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zolakt
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Powering 5 devices with POE and 1 power adapter

Mon Jan 16, 2023 3:44 pm

Hi,

I have 1 x RB4011iGS+5HacQ2HnD-IN, and 4 x hAP ac².

Is it possible to power them all with one power adapter, and some RBPOE injectors?
Specifically, these injectors: https://mikrotik.com/product/RBPOE

The RB4011 is my main router. From it I have 4 cables going to the 4 hAP ac2s.
For those hAPs, I'm limited with power outlets in some places.

So, my plan was to have a single power adapter near the RB4011, to power all of them with POE.
The RB4011 has 1 POE-out port, so I would power 1 hAP from that.
For the other 3 hAPs, I was thinking of getting a POE injector for each of them.

I would place them near the RB4011, and power everything with POE.
I have a DC splitter cable, with 1 input, and 4 outputs. Something similar to this: https://bilder.tragant.de/produkte/orig ... 559108.jpg
I would connect the RB4011 + 3 POE injector to those outputs.

Is that possible?
If so, can someone recommend me the power adapter that is suitable for powering all of this?
Is the one that comes with the RB4011 good enough, or do I need a "stronger" power adapter?
If so, can someone recommend me the specs for the power adapter, that would be suitable for this?
 
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mkx
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Re: Powering 5 devices with POE and 1 power adapter

Mon Jan 16, 2023 4:55 pm

RBGPOE injector (gigabit version of RBPOE you linked) are compatible with all MT devices (so far). They are completely passive, they pass whatever voltage supplied via UTP cable to the other end. These POE injectory are intended to be used with supplied power adapter, so voltage should be fine.

If you want to use DC splitter cable, it should be fine as well. Just make sure power adapter you'll use is a quality one and that it supplies voltage suitable for all devices, powered by it. hAP ac² can work with 12-30V, RB4011 can work with 12-57V. You should not use higher voltage than devices can stand, otherwise they can be damaged.
Proper DC distribution would feature a fuse (use proper amperage, appropriate for each device connected, with slight reserve, such as 20%) per output so a short on one of branches would not cause any damage to any other connected device nor to power adapter. The DC breakout cable you linked does not have fuses. Power adapter should be strong enough to power all connected devices up to rated power consumption. RB4011 is rated at 23W, hAP ac² is rated at 16W. If you want to power all 5 devices using same power adapter and with 24 Volts (which is accepted by all devices), then you need power adapter with at least (23W + 4*16W) 87W power output. At 24V that's almost 3.7A ... and none of Mikrotik's 24V adapter has needed capacity.
 
zolakt
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Re: Powering 5 devices with POE and 1 power adapter

Mon Jan 16, 2023 5:24 pm

Thank you for the reply. It was very helpful.

I haven't bought the injectors yet. I'll definitely get the G ones.
Btw. does anyone know of an alternative for the RBGPOE injector, but with a longer cable?
Or without an attached ethernet cable. So it's just a box with 2 female RJ45 ports, and a DC input.

I do have the DC splitter cable already, but those are cheap. I'll try to find one with a fuse.
I didn't fully understand you though. Does each of those 4 outputs need to have it's own fuse, or is there a single fuse for all of them?
If each of them needs a separate fuse, it might be tricky to find the cable which fits the specs exactly.
I mean that one output has a fuse for the RB4011, and the other 3 for haps. Since the RB4011 and the haps don't have the same amperage.
If you have a specific breakout cable in mind, could you please link it?
If I can't find one, I guess the alternative would be to use 2 power adapters.
One dedicated for the RB4011, and the other one for the remaining haps.
I suppose it would be easier to find, since it wouldn't have mixed fuses.

One more question regarding the power adapter...
I assume too much ampers can't hurt, or am I wrong?
I was thinking of using a power adapter from an old laptop. Those are usually at lease 3A, or stronger.
I would get a 5A one, if too much amperage isn't a problem.

Sorry, if some of these questions are stupid.
I'm far from an expert in this field.
 
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mkx
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Re: Powering 5 devices with POE and 1 power adapter

Mon Jan 16, 2023 6:25 pm

Does each of those 4 outputs need to have it's own fuse, or is there a single fuse for all of them?
The idea is to have one fuse per output. If it's a common fuse (and needs to handle all load), then you may go without it ... perhaps power adapter will have one or it will blow instead of fuse ...

I assume too much ampers can't hurt, or am I wrong?
High-power power adapter doesn't hurt as long as there are no shorts. PA doesn't "push" amperes, it delivers. So if attached devices don't draw much, that's fine.

I was thinking of using a power adapter from an old laptop.
Check PA's voltage, often they are around 19V which is fine with MT devices ... and check its Wattage, it has to be higher than sum of wattages of your mikrotiks (23+3*16 = 71W or 87W if you have 4 hAP ac2s ... you have lost me). Lower voltage at same wattage means higher amperage (which in turn means higher loss in UTP cables, hence need for some reserve in PA output power). However, MT devices will draw almost same wattage regardless supply voltage, so it's easier to calculate with wattages.
 
zolakt
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Re: Powering 5 devices with POE and 1 power adapter

Mon Jan 16, 2023 6:59 pm

The idea is to have one fuse per output. If it's a common fuse (and needs to handle all load), then you may go without it ... perhaps power adapter will have one or it will blow instead of fuse ...
Thank you for the reply again. I see...
That will be difficult to find though, due to different amperage.

As an alternative, could I use a breakout cable without fuses, and use these injectors instead?
https://mikrotik.com/product/gesp_poe_in

Another alternative, I guess, is to use the breakout cable that I have, cut the wires, and solder the fuses that I need.
 
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mkx
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Re: Powering 5 devices with POE and 1 power adapter

Mon Jan 16, 2023 7:13 pm

GESPs will be overkill. And me fussing about fuses ... could be it's just me. I'm pretty sure hundreds of break-out cables you linked are out there and probably none started a fire (yet). So you may get away without fuses just fine.

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