Usually, LED is powered by DC supply, but this circuit can make the LED can be powered by AC supply. This circuit can be used as power indicator for Water pump. There are two circuit versions of AC-powered LED presented here. First is circuit for US or Canadian 110-120V 60Hz AC lines and European or Australian 220-230V 50Hz AC lines. Here is the circuit:
To limit the inrush current in this circuit, a resistor is used. The Voltage is lowered by the capacitor. To limit the reverse voltage across LED, the diode is connected with the LED n parallel. Beside that, diode also used to provide a path for the negative half cycle because the capacitor passes the current in both directions. When the capacitor charges, the resistor drop the inrush current from 150mA to 30mA in a milliseconds. The average current that through the LED is 10mA because 0.47uF capacitor has an impedance of 5600 Ohms at 60Hz for 110-120V 60Hz version and 0.33uF capacitor is 9600 Ohms at 50Hz for 220-230V 50Hz version.
The impedance is determined by following equation:
Z = 1 / 2*Pi*f*C
The current is determined by the capacitor, smaller capacitor will reduce the current and larger capacitor will increase the current. The type of capacitor is non-polarized type with 400VDC or more for 230V AC-lines and a voltage rating of 250VDC vor120V AC lines. When the AC is connected, the resistor will discharge the capacitor C1.R1 must be able to withstand the full half wave peak AC-line voltage. [turbokeu.com/myprojects.htm]