DIY Solution Does PoE On The Cheap


Depending on the scope of your requirements, Power over Ethernet (PoE) components can get pretty pricey. [Fire] wrote in to share a 4-port PoE solution he put together for under 20 euros (Ignore any SSL errors – we’ve checked it out, it’s safe).

The most expensive part of the build was the 8-port patch panel he purchased for 11 euros. He popped it open, wiring the first four ports for power after drilling spots for an indicator LED and the PSU. He wound the power lines through ferrite beads to hoping to dampen any interference that might occur before reassembling the panel.

In the picture above, you might notice that the panel is being powered via the first Ethernet port rather than through the barrel jack, which [Fire] said was done for testing purposes. When deployed in his network, he plans on using a regulated power supply from a junked laptop to provide electricity.

If you need to provide PoE to devices on your network, this is a great way to go about it. Using a patch panel like [Fire] has gives you the flexibility to easily wire up as many powered ports as you need without much hassle.

23 thoughts on “DIY Solution Does PoE On The Cheap

  1. Ok. So If I am following that right it essentially links one of the ports to another one in a 1:1 configuration (1:5,2:6,3:7,4:8) and simply adds in the power. It is NOT using this as a hub splitter right? Just 4 port power injection?

    1. Correct.
      In the picture, for testing, he’s powering it via the left-most port. You plug 4 non-powered ethernet cables on the right, powered out on the left.
      It’s connected ports 8-4, 7-3, 6-2, 5-1.

    2. Its a Passive PoE installation like a lot of wireless equipment uses. The first brand that comes to mind is Ubiquiti.

      Its MUCH MUCH cheeper to do it this way than use 802.11af. Though 802.11af has many more advantages like negotiating load requirements

  2. Nicely done.

    This DOES break gigabit networking however. 10/100 uses 2 pairs, 1000 uses all 4. If you read the spec, the devices think they are negotiated at gigabit speeds because the negotiation is done on the same two pairs as 10/100, but don’t actually hit gigabit speeds with the other two pairs disconnected.

    But not everyone needs gigabit, and this was a clean cheap way to do POE.

  3. I have a similar setup for powering ubiquiti and mikrotik radios. An additional benefit to this setup vs the stock passive POE injectors is that the stock injectors are 24v but long lines can drop that voltage too much. The ubiquiti and mikrotik radios can take up to 30v so you can increase voltage to power the devices over longer distances.

  4. Whoa, use at your own risk. I didn’t see any protection circuitry in there, just a few ferrites in parallel. That will cut down on some noise through the inductance, but you’re still susceptible to surges since you are sharing a wall-wart in parallel. This can be an easy way to fry your entire set of devices if something goes wrong. Check out the 4 port injector on L-com to see a passive injector/midspan done right, I believe they show the plans still.

  5. Definitely use at own risk. Ferrite beads don’t take the place of protection circuitry. Using a wall-wart as a power supply means varying voltage and current, and having this wired in parallel means that each load will affect the others. Hacks are good and get the job done, but 802.3af is a solid standard for a reason.

  6. I build something similar a few years back to power a wireless access point down its cat5 cable.
    (The AP was connected to a home made yagi 70 feet in the air atop a telescopic mast for temporary point to point wireless so an extension lead for the power supply wasn’t an option!)

    The first time I used it up the tower I was using solid copper cat5 – the kind you cable in walls. I attempted the same trick this year and it didn’t work… The difference was I was using flexible patch cable type which obviously has a much higher resistance. The solution, since it was temporary was to just grab my variable bench supply and slowly wind up the voltage while measuring it with a meter at the other end of the cable until it got to the required 5v. A more permanent solution is to use a 5v switch mode regulator at the “top” end and feed it with a higher voltage PSU at the “bottom”.

  7. When I see headlines like “DIY… PoE on the cheap” I assume there is something novel or interesting about it that I can learn. In the case of PoE, the hard part isn’t to just inject a voltage onto unused wires, but to do 802.3af signaling.

    It is great to do this, but it exists in a middle-ground of limited utility; it can be done for way less than half the price for people needing to cheap-skate it, and this is almost as expensive as buying it. For the amount of money spent, I’d really hope to at least get some partial 802.3af compliance, or at least to use an ethernet transformer to get the power off the center taps and not preclude gigabit.

    The reason he doesn’t need that is just that he’s only using Brandybrand(TM) devices, and so it is only for that.

    Sad that so many of these “PoE” DIYs that people share don’t even boost the voltage, or only boost it the minimum amount to keep from burning up the wires at the expected current draw! Even for the simple/cheap type of DIY I would still hope for a pair of cheap DC-DC converters to get the voltage level up and back down. That also gives you a way to limit the current easily so it doesn’t burn up the wiring on a short or other fault in the powered device.

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