NMEA2000 for zero braincells

[nrx500]

NMEA 2000 is essentially plug and play, unlike NMEA 0183. Drop cables and backbone cables have the same end connectors and can be used interchangeably in most cases. You have a chartplotter (MFD) or multi function display. The MFD becomes the central control station for everything on your network. The VHF uses DSC (digital selective calling) and will put DSC distress calls on the screen of your MFD. If it has an AIS receiver, it will plot AIS intercepts on the screen of your MFD. The autopilot has two components, drive motor and control head. There will also be a compass heading sensor that cannot be near electrical or magnetic interference. Look at the back of each autopilot unit to make sure each has an NMEA 2000 (5 pin connector) plug in. Your autopilot also has its own control panel. Be sure the autopilot motor and control head connect to each other all autopilot units only need a single NMEA 2000 drop cable to connect to the MFD. I attached links to Garmin. They will show you a basic installation diagram and the components you will need. The 4 position drop cable shown earlier is the minimum you will need. Additional T connectors like the ones in your starter kit can be screwed on the ends or connected with a backbone cable. Terminators must be on the ends, but not on the bottom connectors where the drop cables are connected.http://https://static.garmin.com/pumac/AIS_800_Install_Instructions_EN.pdf

[sailingharry]

Originally Posted by 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.

To take that further, the N2K spec is fairly insistant that each device be connected directly to the backbone (in theory -- and in practice -- you can have multiple devices on a single tee and some devices actually have built-in connectors for daisy chaining). The thought behind this somewhat complicated requirement is that you can easily disconnect any device at the drop connection and instantly fix any failure.


My comment about "complicated requirement" is that it can result in challenging wiring situations. Imagine a binnacle, where many people have several devices. Instead of one cable up, and 5 devices daisy chained, (or a multi-tee), you need 5 individual drops down to the backbone. Or you could run the backbone up and down (so only 2 cables). Or in simple situations, the backbone could run up and terminate.