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So I was wondering if I could power my 8 or at least 4 ip cameras from my old pc psu.

I have: *500 W psu, where 12 V can use up to 360 W

*GV-EBL1100 ip cameras which require 12 VDC / (IEEE 802.3af), not sure if 7.4 or 15 W per camera (confused from documentation)

*non-PoE router I think (nWay switch)

*CAT5e cables

I want to make a diy injector with at least 4 sockets which connect to ip cameras (data + power) and 4 sockets which go back to router with data only.

Is it possible to connect all 4 cameras CAT5 cable power pairs parallel to a single psu 12V power pair using DC-DC transformer to 48V?

Does this particular ip camera communicates to negotiate power supply over data cables?

Will it work if CAT5e cable is splitted the way that power goes to ip camera but blank to router via (unused?) pairs?

Or just buying the poe switch is the only option here?

Don't hesitate to ask if something is unclear, I don't know if I provided enough information and clearly.

Thanks in advance.

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    \$\begingroup\$ IEEE 802.3af is 48V \$\endgroup\$
    – Jasen Слава Україні
    Commented Aug 1, 2018 at 7:18
  • \$\begingroup\$ ”Will the psu switch to correct amps?” It won’t switch anything. It’s a voltage source and will supply as much current as it can depending on the load. \$\endgroup\$
    – winny
    Commented Aug 1, 2018 at 7:32
  • \$\begingroup\$ Find out what the cameras sue for POE, if its the 802.3 standard then you'll need the appropriate POE supply and DIY won't work. DIY POE works if you do that on both ends \$\endgroup\$
    – Voltage Spike ♦
    Commented Aug 1, 2018 at 18:21

1 Answer 1

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PoE doesn't have "power pairs" and "data pairs". All pairs are both power and data. And those 4 pairs necessarily connect to the non-PoE switch as well. It should tolerate the excess voltage, but it's not designed for that.

As Jasen notes, standard PoE is 48V, not 12V.

The camera will indeed negotiate PoE power.

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  • \$\begingroup\$ Not really. Alternative B uses power on unused wires and thus separates data and power. \$\endgroup\$
    – winny
    Commented Aug 1, 2018 at 7:55
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    \$\begingroup\$ @winny: Fair point. The power source gets to choose the Alternative used, not the powered device. But Alternative B is only available up to -100TX. Above that, all 4 pairs are data pairs. \$\endgroup\$
    – MSalters
    Commented Aug 1, 2018 at 8:08
  • \$\begingroup\$ Please edit your answer accordingly. \$\endgroup\$
    – winny
    Commented Aug 1, 2018 at 8:09
  • \$\begingroup\$ From @winny i understand that my camera supports both mode A and mode B, correct? So if i use transformer to get 48v and use mode B wiring leaving power pairs blank to router, i will still get required data from camera and camera will be powered, right? Or to make this work i need some advanced circuit (PoE switch basically)? \$\endgroup\$
    – Mārtiņš Strazdiņš
    Commented Aug 1, 2018 at 11:23
  • \$\begingroup\$ @MārtiņšStrazdiņš: Keep in mind that you need 48V DC; ordinary transformers use AC. \$\endgroup\$
    – MSalters
    Commented Aug 1, 2018 at 11:29

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