Where to put Raymarine SeaTalk / NMEA E85001

[nigelmercier]

I've recently bought a Raymarine SeaTalk / NMEA E85001 converter, so I can feed my depth and wind instruments back into the chartplotter for display. I've run a 9 metre twin screened cable from the chartplotter to the deck instruments: one cable for the GPS output to a repeater, and one for the return from the SeaTalk bus.

My question is: is it better to put the converter near the SeaTalk instruments, and feed NMEA back down the wire, or should I feed SeaTalk down the wire and put the converter the GPS end?

 

[captainslarty]

either way - no worries.

 

[simonfraser]

if, when ! , u later change the converter to the latest gizmo, what is the best location for that. easier to reach, where is there more space for later ?

 

[captainslarty]

Hi Nige, well, put it where it is easy to reach... simple..

cant really add to that.. not rocket science lol..

 

[Gypsy]

As others have said, either way but also consider:

1) The driest position, the box is splashproof but has electronics and they don't like moisture.
2) There is NMEA in and RS232 Out which you may want to get at later.

I'd suggest inside near to other electronic cabling with reasonable access.

 

[nigelmercier]

Thanks for the replies. My main concerns are to do with signal loss and possible interference between the two cores. Is the SeaTalk bus capable of propagation along a long wire? Would it be better to have signals with the same or different protocol in close proximity?

 

[captainslarty]

Yes..
dont matter,,,,,,,,,,,,,

Hope that answers the point..

its fried potato bits and chips.. dont matter really. int he lengths we are discussing it is NOT a problem, either way.. and no rfi from either!

 

[Gypsy]

As per C'slarty, no real issues unless your boat is veeeery long. The biggest issue for ST is the number of instruments plus cable length and this again only really applies to a large number like 16+ instruments.
ST is a very basic and robust network. NMEA is similar. Use shielded cable with -12v connected to the shield (and ground). That does not say it is immune to other high power signals but generally will not be affected by other similar data cable runs.

 

[nigelmercier]

[ QUOTE ]
Use shielded cable with -12v connected to the shield (and ground).

[/ QUOTE ]

As part of my rewiring exercise, I've been making a point of specifically <u>not</u> connecting the NMEA negative to the battery negative. I figure the GPS has a separate output for a reason.

 

[Gypsy]

It depends so much on the rest of your system as to what to do with the -ve of NMEA but usually it is often at GND potential anyway with mixed types of equipment even if the spec says they should be balanced RS422. Sometimes you simply can't avoid taking NMEA-ve to ground but if you can keep pure balanced NMEA to NMEA then you are right to stay pure as long as you can. In that case use a shielded pair and put the shield to gnd whilst keeping the NMEA balanced lines separate from gnd.

Actually I really meant to refer to the ST cable which is a shielded pair (red and yellow by Raymarine norms) +/-12V and data where the -12v is usually the shield/screen, sorry for any confusion.

Although one can't be totally blase' about these signals, they are either +12v to Gnd or +5v to Gnd low rate data and very robust compared to Rx antennae and other low level signals so they are far less liable to interference unless there is some other poor wiring or grounding elsewhere. Of course, it is not hard to have poor connections in a salt laden boat atmosphere so it still pays to be careful.

 

[nigelmercier]

I've now realised that SeaTalk has 3 wires (power +/- plus data) so it will have to go on the far end anyway!

Now I need a SeaTalk plug, see this thread

 

[Gypsy]

I've never seen a manually wired SeaTalk plug (skt), they have always been moulded. As others have suggested, you can buy a SeaTalk cable and join it to the cable you are installing either in a junction box or with a soldered connection using waterproof heat-shrink tube.
I guess you are considering the connection at the ST60 end as the interface box has screw type (or clamp) connections as I recall. If the rear of your ST60 instruments are in a protected space you can also use miniature spade connectors preferably insulated with heatshrink. The wires to/from the transducers on my ST instruments are connected that way.
You asked elswhere about LED's for ST60. Do you mean for the backlight? Have your incandesant lamps failed or are you just wanting to save current? Either way it will involve opening the instrument which has its own risks.