DIY 12V PoE Injector for Ubiquiti Nanostation

Background

During the Winter of 2012 we faced the challenge of connecting a clinic in Gulbahar to one of our offices.

No landlines were available and there is no line of site with the office, where a VSAT and VPN router were installed. Both sites are over 6km apart.

Plan

The solution found was to install a repeater station in a small village strategically located on a slope with clear line of site of the two points.

Constraints

Of course in Afghanistan electricity is a problem, so the solution had to include an independent self contained power supply. Solar was obvious, plus we had an used kit already in the office.

Optimizing

Using standard equipment, the setup would require:

• solar panels
• solar regulator
• battery
• inverter
• 2 PoE injectors
• 2 bridges

In order to reduce the electrical losses (conversion of 12VDC to 220VAC to 15VDC) and to keep the setup as simple as possible, we found out that the Ubiquiti bridges work well from 9-20VDC.

Therefore it would be possible to feed them straight from the solar regulator.

Solutions

No commercial 12V PoE injectors were found in the local market, so we had to go for a custom built solution.

PoE is a very straightforward thing. The schematics are here and easy to adapt.

We used a standard CAT6 network housing and components from an old UPS.

Schematics:

LED and Resistor are just for control

Capacitors are used as filters

Implementation

PoE Injector (note the 12VDC cables in the bottom)

The full kit before deployment

The operational setup in Gulbahar