I'm new to using Arduino and building my own electronics, and this question may be a total eye roller for some of you, but is there such a thing as a PCB mountable power supply? I only want one cord into my project boxes, not one for the arduino and another for whatever else I need it for. Just a plug into the wall, that's it. Am I barking up the wrong tree? Googling pcb mountable power supply reveals that they do in fact exist, but I guess I really want to know if this is a thing that people do.
Well you have to leave enough space and clearance on the PCB for mains traces and you are
advised to have insulating screen behind the PCB where the mains-voltage traces are (the
principle is make it impossible to touch any live conductor).
For use inside enclosures there are open-frame and boxed type SMPS modules of a huge variety, some
of the smaller ones have a PCB mount option - most are designed to bolt to a chassis though (depends
on size / power).
You will need an appropriate fuse in the live wire if the supply doesn't have its
own mains fuse - the datasheet ought to mention this.