Another Interface Issue - Or Is it ?

[Dreaming Yachtsman]

This post is for all you Furuno wizards out there.

SYSTEM ARRANGEMENT: (See sketch below)
In 2003 our new boat came from the factory with Raymarine speed, depth, wind, and autopilot units installed. Because the folks outfitting the boat for us did not recommend that brand, I chose to install a Furuno model RDR-139 combination radar/chartplotter instead of staying with Raymarine to have a fully integrated system. They also installed an ICOM VHF radio with DSC capability. To provide position input to the VHF, they connected it to the posisiton output from the chartplotter. They provided heading input to the radar by tapping the NMEA output of the nearby autopilot repeater and feeding it to the radar input. Everything worked fine - for a while.

{Sorry about the size of this picture - I haven't mastered that feature of this forum yet.}

PROBLEMS:
1. About two years ago I noticed that the radar would no longer go into North up mode, apparently because it had lost its heading input. Troubleshooting the interface cable between the autopilot and radar verified that it had good continuity. Last February an electronics technician from another boat in the marina hooked his computer to the connecting cable and showed a steady stream of NMEA data coming from the autopilot as long as the connecting cable was disconnected from the radar. When connected to the radar, it showed jibberish.

2. At the same time I noticed that the VHF was no longer receiving a position from the chartplotter.

3. Since December 31, 2008, we have experienced "No GPS Fix" alarms on two separate occasions. See my post at: http://www.cruisersforum.com/forums/...arm-24623.html for more details about that issue.

QUESTIONS:
A. Does Furuno use an Input/Output bus scheme for its data ports? Connections for all three devices that are displaying problems are located fairly close together on the back of the unit. I'm thinking that perhaps gradual failure of the bus is taking out input and output through the data ports.

B. Is there a way to repair any or all of these problems, short of sending the unit to a service center for testing and repair?

If anyone needs more information, please let me know. I won't be back to the boat for another couple of months so I can't do much troubleshooting right now. I wanted to start working the problem now to minimize delays in repairing the unit when I do return and also to have a plan in case the GPS input fails again permanently.

Thanks,

[osirissail]

There are certain Raymarine instruments that have integrated NMEA input/output terminals. These are used to feed equipment that is not Raymarine and vice versa. However there are different versions of NMEA and some "sentences" are not recognized by other equipment if it does not have the ability to read that version of NMEA. If you are feeding various instruments into a integrated system, RayMarine makes a "NMEA" sequencer box. You plug your Raymarine cable into the sequencer and then connect the NMEA inputs and outputs of GPS, radar, compass, etc. to the sequencer. What the sequencer does is collect up the various NMEA data signals and arrange them like ducks in a row and then send them out to the various instruments. NMEA is a sequential system so each data bundle has to be kept in order or the whole data steam goes chaotic. Some brands of equipment are more docile and accept most anything and others are - sort of - hostile to data from a foreign source.
- - The order in which you hook up each component to the system does make a difference (in real life) and can only be determined by trial and error. In general Furuno and Raymarine do not get along very well together data wise. It might be easier to get a separate fluxgate compass to feed the Furuno. Check your Furuno manual to see what brands it likes and dislikes.

[Dreaming Yachtsman]

osirissail,
Thanks for the reply but the problem does not appear to me to be related to mismatched data streams as the lashup used to work fine. I was thinking more along the lines of gradually degrading input/output channels.

Your idea of a separate flux gate has merit. If I can't get this system to work again, I may give that a try.

[richardhula]

Originally Posted by Dreaming Yachtsman

PROBLEMS:
1. About two years ago I noticed that the radar would no longer go into North up mode, apparently because it had lost its heading input. Troubleshooting the interface cable between the autopilot and radar verified that it had good continuity. Last February an electronics technician from another boat in the marina hooked his computer to the connecting cable and showed a steady stream of NMEA data coming from the autopilot as long as the connecting cable was disconnected from the radar. When connected to the radar, it showed jibberish.

This suggests an impedance mis-match which is loading the signal from auto-pilot, or some standing voltage on the radar input. Why this would suddenly happen I can't say.

In any case whilst your original technician did manage to get everything working it was done IMHO an un-proffesional manor. Ideally a GPS position feed should have be sought at source, i.e from the Raymarine mushroom assuming that's what you are using. The problem there is it's probably set to output SeaTalk to feed your other Raymarine devices.

Assuming this case I would suggest the Raymarine Seatalk/NMEA interface box # E85001. This would ideally be connected to your Seatalk instrument bus which in turn is fed directly from the GPS mushroom, this in preference to connecting to your charplotter output which adds a another link to the chain & relies on this device being switched on.

The NMEA output from this device containing position/heading data could then be fed to both your radar & VHF DSC radio.

[goboatingnow]

I suspect the line drivers for the NMEA /inputoutput in the radar have failed, as to the comments re your original setup. IMHO its was fine , theres no requirement for example to "source" the GPS readings direcrlt from the GPS receiver. The NMEA network will quite happily send them around the system

[osirissail]

- - Yes, the Raymaring Interface box #E85001 is what I have to sort out the data streams from the different inputs and "get the ducks in a row" and then it outputs the now orderly data stream to the various instruments/devices. Without it a screwed up data stream will make some NMEA sentences conflict. The Raymarine "Graphic Display" and "Graphic Repeater" display have NMEA connections on the back of the units - but they must be sent to the "Interface" box to make their output/input "fit" into the sequential data stream. And for some reason only known to the gods, the system can get out of sequence and one unit (e.g. the Furuno) no longer displays or uses that particular NMEA sentence. My Furuno radar has a great "data display" for nav data but for some unknown reason will not display the NMEA cross track error sentences whereas all the other interfaced instruments display it just fine. That is why the order of connections to the Interface Box seems to make a big difference in getting the data to other displays/users. Maybe a Furuno "Interface" box would be better than a Raymarine Interface box? I think I will investigate that for my "problem."

[richardhula]

Originally Posted by goboatingnow

I suspect the line drivers for the NMEA /inputoutput in the radar have failed, as to the comments re your original setup. IMHO its was fine , theres no requirement for example to "source" the GPS readings direcrlt from the GPS receiver. The NMEA network will quite happily send them around the system

No absolute need to connect/source GPS directly true. But doesn't it make sense to have fewest links in the chain when feeding devices, especially when there's a safety impact?

Unfortunately John doesn't have an NMEA network just a Seatalk one hence need for converter box.

[Dreaming Yachtsman]

The GPS receiver is actually Furuno and was installed along with the radar/chart plotter.

The Raymarine autopilot outputs NMEA through a special port just for that. The output to the other devices comes from that port. Thus I don't feel that the "problems" I have are from data incompatability.

goboatingnow seems to be pointing at the same component I think is acting up. What is the solution for that?

[osirissail]

- - >>> What is the solution for that? <<< Take the unit to a Furuno shop and see if they can find a bad circuit is a reasonable first course of action.
- - If they cannot find anything wrong then invest in a NMEA Interface unit. That is what I had to do to make the integration work. Look up the signal protocols NMEA uses and your will see that somewhere in the system - if using different brands of instruments - each separate brand unit's output must be sent through an interface to properly order the packets of data. Raytalk does that within the Raymarine loop of their instruments and Furuno also has a proprietary buss for their equipment.

[Dreaming Yachtsman]

During the past hurricane season, I finally took the unit to the Furuno repair depot in Camus, WA, as suggested. They replaced the "processor" card and now everything works again.

Thanks to all commentors for your advice.