NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183)) - SailNet Community

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  #1  
Old 02-04-2013
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Unhappy NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

Hi everyone,

In the past couple of days I have been trying to install a simple NMEA 2K network consisting of a Garmin GMI 10 MFD, an Airmar 800DST Triducer, a Garmin GWS 10 Wind sensor and a Garmin GPS 19X HVS (NMEA0183 version). So far I have only dealt with the triducer, gps and the display, since weather has not allowed to install the wind sensor.

I have followed the installation instructions to a tee, but I have run into two problems that have me at my wits' end. The cabling is correct to my knowledge and a diagram of the installation is available in the location below but I cannot add the image to the post due to low post count.

h t t p://i.imgur.com/1Djt3On.png

Here are the problems:

1. No GPS data at all!! I have moved the antenna to a clear view of the sky but not even satellite view comes up on GMI10.
2. On a dry fit, all triducer data showed up correctly, but after installation of the triducer in the thru-hull and running the cable through the bilge, speed & temperature shows up from the triducer but depth shows up some times and sometimes it doesn't!!! Funny thing is that when depth showed up at some point it was only when the GPS19X was disconnected from GMI10, which does not make any sense, since they are not on the same data bus! (the gps is directly connected to GMI as a NMEA0183 device.

I tried different connections of the drop cables (power drop cable in the middle, left or right) to the backbone which consists only of 3 T-connectors, 3 drop cables, terminating resistors and no backbone cable.

The two things I haven't tried so far is to ground the power cable (the bare wire it contains was not shown to be needed to connect to the ship's ground in the instructions so I left it unconnected) and to use the limiting resistor for 1Hz operation of the GPS (instead of 10Hz, which I was under the impression that GMI10 supports)

If someone can help me sort out this mess, I would be grateful, since I spent an entire weekend passing cables through very tight spots only to have only half of the functionality...

Thank you in advance

Last edited by atsakir; 02-04-2013 at 06:00 AM.
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Old 02-04-2013
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

you need to ground the power cable. put a meter on the wire going into the network to verify.
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Old 02-04-2013
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

Thank you for the reply. I will ground the power cable and test again but I don't understand why it should cause an issue not grounding the power (and why it is not explicitly included in the installation instructions that the power drop cable must be grounded).

EDIT: in another document from Garmin I found online it clearly states that the power cable must be grounded (w w w.cnerd.com/interesting/boating/GPSMAP4008_NMEA2000NetworkFundamentals.pdf page 5). I wonder why this is not included in the GMI10 installation instructions!

As far as the GPS 19X goes, I checked the cable end connector that goes to the gps unit with a multimeter on the V+ an V- pins (2 & 3, if I recall correctly) and it registered a normal 12.70Volts without fluctuations.

For the triducer problem, since I don't have a NMEA2000-PC gateway, I cannot test the NMEA sentences sent throughout the network to analyse for potential errors but since some data is transmitted (temp, speed) I don't understand what would cause the erratic behavior of the depth data.

Last edited by atsakir; 02-04-2013 at 08:58 AM.
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Old 02-04-2013
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

Don't mean to insult you, but I saw a "professional" do it wrong. The inputs are each going into the short center part of a T. One each for the MFD, the triducer, the power, with terminator caps on the 2 ends?

Don't know the Garmin stuff, but doesn't the MFD have an internal antenna?
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Old 02-04-2013
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

Don't worry, I am not insulted. Although a computer programmer by trade, when it comes to NMEA network installations I am a neophyte

To answer your questions, yes, all connections are as in the diagram I included in the first post. In detail:

Backbone: female terminator - T -T - T - male terminator.
Drop cables: GMI 10 - Power - Triducer to each respective T middle connector

GPS 19X cable connected to the respective cable that ends at the Power/NMEA0183 connector at the back of GMI 10 and both GMI 10 and GPS 19X get power from direct wire connections to a switch on the 12V electrical panel and NOT from the NMEA2000 bus.

GMI 10 is a headless MFD, it just displays information from external sensors, it is not a chartplotter or GPS receiver itself.
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Old 02-04-2013
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

Better diagram than I got from Ray! If the Garmin Tees get bent the wires inside break. I learned the hard way. I'd still start with the 12 volt connection.
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

I suspect that the depth is dropping out because it is genuinely not getting a reflection off the bottom. This could be because you are in very deep water (but it is unlikely that your slip is more than 200ft deep ) or, more likely, because you have marine growth around, or even inside, the through-hull.

I had a problem with speed always reading zero on my DST800, and it was marine growth jamming the paddle. I now have a round foam dish scrubbing brush, bought from the supermarket, that fits nicely down the through-hull. I give it a scrub now and then.

When was your bottom last cleaned? Even if it was cleaned recently, they can't reach inside the
through-hull.

Word of warning for later when you install the wind instrument : they normally have a terminating resistor, so get installed on the END of the network (in place of one of the terminators) - NOT as a drop.
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

PS, you are in the water aren't you? Not on the hard?
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

Quote:
Originally Posted by atsakir View Post
Hi everyone,

In the past couple of days I have been trying to install a simple NMEA 2K network consisting of a Garmin GMI 10 MFD, an Airmar 800DST Triducer, a Garmin GWS 10 Wind sensor and a Garmin GPS 19X HVS (NMEA0183 version). So far I have only dealt with the triducer, gps and the display, since weather has not allowed to install the wind sensor.

I have followed the installation instructions to a tee, but I have run into two problems that have me at my wits' end. The cabling is correct to my knowledge and a diagram of the installation is available in the location below but I cannot add the image to the post due to low post count.

h t t p://i.imgur.com/1Djt3On.png

Here are the problems:

1. No GPS data at all!! I have moved the antenna to a clear view of the sky but not even satellite view comes up on GMI10.
2. On a dry fit, all triducer data showed up correctly, but after installation of the triducer in the thru-hull and running the cable through the bilge, speed & temperature shows up from the triducer but depth shows up some times and sometimes it doesn't!!! Funny thing is that when depth showed up at some point it was only when the GPS19X was disconnected from GMI10, which does not make any sense, since they are not on the same data bus! (the gps is directly connected to GMI as a NMEA0183 device.

I tried different connections of the drop cables (power drop cable in the middle, left or right) to the backbone which consists only of 3 T-connectors, 3 drop cables, terminating resistors and no backbone cable.

The two things I haven't tried so far is to ground the power cable (the bare wire it contains was not shown to be needed to connect to the ship's ground in the instructions so I left it unconnected) and to use the limiting resistor for 1Hz operation of the GPS (instead of 10Hz, which I was under the impression that GMI10 supports)

If someone can help me sort out this mess, I would be grateful, since I spent an entire weekend passing cables through very tight spots only to have only half of the functionality...

Thank you in advance
Looking at your diagram you are feeding the GMI10 with power two ways.
-Via the N2K drop cable
-Via the NMEA 0183 harness

Don't think this i correct..
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Re: NMEA 2K Network Problems (Garmin GMI 10/Airmar DST800/GPS 19X (NMEA0183))

I don't see why that would cause problems - it is fine to feed NMEA 2000 with power in more than one location (as long as the polarity is the same!) to overcome voltage drops in long cable runs.

Edit : It isn't fine. See below.
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Last edited by MarkSF; 02-05-2013 at 01:14 PM.
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