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post #1 of 6 Old 07-19-2016 Thread Starter
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NMEA 2000 and voltage drops

Hi folks - a couple of things I am puzzled by.

Upgrading the boat to NMEA2000 - anemometer, depth, speed, GPS, VHF. Mainly Garmin kit. Really liking the flexibility and simplicity - quite a step up from 1980s tech - but occasionally the data on the display flashes, or disappears. I have seen the GPS depth display flash (number unchanging), while the helm display shows normally; or the data at the helm disappears, while the GPS still displays it (power is on at the display, just no data being displayed). Any ideas? Loose connection? Power drop? I have the power connector in the middle of the NMEA connectors, as recommended given the total load, and checked the connections carefully...

My second question - possibly related - when the autopilot is engaged, I see a voltage drop warning on the GPS (set to warn me if voltage drops under 12v). Possibly related? e.g. undersized wire somewhere in the spaghetti (oops, I mean wiring harness)?

Thoughts would be welcome!
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post #2 of 6 Old 07-19-2016
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Re: NMEA 2000 and voltage drops

Hey,

It really sounds like you have a power problem. Salt water and electricity don't get along! Check all your connections. Try to upside the wiring size to minimize voltage drop. Standard stuff.

Good luck,
Barry

Barry Lenoble
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Re: NMEA 2000 and voltage drops

The depth number flashing might be normal. I get this under certain circumstances, due to the transducer losing the bottom. Passing behind a tug usually does the trick - the water is too turbulent to get one clear reflected signal. When this happens, the display is told to flash the last reliable depth reading.

This is better than my ancient IMI transducer, which just displays any old drivel when it gets confused.

Bristol 31.1, San Francisco Bay

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Re: NMEA 2000 and voltage drops

A quick check of the voltage at the ends of your N2K runs would be easy to do with a meter.
Where is the power injector for your N2K?

on my system the H5000 CPU, Zeus MFD, SonarHub and H5000 Autopilot all have power feeds independent of the N2K, which has an injector midway down its length.

I get a "voltage" number on the Zeus2 that the B&G techs tell me is about 1V below the actual supplied voltage, (verified by meter) and see that the displayed voltage tracks the engine RPM/shorepower/battery state.

If your Autopilot engagement trips off others stuff, you need to re-wire, put it on it's own circuit etc, Autopilots can pull multiple amps (mine up to 30) and voltage drops will show up quickly.
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Re: NMEA 2000 and voltage drops

If you haven't done it already, you might check out the Maretron software for designing NMEA2000 networks. It's free and will model what your voltage drops should be. It's also pretty cool.
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post #6 of 6 Old 07-20-2016
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Re: NMEA 2000 and voltage drops

Quote:
Originally Posted by paul323 View Post
Hi folks - a couple of things I am puzzled by.

Upgrading the boat to NMEA2000 - anemometer, depth, speed, GPS, VHF. Mainly Garmin kit. Really liking the flexibility and simplicity - quite a step up from 1980s tech - but occasionally the data on the display flashes, or disappears. I have seen the GPS depth display flash (number unchanging), while the helm display shows normally; or the data at the helm disappears, while the GPS still displays it (power is on at the display, just no data being displayed). Any ideas? Loose connection? Power drop? I have the power connector in the middle of the NMEA connectors, as recommended given the total load, and checked the connections carefully...

My second question - possibly related - when the autopilot is engaged, I see a voltage drop warning on the GPS (set to warn me if voltage drops under 12v). Possibly related? e.g. undersized wire somewhere in the spaghetti (oops, I mean wiring harness)?

Thoughts would be welcome!
Paul,
When I installed my NMEA2000 instruments the wind sensor (GWS-10) wire from the mast connected to a NMEA2000 terminator. The other side of the terminator connected to the NMEA2000 backbone at the helm via an extension cable. That extension cable becomes part of the NMEA2000 backbone and if the voltage is marginal you'll get dropouts. In my case it was the transducer and GPS signals on the backbone.

The solution was a second power feed to the backbone inserted between the terminator and the extension cable per a Garmin tech and it fixed the problem. I'd assume the connection would be the same on current models...

Hope this helps,
Jim

Currently Boatless

The sail, the play of its pulse so like our own lives: so thin and yet so full of life, so noiseless when it labors hardest, so noisy and impatient when least effective." - Henry David Thoreau

Last edited by JimMcGee; 07-20-2016 at 10:49 AM.
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