Hello everyone,

I would like to use Mikrotik SXT LTE kit to provide internet and power for an IP camera (Uniarch IPC-B314-APKZ).

The Mikrotik kit comes with a 24V adapter and a passive PoE injector which I would use to power it via eth1 (PoE-in), leaving the other side of the ethernet disconnected. Then, I would use eth2 (PoE-out) to connect the camera.

However, I’m not sure if this will work or if it is safe.

According to the camera’s specifications, it requires 12V DC or PoE, but no more information is provided. I’m not sure how the output voltage of Mikrotik eth2 passive PoE-out port is controlled, if it is the same as input (so it will be 24V), or if it is possible to adjust it in settings.

My alternative plan is to use a 12V adapter to power the Mikrotik, and maybe a passive PoE splitter to power camera via DC. This seems like the safest option to me.

The Mikrotik will deliver from the out-Poe port the same voltage it receives on the in-Poe port.
Additionally, the amount of current delivered will be limited by the Mikrotik at around 600 mA.
600 mA @ 24V are around 14.4 W, but depending on the length of cable between the SXT and the camera it may drop a few volts, thus providing less than 14W, that camera needs only 7.5 W so it is fine, BUT you need a converter from 24 V to 12 V.
Poe splitters converting from 24 V to 12 V do exist, if the camera has (as they normally do) a 5.5 mm jack, that's all you need, otherwise you can use it to split and convert and then use an injector to re-inject the 12 V to the ethernet cable going to the camera.
Additionally it has to be seen if the PoE 24 V power supply you got with the SXT is powerful enough for both devices, it is a 24 V 1.2 A one so it delivers in theory 24*1.2=28.8 W.
The SXT is rated to be between 5 and 22 W by itself so when you add to it 7.5 W you are a little beyond the limit of the adapter (in normal operation the SXT won't likely reach 22 W, still ...).
You can power the SXT with its original adapter and have a second 12V Poe power supply for the camera, it depends on where you have the mains.
To power the 7.5 W of the camera at 12 V you will need 7.5/12=670 mA in practice a 800 mA or 1A will do, I have to repeat how the length of CAT5/6 cable between the power supply(ies) and the device(s) will lower the voltage (and power) delivered, and this effect is more relevant when using low voltages such as 12V.

Thank you for your detailed response.

IMHO SXT itself uses max 5W only, and the 22W is meant to be with an attached device in PoE-out. But maybe i'm wrong here.

The power consumption under maximum load can reach 5 W, with attachments 22 W.
- https://help.mikrotik.com/docs/display/ ... s-Powering

24V to 12V PoE splitter would be great, but I can’t find one locally.

I’m still not sure if the PoE in camera is limited to 12V only like a DC jack or what voltage range is supported, as there is no more information available. If it supports 24V, then the problem would be solved. I have already asked the camera manufacturer support but haven’t received an answer yet.

I'm considering two other options
- using a 12V input instead of 24V, but the current from STX PoE-out to camera will be a bit over the STX limit (7.5W/12A=625mA).
- using a 12V adapter, split output and and connect camera directly to DC and use injector to power STX connectet to eth1.

Thank you again, I appreciate your help.

Google says your camera supports 802.3af POE only, which SXT LTE does not support.
You may have some luck if you power your SXT with a 48V power supply and then force the POE-out to be always on, but this may as well not work (or even burn your camera).

Usually (but not always) cameras have a 5.5 mm jack and are powered at 12 V, then they may have additionally Poe functions, the ,pdf with the specs you pointed to is - to say the least - vague on the specific matter.
Poe on itself can be anything and the contrary of it.
There is also the not-so trifling issue of which wires are used for Poe (they could be Mode A or mode B if actually 802.3af compliant) or however either use 1/2 and 3/6 or 4/5 and 7/8.

It's a mess.

If (and it is a big if) mode B is used you can "extract" the voltage without any particular circuit (and then use any 24V(or 48V) to 12V step-down converter you can find) but it is mode A (i.e. the power is on the same wires as data) you do need a splitter, you still can use a compatible splitter and then use an external 24V (or 48V) to 12V converter.

Mikrotik docs are only slIghtly better, I also have a doubt on what Mikrotik says about with or without attachments.

It sounds to me strange if the device by itself is only 5W that they provide a 24 V 1.2 A power supply (usually these power adapters/converters are more efficient when the load is a certain fraction, like 2/3 to 3/4 of the maximum output and even if we are talking of a handful of Watts it would not be as efficient as it could be).

By the way, the page:
https://mikrotik.com/product/sxt_lte_kit
talks of 24 V / 1.2 A power adapter, while the page here:
https://help.mikrotik.com/docs/display/ ... s-Powering
talks of 24 V/ 0.8 A power adapter, it is well possible then that the 22 W are the total and that new units with the 1.2 A PSU cover those also.