1. What is an LED Circuit Resistor Calculator?

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

Purpose: It helps electronics enthusiasts 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 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 calculates the voltage drop across the resistor (supply voltage minus total LED voltage drop) divided by the desired current.

3. Importance of Proper Resistor Calculation

Details: Correct resistor selection prevents LED burnout, ensures proper brightness, and maintains circuit stability.

4. Using the Calculator

Tips: Enter the power supply voltage, LED forward voltage (typically 1.8-3.3V), number of LEDs in series, and desired current (usually 10-30mA for standard LEDs).

5. Frequently Asked Questions (FAQ)

Q1: What happens if I don't use a resistor?
A: Without a current-limiting resistor, LEDs will typically draw excessive current and burn out almost instantly.

Q2: What's a typical LED forward voltage?
A: Red LEDs ~1.8-2.2V, Blue/White ~3.0-3.4V. Check your LED's datasheet for exact values.

Q3: What current should I use for standard LEDs?
A: Standard 5mm LEDs typically use 20mA, but check your specific LED's maximum rating.

Q4: Can I use this for parallel LED circuits?
A: No, this calculator is for series connections only. Parallel circuits require separate resistors for each LED.

Q5: How do I choose the nearest standard resistor value?
A: Round up to the next standard resistor value (E12 or E24 series) to ensure current doesn't exceed your calculation.