculator

Tips: Enter the supply voltage, LED forward voltage (default 2.1V for standard LEDs), and desired current (default 20mA). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value to ensure safe current levels.

Q2: What's a typical forward voltage for LEDs?
A: Red LEDs ~1.8V, Green ~2.1V, Blue/White ~3.3V. Check your LED's datasheet.

Q3: What current should I use for standard LEDs?
A: 20mA (0.02A) is common, but high-brightness LEDs may need less (5-10mA).

Q4: Can I use this for multiple LEDs?
A: For series LEDs, sum their forward voltages. For parallel, calculate resistors separately.

Q5: What about resistor power rating?
A: Calculate power with P = I²R and choose a resistor with at least 2x that rating.