I am planning to power multiple Raspberry Pi's around the house. Some will be security cameras, one will be a media player connected to TV and another one will manage home network and maybe a website or something. I have phone and cable-TV cables running through walls to rooms and to the living room.
I was thinking about replacing these with ethernet cables by attaching ethernet cables from one side and pulling the original cables (in this case phone or cable TV) out from the other side. I won't need the phone (as we are not going to use land lines) but I might also insert a new phone cable to have them for a potential use in the future. But that is not the point.
As I am going to bringing ethernet (Cat6) to raspberries, I was thinking about using power over ethernet (PoE), which is an awesome technology, to spare 5-6 separate power adapter for raspberries. However, PoE ends up being more expensive than I thought. Switches are 5-6x more expensive. Standard PoE modules to extract energy to raspberries are also expensive (I will need 5 of them). There are however DIY plans, but they are not the exact PoE standard, which is a minus.
Buying multiple injectors is not a solution either. Then again I have a mess of cables and adapters.
My current plan and idea is to have a 48V DC power source next to the main switch. I need to distribute ethernet cables from there anyway. I could simply distribute 48V DC power with 2 extra copper cables (self soldered on a board to distribute the output to each raspberry) wrapped and nicely taped around each CAT6 cable. On the raspberry side, I can use a voltage regulator to bring it down to 5V. This can then be connected to raspberry with a micro USB interface.
This way I can provide gigabit connection with a relatively cheap switch and power with a single power supply.
With 48V, resistance in the cables will not be an issue over ~10 meters.
My only concern is to have 48V running close (taped from outside) to Cat6 inside the walls! Is it a fire hazard? Does this affect data transmission? Aren't shielded cables protected from such an effect?
Are there any better options, which I did not consider?
EDIT: I ended up buying a 8 port switch with 4 ports of PoE. I have found some good deals on active PoE splitters. And all together they work great!