NMEA2000 for zero braincells

[vindoga]

Hello kind sailors of the world,


I have been researching NMEA2000 and the relevancies for a brief amount of time. It makes me glad to have such vast amount of information about the protocol, but it is also a little frustrating as there is too much information to comprehend for a completely new sailor.

My current electronics include a Standard Horizon GX2400 VHF station, Lowrance HDS 5m and a Raymarine ST1000 or ST2000 auto-pilot to go with the chartplotter.

There is attached photo of a NMEA2000 starter kit I am planning to purchase.

My question; Will I be able to link the VHF station and the chartplotter with that specific NMEA2k starter kit? Would the chartplotter receive GPS and AIS receiver information from the radio station?


Thank you,
For a better sailing experience

[nohal]

With this specific starter kit you are at least missing one T-piece. You need one for the VHF, one for the plotter and one for power as an absolute minimum.
For the super simple system like yours, depending where exactly on the boat the units and power source are, you may look at a starter kit with the 4port connector.




Both your radio and plotter claim to support NMEA2000, so they should talk to each other.

[Ryban]

A couple bits of info that are also helpful:

• The ends of the connectors on the backbone can be connected to devices, or capped for expansion later (there will only ever be 2 of these).
• For each additional connection you'll need 1x T-connector, because adding a T-connector really only adds one NEW connection to your backbone.
• One connection will be dedicated to input power (the NMEA2K network needs 12V) -- this is the yellow cable in your photo. You can hook this up to a switch or appropriate breaker to turn on your network as needed.
• You MUST terminate the backbone if it is open at either end with a proper terminator (including in the kit you posted a photo of). You do not, and should not termiante the "drop ins"/Ts. If you don't install the terminator on the backbone, the network won't function.

It's honestly only confusing until you get it setup on the boat and start playing with it, then it becomes very straightforward and simple, and you'll wonder why you ever bothered doing anything else.

[nohal]

Originally Posted by Ryban

The ends of the connectors on the backbone can be connected to devices, or capped for expansion later (there will only ever be 2 of these).

If you mean that instead of the obligatory 120 Ohm terminator resistors on each end of the backbone you can connect a device there, that is false information. Something like that works just by pure coincidence or in special cases where the device actually integrates the terminator in it (In which case such a device must not be connected the usual way).

[vindoga]

Originally Posted by Ryban

• You MUST terminate the backbone if it is open at either end with a proper terminator (including in the kit you posted a photo of). You do not, and should not termiante the "drop ins"/Ts. If you don't install the terminator on the backbone, the network won't function.

Thank you kind stranger of the internet for the valuable information. Are the terminators the two small nipple looking things at the bottom of the kit?

[nohal]

Originally Posted by vindoga

Thank you kind stranger of the internet for the valuable information. Are the terminators the two small nipple looking things at the bottom of the kit?

Yes, those are the terminators and must be installed on each end of the network backbone.

[sv_pelagia]

Actisense has a 4-port starter kit with each port having self-contained termination

[Ryban]

Originally Posted by nohal

If you mean that instead of the obligatory 120 Ohm terminator resistors on each end of the backbone you can connect a device there, that is false information. Something like that works just by pure coincidence or in special cases where the device actually integrates the terminator in it (In which case such a device must not be connected the usual way).

Whoops! My mistake. I think it did work for me at least on one end.

[markrsimon]

Originally Posted by sv_pelagia

Actisense has a 4-port starter kit with each port having self-contained termination

This device simply has the end terminators integrated within -- which while helpful in small installations, also limits it to 4 devices.


https://actisense.com/wp-content/upl...1.01-PRINT.pdf

The equivalent of four T-pieces in a single
case provides a cost effective solution
and significant time and space saving.
Termination resistors are built in making the
SBN an entirely self-contained NMEA 2000
network.

[Redboat]

Follow up question:

If I have a chartplotter a radio, and other devices on a NMEA network and one device fails, do they all quit working? Or is it just that shared data from the failed device stops coming through the network.

[nohal]

Nothing should happen, the rest of the network should stay unaffected.
So far the theory, but really it depends on the device and the type of failure.
Some examples:
- The power part of the device powered from the NMEA 2000 bus fails in a way so unfortunate that it shorts the power -> The main fuse powering the bus burns -> everything powered from the NMEA 2000 bus dies because there is no power
- The data part of the device dies in a way so unfortunate that it shorts the data wire pair -> the whole bus is dead. That is why good NMEA 2000 devices have the data port optically or galvanically isolated, so that the possibility of this type of failure is pretty much eliminated.

[Pete7]

Originally Posted by vindoga

a Raymarine ST1000 or ST2000 auto-pilot to go with the chartplotter.

Thought the RM ST1000 and ST2000 tiller pilots were RM Seatalk or NMEA1830 with different plugs. This might be a problem with a NMEA2000 network.

We avoided the issue by only using the ST2000 in stand alone mode which it was quite happy with, though no steering to wind angle of course. Later replaced with the Evo 100 so the problem went away as it was an all SeatalkNG network then. Oh apart from the new RM chart plotter, that needed a different cable NMEA2000, just to be or awkward.

[rls8r]

vindoga -

The starter kit you show will be fine - but get a 4-post connector like nohal shows in Comment #2. You can put the connector anywhere that's convenient. I put mine near the main DC breaker panel.

The yellow cord is the power cord. I dedicated a 5 amp breaker on my main DC panel for the N2K network. Run the power cord from the breaker to one of the ports on the 4-port connector (doesn't matter which). Try to leave a port next to the power cord unused as long as possible. You may, in the future (if you system gets more complicated), have problems and you'll want a port near the power port to attach an N2K meter/diagnosis tool. But I wouldn't worry about that just now.

Run one of the drop cords in your starter kit from the back of your SH GX2400 to one of the ports on the 4-port connector (doesn't matter which). Then, run a drop cord from the N2K port on the back of your HDS 5M (that's your MFD - right? - if not, what type MFD do you have?) to one of the ports on the 4-port connector. You'll probably want to find a way to label the cords as they enter the 4-port connector.

As Pete7 says, the autopilot will probably be NMEA 0183 so it will be connected directly to the MFD - not through the N2K network. The NMEA 0183 input to your HDS 5M is through the power cable. Your power cable should have eight wires separated into two "branches"; three wires in one branch (red, black & yellow) provide power to the unit; 5 wires in the other branch [yellow (Tx-A), blue (Tx-B), orange (Rx-A), green (Rx-B) & gray (ground/shield)] are for NMEA 0183.

Attach the two terminators; one on each end of the 4-port connector. One terminator will be male; the other one female, so no way to mess that up. Put a cap/cover (that you may have to buy) on the unused port.

You'll have two T-connectors from your kit to spare. Use those to connect other N2K units as you get them (e.g., depth meter, anemometer, cockpit marine device, etc.). Just remove one of the terminators (doesn't matter which) - connect one of your spare T-connectors to one end of the 4-port connector - and replace the terminator on the open end of the newly-added T-connector. Rinse, repeat.

Easy peasy! Unless you have a verrrry long boat, with this simple setup you probably won't have to worry about exceeding LEN maximum (60) or maximum lengths of drop cables (20' to single unit from T-connector; 256' combined total length).

[nohal]

One more thing, the maximum current allowed on NMEA 2000 network is 60 LEN, which is 3A. The fuse in the power cable will take care of that by burning, but if you put a breaker in front of it, make sure it is not too big - the 5A rls8mr used is about the absolute maximum that makes some sense...

[rls8r]

vingoga -

I just re-read your initial message and realized that I didn't answer your second question. Sorry.

The answer is "yes" to both GPS and AIS.

With regard to the GPS ... your MFD does have an internal GPS as does the SH GX2400 so connecting your GX2400 through the N2K network will give you the choice of which GPS source the MFD uses. You can select that by going to the "Network" area of the "Settings" menu on your MFD.

With regard to the AIS ... you set that up by going to the "Vessels" area of the "Settings" menu on your MFD. You'll have to enter your boat's MMSI number if you want to receive MMSI messages on your MFD. You should have gotten an MMSI for your boat when you purchased your GX2400 (if you didn't have one beforehand).

P.S. I used a 5 amp breaker because it was the smallest one I had laying around when I put in my N2K network. In fact, I believe Blue Seas does not make a 3 amp Series A breaker ... the next smaller one is 2.5 amp, so I'll stay with the 5 amp one. Since the power cable on the N2K is fused - I just need the breaker as a switch. Of course ... if nohal tells me to do otherwise, then ...