SeaTalk to NMEA

[whucky]

hi,newcomer to this forum, and to electronics, but you could stop my boat from collecting anymore dents from flying screwdrivers,if you could explain how to conect my st1000 autopilot to a cp300 chartploter and cliper wind instr. thanks whucky.

[Roy M]

Whucky, try this site to understand the difference between Seatalk and NMEA: Thomas Knauf ****SeaTalk Technical Reference

Seatalk carries power in the red wire. The data is the yellow wire. Ground is black.

NMEA is a on-way street, no back and forth communication. GPS would send its position data to the chart plotter. The autopilot sends and receives on the NMEA IN and OUT terminals. Seatalk is a Raymarine proprietary product, so the three wire cable won't do you any good when trying to interface with a non-Raymarine unit. You can try a Seatalk-to-NMEA multiplexer, but read the owner/installation manuals first to see if it will meet your needs. I've also wired all my NMEA data wires (the yellow wires ONLY) into a common buss (a common buss terminal, a brass strip with muliple screws) and output that to my Raymarine chartplotter via the NMEA input. By reading the previos reference to how NMEA works, you can see the logic of this. Even the Raymarine people agreed with me after I demonstrated that it worked.

[whucky]

hi, roy heading to boat at weekend ,so i will give that a try, thanks for your help,whucky

[iain_scott]

I've got the clipper wind inst.

IIRC, it doesn't have any NMEA output/input. So you can't connect it to anything. That's a pest since it would be nice for the autohelm to steer to the apparent wind. I think it's a case of you get what you pay for with the Nasa stuff.

Regards,
Iain

[whucky]

hope you are wrong about that, i asked before buying the wind instr and was assured it had nmea output

thanks, whucky.

[SoonerSailor]

Originally Posted by Roy M

I've also wired all my NMEA data wires (the yellow wires ONLY) into a common buss (a common buss terminal, a brass strip with muliple screws) and output that to my Raymarine chartplotter via the NMEA input. By reading the previos reference to how NMEA works, you can see the logic of this. Even the Raymarine people agreed with me after I demonstrated that it worked.

Roy M, are you saying that the simply paralleled all of your NMEA sources/receivers without any special interface, and all of that NMEA data is available to whatever equipment needs/uses it?

[Redcoat]

Raymarine interface e-85001

[Roy M]

Soonersailor, read the site listed in the beginning of the thread regarding how SeaTalk works. It will give you an idea of how this type of network is transporting information, as well as its limitations. It's pretty cool, once you get it. NMEA can ONLY send or receive these strings of data. That's why you have NMEA input positive and output positives, plus the accompanying negative wires. Add a 12 volt power wire, and the software to process stuff in two directions, and you have Seatalk. It was a pretty clever idea in its day. Then came ethernet cable and that was the advent of the high speed network. Then, along came the later network of a single cable with junction nodes called Seatalk ng (for next generation). This is evolution in action.

Regarding the use of a single buss terminal as a distribution node for NMEA 0183, it's probably not discovery on my part, I simply observed that an NMEA 0183 device that is outputting data doesn't need to coordinate its data with the stream from other units doing the same. Information either slips into the line of data, or it crashes into another sentence, thus negating the two pieces of data for a millisecond until the next pieces fall into sync. Same for a device reading (input of data) the stream of sentences. If it is programmed to accept only the info for water depth or wind angle, only that info gets shown on the display. So, I tried it, dumping NMEA 0183 outputs into a terminal buss, and wiring the inputs into the same buss. Think of it as plumbing with one way valves and a big manifold. It has limited use, but it seems to work fine.

[whucky]

the bus bar idea sounds good, tried it out but autopilot still not getting any data, its a 7 year old unit, begining to wonder if it has a fault, any way you know of to check this out, thanks bill.

[Roy M]

You mention that the autopilot is not getting any data. I know that you can test the GPS for sending its data by connecting the yellow NMEA 0183 wire to the positive probe of a digital voltmeter, and the black to the negative probe, then watch the voltages change from 0 to about 6-8 volts as data rolls along. I haven't done that yet with the fluxgate compass, but I'm going to give it a try sometime. Other than a rudder position indicator, what else is input to your autopilot? Oh yeah, the control head in the cockpit. Look for some interruption in the data coming to the autopilot control that sends directions to the drive motor. Sorry I can't be more specific but I'm operating at the fringes of my knowledge and experience. Hope this helps. At a certain point, you might begin considering a new autopilot that integrates with your other electronics. Maybe, to act as a personal contribution to the international economic stimulus, and to increase the personal and economic value of your boat, you could rationalize this as a patriotic duty and then go sailing as a reward for such stalwart sacrifice.

[iain_scott]

Originally Posted by whucky

hope you are wrong about that, i asked before buying the wind instr and was assured it had nmea output

thanks, whucky.

Hi Whucky,

Just done a bit of digging into the NMEA output on the NASA clipper wind. It looks like they introduced NMEA output on post January 2003 models.

Mine looks identical to the current models but doesn't have the output nor does it mention it in the manual.

Interestingly the "current" manual link on the nasa page doesn't mention it either. Perhaps its just an old manual?

http://www.nasamarine.com/pdfs/Clipper%20wind.pdf

Does anyone know if the repeater port uses an NMEA output or is it just a pass-thru connection from the masthead sensor?

The last page of the manual refers to the "remote repeater facility" but doesn't mention what the signal protocol is.

Hope you are getting everything to work!

Regards,
Iain

[Sailndive345]

Don't know about the wind instrument but your Raymarine autopilot should accept NMEA input. I also use a Raymarine autopilot (different model than yours) and connect a Northstar GPS/chartplotter through its NMEA port to interface the two.

I had very good luck in receiving technical assistance from Raymarine in the past for this type of question - you may want to send them an email or a call them as well.

Good luck!

Sailndive

[whucky]

Originally Posted by Roy M

You mention that the autopilot is not getting any data. I know that you can test the GPS for sending its data by connecting the yellow NMEA 0183 wire to the positive probe of a digital voltmeter, and the black to the negative probe, then watch the voltages change from 0 to about 6-8 volts as data rolls along. I haven't done that yet with the fluxgate compass, but I'm going to give it a try sometime. Other than a rudder position indicator, what else is input to your autopilot? Oh yeah, the control head in the cockpit. Look for some interruption in the data coming to the autopilot control that sends directions to the drive motor. Sorry I can't be more specific but I'm operating at the fringes of my knowledge and experience. Hope this helps. At a certain point, you might begin considering a new autopilot that integrates with your other electronics. Maybe, to act as a personal contribution to the international economic stimulus, and to increase the personal and economic value of your boat, you could rationalize this as a patriotic duty and then go sailing as a reward for such stalwart sacrifice.

patriotic duty sounds fine to me, will not feel so guilty about spending now.

[whucky]

Originally Posted by iain_scott

Hi Whucky,

Just done a bit of digging into the NMEA output on the NASA clipper wind. It looks like they introduced NMEA output on post January 2003 models.

Mine looks identical to the current models but doesn't have the output nor does it mention it in the manual.

Interestingly the "current" manual link on the nasa page doesn't mention it either. Perhaps its just an old manual?

http://www.nasamarine.com/pdfs/Clipper%20wind.pdf

Does anyone know if the repeater port uses an NMEA output or is it just a pass-thru connection from the masthead sensor?

The last page of the manual refers to the "remote repeater facility" but doesn't mention what the signal protocol is.

Hope you are getting everything to work!

Regards,
Iain

hi ian, my book is new and there is no mention of nmea in it .