'Roblink' cable: carries both NMEA data AND 12V power?!

[BelleSerene]

Simrad's old IS15 instruments are connected to each other with a 'Roblink' (proprietary NMEA-type network) cable.

Another 'Roblink' cable connects them to the IS15 'transceiver' unit that takes data from sensors and powers them with 12V.

These cables contains only two wires. So somehow, this is both powering the instrument with 12V and providing its NMEA data.

I guess what's happening - which would be quite clever I suppose - is that as the NMEA line is normally at 12V as opposed to open or 0V as most data protocols) except for a squirt of data every 2s or so, and the LCD instrument requires little power to operate, they're feeding it with 12V power, using capacitance to maintain that power during the data squirt which also feeds its NMEA input lines, and then maintaining the power.

In which case, if I'm now trying to take NMEA out of an instrument in the chain to a low-power wifi transmitter, I'd take it from a spare Roblink connector in the chain, but I'm not going to be able to power the unit from the Roblink cable unless I sort out a similar R/C circuit such as I imagine Roblink are using in each instrument.

And I suppose the data voltage swing is that full supply 12V, which might bust the wifi unit which is powered off 5-9V.

Have I got this right, or am I missing a trick? My challenge is that in the part of the target boat where the instruments are, there's no separate 12V source to drive my wifi unit from.

I'd be grateful for any experience here.

 

[TSB240]

We have Simrad IS 15 System.
You are basically correct in that they are interconnected by a robolink cable and one dedicated power cable.
However each instrument has an NMEA port so you can feed your robolink network with info from a GPS or A IS plotter. You can use any spare NMEA port to access any NMEA data to feed a laptop via serial to usb converter or an autohelm or possibly your WiFi unit. There is no nmea port on the transceiver unit.

Confusingly the nmea ports use the same robolink connectors !

 

[Topsailer]

I note this thread is rather old but hope there is some chance of a reply.
I have the Simrad IS15 system, including a Simrad DSC radio with a Garmin plotter. The NMEA0183 connection from the plotter to the radio appears to be the only NMEA connection. I have just replaced the plotter with a raymarine ES78 and also installed the raymarine AIS 350, Quantum Radar and ACU200 Linear Drive Autohelm. I would like to connect up the Simrad wind, depth and speed instruments via the raymarine NMEA0183/Video cable connected to the plotter but I dont have a network diagram so hope someone has information on the Simrad system to tell me if I can just connect the J4 output (I believe this is the NMEA0183 output on these simrad instruments) direct to the raymarine NMEA cable without causing any damage to the new kit as I have read the NMEA 0183 output from the IS15 system also carries 12volt power?

 

[TSB240]

I note this thread is rather old but hope there is some chance of a reply.
I have the Simrad IS15 system, including a Simrad DSC radio with a Garmin plotter. The NMEA0183 connection from the plotter to the radio appears to be the only NMEA connection. I have just replaced the plotter with a raymarine ES78 and also installed the raymarine AIS 350, Quantum Radar and ACU200 Linear Drive Autohelm. I would like to connect up the Simrad wind, depth and speed instruments via the raymarine NMEA0183/Video cable connected to the plotter but I dont have a network diagram so hope someone has information on the Simrad system to tell me if I can just connect the J4 output (I believe this is the NMEA0183 output on these simrad instruments) direct to the raymarine NMEA cable without causing any damage to the new kit as I have read the NMEA 0183 output from the IS15 system also carries 12volt power?

You are correct to use the dedicated NMEA port from any IS 15 unit to provide the NMEA signal to your plotter. I think I am correct in saying that port 1 is for 12v supply port two is for only interlinking that instrument with other simrad is15 instruments (robolink is basicaly NMEA and 12V) I cant remember the function of port 3 possibly for direct connection of sensor and port 4 is for NMEA connection to other non simrad NMEA equipment data only. NB this port can only operate in one direction. I seem to remember to set this port automatically you turn your " Talkers " on first then start up the simrad instruments and it will set itself to either talk or receive

What ever you do not connect the power supply cable into the NMEA port. I did this by accident and sourcing a replacement instrument head with a working NMEA port has taken some time and was very expensive.

For what its worth here is a link to the IS15 Manual if you want to get in touch with your feminine side!

http://www.dwcsystems.com/SiteAssets/outlet/20220760L IS15 General.pdf
Read page 71

Steve

 

[BelleSerene]

That's great Steve - and thanks for your reply to my original question too!

pp66-69 of that confirm that port 4 on any of the instruments is an NMEA port, and p69 gives its pinout (treat your chart plotter as the NMEA 'listener'). I remember I had to buy a Roblink cable from eBay to do my friend's system. You'll have to do the same unless you want to get your smouldering iron out and do surgery on the instrument.

 

[Topsailer]

That is great info chaps and far quicker response than Simrad from whom I have still not had a reply. I also believe I can connect all the J4 outputs together on the plotters NMEA 0183 cable of the correct Baud Rate which I think is 4800. Once I have confirmed no 12volt on this I will also check with Raymarine technical on the existence of any voltage block on the plotter input. I will also check the twin connectors on J4 socket on all instruments and if no 12volt is present will likely try the second connection option of doing a little soldering on the J4 connections, as sourcing a cable looks to be an impossible task and very expensive.

Cheers,

Rob