How to Ballast an LED with a Series Resistor

适用场景

For indicator LEDs, a series resistor sets current given your supply and the diode forward drop. Use it as a first-pass check before you confirm with datasheets, temperature, and drive topology.

要使用的工具

由电源、正向电压与目标电流估算串联电阻。

打开 LED 限流电阻 →

步骤

  1. 1Read target forward current and typical Vf from the LED datasheet (or lab guess for hobby parts).
  2. 2Enter supply voltage, Vf, and desired current in mA.
  3. 3Note the resistor value and power dissipation; pick the next standard value with margin.
  4. 4For networks, check series/parallel equivalents separately from a single ballast.
  5. 5For divider taps, remember loads draw current—unloaded Vout is an upper bound.

示例

  • 5 V supply, 2 V Vf, 20 mA target → ballast in the hundreds of ohms.
  • Two resistors in parallel for equivalent R when you only have standard values.

应避免

  • Using peak PWM current as if it were DC average.
  • Ignoring resistor power rating and overheating at small packages.
  • Treating a loaded voltage divider like an unloaded calculator output.

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常见问题

Constant-current driver?

This flow is for resistive ballast. CC drivers need a different design checklist.

Multiple LEDs?

Series strings share current; parallel branches need their own limiting.

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