Installing a NMEA 2000 backbone

One of the things we liked about our new Garmin chartplotter that we installed in December was its connectivity.

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The chartplotter was our first electronic device with a NMEA 2000 plug.

NMEA stands for National Marine Electronics Association, and 2000 is the standard set for communication between devices. Garmin sticks with a NMEA 2000 nomenclature, but Raymarine SeaTalk, Simrad Simnet, and Furuno CAN are all rebranded NMEA 2000 systems that only need a plug adapter to be compatible.

Theoretically, any two NMEA 2000 devices will connect and communicate with each other no matter the brand. However, since we’re starting from scratch when it comes to the electronics on Gimme Shelter, we decided to stick with Garmin as much as possible.

The first step to setting up any NMEA 2000 system is to install the backbone. We went with this Garmin NMEA 2000 Starter Kit that cost about $60 through eBay.

NMEAstarterkit

The only directions that came with this kit was the diagram on the label. That’s it. It’s THAT simple. However, I chose to hook the yellow cable, which is the 12 volt power cable, to the chartplotter circuit on the back of my breaker panel instead of directly to the battery.

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Once it was tied into the power system, I started adding T connectors. (Note that there was terminator plugged into the open end of the backbone when I finally took the photo.)

Tconnectors

The starter kit came with two T connectors and two terminators. I ran a cable from one T to my chartplotter. I ran the other cable to my GWS 10 Wind Instrument.

GWS10

I switched the chartplotter to the “gauges” setting, chose wind, and … nothing.

Nothing happened at all. It didn’t work.

I stared at the diagram. I retraced my wiring. I pulled the breaker panel off again and re-checked my power connection. It just wasn’t doing anything.

I finally resorted to Google and almost immediately I found out the most important detail of this system.

NMEA 2000 doesn’t work unless there is a terminator on every open T plug!

The starter kit had come with two terminators, and I hadn’t bothered to put them on. I figured they were just to keep the dust out or something. Wrong. It turns out there’s a resistor in those terminators, and unless they’re on the open plugs, no signal gets sent anywhere.

So after plugging a terminator onto the end of the backbone, I turned on the chartplotter again. This time I had success!

windinstrument

Now all it takes to add new devices to my system is another T and a NMEA 2000 cable.

Of course, setting up the backbone was the easy part. The real fun starts this weekend when I climb the mast to drop a new cable and mount the wind instrument.

Catching up on projects

It rained all weekend here, but just because we couldn’t be out on the boat didn’t mean we couldn’t catch up on some long-running projects we’d been putting off.

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About a year ago a friend snagged us a free sail for some unknown boat off craigslist because we had seen bags made from sail material at the boat show, and Mary was going to try to make us one. She got it started, but you know how it goes, things get busy, you forget what you were doing, etc. After some weekend work, prototype bag #1 is finally coming together. Hopefully it won’t be another year until it’s finished, but don’t hold your breath waiting on a line of hand-made Gimme Shelter boat bags to be available any time soon.

But Mary isn’t the only one with long-running projects. I started laminating together oak and poplar for a new table many months ago. Then about halfway through the job, I got distracted.

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I’m catching up. Just one more plank to glue on before I start planing it down. Then there’s the sanding. Then there’s the routing. Then there’s the staining and varnish — yeah, it may be another month or two before I finish this one.

Meanwhile the garden is growing like crazy. We have so many greens we can hardly eat them all, the cauliflower is ready to eat, and we will have squash very soon.

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Mary is doing her best to come up with new ideas for all this garden food. She also just purchased The Boat Galley Cookbook, so hopefully we’ll learn some new recipes for when we’re afloat.

And then there’s the new projects we’re starting together even though we haven’t actually finished these old projects.

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After our trip to Laguna Harbor we decided we wanted to know wind speed and direction, so I’ve got to get our NMEA2000 backbone installed and mount the new Garmin GWS 10 wind instrument at the top of the mast.

When I look at the list of projects, sometimes I wonder when we ever have time to go sailing.