Why are incandescent bulbs blowing/burning out? How to prevent?

So why not use a 12 c dc power supply with a voltage regulator or a buck converter?

I will get a 5vdv to power the Arduino and 5v for the lights.

Incan made to work with AC and enough in series to dissipate the expected 110-120V. I may have lost the reason why talks are of using a DC power supply and not just relaying the damn thing if control is required.