What is the maximum current of 12V (PoE) in the UTP twisted pair?

Hello,

I am replacing analog monitoring with digital - it was IP cameras on POE. Since I will use a buffer power supply (30A capacity), the idea came to power the rest of the active and passive elements of the network also from this power supply (i.e. switches, router and network recorder). While there was no problem in the case of switches, I have a problem with powering the recorder. The power supply has dedicated 12VDC / 5A outputs, I connected a POE splitter to it and ran the power via twisted-pair cable up to the recorder (23m) - the recorder works, but it does not detect the disk. After connecting the original power supply supplied with the recorder (12VDC / 5A), the disk is detected without any problem.

Therefore, the question is - is there any upper limit of power that can be transmitted using PoE on UTP category 5e (wire)?

It all depends on the distance, the current, which results in voltage drops and probably the recorder does not have these 12V. Unfortunately, apparently the cross-section of the twisted pair is too small at this distance and with a receiver such as a recorder. All you have to do is power the recorder at the place of its installation.

If you want to power it from one buffer, it can be solved with a converter from 12v to 48v, send a 48v twisted pair and another converter from 48v to 12v next to the recorder.

The voltage drops are quite significant on particularly poor quality twisted-pair cables.

Therefore, you have active PoE at 48v

Hmm, this buffer has outputs for 12V cameras protected by a 1A fuse, and if it is as my colleagues write - i.e. that the problem is voltage, not current - maybe I could try to connect to several such outputs (plus change the fuse) and raise the voltage on them (from what I remember from the catalog card, there is a range of adjustment there - maybe that's enough) ... Because this dedicated 12V / 5A output, unfortunately, does not have any regulation. Fun with up / down converters that will pull these 5As, from what I can see quickly another few good stakes costs ...

EDIT: I just entered "step down" and "step up" on a well-known auction site, and the whole set will come out several dozen zlotys

The problem is with voltage drops, not voltage, and this is a difference, if you increase the voltage, it may turn out that when the recorder starts the disk and the load drops, the voltage will go up and may damage the recorder. The voltage drop depends on the consumed current, which is not always constant and the voltage will also flow when the conductor cross-section is too small.

Ok thank you - I will keep that in mind. The power supply allows you to increase the voltage to a maximum of 13.8V, so it should not be dangerous for equipment dedicated to 12V. Anyway, I will not be combining, since for a few nozzles I can have a proven and safe solution with converters.

The buffer always gives more and without any changes it always outputs 13.6-13.8
It is similar in the case of 24v and the real value is around 27.6v
At 48v it is almost 56v

The intensity cannot be too high, because you will burn a twisted pair.
I would not suggest more than 3-4A and the maximum is 5A.
Therefore, the higher the voltage, the better

Moderated By DriverMSG:

3.1.11. Don't post messages that add nothing to the discussion. They are misleading, dangerous or do not solve the user's problem.

smario11 wrote:

The current cannot be too high because you will burn a twisted pair.
I would not suggest more than 3-4A and the maximum is 5A.
Therefore, the higher the voltage, the better

What are you typing? It has no DC source, only a power supply and increasing the voltage may damage the device.
A simple situation, the recorder takes 5A with the disk working and the voltage on the recorder is 12V and at the power point of 20V, when the disk stops, the current drops to, for example, 1A and the recorder is suddenly powered with 19V and the fun is over, burnt.
The device will consume the amount of electricity it needs.
Referring to the active PoE 48V, it results only from the fact that devices in this standard have built-in converters, not that they are for 12V and the voltage is boosted to 48V only because of voltage drops because the device would go up in smoke.
The higher the voltage, the smaller the currents and the lower the voltage drops, and this is the sense of PoE 48V because a smaller wire cross-section can be used.

Belialek wrote:

is there any upper limit of power that can be transmitted using PoE on UTP cat.5e (wire)?

http://www.dipol.com.pl/zasilanie_poe_-standard_ieee_802_3af_oraz_ieee_802_3at_bib746.htm

spinacz wrote:

smario11 wrote:

The intensity cannot be too high, because you will burn a twisted pair.
I would not suggest more than 3-4A and the maximum is 5A.
Therefore, the higher the voltage, the better

What are you typing? It has no DC source, only a power supply and increasing the voltage may damage the device.
A simple situation, the recorder takes 5A with the disk working and the voltage on the recorder is 12V and at the power point of 20V, when the disk stops, the current drops to, for example, 1A and the recorder is suddenly powered with 19V and the fun is over, burnt.
The device will consume the amount of electricity it needs.
Referring to the active PoE 48V, it results only from the fact that devices in this standard have built-in converters, not that they are for 12V and the voltage is boosted to 48V only because of voltage drops because the device would go up in smoke.
The higher the voltage, the smaller the currents and the lower the voltage drops, and this is the sense of PoE 48V because a smaller wire cross-section can be used.

Read it again, but this time with understanding because you are confusing.
Nothing will burn because there is no way
I don't know where you got 20v and then about 19v.
There is no voltage drop and it will not be at 1m or how much it will do from the 48v converter

The voltage that comes out of the buffer is very important information, especially at 24v.
While in the case of 12v devices, 99% will work properly on the elevated one. In the case of 24v where it is already over 27v, strange things are happening on some devices. It is enough to read on the forums what the ubnt equipment does with such a power supply and therefore it is recommended to connect the 24v rectifier so that it is equal to 24v.
Therefore, at the very beginning, I proposed 12/48 and 48/12 converters right away because the voltage drops fall off, and with this voltage it does not have to worry about the intensity because on the other side it will not have the load requirements of 300-400W

I guess you don't understand anything where there is no voltage drop ??
Why is it not detecting his disk? It just does not detect the drive by the voltage drop because at this distance with a current of 5A the drop can be up to 5V.
On the current buffer, without adding an additional cable, there is no option to start, even if it turns up to 14V, this drop can give 9V at the recorder during startup, which will make it impossible to detect the disk.
There are three options:
1. powering the recorder directly from the network in the place where the recorder is
2. use of a second power supply, e.g. 24V, preferably 48V, and a suitable converter at the recorder, lowering the voltage to 12V
3. adding a wire with a larger cross-section to eliminate the voltage drop at this distance

I cannot add another power cord - currently the recorder is powered from the mains where it stands.

Tomorrow I would like to buy:

1) step-up converter (5A), IN = 12-32V, OUT = 12-35V
2) step-down converter (8A), IN = 4-32V, OUT = 0.8-24V

I will connect the step-up to the output of the power supply and set the output to, say, 24V, connect the step-down to the recorder and set the output to 12V. Will such a set work?

It should go, set the sending voltage to 30V so that the current is as low as possible.
At 30V, about 2A will fly.

spinacz wrote:

It should go, set the sending voltage to 30V so that the current is as low as possible.
At 30V, about 2A will fly.

I am glad that you finally understood what I wrote earlier and recommended my solution

Then write, buddy, a complete solution, not that higher voltage will not hurt, because someone will read the input to 20V and finally no converter and the device is burned.