LED Current limit Resister for 3.3V such as Xiao

Ref. ラズパイでLEDライトを光らせるときに使う抵抗器の選び方

Example

VCC(3.3V) - VF(2.1V) = 1.2V
V=IR  
R=V/I = 1.2V/20mA = 1.2/0.02A = 60 ohm  <100 ohm < 1k ohm  

VCC(5V) - VF(2.1V) = 2.9V
R=V/I = 2.9V/0.02A = 145 ohm < 1k ohm

class site

• Red LED

  • IF: 20mA
  • VF: 2V
  • R = (3.3V - 2VF)/0.02A = 65 ohm < 100 ohm < 1K ohm

• Blue LED

  • IF: 20mA
  • VF: 3.2V
  • R = (3.3V - 3.2V)/0.02A = 5 ohm < 10 ohm < 100ohm < 1K ohm

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Last update: February 15, 2024