- Référence externe : https://en.wikipedia.org/wiki/LED_circuit
LED circuit - Wikipedia
Typically, the forward voltage of an LED is between 1.8 and 3.3 volts. It varies by the color of the LED. A red LED typically drops around 1.7 to 2.0 volts, but since both voltage drop and light frequency increase with band gap, a blue LED may drop around 3 to 3.3 volts.
- R = (Vpower - Vled) / Iled
20 mA (0.020A) is common for many small LEDs
Then, as a rule of thumb, because the voltage of the LED is around 2 and the current can be 5mA without harm, I can always start with the resistance of value (V - 2) / 0.005 = (V -2) * 200.