The future of boat electronics - Power over Ethernet (PoE) and OneNet

Power over Ethernet has become increasingly popular among routers through the sheer power of due to its availability and the possibility of flexible installations. The technology makes it possible to send power via network cables. This makes PD (Powered Devices) work with only the network cable connected, rather a separate cable for power.

PoE works without special cables or connectors, it uses nder the 8 wires (4 pairs) already present in a standard Cat5e cable. They can be used to send both current and data over the same pair, or separated between current and data pairs depending on; connection method and speed.

As the new OneNet standard supports PoE, we will likely see more installations using it. Så let's find out what it's all about...

Methods to transfer power

There are 3 standard methods to transfer different effect, such as "Option A", "Option B" and 4PPoE. These are standardized in IEEE 802.3.

Options A and B are used for 10BASE-T, 100BASE-T and 100BASE-TX because only two of the four pairs in a cable are used for data transmission. 4PPoE is used for higher speed connections of 1000BASE-T, 2.5GBASE-T, 5GBASE-T and 10GBASE-T because all four pairs are used for data transfer.

< p>Alternative A (common-mode) uses the same cables for data and power in both 10 and 100 Mbit connections. This can be achieved using a technique similar to Phantom Power. (More on this later...)

Option B (spare pair) takes advantage of the fact that the spare pairs are not used for data transmission, by sending power ö ;ver they twoå unused pairs.

4PPoE (4 pairs) uses all 8 wires (4 pairs) within a category cable for data transmission, enabling much higher speeds . This also makes it possible for all four pairs to add power, allowing much higher power devices to use PoE.

Nördlä ge

Phantom Power is common in the audio equipment industry, where DC is sent through microphone cables to control the internal electronic circuitry of the microphone. The term "phantom" is due to that the power cannot be seen because there is no power cable. Although Common-Mode (A) does not use this exact method, it does use something very similar.

The way this works is that current is supplied each pair of data lines with a common voltage. Since differential signaling is used with twisted pair Ethernet, this means that the current does not affect the data. The common voltage is removed/extracted via the Center Tap, leaving only the differential voltages. This voltage is usually between 44 and 57 volts, usually at 48-50V.

For example; If 50V is applied, the current signal (let's see bit 0) is 50V, while the data signal (bit 1) is now 55V. When this 50V common voltage is removed at the other end, bit 0 @ 0V and bit 1 @ 5V remain. These 0V and 5V are your data, which is then sent to the differential receiver for data.

Where does OneNet come into this?

OneNet supports PoE because the standard is based on IEEE 802.3 Ethernet Local Area Network. Specifically, it will allow up to 25.5 W of power to be transferred via Ethernet, according to IEEE 802.3at PoE+. This provides a much greater power capacity.

It is worth noting that although there are older Category 3 (Cat3) cables etc. being used for PoE, the OneNet standard specifies that a minimum of Cat5e cable should be used. Everything that refers to Ethernet cables and wires in OneNet is from Cat5e or higher. Cat6 and Cat6e cable for example are also supported; for higher speeds.

Cables older than Cat5 such as Cat4 are untwisted wire pairs, which are more susceptible to interference. ;n twisted pairs of wires.

PoE offers a number of advantages;

– Network expansion
to have power available at The network already means that the expansion of the network is easy with the use of PoE injectors and switches. The maximum length of an Ethernet network is not unlimited, but it is much longer than NMEA 2000 when Ethernet switches are used.< /p>

– Flexible installations
A device that requires power from a battery or wall outlet is limited to; the installation location. Having devices powered via a network connection means that there is no longer any limitation on; installation location or distance from an outlet/battery. In addition to this, when installing in narrow areas such as bulkheads, two cables always to be more difficult to mount one. Halving the cable number creates double så lots of room to work with.

– Time + Cost
Since there is no requirement for outlet or battery connection with power cables, the installation time is reduced in addition to the installation cost thanks to the absence of a separate power cable. A lower installation time means a lower cost from a price/hour perspective.

– Reliable and safe
All power delivered over Ethernet is safe because the PoE technology is intelligent, with an interface process between the PSE (Power Sourcing Equipment ) and PD (Powered Device) which allows the device to be detected by the source and determine how much current is needed to avoid over