1. What is an LED Resistor Calculator?

Definition: This calculator determines the appropriate resistor value needed when connecting LEDs in series to a power supply.

Purpose: It helps electronics hobbyists and engineers properly limit current through LEDs to prevent damage and ensure proper operation.

2. How Does the Calculator Work?

The calculator uses Ohm's Law with the formula:

Where:

• \( R \) — Resistor value (ohms)
• \( V_{supply} \) — Power supply voltage (volts)
• \( V_{LED} \) — Forward voltage per LED (volts)
• \( n \) — Number of LEDs in series
• \( I \) — Desired current through LEDs (amperes)

Explanation: The formula subtracts the total LED voltage drop from the supply voltage, then divides by the desired current to calculate the required resistance.

3. Importance of Proper Resistor Calculation

Details: Correct resistor selection prevents LED burnout, ensures proper brightness, and maximizes LED lifespan.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What if I get a negative resistance value?
A: This means your supply voltage is too low for the number of LEDs. Either reduce the number of LEDs or increase the supply voltage.

Q2: What's a typical LED forward voltage?
A: Most standard LEDs are around 2.0V (red) to 3.3V (blue/white). Check your LED's datasheet for exact values.

Q3: What current should I use for LEDs?
A: Standard LEDs typically use 20mA (0.020A), but high-power LEDs may require more. Always check specifications.

Q4: Can I connect LEDs in parallel?
A: This calculator is for series connections. Parallel connections require separate resistors for each LED.

Q5: What wattage resistor do I need?
A: Calculate power with \( P = I^2 \times R \). Choose a resistor with at least double the calculated wattage for safety.