Merging N2K with Simnet

[Gumshoe]

I have purchased a new N2K Adapter “T” to Simnet cable…no instructions or explanation of operation…since both systems are 12v DC, am I going to have any issues connecting the two systems together? Anyone know if these types of adapters block voltage crossover and allow only a signal path ??

[ItDepends]

Simnet is N2K exactly, just with different connectors. They play happily together. They are not just siblings, they are identical twins.

Treat them as a SINGLE N2K network for power distribution purposes

[Dockhead]

ItDepends is exactly right.


The adapter merely makes the connection; there are no electronics involved. Just screw it all together and don't worry about it. SimNet and N2K, other than some certification issues, are exactly the same.


I have an old B&G steam-powered Zeus MFD that has a SimNet connector. I have no issues connecting that to my N2K network.

[Gumshoe]

Thank you fellow sailors, this relieves my mind in that I will not have to witness a smoke test when I get ready to marry the systems…appreciate the assist….

[Gumshoe]

Dockhead, would I be correct in believing that the interconnecting cable would not pass the 12 volts DC just the data leads?

[smac999]

No it will pass 12v

Just plug it in.

[Gumshoe]

smac999..as I am new to N2K, I believe I read installation instructions that the system should only have a single source for voltage supply…would not connecting these two systems together create two 12v sources ?

[smac999]

Are you trying to join a single simnet device to a n2k backbone? Using the adapter cable. Or join a simnet backbone and n2k backbone together?

If the first plug plug the device in.

If the later. You need to remove 2 terminators, one power source, and join them end to end.

[SCarns]

I’d also point out that if you have two power taps on the same battery, you effectively have one power source. You run into issues with one network powered from two different sources, such as two separate batteries or power supplies.

[smac999]

Originally Posted by SCarns

I’d also point out that if you have two power taps on the same battery, you effectively have one power source. You run into issues with one network powered from two different sources, such as two separate batteries or power supplies.

but then you have 6a of power (two 3a fuses) instead of a single 3a fuse if something goes wrong. also sometimes they are from different switches or breakers. which even if from the same battery causes issues. so they end up back feeding each other if one is off and causing headaches.

the only correct way is a single power source. unless there is a power isolation tee.

[RaymondR]

Being familiar with nmea0183 I was baffled as to why my N2K connection between mt Simrad autopilot and Raymarine MFD via the adapter cable would not work.

Enlightenment occurred when I discovered that N2K has optoisolators included in the instruments being connected. Read up on N2K and discovered the need for power injection so cut the cable and applied 12V to the power cables and everything worked.

Baffled again when I started to replace instruments which were fully powered from the N2K backbone,

If one includes optoisolators to make the electrical power connections for the communications network independent of the instrument power why then have some instruments powered from the N2K power network?

[Gumshoe]

SCarns…What you explained makes good sense…I will have to check my schematics for my Simnet voltage source as it has been a number of years since the install…I will tap that same source for the N2K backbone…thanks again

[Gumshoe]

RaymondR…Are not optoisolators for fiber optics cables only? My system has NO fiber optics cabling..

[Gumshoe]

smac999, if this is the case then it would seem to make sense that adapter cables from Simnet to N2K should NOT pass voltage unless labelled to do so..the adapter cable I purchased had no such claim…the only real method of resolving this is voltage measurements at the adapter cable to see if crossover voltage occurs, or make certain that the new N2K system is sourced from the same power supply as the Simnet System with appropriate fusing of course…

[smac999]

the adatper cables are designed to go from a device to a backbone so they must pass power. the entire backbone is the same type, and any odd devices each get an adapter cable to the backbone.

once you start to get into mixing backbones, that is advanced work and it simply needs to be done by someone who knows what they are doing...

if you want to connect two seperate backbones without creating a new single one, then you need a bridge. with a small network it's better to just create a new single one.

https://www.maretron.com/products/nbe100.php