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How I built the NMEA network


I must start by saying that I don't understand electronics very well, and not at all how all the devices are connected on a boat. However, with the help of the Internet, and as a result of a forced stay on land, I decided to build a complete network of devices for my boat in the comfort of my own home.


NMEA


This mysterious word is an abbreviation of the letters of the National Marine Electronic Association, an international organization founded in 1957 in New York, which brings together electronics manufacturers for the maritime industry. The NMEA has established communication standards so that the products of individual manufacturers can communicate with each other without restriction.


There are currently two standardised systems on the market, the older NMEA 0183 and the newer NMEA 2000. In addition to these networks, there are several other interfaces, such as SeaTalk from RAYMARINE, which although they have different connectors, they can be interconnected.


What does it actually allow? Thanks to a unified communication system, you can connect products (displays, chartplotters, information collectors, etc.) into a common network, and they will understand each other and share information.


NMEA 2000 network


To build a network for my boat, I chose the newer NMEA 2000. The structure appears very simple, a backbone network to which individual devices are connected. Low power devices can draw energy directly from the network, high power devices (such as a chartplotter) must still have their own power supply.


The network is illustrated in the diagram above (source www.svb.de). The description is as follows.


1. Backbone network. A cable that runs throughout the boat, with a maximum length of 100 metres, so satisfactory for most leisure boats.


2. Network termination. The network cable must have a terminator (a special resistance connector) at both ends of the cable.


3. Drop cable. A cable connecting the individual devices with the network (maximum 6 metres in length). This cable is connected to the network by a T-piece, allowing through connection of the network cable through the horizontal male/female connectors, and a device port on the vertical leg. T pieces are available with 1, 2 or 4 device ports, but can also be connected directly together for any combination of device connections.


4. Power source. Connected to the 12V marine batteries, and connected near the middle of the network to reduce voltage drop between the extreme ends of the network.


5. Devices. Any NMEA 2000 compliant device or information source can be connected to the network. These include chartplotters, display units, VHF radio, hi-fi system, etc.


6. Data sources. Any NMEA 2000 compliant information source, autopilot, GPS, compass, wind vane, tridata (depth, speedometer, temperature), AIS, wi-fi interface, internet router, etc can be connected to the network.


The advantage of the whole system is that individual devices can share information. As an example, you can display the wind direction and strength directly on the chartplotter. Adding further devices is simple, just add another T-piece and connect the new device directly into the network (such as a second plotter to the chart table or skippers bunk).


If you have a wi-fi interface connected, it is possible to stream this data direct to a smartphone or tablet.


Even if you have an older NMEA 0183 network installed on your boat, it is possible to connect these devices to the NMEA 2000 network using an adapter.


The network is built on the ‘plug & play’ principle, so the devices can read all the data automatically. Another advantage is the ease of installation, no soldering or complicated cable interconnection. It just all plugs together using standardised connectors.


COSTS


What are the hardware costs for all this?


The costs for networking will depend on the complexity of your onboard equipment, but for a typical leisure yacht would be:


· Garmin GPSMAP 922 - 650 EURO

· Garmin Wind and tridata + two displays - 850 EURO

· Garmin GPS antenna - 200 EURO

· Network cable 10 metres - 50 euros

· Device connecting cable - from 16 EURO for 0.5, to 50 EURO for 10 metres

· T piece (1 port) - 16 EURO

· T piece (4 port) - 45 EURO

· Starter kit (contains three T-pieces, termination connectors, power cable, one 5 meter cable, one half meter cable) - 85 EURO This link provides detailed instructions for setting up an NMEA 2000 network.


The advantage of the whole system is the relative ease of installation, so nothing prevents you from installing the NMEA network around your boat yourself.


And whilst locked down with COVID 19, you can mock up the installation around your house.

I wish you much success.


https://static.garmin.com/pumac/Tech_Ref_for_Garmin_NMEA2k_EN.pdf

Honza





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