powerline communication circuit
Just a word of warning:
Connecting anything to the mains wiring is potentially very dangerous. The two main risks are shock hazard and fire hazard. Therefore, besides following the application notes, one has to take special care of the safety issues.
For instance, use fuses to limit an eventual fault current and use only proper capacitors, "X" capacitors are intended for circuits "between lines" and "Y" capacitors for line-to-something-else. Be also aware of capacitive leakage currents, which often limit how large the "Y capacitor can be.
Also use proper housing for the device. If the housing is metallic, in most cases it should be safety grounded. If it is non-metallic, it should be physically and electrically strong enough and not flammable. Be aware that certain isolation distances should be respected, and on surface of a PCB the distance is "creepage" distance, which has to be longer than it would be in free air. For example, if I remeber the rules right, the distance on PCB between mains and the user-touchable part of circuitry should be over 5 mm for class II (enforced/double isolated device).
Even a hobby design should be constructed with electrical safety standards in mind, exactly as it would be some day type approved.
Another story is that in most cases it is simply illegal to connect non-approved devices to the power network, and one can get nasty surprises with authorities and/or insurance company if something happens....