Mixing SIMNET and NMEA2000 networks?

[maby]

Just been trying to install a Lowrance plotter into our boat which has a pre-installed (but until now) unused SIMNET network. The Lowrance is a vanilla NMEA2000 device - ok, I know that SIMNET is effectively NMEA2000 on different plugs, but it also supports both daisy chain as well as NMEA2000 style drop cabling, so it's not exactly the same.

I bought a SIMNET to NMEA2000 cable plus an NMEA2000 tee-piece, terminator and drop cable to go to the plotter. Boat already had a SIMRAD SonicHub installed and I hoped to control it from the plotter.

Having connected everything and powered on, my new plotter cannot see the SonicHub (which is hanging directly off the SIMNET). Also, the network diagnostic screen on the plotter says "Bus Off" - sure sign the network is not powered! I trace it through, and sure enough the idiots have not bothered to connect power to the network!

No big problem - I have plenty of space on the Simnet hubs to plug in a power cable - just need to order one. But it did get me to wondering - what I have now built is a full Simnet running the length of the boat and a short NMEA2000 network just in the lounge - bridged together - do I need to power them both? I'm hoping that if I apply power to the Simnet network, it will be coupled through to the NMEA2000 network - anyone know for sure?

Thanks in advance!

 

[David2452]

If there is no power break T in the 5 core Simnet then it should carry through the N2K backbone. I assume you have simply used a miro C to Simnet adaptor cable. This document will be of use.

http://www.hellasmarine.com/Simrad Documents/SimNet/Simnet-Install-Man.pdf

 

[Shoalcove]

I'm not an expert but have been reading up on this prior to installing some new Simrad gear this spring. I believe you should only power one network based on what I've read. If you add a power cable to the Simnet system, you just connect with the Simnet-nmea2000 adapter. Depending on the setup of the network, adding a extra terminator will cause problems. There should only be 2 terminators in the system. The Simrad site has a downloadable manual for Simnet and the Maretron site has the same for NMEA2000. Reading those manuals will provide you with the answers to your questions (and then some!) Good luck!

 

[maby]

Thanks guys, I was hoping that it would work out as you are suggesting. I had read the manuals on building a Simnet network, but they do not address exactly my situation - they talk about either dangling a single Simnet instrument off a working NMEA2000 network, or the other way round. For a variety of reasons (which I am beginning to regret) I actually installed a short NMEA2000 network complete with terminators, and bridged it to the Simnet network. I guessed that either could power the other, but wanted some confirmation!

 

[maby]

P.S.my Simnet network has no terminators - it is star connected, not daisy chained. There are two 7 way Simnet hubs - one in the lounge and one in the transom space, coupled together with a long Simnet cable and instruments connected to one or other of these hubs with drop cables. As I say, I've never actually seen this work - it was installed by Jeanneau as standard at the factory, but I have Tacktick wind and depth instruments fitted, so the Simnet has not been active till now.

 

[Shoalcove]

Having a NMEA2000 network isn't a bad thing IMHO. It allows you to add a variety of instrument brands on the same network if you make future changes. If you use the NMEA2000 network, each Simnet item will need a drop cable. If there are several things on the Simnet network if may be easier to use your adapter cable to hook into that. You can buy power cables for the Simnet with a built in terminator depending on your needs.

 

[maby]

If I had started from scratch, I would probably have put in NMEA2000 - even Simrad have stopped using Simnet on their latest gear. Thing is that new Jeanneaus come ready wired with Simnet.

 

[Dockhead]

Did you ever solve this problem? I'm struggling with exactly the same thing.

 

[Playtime]

There are 2 things to remember with a NMEA2000 (N2K) and/or Simnet network.

1. There should be 2 terminators (and only 2) - one at either end of what you designate as the 'backbone'. It doesn't matter whether this is N2K or Simnet (they are identical electrically, only the plugs are different.

2. There should be only one power feed on a typical small yacht network.

If you follow those rules, it is pretty much plug and play. As said above, though, it is worth reading the manuals identified. There is also a very good free Maretron design aid that can be used to draw (and check) your network http://www.maretron.com/support/n2kb_downloadform.php.