Redundancy

We are docked at the Cocoa Village Marina in Cocoa, Florida (map), not to be confused with Cocoa Beach which is a half dozen miles due east and across two rivers from here.  We have friends in Cocoa Beach who have generously provided us with RV parking on many occasions, but no practical way to visit them on this pass.

Today's temperatures soared back up into the 60s and we did not really need another marina tonight, but we had a certificate for a night's stay, and so our visit here is costing us just $12, for electricity.  It's one of the nicest marinas we've seen, with a nice lounge, laundry, and rest rooms.  We'd never have ventured in here without the incentive, as the channel is a mere seven feet deep, and we saw sounder readings as low as 6.3' on the way in, but we're glad we came.

We've been to Cocoa before -- there is an Elks lodge just a few blocks from here where we've stayed in Odyssey more than once.  It has a functional, if not vibrant, downtown with a handful of restaurants and a famous hardware store, and we wandered over to Ryan's for dinner.  It was a nice break in an evening filled by an unscheduled project.

That project would involve the complete failure of our primary chartplotter mid-cruise today.  Fortunately, I was steering with the autopilot on heading mode, with no route entered on the plotter, and the backup plotter was fully functional, if a bit slow.  We were tied up here by 2:30 in the afternoon, having shoved off around 11 this morning, so I had plenty of time to work on it.

This plotter, a Northstar M121, was added to the boat in 2007 by the last owner, along with an AIS receiver.  It was state of the art in its day, and has been a pretty good plotter for us, but it's had it issues.  For example, several times the GPS position has "jumped" back and forth between our actual position and some random position half a mile or so away -- once, it even had us jumping over to the Med and back.  Fortunately this has never happened under way, but rather only while we were docked or anchored.

A couple of weeks ago, some sort of GPS error cause our total mileage to jump from under 2,000 nautical miles to over 5,000.  We'd been using this information for our log entries; fortunately, the backup plotter also has a mileage total and we were able to simply switch over to it -- the figures differed by a mile or so and we noted that in the log book.

In addition to the actual errors, the unit had some limitations that has had me working toward replacing it anyway.  Chief among these is a lack of overzoom -- on some charts, you just can't zoom in far enough to see what you're doing.  The user interface is clunky, and certain alarms that ought to be configurable aren't, such as constant complaining that there are no AIS targets in range.

Today's failure was the CCFL backlight, which quit entirely.  At first I though the plotter had lost power or otherwise been switched off, but a reboot revealed that the screen was still there, just unreadable.  Unfortunately, this sort of LCD can not be read at all without backlight, and so the unit is basically defunct.  If I leave it on, at least the GPS position data will continue to flow to the VHF radio, but that's about it.

Ironically, the backup chartplotter, which is original to the boat and thus twice as old as the Northstar, is still running like a champ.  Being much older technology, it is much slower to update the screen, and lacks the ability to display AIS target data, but it is serviceable and is also passing information to the other VHF radio, the depth display, and a plotter screen on the flybridge.  It also runs the radar and can overlay that on the chart.

I can still get parts and service for this much older system, a Furuno unit.  Northstar, on the other hand, ceased to exist years ago, being subsumed into Simrad before, they, too, were swallowed up by Navico.  A call to Navico this afternoon revealed that they stopped servicing these units over a year ago and parts are no longer available.

With nothing to lose, I opened up the case, and I think I can get a generic replacement CCFL online and get this working again.  If so, it will end up on the flybridge, where I can use a second daylight-readable display, which had been my plan for this unit when I replaced it anyway.

Replacing the CCFL and getting this back together and functional is more of a long-term project -- it will take at least a week to get the tube once I have the old one out to measure it, a project which will likely take me another couple of hours at least.  That's too long to go without a working display in the pilothouse that updates faster than the old Furuno and can display AIS, and so I ended up tackling the critical two thirds of the PC-chartplotter project, which I had planned to get to later in a more leisurely manner, this afternoon.

Some time ago I had already spliced in a serial cable to the AIS receiver NMEA output for exactly this purpose, and so today I did not have to monkey around under the helm.  Also, I already had two critical components on hand and standing by -- the display, which is a $99 LCD TV we bought at HH Gregg back in March, and the PC, which is the Acer notebook that I recently replaced with an Asus Linux notebook for my daily use.

I ultimately need to mount the Acer under the helm someplace and run all the cables properly, but I was able to get all the pieces working together and the display properly positioned today.  The AIS unit happens to include a GPS receiver and so the single NMEA cable carries both position and AIS information to the PC where it is processed by either Polar View or OpenCPN chart software.  It's all working fine here at the dock, and tomorrow we'll find out if all is working properly under way as well.

Accelerating this project means I will have to work some more magic later to get our new AIS transponder working.  The idea had been to replace the current AIS receiver with the new transceiver, but that will now mean finding a new source of position information for the PC.  As it stands now, both the PC and the older Furuno plotter are fully separate and thus redundant systems -- they do not share any inputs.  The new AIS unit will be taking position from the Furuno.

Eventually I will find a way to make it all work.  We have no fewer than ten working GPS receivers on the boat, not counting embedded ones whose data we can't read directly (such as the ones in the EPIRB or the Spot tracker).  Half of those are connected in some way to functional chart plotting systems, so we always have a way to plot our position.