Calculadora de Resistor para LED

Calcule o valor do resistor necessário para limitar a corrente em um circuito com LED.

V
V
mA

Required Resistance

150.0 Ω

Resistor Power Dissipation60.0 mW

Required Resistance vs Supply Voltage

Ver formula →

Formula

How to Size a Resistor for an LED

An LED needs a series resistor to limit current.

Formula

R = (V_supply - V_led) / I_led

Where:

  • V_supply = Source voltage
  • V_led = LED forward voltage drop
  • I_led = Desired LED current (commonly 20 mA)

    • Power dissipated in the resistor is P = (V_supply - V_led) x I_led.

    Exemplo Resolvido

    Drive a red LED (2.0 V forward) at 20 mA from a 5 V supply.

    1. 01Voltage across resistor = 5 - 2.0 = 3.0 V
    2. 02Current in amps = 20 / 1000 = 0.02 A
    3. 03R = 3.0 / 0.02 = 150 ohms
    4. 04Power = 3.0 x 0.02 = 0.06 W = 60 mW

    Perguntas Frequentes

    What happens without the resistor?

    The LED draws excessive current and burns out within seconds.

    How do I know my LED forward voltage?

    Check the datasheet. Typical: red 1.8-2.0 V, green 2.0-2.2 V, blue/white 3.0-3.3 V.

    What if the exact resistor is unavailable?

    Round up to the next standard value. Slightly higher resistance is safe for the LED.

    Aprender

    Ohm's Law Guide

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