NMEA 2000, smart mixing

Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now excited to have Ben Stein as very able publisher, webmaster, and editing colleague. Panbo is going to the next level in 2019 and beyond.

5 Responses

  1. Sandy says:

    Ahhhh, Panbo! Where else can you go if you get excited about the back of an instrument panel?

  2. PSDave says:

    Did you know that………. you cannot connect the new Garmin GMI-10 data displays as nodes off of the NMEA 2000 backbone cable without powering EACH GMI-10 display. What gives with that, completely negates the advantages of NMEA 2000. Even the photo on the outside of the GMI-10’s box showing a sample connection to a NMEA 2000 back bone is wrong. Only on page 5 of the installation manual, last line is the secret reveled “The GMI 10 is not powered by the NMEA 2000 network, it must be separately connected to the power source”. So the installer has to power the backbone cable in accordance to the LEN load factor, and then power EACH GMI 10 display.
    Call the GMI-10 what it is, a glorified NMEA data repeater, being marketed as a NMEA 2000 device. False advertising.

  3. PSDave, I think you’ve gotten a little carried away. Yes, it’s true you have to individually power the GMI 10s, as I’ve mentioned here a couple of times, but otherwise the GMI 10y are good NMEA 2000 citizens. I guess Garmin made this decision so that it could put especially bright backlighting in the instrument without putting a big power load on the backbone.
    I was disappointed to learn that NMEA 0183 data coming into a GMI 10 is NOT bridged onto NMEA 2000.

  4. Dan (b393capt) says:

    I like the power being seperate, even if there was enough current capacity for my devices …
    I have an overall preference that my power and data signal are seperate, and only the devices that obviously need to be on when the N2K bus is operating are powered from it. I don’t know if I need that from my displays, as an on/off button will do, but in general I favor the idea.
    As N2K permeates into all sorts of boat systems, we might find ourselves keeping the network “up” many hours before and after our boats are underway. Between a combination of limited battery capacity and when at dockside limited charging capacity (e.g. power unnecessarily going to network devices isn’t available to charge hungry batteries) I actually can’t envision any devices I wouldn’t want to individually or as a group power up/down seperate from the network.
    Until we can command sensors and displays to turn on/off over the network (I read that there is an N2K standard being developed for this), the only other option is to have seperate power to sensors and displays for boats that have extremely limited power sources.
    However … it would have been ideal if the power cabling was setup for daisy chaining (e.g. two power connectors per display), and in doing so the choosen connectors were extremely easy to splice onto standard wire, so an installer can get just the right length without any extra weight, nor need to buy pre-built cable.
    Come to think of it … would be nice if such an auxillary power arrangement was part of the N2K standard so all N2K devices seperatly getting power use the same type of connectors, and can be daisy chained just as I suggest here for displays.

  5. Dan (b393capt) says:

    Disregard my comments about that N2K standard under development.. that is to support three wire power systems, and probably dosn’t exactly apply to commanding the device itself to power up/down, but rather to a special circuit breaker doing so.

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