I’m re-doing some network at home and want to power my incoming fiber’s CPE switch with PoE from my RM4011iGS+RM. The port is said to be passive and I’m using the original 24V PSU for the RB4011 so then I guess the passive PoE is also 24V.
The original PSU is 12V 1A so I’m searching for a gigabit passive PoE splitter that can step down 24V to 12V and deliver at least 1A. I seem to only find 802.3at/af ones with no clear description if they in any way support passive PoE. I guess I also could change the routers PSU to a 12V one but it feels better to keep the original and stay on a higher voltage with less current.
The issue is not so much in the splitter, but in a splitter using the actual Mode (B) the Mikrotik uses AND being capable of 1 Gbps connection (most are for cameras and 100 Mbit capable only).
The makers/sellers of these products tend to be extremely thrifty with technical details, so it is very easy to get the "wrong" device.
It may appear a little clunky, but this way you put "online" (on the cable) a surely good device capable of passing 1 Gbit and Mode B and you are sure of what you get out of it and power the CPE with.
Do you have a major reason to power it via PoE? When you only want to save an extra power supply, I would recommend using a splitter cable on the power input to the router (male and female barrel plug) and a 24→12V stepdown converter. Such components are easily available on Aliexpress or local electronics webshops.
Thank you for your answers!
Indeed there is a lot of PoE splitters out there that doesn’t specify what Mode they support. Thank you for the Mode info on the Mikrotik passive PoE as I had missed that. Should make it somewhat easier to narrow down.
A buck converter might be a solution but I hope to avoid it. Though using the Mikrotik PoE injector as a splitter was news to me, might come in handy. I already have those from my APs.
Only major reason is that I want to run all my network equipment on the UPS. It’s just for home so can’t say I really NEED it though…
Don’t really want to save on using an extra PSU either, it’s just that I fear that if I inject PoE using the CPEs original PSU then it would be too much voltage drop over the network cable. Then your suggestion of splitting the RB4011s PSU cable or just buying a adjustable PSU is an option. But then I think the buck converter at the CPE like jaclaz suggested is a better solution.
My search will continue and if I find something viable I’ll report back!
Yep, essentially a "passive" (NOT 802.3af/at/bt) injector has provisions to:
allow data (only) to pass through the device
inject the voltage from the DC jack to the "PoE" side
Most if not all such devices are bi-directional. i.e. the splitter has provisions for:
allow data (only) to pass through the device
split voltage from "the PoE" side and provide it to the DC socket (or - in other words - inject the voltage from the "PoE" side to the DC socket)
The pairs of passive splitters that are common for non-PoE cameras are actually two of the same device splitter/injector the difference between them is only that one has a DC jack and one a DC socket.
This doesn't mean that all injectors can also be used as splitters (with the addition of a DC jack/socket "gender changer"), but most will, and the Mikrotik ones can, see as reference: MikroTik RBGPOE - usable as PoE splitter?
There also exist devices that can take 802.3af/at on an input and provide passive PoE on the output. They only have 2 RJ45 connectors.
As they usually output 24V (with 48V input) they are not usable for the use-case of this topic (which would have required something like an RB5009UPr anyway).
