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Help needed with evinrude interface

Old 02-25-2013, 08:12 PM
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Default Help needed with evinrude interface

Hi guys

I'm trying to wire up my NMEA 2000 network.I have the Evinrude interface cable pluged in to the engine but it isn't long enough to reach the dash, can I use the 15foot starter kit cable as an extension to reach?


Thanks Andrew
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Old 02-26-2013, 01:33 AM
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Yes, that will be fine.
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Old 02-26-2013, 03:35 AM
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Too easy.. Thanks for that



Andrew
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Old 02-26-2013, 01:05 PM
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Originally Posted by churchy View Post
Hi guys

I'm trying to wire up my NMEA 2000 network.I have the Evinrude interface cable pluged in to the engine but it isn't long enough to reach the dash,
It's not supposed to.

The engine interface cable is simply another "drop cable" off the main NMEA 2000 bus, or "backbone cable" (which can run the full length of the boat, and then some, if need be). As such, it MUST NOT be more than 6 meters (approximately 20 feet) long. In the unlikely event that you need to add an extension cable to the existing engine I/F cable in order to reach your backbone, that's OK as long as you keep the combined length of both cables below this limit.


can I use the 15foot starter kit cable as an extension to reach?
That cable is intended to be used as the first chunk of your "backbone". You connect any drop cables (including the one for the engine interface) to it via standard T-connectors. A proper 120-Ohm terminator MUST be installed at each end of the backbone cable; these were presumably also included in your "Starter Kit".


Originally Posted by Moonlighter475 View Post
Yes, that will be fine.
NO, it won't be.



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Old 02-26-2013, 05:14 PM
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I did over a year ago and works great. Try and see if it works for you.
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Old 02-26-2013, 06:02 PM
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So many assumptions..........

Churchy tells us he's installing his network, and the interface cable isnt long enough to reach the dash. A pretty common scenario, given that the interface cables are often only around 4 ft long.

It is perfectly acceptable to simply plug the interface cable into a NMEA extension cable, and plug that into the leg of a T piece up behind the dash. The only proviso, of course, is that the drop from the device (ie the interface cable) to the T piece is less than 6 meters. The "device" in this case is the interface cable, not the engine.

Which it will be since he stated the cable he is using is 15 ft long. Even counting the interface cable length, which you dont need to do, he is still fine. And frankly, even if the interface cable is a bit longer, most likely it will still be fine, as the 6 m is more advisory due to the possibility of voltage drop, than a hard rule.

15 ft extension plus 4 ft interface = 19 ft which is just under 5.8m.

That being the case, what he is proposing is, as i originally said, just fine. this approach has the advantage of keeping all the T pieces up behind the dash where they are not only all together in one place if you need to get to them, but they are also nice and dry and out of the weather.

I have it set up this way on my boat and works just fine.

His other option of course is simply to plug the interface cable into a T piece, and plug the extension cable into the side of the T piece and a resistor into the other side. Means that he will have a T piece somewhere up under the gunwhale, which can be harder to get at and possibly exposes more joins in the network to the elements.

That would be the preferred way to do it if the length from the end of the interface cable to the dash is longer than 6 m. But since he indicates that hes contemplating using the 15 ft extension cable, that seems very unlikely to be the case.

But otherwise, it is 6 of one, and half dozen of the other.
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Old 02-26-2013, 11:32 PM
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Originally Posted by Moonlighter475 View Post
So many assumptions..........

Churchy tells us he's installing his network, and the interface cable isnt long enough to reach the dash. A pretty common scenario, given that the interface cables are often only around 4 ft long.

It is perfectly acceptable to simply plug the interface cable into a NMEA extension cable, and plug that into the leg of a T piece up behind the dash. The only proviso, of course, is that the drop from the device (ie the interface cable) to the T piece is less than 6 meters. The "device" in this case is the interface cable, not the engine.
This is not correct.

The effective length of the drop cable INCLUDES the entire distance from the T-connector to the connection point under the engine cowling. It does not matter if this is one contiguous cable or several shorter cables daisy-chained together, they ALL must be included in the total distance measurement.


Which it will be since he stated the cable he is using is 15 ft long. Even counting the interface cable length, which you dont need to do, he is still fine.
A ~19-foot drop cable is technically "legal", but should be avoided if possible, for several reasons:

-- All drop cables constitute unterminated network segments. The longer these segments are, the more chance for reflections and signal loss. This is the main reason why drop cables are limited to 6m by the spec, while the trunk line can be up to ~100m (328 feet) long.

-- The cables typically used for the backbone are larger/heavier, and therefore exhibit less capacitance and induce less voltage drop for any given-length run. Hence, the greater the proportion of the device-to-device run that is comprised of backbone cables vs. drop cables, the more reliable the signal propagation will be.

-- The "short-backbone / long-drop" scenario effectively puts at least one terminator more-or-less in the middle of the signal path. This is counter to both the letter and the spirit of the spec.


And frankly, even if the interface cable is a bit longer, most likely it will still be fine, as the 6 m is more advisory due to the possibility of voltage drop, than a hard rule.
Not really. The "as short as practical" is an advisory; the "up to 6 meters maximum" is indeed a hard-and-fast part of the spec.



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Old 02-27-2013, 05:50 PM
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Thanks guys for your help. I'll try Moonlighter's idea first.You would think they would make the interface cable longer for these types of situations, I couldn't be the only one you had this problem!
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Old 02-28-2013, 03:02 AM
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Thanks Churchy. I didnt notice that you were in Perth until just now! Im on the opposite side of Oz, just outside Brisbane. A mere 5 hours flight away from you!

If you get stuck, feel free to pm me and i will send you my mobile number and you can give me a call.
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