0 Mains AC Detector Circuit

This circuit is connected to the main AC supply to monitor if there is an incoming voltage from the supply to the device or appliances. The monitoring is isolated to high voltage by  opto-coupler.

Part List:
R1 - 470 kilo ohms 1/4W
R2 - 330 ohms 1/4W
R3 - 2.2 kilo ohms 1/4W
R4 - 4.7 kilo ohms 1/4W
RL - relay, bulb or any indicator
D - 1N4007
C1 - 100nF capacitor rated 350V (I use 1000V) or higher
C2 - 10uF electrolytic capacitor rated 50V
Q1 - 2N2222, CS9013 or similar NPN transistor
CNY64 - any opto-coupler, CNY65, and others
fuse - dependent on device or appliance power requirement