Written by Ben Ellison on Feb 22, 2013 for Panbo, The Marine Electronics Hub
There's lots more to report on from the Miami show, but partially installing a Maretron DCR100 Direct Current Relay on Gizmo just got me so excited I want to share. This boat has never had switches for running and flood lights on the fly bridge -- especially annoying when I wanted to light myself up when crossing paths with a possibly unaware stranger -- and it didn't have a switch for the new bow LED spot at all (to be explained). Now for relatively little effort and expense, I'll not only have switching at both helms but also be able to monitor and even alarm on real-time circuit currents. The installation isn't complete but I'm fairly confident that Gizmo will trek north with that often-cited feature of digital switching, an immediate warning if any one of the four incandescent running light bulbs blows. Plus I got to experience the beauty of NMEA 2000 Labeling, a feature that Maretron has trail blazed but which will hopefully become common across brands...
First let me be clear about what the DCR100 can and can not do. It is not a distributed power system and it does not provide solid-state circuit protection. It is simply a set of six solid-state relays each able to handle up to 10 amps and to be controlled and monitored with N2K messages (PGNs) . Moreover, the DCR's six "channels" will all be open (off) if the N2K network is powered down. So for loads that you want to switch irregardless you'll need to wire in a parallel mechanical switch as explained in one of many useful Maretron DCR FAQs (note how they also frankly explain why a double throw switch might be warranted in some cases).
At any rate, I plan a separate switch for a couple of the six circuits that I use sometimes on a mooring but I've mostly chosen loads that are only used underway and, besides, it would be trivial to jump a relay if needed. So for loads like the running lights installation was simply a matter of cutting the short wire that went from the circuit breaker to a distribution terminal strip, adding ring terminals and screwing them to the in/out sides of relay channel #1 channel (well, in my case there was more to it than that, which I'll get to eventually). As for the Rigid Industries LED spot -- which I'd already installed on the bow pulpit where a redundant combined side light fixture had once been (and which is great at illuminating the waters just ahead of the boat) -- I simply moved its feed terminal from the nav light strip and put it on channel #2 (whose current feed is jumped to #1). Then I switched on the fused Nav Light and NMEA 2000 circuits and the real fun began...
Because Gizmo has a Maretron USB100 gateway to the main computer (also useful for navigation), I could configure the DCR100 using N2KAnalyzer, as shown above. This can be done with the Maretron DSM250 display, or the new and economical DSM150, but it would be a very tedious process (as I once experienced). With my setup I quickly typed in those verbose Labels -- which cover both the device and its channels, and also a related "Installation" field -- and even did the first switch test by setting "Switch Control" to ON and then writing the configuration to the DCR (the bottom button "Put Config to Device"). Then when I built the snazzy DSM250 screen below it only took a few minutes mainly because I could tell each section to use the programmed Label for a title. And when I install the DSM150 on the fly bridge I believe I'll be able to easily clone that and all the other 250 screens. Nice!
Now I am not expecting any other device on Gizmo's N2K network to understand the Labels programmed into the DCR or to do the switching, but it might happen eventually. The official Label PGN is part of just-out NMEA 2000 Edition 3, the Switch and Switch Status PGNs are already in place, and the other Power PGNs have been long in the works. (Where needed, Maretron wrote their own PGNs, but they'll be replaced with Standard ones when possible, and updating the devices is easy with a USB100).
But to continue my partial install story, there was a dramatic low point in its arc. That was when I built the simple switch screen seen at the top but then couldn't figure out how to actually switch the circuits with the DSM. I found nothing about it in the DCR manual and then when I looked again at Maretron's DCR product page it seemed like I needed their elaborate N2KView software. I should have looked at those DCR FAQs but instead I commenced to kicking myself for an impetuous purchase...until I got in touch with customer support. Darned if Maretron hasn't built a slick "Command" mode into the DSM displays. It's invoked with a long push on the right button and then the up/down keys select fields (instead of other display pages) and a tap on the power button does the switching. Not quite as quick as a regular switch but quick enough and with many side benefits. I'm delighted with my DCR experience so far and, like the DSM150, I think we're seeing that Maretron's great technology is now within reach for smaller boats, retrofits, and even do-it-yourself installs.