What will your application be? Will the entire load be isolated from the user and the probing fingers of children?

 

What will your application be? Will the entire load be isolated from the user and the probing fingers of children?

Yes, there will be no interaction of user. I just want to drive small microcontroller and thus control the relay.

 

Actually I want to make very compact and cheap circuit , and then I have found such circuit on web.

This is something you should just buy. Commercial units will be smaller, cheaper, and have certifications for line operation. You just need to watch out for fakes.

 

The used electronic store has cell phone chargers for $1.00. I have a box of old phone chargers.

 

If I had an application that need 5V at a low current I would fist consider using a little charger like the one ronsimpson mentioned and treat it as a component rather than going off and creating possible hazards.