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Suzuki + 2 Garmin 741xs NMEA 2000 network

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Suzuki + 2 Garmin 741xs NMEA 2000 network

Old 01-15-2020, 10:06 AM
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Default Suzuki + 2 Garmin 741xs NMEA 2000 network

So last weekend I snapped my antenna on a bridge - need less to say, I am cutting a bunch of rigging zip ties anyway so I thought it would be a good time to build a NMEA net work.


What I currently have is the typical Suzuki network including the c-10 & fuel sending unit. My two 741xs are wired independent of each other and using the NMEA 0183 outputs on the back of them. One has radar to it and the other a transducer.

My Goal is to connect the two 741xs together and hook them to the Suzuki network so I can get an actual MPG while running, display Suzuki information on Garmins. Also, want to have my Gamins use power other than the Suzuki network.

To accomplish it appears I need the following parts:

2 garmin drop cables
1 NMEA power cable
2 regular t's
1 tee with a power isolator on it.

This appears to be as simple as removing my NMEA 0183 cables currently in use and replacing them with the garmin drop cables to the new tees in network and routing a NMEA power cable. Seems very simple to me but what am I missing?


EDIT: as I read more it appears the second option is to leave the garmins powered the way they are, get a power isloator and just add 2 tees with drop cables to my Suzuki network. no need for a separate 12v source since the garmins already have a separate power source.

Last edited by tcijoe; 01-15-2020 at 10:41 AM.
Old 01-15-2020, 01:46 PM
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You “edit” comments are close to the correct way. Just add 2 x T’s to the existing NMEA2000 network plus drop cables between the Garmins and the T’s. Done.

The Garmin displays will always need their own power cables to be connected. They do NOT get operating power from their connection to the NMEA2000 network. and there is no need for a expensive power isolating T between the Garmin part of the network.and the rest. In your setup, it achieves nothing. A power isolating T is only needed if you are joining two separate networks and Making them into one.

Once you have connected up the Garmins to the network, turn everything attached to the network on, including Engine keys on. Then in one of the C10 menus, open system then network, then device list and select the option to auto-select data sources. This refreshes all network data sources and sets them where they should be after new devices are added.
Old 01-15-2020, 01:50 PM
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Thank Moonlighter....you have helped me through a bunch!
Old 01-15-2020, 01:52 PM
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Originally Posted by tcijoe View Post
Thank Moonlighter....you have helped me through a bunch!
no probs. Just recehck my reply as I edited it slightly while you were responding.
Old 01-15-2020, 02:47 PM
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Originally Posted by Moonlighter475 View Post
A power isolating T is only needed if you are joining two separate networks and Making them into one.
I have
4 Suzuki C10 gauges
2 Suzuki Engine interfaces
2 Lowrance Fuel level Interfaces
This NMEA2000 network get their power from the +12V from the engine harness and one of the engine batteries

Then i Have:
1 Garmin 7610XSV
1 Garmin 7xx
1 Garmin VHF200
1 Fusion 720
All those are on another network and the newtwork power shoud come from house battery bank as their +12V to make them work is coming from

The Power Isolator should electrically isolate the NMEA2000 network so that there is no current flow between engine and house battery if one of both has less charge, or am i wrong?

Chris
Old 01-15-2020, 03:46 PM
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Originally Posted by ChrigelKarrer View Post
I have
4 Suzuki C10 gauges
2 Suzuki Engine interfaces
2 Lowrance Fuel level Interfaces
This NMEA2000 network get their power from the +12V from the engine harness and one of the engine batteries

Then i Have:
1 Garmin 7610XSV
1 Garmin 7xx
1 Garmin VHF200
1 Fusion 720
All those are on another network and the newtwork power shoud come from house battery bank as their +12V to make them work is coming from

The Power Isolator should electrically isolate the NMEA2000 network so that there is no current flow between engine and house battery if one of both has less charge, or am i wrong?

Chris
You are indeed Wrong.

Your rationale about power flowing between house and engine battery is totally incorrect.

The issue of having 2 power supplies to power the network is the reason for having the power isolator. Doesnt have anything to do with which battery they come from.

Networks can only have one power supply, unless there are particular circumstances that require otherwise eg large, complex networks with numerous devices and typically multiple long backbone segments, where voltage drop would be excessive due to these factors. Suffice to say that for most of us, there is a simple rule: power must be connected to only one T on the network.

The reason for using a power isolator is simply so that there can be a section of the network that will continue to have devices communicating with each other when the engine key is turned off. That section of the network therefore has its own power supply. The isolating T simply stops power running from one side to the other and therefore breaking the “one power supply” rule.

As you know, the normal/typical way that the Suzuki network is powered is by connecting the network power node to a spare + wire on the harness that only gets power when the engine key is on. This is effective because it means that simple network devices (such as C-10 and SMIS gauges) that actually get their operating power from their connection to the network, turn on and off at the same time as the engine. This makes people feel good because the gauge displays turn on and off at the same time the engine is turned on and off, so it operates just like traditional analogue gauges that do the same thing.

The only reason for having the network effectively separated into 2 halves (by using the isolating T like you have) is so that one half can be powered by a second power source and therefore continues to allow devices on that half to continue to communicate with each other when the engine half is turned off.

Its a COMMUNICATION ISSUE, not a device operating power issue, or anything else.

There is actually no technical reason why the Suzuki network could not be powered from the same source as the Garmin side of your network. In other words, you could disconnect the network power wires from the ignition source and remove that T, and take out the isolating T. You now have one simple combined network. What would happen if you did that, I hear you ask? Well, all that would be different is that the C-10’s would stay on all the time, they would just have no engine data on them, just dashes. That doesnt hurt them at all. And you have saved 1 x standard T and one expensive isolating T.

I actually have my network powered this way, on a separate switch on my switch panel.

The other way of looking at this, is that if you had NO DEVICES on your network that would need to continue to communicate with each other when the engine is turned off, then there is absolutely no reason to separate the network into 2 halves with 2 separate power connections and using the power isolating T.

Some relevant facts to understand:

1. MOST devices on a network DO NOT get their OPERATING power from their connection to the network. In fact any device that has its own power plug and cable gets their operating power from there, not from the network.

2. only small simple low power consumption devices such as gauge displays and GPS pucks get their OPERATING power from the network.

3. The network needs a power source in order for devices attached to it to communicate with each other. This is because all networked devices have separate internal network circuitry that only operates when they receive power from the network and this allows them to communicate with the network.

4. So, to communicate with the network, a device must first be powered on, and secondly, the network itself must be powered on. You can prove this fact simply by opening the network device list on a display, check the list of devices, then turn one of them off, and that device will disappear from the device list. Or, turn the network power off or disconnect the power from its T, and NO devices will be shown on the device list (except the device that you are using)

Last edited by Moonlighter475; 01-15-2020 at 06:59 PM.
Old 01-16-2020, 05:14 AM
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can't think of a scenario when it would matter but if I use option two in my post - just add 2 tees and drop cables from my 761 gamins, will the gamins talk to each other when when my Suzuki key is off?
Old 01-16-2020, 06:26 AM
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Thanks Moonlighter!

The only reason for having the network effectively separated into 2 halves (by using the isolating T like you have) is so that one half can be powered by a second power source and therefore continues to allow devices on that half to continue to communicate with each other when the engine half is turned off.
This is what i want to have so i will install the Isolating T as soon it arrives.

I am still not sure if you undertstood what i am thinking the problem is so i explain it again:

All NMEA2000 bus is connected to one battery
connected to house battery --> all NMEA connected devices get data and Suzuki Gauges are always on
connected to key +12V from engine harness --> all NMEA connected devices get data (including Suzuki gauges are on) only on if key is on
If engine Batterie dies, NMEA2000 Bus dies --> no data everywhere and Suzuki Gauges are dead, Engine is dead too

NEMA2000 Bus ist split in two, Suzuki gauges are on engine harness key on +12V and all other instruments are on house battery +12V
All NMEA2000 devices get data but Suzuki gauges are on only when key is turned
IF one or either battery dies or has considerable less charge than other battery so from my point of view that will happen:
Good battery will "charge/send current to" weak/dead battery thru the NMEA2000 bus as there is no power isolator


This is my - maybe overthinking - Problem AFAIK engine and house batteries should be strictly seperated to not create "jumper cables" between them

Chris
Old 01-16-2020, 01:18 PM
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Originally Posted by ChrigelKarrer View Post
Thanks Moonlighter!


This is what i want to have so i will install the Isolating T as soon it arrives.

I am still not sure if you undertstood what i am thinking the problem is so i explain it again:

All NMEA2000 bus is connected to one battery
connected to house battery --> all NMEA connected devices get data and Suzuki Gauges are always on
connected to key +12V from engine harness --> all NMEA connected devices get data (including Suzuki gauges are on) only on if key is on
If engine Batterie dies, NMEA2000 Bus dies --> no data everywhere and Suzuki Gauges are dead, Engine is dead too

NEMA2000 Bus ist split in two, Suzuki gauges are on engine harness key on +12V and all other instruments are on house battery +12V
All NMEA2000 devices get data but Suzuki gauges are on only when key is turned
IF one or either battery dies or has considerable less charge than other battery so from my point of view that will happen:
Good battery will "charge/send current to" weak/dead battery thru the NMEA2000 bus as there is no power isolator


This is my - maybe overthinking - Problem AFAIK engine and house batteries should be strictly seperated to not create "jumper cables" between them

Chris
Chris I think you are overthinking things.

In any case, your second scenario (without the power isolator) breaks the rule of network design that says there shall only be 1 network power supply. If set up that way, the network will not work and may well damage devices connected to it or blow fuses.

Last edited by Moonlighter475; 01-16-2020 at 01:34 PM.
Old 01-16-2020, 01:24 PM
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Originally Posted by tcijoe View Post
can't think of a scenario when it would matter but if I use option two in my post - just add 2 tees and drop cables from my 761 gamins, will the gamins talk to each other when when my Suzuki key is off?
If the network power is turned off, devices cannot communicate with each other. So, the answer is no, the Garmins will not talk to each other when the key is off.

Suzuki also makes a special multi-power node - a T piece that has several sets of power wires going into it. It is designed so you can connect to several power sources and the node selects whichever source is active. So for example if the engine key is turned off, it will automatically use one of the other connected power sources. So unless all sources are turned off, the network will always be turned on. Although, you might just as well simply have the network power connected to a separate switch.

edit:
I like the KISS rule: keep it simple, stupid!

Unless there is a good reason to do something, dont do it, keep things simple. Dont spend $ and add complexity (and thus additional points of potential failure) unless its truly necessary.

Last edited by Moonlighter475; 01-16-2020 at 01:32 PM.
Old 01-16-2020, 02:17 PM
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I have my Suzuki NMEA2K segment powered by the engine key as per the DF200 installation instructions and cabling kits, so the C10, DF200, water pressure sensor and fuel gauge sensor are up on the network when the engine is started. I than have a power isolator separating the Suzuki NMEA2K segment from the house electronics NMEA2K segment. The electronics NMEA2K segment is powered separately by a switch on the dash, and supports both Garmin MFD's, the Heading sensor, the GPS antenna, VHF and Fusion stereo.

That way if I turn the engine off, I can still keep the house electronics NMEA2K network up.

Jim
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Old 01-16-2020, 04:13 PM
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Originally Posted by jfwireless View Post
I have my Suzuki NMEA2K segment powered by the engine key as per the DF200 installation instructions and cabling kits, so the C10, DF200, water pressure sensor and fuel gauge sensor are up on the network when the engine is started. I than have a power isolator separating the Suzuki NMEA2K segment from the house electronics NMEA2K segment. The electronics NMEA2K segment is powered separately by a switch on the dash, and supports both Garmin MFD's, the Heading sensor, the GPS antenna, VHF and Fusion stereo.

That way if I turn the engine off, I can still keep the house electronics NMEA2K network up.

Jim
A perfect setup for your needs Jim.

My point earlier though is simply that if there is no need for connectivity between the “house” elements of the particular network, then there is no need to create 2 network halves by inserting the isolating T.
Old 01-17-2020, 05:24 AM
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an update. Last night I quickly hooked up the two drop cables and new tees (actually one double tee). Fired up the electronics and all seems good. will route the wires and sea trial this weekend.
Old 01-17-2020, 06:26 AM
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Originally Posted by Moonlighter475 View Post
A perfect setup for your needs Jim.

My point earlier though is simply that if there is no need for connectivity between the “house” elements of the particular network, then there is no need to create 2 network halves by inserting the isolating T.
I agree with that

Jim

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