1. What is a Constant Current for LED Calculator?

Definition: This calculator determines the appropriate resistor value needed to maintain constant current through an LED.

Purpose: It helps electronics hobbyists and engineers properly drive LEDs without damaging them by limiting current.

2. How Does the Calculator Work?

The calculator uses Ohm's Law:

Where:

• \( R \) — Resistance needed (ohms)
• \( V \) — Voltage across the resistor (volts)
• \( I \) — Desired current through LED (amps)

Explanation: The voltage across the resistor divided by the desired current gives the resistance value needed.

3. Importance of Constant Current for LEDs

Details: LEDs are current-driven devices. Proper current limiting prevents overheating and ensures consistent brightness and long lifespan.

4. Using the Calculator

Tips: Enter the voltage across the resistor (typically supply voltage minus LED voltage drop) and desired current (default 20mA). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical LED current?
A: Most standard LEDs operate at 20mA (0.02A), but check your LED's datasheet for exact values.

Q2: How do I determine the voltage across the resistor?
A: Subtract the LED's forward voltage (typically 1.8-3.3V) from your power supply voltage.

Q3: What resistor power rating should I use?
A: Calculate power with P = V×I and choose a resistor rated for at least twice that value.

Q4: Can I use this for multiple LEDs?
A: For series connections, sum the LED voltages. For parallel, calculate each branch separately.

Q5: What if my calculated resistor isn't a standard value?
A: Use the next higher standard resistor value to ensure current doesn't exceed your target.