Power connection on Ubiquiti devices

[Authorless]

I would like to know how to connect the cables between the Nanobridge M5 and the power supply Active POE injector and between the power supply and the HUB, because there is no diagram in the box.

[Sergio Bertana]

All Ubiquiti products are devices Power over Ethernet o PoE (its acronym), this is a technique that allows you to power the equipment using the same cable that connects them to the Ethernet data network. The IEEE has defined the rules for PoE with the standard called IEEE 802.3af (Connection scheme).Warning! The Ubiquiti devices while being PoE, are not compatible with the 802.3af standard regarding the supply voltage. The 802.3af standard requires devices to accept 48 Vdc voltages while Ubiquiti devices accept 24Vdc at most (See post). To make Ubiquiti devices compatible with the 802.3af standard, the 802.3af POE adapter must be inserted on the network cable that connects them to the PoE switch. L'active POE injector and passive POE injector they must be plugged into the network cable that connects the device to the Ethernet network. The two devices are identical in operation, on the outlet LAN the incoming ethernet network (switch / company hub) must be connected to the socket POE the Ubiquiti device must be connected. Any network cable (See diagramThe active power also has the power supply circuit inside, so just connect it to the mains, while the passive power will be powered with an external power supply.

[Sergio Bertana]

To connect the power supply or the passive PoE to the device, a normal ethernet patch cable, compatible with the EIA / TIA-568A standard (used in Europe) or EIA / TIA-568B (used in the USA).

Since the pins used for the power supply are the 4/5 pair for the positive, the 7/8 pair for the negative, a cross cable can also be used but it is necessary to be sure that the inversion of the Tx and Rx signals is accepted. from the connected device (All modern devices self-adjust). Connections diagram patch and crossed cables.

Warning! do not use Gigabit crossover cables, this type of cable crosses the 4/5 pair with the 7/8 pair, reversing the polarity of the power supply on the device.

[Raffaele]

I would like to know if I can use this POE power supply for a generic IP camera. I report the power specifications taken from the camera datasheet:

Operating voltage: Power-over-Ethernet (802.3af Class 0); 24 V CA / CC to 0,29 A;
Energy consumption: 24 V to 0,33 A / max 8 W

[Sergio Bertana]

The POE 802.3af adapter provides an output voltage of 16Vdc @ 0.8A so unless your camera does not work even with a minimum voltage of 16Vdc this adapter is not good. You can optionally use a Active POE injector from 24Vdc. I am not a POE expert but I take the following from Wikipedia:

L’alimentatore compatibile 802.3af applica inizialmente una tensione compresa tra 2,7V e 10,1V e misura la resistenza da 25K che dovrebbe trovarsi in uscita. Se la resistenza di riferimento non viene trovata fornisce un’alimentazione di 24V (considera l’utilizzatore non compatibile 802.3af).

So if your POE switch is compatible with the 802.3af specification it should already automatically power the camera at 24Vdc without inserting any adapter between the two.

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