Homework: Marine Electronics

I wouldn’t say that Journey has state-of-the-art electronics, but she has a good system that should have a couple more years left.  The issue is that some pieces are talking to each other, but others are not.  The thing about boats, the older ones anyway, is that the systems are often aftermarket installations as upgrades or replacements, and there are sometimes compatibility issues between the different pieces of hardware.  But part of new technology is interfacing with old technology, so usually there is a way to get everything talking to each other.  We technically have all the information that we need without going to the trouble of trying to network the different pieces together, and there are definitely those that go with less, but since it should only be a matter of additional wiring, I think it is worth the expense and effort in exchange for the additional functionality of the instruments which should prove to be very helpful when underway.

One thing that simplifies the network is that all the instruments are the same manufacturer except one, the chart plotter  and getting most of the components talking should not be that complicated.  Unfortunately, the GPS information from the chart plotter is really the information that needs to be communicated to the other instruments so I also have to deal with connecting components of two different manufacturers.  After taking the nav pod covers off and taking a look at what was connected to what, I figured out why the instruments were not talking to the autopilot, they are on different power circuits.  This should be just be a matter of buying a proprietary (read as $$) cable for plugging into the empty port on the autopilot and splicing into some existing wiring.  The instruments and autopilot all speak the same language so it should be pretty much “plug & play” assuming I splice the connections right.

Marine Instrument Wiring

Hmmm, a lot of wires all the same color.  At least it’s dry in there!

Getting the GPS data to the network is going to be a little more difficult though less costly than what I described above because no proprietary plugs are involved, only plain-end wiring.  I have done some research through the owner’s manuals and internet, and found that there is a standard marine electronic language that both equipment manufacturers speak and figured out that the autopilot course computer should be able to then convert and send the GPS information to the other devices on the network.  The biggest issue is that I will need to run 2 cables from the nav station to the base of the helm in order to make the connections.  I would prefer to just run one cable consisting of more wires inside, but I read that the cables should be shielded and grounding the shield is required.  All I could find that would keep the project cost to a minimum was two-wire cable with a shield and drain, so I will just run 2 of those.  It all sounds good in plan, but who knows if it will work.

I have had this little project in my brain for a long time now.  It was not high on my priority list, especially since I knew it was going to require homework, but I felt it was good to understand how the electronics were communicating with each other in the event that something quits one day.  The homework part so far has taken several hours comprised mainly of reading owner’s manuals and internet research, but also some time for tracing wires and planning the connections was involved.  I found a lot of useful information on some of the older communication protocols at these links: NMEA Beginner’s Guide and Beginner’s Guide to Seatalk.   I am pretty sure I know what I am going to connect to what, all that is left is to purchase the cables, do the installation, and hope for the best!  Stay tuned for the results!


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