Ingénierie et Électronique

Free LED Series Current Limiting Resistor Calculator

Light Emitting Diodes (LEDs) are current-driven semiconductor devices that require a series current-limiting resistor to prevent excessive current from destroying the LED. Ohm's Law determines the required resistance ($R = rac{V_S - V_F}{I_F}$). Our free led resistor calculator enables electronics hobbyists and engineers to use a current limiting resistor calculator, apply the calculate led resistor ohms formula, and find the standard resistor value for led.

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Mathematical Formulas & Calculation Methods

LED Series Resistor Formula

Ohm's law applied to LED series voltage drop.

Resistor (R) = (Vₛ - V𝆞) / I𝆞 | Power Dissipation (P) = (Vₛ - V𝆞) × I𝆞

Worked Step-by-Step Examples

Example 1: Red LED (V𝆞 = 2.1V, I𝆞 = 20 mA = 0.02A) powered by a 9V Battery (Vₛ = 9V)

"Calculate required resistor ohms and wattage."

Steps:

Voltage Drop across Resistor = 9V - 2.1V = 6.9 Volts.
Resistance R = 6.9V / 0.02A = 345 Ohms.
Nearest Standard E24 Resistor = 390 Ohms (or 360 Ohms).
Power Dissipation P = 6.9V × 0.02A = 0.138 Watts (138 mW < 0.25W standard 1/4W resistor).

Result: Use 390 Ω (1/4 Watt) resistor.

What is Calculateur de LED Series Current Limiting Resistor?

An led resistor calculator computes the series resistor required to regulate current flowing through an LED.

Standard **E24 resistor values** represent preferred resistor values available in standard commercial electronic components.

How to Use Calculateur de LED Series Current Limiting Resistor

1Enter Power Supply Voltage V⛛ (Volts).
2Enter LED Forward Voltage V𝆞 (Volts, e.g. Red ≈ 2.0V, White ≈ 3.2V).
3Enter desired LED Forward Current I𝆞 (mA, e.g. 20 mA).
4View exact resistance in Ohms, recommended standard E24 resistor value, and power dissipation rating.

Key Features

Calculates exact series resistance in Ohms ($Omega$).
Recommends nearest standard E24 resistor value.
Calculates resistor power dissipation in mW and recommends 1/4W vs 1/2W rating.

Benefits of Using Calculateur de LED Series Current Limiting Resistor

Prevents burnt-out LEDs during breadboard electronics prototyping.

Essential tool for Arduino, Raspberry Pi, and DIY electronics makers.

Practical Use Cases

Arduino & Raspberry Pi Makers

Size current limiting resistors for indicator LEDs and microcontrollers.

Electronics Technicians

Calculate component values for custom PCB and LED array designs.

Frequently Asked Questions

What happens if you don't put a resistor with an LED?

Without a current-limiting resistor, an LED will draw excessive current due to its low internal forward resistance, rapidly burning out or destroying the microcontroller pin.

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