Detect circuit break or voltage at 220V?

Hello,

i have simple motion detection sensor which is powered directly at 220V.

I want to detect when the sensor switches the circuit ON with arduino chip.

There must be many different ways to detect that, however, i need the most simple one and the one which would require less as possible additional parts.

pls post any idea which could help.

You need an opto isolator at the very least. Basicay input side is an LED so you need a resistor to limit the current as well. You will find that this resistor will get hot and so to limit the power it dissipates you could add a seriese capacitor as well as the resistor.

If this can be of any help, this is a series of photo showing the device:





Looks like a PIR sensor for switching on lights. My advice would be the same unless you want to hack the devices wiring so that the relay is not pre wired to the mains. If you do then you can just connect the contacts between arduino pin and ground and enable the internal pull up resistors.

Please, could you look at the flat 3 wire cable between the boards.

Would i be able to get the signal for switching there and avoid the rest of the circuit?

No idea, but I suspect not.