1. What is an LED Series 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 formula:

Where:

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

Explanation: The formula calculates the resistor needed to drop the excess voltage after accounting for the LEDs' voltage drops, at the specified current.

3. Importance of Current Limiting for LEDs

Details: LEDs require precise current control. Too much current can destroy them, while too little results in dim operation. The series resistor provides this current limiting.

4. Using the Calculator

Tips: Enter the power supply voltage, typical LED voltage drop (default 2.1V for standard LEDs), number of LEDs, and desired current (default 20mA for many LEDs).

5. Frequently Asked Questions (FAQ)

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

Q2: What's a typical LED voltage drop?
A: Red LEDs ~1.8-2.2V, Blue/White ~3.0-3.6V. Check your LED's datasheet for exact values.

Q3: How do I choose the right current?
A: Most standard LEDs operate at 20mA (0.02A), but high-power LEDs may need more. Always check specifications.

Q4: Why does the calculator show power dissipation?
A: The resistor must be rated to handle the calculated power (use a resistor with at least double the calculated wattage).

Q5: Can I use this for parallel LED circuits?
A: No, this is for series connections only. Parallel LEDs each need their own current-limiting resistor.