Gigabit PoE wiring (e.g RBGPOE)

Hardware MikroTik hardware general
1

Can somebody show me how a Gigabit PoE injector is wired? Is the wiring of an RBGPOE different from an RBPOE?

I am a bit confused because I thought I understood that Gigabit uses all four pairs for data and yet the wording in the brochure for the RBGPOE injector http://routerboard.com/pricelist/download_file.php?file_id=309 suggests that the wiring is exactly the same as a 10/100 PoE injector (i.e. pairs 4,5 and 7,8 are unused, and power/ground are supplied over them).

If pair 4,5 is used for “+”, does this mean that the PoE injector ties wire 4 and wire 5 together? (in which case they would be shorted out, and differential-mode data could not be sent over this pair) Or does it insert “+” power via a diode onto each of them (and a complementary arrangement on 7,8)?

FWIW my motivation in asking this is to know how I should manually field-modify devices (such as RB250GS, RB750G) to provide field-expedient PoE.

2

those devices already support PoE with the gigabit PoE injector, why do you need to modify them?

3

normis, is that poe only allow 100mbps? you cant get gigabit without all 8 wires and thus the reason they came up with the 802.3af power supplies - is this yet another standard?

4

True. I am interested in knowing if/how I can do this without using external PoE injectors. Not so much for cost reasons, but for parts count / clutter reasons. BTW the devices I am attaching need very little power (currently about 150ma each but in the next generation of our hardware they will be about 50ma each) so there is a certain minimum-parts-appeal to having the power connections simply bridged inside the the switch.

5

Yes, gigabit uses all 8 wires. The power is phantom power, similiar to the technique used with 802.3af, but it appears to be modified to be mikrotik proprietary.

6

If you want to make PoE output on the other ports, sorry but for these products it’s not easily possible. You need to wait for our RB750UP and Omnitik UPA

7

Normis

Is there any plans for a 450GUP or something with 5+ ports and spec like/better than the 450G?

8

We will start with two products, and we will see where we go next with this feature.

9

So if I use a RBGPOE to eth1 on a RB450G it will or will not be gigabit?

10

yes, if you use Gigabit PoE injector on a Gigabit RouterBORD, connection will be Gigabit

11

THAT would be a great device! +1 for sure!

12

Any idea how to make home-made gigabit poe? Schematics?

Thanks…

13

Whitepaper from Texas Instruments will help you to understand.

Basicly you just need magnetics for seaparatinf the DC (power supply) from AC current (data transfer). So other capacitors, and resistors for make it clean.
POE TI snoa464b.pdf (1.49 MB)