How to choose a power supply for microcontrollers?

Question

Microcontrollers

Hello!
Faced with the problem of choosing a power source.
What I have:
1) 30+ controllers located in different parts of the building.
2) There is a 220 volt cable near each.
3) In the future, access to controllers will be extremely difficult.
4) The controllers are surrounded on all sides by foam, that is, a high degree of thermal insulation and there should not be any excess heat.
5) Constant power consumption of about 100 mW.
6) Autonomous battery power is not considered.
It is required to provide each controller with five volts.
I am considering a choice of the following options:
- Semiconductor AC / DC converter 220 -> 5 volts.
- Microtransformer.
- Lay a five-volt power line to each controller.
I'm leaning more towards the latter option, but would like to know the community's opinion.

Answer 1

First you buy the Bastion for the incoming filter, then the slope for lowering and redundant power, then you put the UPC to protect against reverse current, the SCATS seem to be able to do it themselves, and let 12 volts up to mikruh, there you already lower it to 5 volts on the 7805 roll, why you need lower already at mikruha, tk. voltage drop is greater the further the distance.