Here are a few of the types of data you can view on a state-of-the-art network display (B & G Zeus Z12): Chartplotter display at left that has your layline with tidal corrections (red and blue lines); Broadband Radar at upper right; 30-minute time plots showing history of True Wind Direction (TWD) and True Wind Speed (TWS) at lower right; Instrument readings across the top from left—Speed Over Ground (SOG), Course Over Ground (COG), GPS Position, Time.
Networking Your Boat’s Electronics
In this era where you can surf the web, take photos and play your MP3 song files on your smartphone, it’s all about being connected. Boaters want to connect their VHF radio to a GPS, monitor their fuel consumption and see radar images on one display. Our electronics suppliers have made all of these networking tasks simpler, and our web site shows an exploded universe of choices, especially products built to the NMEA 2000 network protocol. We’ve provided diagrams showing systems by Raymarine, Garmin, Simrad and Mastervolt, so you can look and compare.
Do you own an older boat? We’ve owned a few, most recently a 1975 “Plastic Classic” 30-footer with a rat’s nest of wires behind the ancient, basic electrical panel. Other than the new VHF radio, the electronics are equally obsolete. Sound familiar? This nearly hopeless mess just begs for a complete tear-out and rebuild, and we’re still working on that. As we’ve designed our new system, we have found the resources listed on this page a big help. Standard-setting organizations (NMEA and ABYC) create the rules for designing your network. Manufacturers like Garmin, Lowrance and Maretron have loaded their web sites with educational material, and journalists like Ben Ellison (proprietor of the Panbo blog) astound us with tests and reviews of the latest incredible electronic gadgets. We enthusiastically recommend his blog.
You may want to connect your laptop to your onboard network, or interface your new AIS unit with a new VHF radio, so you can view information from all these sources onscreen. How easy is this? A quick look at the current assortment of networking standards will show what the choices are.
NMEA 2000: Our three primary manufacturers (Garmin, Raymarine/FLIR and Simrad/Lowrance) all provide comprehensive systems built to the newest networking protocol. When we first heard about NMEA 2000 it represented something like the “Holy Grail” of networking, because it allows plug-and-play connection of any product from any manufacturer, as long as they are all built to the certified specifications. Build your own network with a Lowrance fishfinder, Simrad Broadband 3G radar, Mastervolt inverter/charger, engine monitor, laptop computer, Maretron ultrasonic wind sensor, Teleflex controls, etc. Pick the best model of every type of device, stick them together like Tinkertoys with standardized wiring and information exchange language, and assemble your own instant plug-and-play network. With five conductors (two for data, two for power and a ground), keyed male and female ends, heavy shielding from electro-mechanical interference (EMI) and waterproof construction, the system is virtually idiot-proof.
CAN Bus Networks: NMEA 2000 is a Controller Area Network (CAN) bus technology, developed for automotive, robotics and industrial control applications. It uses standardized “trunk” or backbone cables, tee connectors, and branch lines called “drops” or “stubs.” A similar and compatible standard, J1939, was developed by the auto industry, and is being used in new marine diesel engines. They can communicate via NMEA 2000 with an interface adapter, as can many newer Evinrude, Mercury, Suzuki and Yamaha outboards. When connected to the network, some displays show “virtual engine gauges” onscreen.
In our Electrical section is a CAN bus system developed by Mastervolt. Three diagrams show systems for boats ranging is size from a small center console up to large yachts. Even more interesting are their electric hybrid propulsion systems, in our Boats and Engines section (see our West Advisor Electric & Hybrid Propulsion Systems).
Simplified drawing shows the backbone and drop cables of an NMEA 2000 network, connecting various devices and power sources.
Ethernet-based Networks: Raymarine, Navico (parent company of Simrad, B & G and Lowrance), Garmin, Furuno and other manufacturers have created their own proprietary communication protocols and cables, connecting devices with high-speed Ethernet connectors. With the greatest available bandwidth of 100 megabits/sec., these systems have become the standard for sharing large amounts of data from radar imaging, electronic cartography and video cameras. Usually they’re installed alongside NMEA 2000 networks, which handle systems monitoring and control.
Garmin’s very elaborate diagram shows Ethernet cables (green Garmin Marine Network) that handle the video. Blue cables are NMEA 2000 network that tie most of the devices together. Some receive 12V power on the NMEA 2000 bus. Garmin Network Diagram
NMEA 0183: We still have more of the “old-style” NMEA 0183 products in our catalog than their replacements, and we can’t declare this staple of the marine industry dead quite yet. The end of “oh won ate three” may not come soon, even with all the proprietary and high-speed network protocols on the market. NMEA 0183 has served us reasonably well since, well, 1983, but as devices have become more sophisticated, newer standards have increasingly replaced it. Simple devices, like a basic fishfinder, still use 0183 as a serial data interface, even if it is not a true network.
NMEA 2000 Technical Details
Groups of Data: All data transmitted on a NMEA 2000 network is organized into groups, referred to by Parameter Group Numbers (PGNs). NMEA 0183 data was grouped into smaller packets that were called Sentences.
Power for NMEA 2000 Networks: NMEA 2000 networks operate on 12V DC power only. Use an NMEA 2000 power cable to connect your NMEA backbone to the auxiliary power switch on your boat. If you do not have an auxiliary power switch, or if connecting to the auxiliary power switch causes electrical interference, connect the NMEA 2000 power cable directly to the battery and install an in-line switch. Be sure to ground the NMEA 2000 power cable. Ground the drain wire (bare) to the same location as the ground wire. Simrad network for a large powerboat
Load Equivalence Numbers: All NMEA 2000 certified devices have a Load Equivalence Number (LEN), which represents the current requirement in multiples of 50mA. The LEN for each device should be printed on the device, or provided with its documentation. A LEN of 4 means that the device consumes up to 4 x 50 mA = 200mA. The installer should ensure that the network can supply enough power to support the connected devices by totaling the LENs of all devices. Mini cable used on most recreational boats, with a 4-amp rating, has a LEN capacity of 80 (80 LEN or 80 x 50mA).
You can connect power to the backbone at either end or in the middle. When planning where to place the power cable and T-connector on your NMEA 2000 network, you will need to evaluate how the devices that use power are connected to your network. NMEA 2000 networks will work properly as long as there is no more than a 3V DC voltage drop between the device located farthest from the power source on the NMEA 2000 network. If the calculated voltage drop is less than 1.5V, then it doesn’t matter where along the backbone the power is inserted. If the calculated voltage drop is between 1.5V and 3V, the power connection should be near the mid-point of the backbone. To determine the voltage drop on your network, use this equation:
Voltage Drop = Cable Resistance (ohms/m)* x Distance (from the battery to the farthest device, in meters) x Network Load** x 0.1
*Typical resistance value for Mini cable: 0.053 ohms
**Network Load = the sum of the Load Equivalent Numbers (LEN) between the battery and the end of the network. The LEN for each device should be visible on the device or provided with its documentation.
Cabling Standards and Variations: Garmin, Maretron and Lowrance (red cabling) use standard NMEA 2000 connectors. Lowrance with LowranceNet Blue, Simrad with SimNet and Raymarine with SeaTalkNG have built proprietary cabling that is electronically compatible, but doesn’t conform to the NMEA size and shape standard. You can create mixed networks with standard and non-standard wiring, using adapter cables to connect the two cabling types. All connectors contain O-rings and are designed to be watertight. Connectors are either male or female, and when planning a network the gender sequence of the cabling must be mapped out carefully.
Don’t be intimidated! NMEA 2000 really will make building a new network much simpler than under the old 0183 interface standard. Just dive into the resources that are available, then start the Plug-and-Play networking.