A interesting montage is a led flasher.. if it put on lamp switch is more interesting, but this is not for beginner because this montage is powered at main supply, in my case 230V/50Hz but works also at 240V/60Hz and with minimum change at 110V/50 or 60Hz.

Step 1: Base Schematic

Original schematic if from an old ELEKTOR magazine...

Schematic has few pieces:

- 1N4007 diode (any rectifiers diode 1A and minumim 400V)

- electrolitic capacitor with value from 10uF to 22uF at minimum 50V

- 470k to 750k resistor for 230..240V (half value at 110..120V)

- 1k (one or two) resistor

- diac 30..33V (DC32, DB3 or equivalents)

- led (any colour)

Step 2: Using

You can use this schematic in 2 version with a classical lamp (incandescent bulb)... led flash when lamp is on or when is off... but you can use as indicator for main power supply... see the movie from youtube !!!

Bibliography:

- http://www.arduinotehniq.com/index.php/2016/03/29/230vled-flasher/

- http://www.arduinotehniq.com/old/LED_flasher/LED_flasher.htm