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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!

  • Where did you look for your PoE pricing? – WarLoki Aug 26 '15 at 0:15
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    I think this is the wrong group for this question - electronics.stackexchange.com would likely be more receptive. That said, you can use 2 pair of your CAT-5 for 100Mbit ethernet, leaving 2 pair for power. – Johnny Aug 26 '15 at 0:31
  • @WarLoki German Amazon and other price check website. – Genom Aug 26 '15 at 0:58
  • @Johnny I want to have 1000Mbit if I can. Otherwise 100Mbit will be enough too. Still switches/PoE modules are too expensive. – Genom Aug 26 '15 at 1:00
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    One of the benefits of actual PoE (802.3af/at) is that it doesn't send power to a non-PoE device. If someone plugs a non-PoE device into your DIY injector, it may do nothing, or it may fry it. Also, tip on pricing: you don't have to go 100% PoE. In my house, for example, I have a main gigabit switch, then a separate 8-port 10Mbps PoE switch for phones/cameras. The phones, cameras and raspberry PI's don't have or need gigabit, so why pay the premium? – gregmac Aug 26 '15 at 6:58
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If you are going to spend the money on the CAT6, why not go for the PoE Switch? I found this one at Amazon, which is not that expensive and would give you what you're trying to accomplish with room to grow. Shoot, at that price I may get one myself.


  • Prices for switches (8 port + PoE) start around 100€! Cat6 50m is 18€ and Cat5(e) 13€. I would rather spend that 5€ once, since 50m, will be enough. But a 8-port switch wıthout PoE is 20-25€. So PoE itself is here, what is expensive. If I can implement my own solution, I would like to save 70-80€. With the expensive PoE modules, it is going to be way more expensive. – Genom Aug 26 '15 at 1:03
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    Have you tried asking the folks about this in the "Raspberry Pi" Stack Exchange group. I think someone there must have tackled this. – BrownRedHawk Aug 26 '15 at 14:22
  • You can get a a 6 port PoE injector for $60 ($10 per port). See my comment on the other answer. ;-) – Craig Aug 27 '15 at 16:19
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First of all you don't need Cat 6 for Raspberry Pi's Cat 6 supports gigabit and the Pi only supports 100M, so I assume you are running cat 6 for future upgrades.

Fundamentally your plan should work with a few caveats listed below.

The Cat6 is deferentially signaled meaning it shouldn't care about having a dc power line very close and at 48V the current is going to be pretty low so it really shouldn't be a problem.

Make sure you don't use a linear regulator to power the raspberry pi's it will be ludicrously inefficent, get very hot, and negate the "low current" comment from above.

Really this is an electronics question, I would ask at http://electronics.stackexchange.com

  • So also running 48V inside the walls is not a problem (fire hazard, etc.), right? – Genom Aug 26 '15 at 22:52
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I installed a non POE outdoor camera at a location on our property that doesn't have easy access to an outlet. The solution I came up with was to run the camera via POE with a POE to USB Splitter. A quick web shopping outlet search led me to these:

POE to USB Splitter

They are pretty cheap, and come in a variety of configurations / flavors. I opted for removable USB female adapter, but there are versions that have built in Micro USB plugs.

My Setup:

Indoors [Wall outlet -> POE Injector] -> 50 ft Cat 6 Ethernet Cable -> [POE Spliter -> Micro USB Cable -> Camera] Outdoor (in Plastic Project Box)

I could see this easily being implemented using a POE Switch, and routing Ethernet to where needed.

  • Yes, I did the same at the end. By the time I asked the question PoE was expensive. Now it is relatively cheaper. – Genom Jul 9 '18 at 21:05

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