1. What is a Series LED Resistor Calculator?

Definition: This calculator determines the appropriate resistor value needed when connecting LEDs in series with 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 the formula:

Where:

• \( R \) — Resistor value (ohms)
• \( V_{supply} \) — Power supply voltage (volts)
• \( V_{led} \) — Voltage drop across each LED (volts)
• \( I \) — Desired current through LEDs (amps)

Explanation: The total LED voltage drops are subtracted from the supply voltage, then divided by the desired current to get the resistor value.

3. Importance of Proper LED Current Limiting

Details: LEDs require precise current control. Too much current can burn them out, while too little makes them dim. The resistor limits current to the desired value.

4. Using the Calculator

Tips: Enter the supply voltage, LED forward voltage (typically 1.8-3.3V depending on color), 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 resistor, LEDs typically draw too much current and burn out almost instantly.

Q2: How do I know the LED voltage drop?
A: Check the LED datasheet. Typical values are: Red (1.8-2.2V), Blue/White (3.0-3.4V), Green/Yellow (2.0-2.4V).

Q3: What current should I use for standard LEDs?
A: 20mA (0.02A) is common for standard LEDs, but check your specific LED's maximum rating.

Q4: Can I connect multiple LEDs in series?
A: Yes, but the supply voltage must be greater than the sum of all LED voltage drops.

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