Series LED circuit

Series LED circuit
(Source Voltage – LED Voltage Drop) / Amps = OHMs
Amps = mA/1000

Example:
Source Voltage = 9 volts
Voltage Drop = 3.1 volts typical for a blue or white LED
Desired Current = 13 milliamps

So the resistor we need is: (9 – 3.1) / ( 13 / 1000 ) = 452 ohms so we will use a 470 Ω resistor.

220 volt LED circuit

Caution: Do not try this circuit unless you have good knowledge about electronic devices. This circuit is connected to main power source (220V) and can give you a high electrical shock

We use one capacitor, a zener diode, a resistor and the LED.
The capacitors value depend on LED current. With a 100 nF capacitor, the LED current is 4 mA; at 470 nF the current is 20 mA.

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