1. What is an LED Voltage Drop Resistor Calculator?

Definition: This calculator determines the appropriate resistor value to safely operate LEDs in series from a given 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 resistance (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 desired current.

3. Importance of Current Limiting for LEDs

Details: LEDs require precise current control. Too much current can burn them out, while too little makes them dim. This calculator ensures proper operation.

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). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical LED voltage drop?
A: Standard LEDs drop about 1.8-2.2V, white/blue LEDs about 3-3.6V. Check your LED's datasheet for exact values.

Q2: What current should I use for standard LEDs?
A: 20mA (0.02A) is common for indicator LEDs, but high-power LEDs may need more (check specifications).

Q3: What if my calculated resistance isn't a standard value?
A: Use the next higher standard resistor value for safety.

Q4: Why does the calculator show power dissipation?
A: The resistor must be rated for the calculated power (typically use a resistor rated for at least twice the calculated power).

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