Adding a NMEA 2000 device to my SeaTalk-NG network

[mrming]

My boat came with Raymarine electronics:

• e Series plotter
• EV-100 pilot with P70 control head
• Wind, depth, log

The rotary controller on the plotter is failing, so am planning to upgrade it.
My Em-trak b924 AIS transponder is currently connected direct to the plotter via NMEA0183.
The Axiom+ plotter I want to upgrade to doesn't have a 0183 socket, so I'd like to bridge the AIS transponder into the SeaTalk-NG network.

Am assuming I can use one of the Raymarine adapter cables to connect the AIS from its NMEA 2000 connector. Is this correct?
The current STNG devices are all connected via a 5 way connector which is full. How do I add another socket so I can add the above as a spur cable?

Any pointers greatly appreciated.

 

[KompetentKrew]

SeaTalkNG is NMEA 2000, just with different connectors.

NMEA 2000 has a "backbone" configuration like this:

You should always try to think of your network in these terms - your backbone might only be a short one right now, but conceptually it can go from bow to stern, with different devices T-ing off it wherever necessary.

The backbone has a terminator at each end, and in between is backbone cable and T-connectors.

The T-connectior is the "junction" by which actual devices are connected. (The cable between the device and the T is called a "drop cable".)

This is a SeaTalkNG style T-connector:

I think this is what you have:

This is really just 3 T-connectors in a single plastic case,​

With the Raymarine SeaTalkNG styling, the white connector is for the drop cable and the blue connector is for the backbone.

Probably the easiest thing to do is to buy another Raymarine "5-way" and then join the two with a SeaTalkNG backbone cable.

Then add the Em-trak transponder and the new plotter to the SeaTalkNG backbone using the appropriate NMEA 2000 to SeaTalkNG drop cables. I can't remember what gender you need, sorry, but it'll probably be apparent from inspection.

Useful search: Search Results for stng nmea |

 

[PaulRainbow]

The advice in post #2 is all correct, but there is also another option.

Remove one of the blue terminators and in it's place fit a STNG to N2K backbone adaptor. Connect two N2K T connectors to the backbone adaptor cable and fit a N2K terminator to the second T. You can now use standard N2K cables for the Axiom and AIS and if you decide to fit any additional N2K devices in future you can just add another T connector.

Another option would be to fit a 4 way N2K port instead of separate T connectors.

 

[Buck Turgidson]

One thing to look out for is the orientation of t connectors if extending the network they are not all oriented the same way which can be annoying. I wanted to extend one of my multiple drop connectors but the T I bought was a different brand and 90° offset to the original so I couldn't just plug it in to the end as it was fixed on a bulkhead.

 

[mrming]

Very helpful thanks all. I’m going to reccy it this weekend, and now I feel like I’m more informed. Sounds like I need to make a choice between adding a little N2K backbone or extending the SeaTalk-NG one. Will have a think!

 

[KompetentKrew]

This NMEA 2000 network fundamentals PDF is good. Only about a dozen pages, so might be worth printing out to take to the boat with you.

 

[DrSpock]

The failing rotary control can normally be fixed by dismantling and cleaning with electrical cleaner.

 

[mrming]

Thanks for all the help so far! We've now done a bit of a reccy:

• Plotter will be sited by the companionway (where the current one is)
• AIS is at the nav table
• I'm going to get a NMEA 2000 VHF (also at the nav table) and bring that in to the network as well
• There's a compartment under the quarter berth where batteries, autopilot computer, charger, MPPT controller etc are sited
  • There's an easily accessible 5 way SeaTalk-NG connector here, the backbone continues astern after this connector.
  • If we take option 1 from @KompetentKrew above we can
    • Add in another 5 way connector to the backbone
    • For the VHF and AIS Run 2 x NMEA 2000 cables from the nav table, fit the SeaTalk-NG adapter cables and plug them in to the new 5 way
    • For the new Axiom+ plotter do the same, but from it's location by the companionway
  • If we wanted to take option 2 as suggested by @PaulRainbow
    • This would allow us to only have one cable running from the nav station (easier to route)
    • We could then easily add new N2K devices in the nav station area in the future
    • So this sounds great, BUT:
      • I have one question. The part of the SeaTalk-NG backbone that's convenient is not at the end - the backbone continues aft, presumably to reach the autopilot control head etc.
      • If I'm understanding correctly, the N2K backbone must be joined to the END of the SeaTalk-NG backbone.
      • Is that correct? Or is there a way to join in a N2K backbone part of the way along the SeaTalk-NG backbone?

Any more help from the experts would be greatly appreciated. Confident we can do option 1, but option 2 would be neater and more future proof.

 

[PaulRainbow]

You can use option 2. Disconnect the STNG backbone cable from the 5 way connector, fit a STNG to N2K adaptor cable, fit 3 T connectors, then fit another STNG to N2K backbone adaptor cable to the STNG backbone cable going aft.

 

[mrming]

You can use option 2. Disconnect the STNG backbone cable from the 5 way connector, fit a STNG to N2K adaptor cable, fit 3 T connectors, then fit another STNG to N2K backbone adaptor cable to the STNG backbone cable going aft.

That’s great thanks Paul!

The 3 T pieces in your suggestion would be “drops” for individual N2K devices, is that correct?

Ideally I want to run a single N2K backbone cable over to the nav station area where I can T multiple devices onto it. But am I right in thinking this would ultimately have to come back and re-join the STNG backbone? I might be able to figure out a route to do that if so…

 

[KompetentKrew]

It's all one backbone. SeaTalkNG is literally just NMEA 2000 with different connectors on.*

So you have a terminator at the chart table, a couple of T's at the chart table, and then the backbone runs back and joins your current deices wherever they are.

If you add an NMEA 2000 speed or wind transducer then you just remove the terminator at the chart table and run the backbone forward from there.




* unless you also connect SeaTalk1 devices, but hopefully that doesn't apply

 

[mrming]

Yes the penny has dropped on it all being one backbone - finally.

My issue is I’m adding into the middle rather than onto an end, but if my new understanding is correct, that will be fine. Obv you chaps can’t see the layout in the boat, but I think it will require the N2K part to go to the nav station area and come back, at which point it’s joined to the aft section of the STNG backbone.

 

[PaulRainbow]

Yes the penny has dropped on it all being one backbone - finally.

My issue is I’m adding into the middle rather than onto an end, but if my new understanding is correct, that will be fine. Obv you chaps can’t see the layout in the boat, but I think it will require the N2K part to go to the nav station area and come back, at which point it’s joined to the aft section of the STNG backbone.

That's correct.

 

[mrming]

Excellent - thanks very much both!