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Old 02-02-2015, 11:44   #1
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Connecting heading sensor to laptop

Hi,
In order to overlay Navico radar display on the chart display one needs a heading sensor. The affordable Simrad GS25 looks like it will work but outputs NMEA 2000. Can anyone provide advice on cabling this into a USB port on the laptop ? Or more generally, how does one get a NMEA signal into a laptop.

It would also be most helpful to start a thread for non-technical users the details of successful Open CPN intallations such as equipment used, cabling, and insights into making it all work. These would be a great reference.

Thanks for the help

Mike
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Old 02-02-2015, 18:25   #2
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Re: Connecting heading sensor to laptop

Mike..
The GS25 can for sure be used as an GPS and Heading sensor but since it meant to be connected to a NMEA2000 network you need a T-connector, and perhaps a terminator. It depends on what you have before in terms of NMEA2000. Since OpenCPN can't use NMEA2000 you also need a NMEA2000-NMEA0183/USB converter connected to the "T" and to your OCPN PC. (The converter can be something like this: NGW-1-USB - Actisense NMEA 2000 to NMEA 0183 Gateway NGW-1-USB for only 192.95 !)

Håkan
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Old 02-02-2015, 19:24   #3
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Re: Connecting heading sensor to laptop

Thank you Hakan for your quick reply. Do you (or anyone) know what people are using for a heading sensor in order to do a radar overlay? I haven't found any posts that give specifics, just mention the need.

Mike
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Old 02-02-2015, 21:53   #4
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Re: Connecting heading sensor to laptop

Wasn't a "heading sensor" also known as a "compass" back in the 20th century?

Do you have an autopilot that communicates via NMEA? If so, its compass would output heading via HDG or HDM sentences.

In general, NMEA 0183 can be passed into a laptop via an inexpensive serial-USB converter. Be sure to get one that has drivers that are supported by your OS.
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Old 02-02-2015, 21:56   #5
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Re: Connecting heading sensor to laptop

Yep, most installs use the Autopilot heading sensor NMEA 0183 via a USB-RS232 adapter available from any computer store, or ebay etc. If you dont have NMEA 0183, you'll need to convert the NMEA2000 first.
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Old 03-02-2015, 06:51   #6
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Re: Connecting heading sensor to laptop

Thanks, but I do not have an autopilot that speaks NMEA. It sounds like the solution is a heading sensor that uses NMEA 0183 if one exists.

Mike

edited to add:
If an affordable one exists.
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Old 03-02-2015, 09:30   #7
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Re: Connecting heading sensor to laptop

Quote:
Originally Posted by mwybo View Post
Thanks, but I do not have an autopilot that speaks NMEA. It sounds like the solution is a heading sensor that uses NMEA 0183 if one exists.

Mike

edited to add:
If an affordable one exists.
What does your AP speak? Best to use what you already have.
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Old 03-02-2015, 10:10   #8
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Re: Connecting heading sensor to laptop

It is an older Raymarine wheel pilot. I am not yet ready to replace it but when it does go I am considering a CPT which apparently cannot share heading data. I am striving for simplicity. I have no plans to drive the autopilot from the chartplotter. My interest in the OCPN option is as a backup to the chartplotter (and for its additional route planning functionality).

Along this line of thought, can the radar output be displayed with OCPN without charts, that is simply as a backup radar display? Does this eliminate the need for a heading sensor? And how would you get this display? It seems that I have seen it on a post somewhere but cannot find it again.

Thanks in advance.

Mike
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Old 03-02-2015, 12:06   #9
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Re: Connecting heading sensor to laptop

Straying off-piste into hackspace for a moment (given how the raspberry pi is du jour encour...)

I currently have a raspberry pi with GPS unit hooked up to the onboard uart, acting as a wireless access point (although it could just as well connect to an existing network if I had one) and multicasting NMEA GPS info which could be used by OpenCPN using a network data connection. Adding accurate heading is something I've been thinking about.

Magnetometers and accelerometers are cheap. If you want to minimise the soldering and spend a bit more cash you can get breakout boards from the likes of sparkfun for under USD30 for both. If you want to minimise the soldering *and* most of the math you can get something like an HMC6343 for USD150 which will put out compensated heading. Of course then there's translation of the heading data into NMEA but that should be trivial compared to the math if going for the cheaper options :-)

Not exactly a turnkey solution but might be a thought for some folks
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Old 03-02-2015, 12:14   #10
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Re: Connecting heading sensor to laptop

Quote:
Originally Posted by mwybo View Post
.........Along this line of thought, can the radar output be displayed with OCPN without charts, that is simply as a backup radar display? Does this eliminate the need for a heading sensor? And how would you get this display?............Mike
Mike..
Even if not you install any charts there is a background world map in OCPN so theoretically you can always display the radar picture. But OCPN still needs to know your position, a GPS, and the radar plugin needs a compass heading to be able to locate the echoes received from the radar on screen. A "stand alone" radar function is not implemented.

But... you mentioned you will use OCPN as a back up radar display. Does that implies you have a a radar viewer? Doesn't that one need a compass heading??

BTW, of course there are electronic compasses using NMEA 0183 out there.

Håkan
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Old 03-02-2015, 14:37   #11
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Re: Connecting heading sensor to laptop

Muttnik, Thanks but way beyond my abilities or interests but could be an interesting project for others.

Hakan, the GPS is no problem, I have a USB GPS puck which works fine. My understanding is that a GPS feed is not required for the radar only display and that a compass is only required for a radar image overlay on charts, hence my question about using a null background (or the world map as you suggest) in order to have a simple radar display backup (with GPS disconnected?).

The way the Simrad documentation for the chartplotter is written, one can view the radar OR chart display individually, but a radar overlay on the charts requires a compass/sensor.

So the GS25 would work directly with the Simrad NSS display to provide radar overlay on charts on the plotter but without the NMEA 2000 to NMEA 0183/USB converter this overlay would not work on a laptop running OCPN.

In a backup scenario:
- with a dead chartplotter I would use OCPN.

- with a dead compass/sensor I would switch between these two views on the plotter or the OCPN laptop (no overlay).

- with a dead GPS antenna on the plotter I would use the GPS puck on OCPN for charts and the plotter screen for radar.

- with a dead radar unit I would use either the chartplotter or OCPN for location and my foghorn!

Anyway, it would be interesting to confirm my assumptions about how all the pieces work together for various functionality. Except for the compass/sensor the components of the OCPN based backup are likely to already exist for most users for everything except radar overlay on charts (assuming a stand alone radar display is possible) so maybe that is good enough. A Chart/Radar split screen or switching display might be an interesting enhancement. US electronic charts are free but Canadian electronic charts are now at 600$CAN for a regional chartbook so the OCPN backup can get expensive for sailing Canadian waters.

Of course there is always the Navionics charts (US and Canada) on a tablet for 17$ per year and paper charts as the ultimate backups but no radar.

What do you think ?

Mike
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Old 03-02-2015, 18:54   #12
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Re: Connecting heading sensor to laptop

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Originally Posted by mwybo View Post
It is an older Raymarine wheel pilot...
Then all you need is a Seatalk-to-NMEA converter (and maybe an additional Seatalk cable). There are several different converters available.
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Old 03-02-2015, 21:12   #13
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Re: Connecting heading sensor to laptop

It looks as if Defender has a NMEA 0183 to USB cable (55$) and a Sea talk to NMEA 0183 gateway (230$). That may be the way to go for my particular application. I only wonder if the flux gate compass will really output, through Seatalk, the required NMEA sentences. It is a Raymond ST 4000 autopilot. Anyone know?


Mike
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Old 04-02-2015, 02:01   #14
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Re: Connecting heading sensor to laptop

Mike...
Reading the manual for your AP, page 40 and forward, it's clear it can listen to NMEA0183 from for example OCPN to navigate to a way point or act like wind vane. All depends on what NMEA sentences are available. But there seems to be no NMEA talker from the AP so it's not sending header info that way. But it's likely that the header info from the AP is communicated to SeaTalk. So if you have a SeaTalk instrument next step to find the header info is to check what you can get out of that. Is there a NMEA connection on the instruments or on the SeaTalk bus itself?
I don't have any SeaTalk myself so my experiences in this matter are limited. Others here may have some info like the tip from RD some posts up?

For the BR24Radar_pi no stand alone radar screen is, as said, implemented. And as always for a open source project like this, everyone who would like to contribute to program that are welcome. There have been some previous requests.

And, Mike, as you may have experienced, you have started to find you a way out of a jungle. All different instrument suppliers are protecting there business by there own technical solutions and data communication buses. They like to stuck every customer to their own gadgets and not easily allow mix with other marks or "suspicious" things like free and generous software. To find our way out we all have to look for more or less hidden information by own investigations and/or listed to others, like in this forum.

My solution to get a radar overlay on OCPN was to build my own electronic compass since I couldn't find a affordable one on the market.(Inexpensive heading sensor?) All you need is some enthusiasm, computer friendly attitude and time.

Hope you'll find your way/ Håkan
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Old 04-02-2015, 03:26   #15
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Re: Connecting heading sensor to laptop

My Raymarine ST1000+ does only output on Seatalk. Recives from both NMEA and Seatalk.
However , my AP , and probably yours too , has a gimballed fluxgate compass , wich I will say is not suited for radar overlay.

A NMEA2000 (or 0183) heading sensor and a NMEA 2000 converter or input device will give you Radar overlay and all other NMEA2000 data on both the plotter and the computer.

This one is open source , and a lot cheaper than most.
vYacht Yacht automation
It will allso make your NMEA data available on wifi for your computer/I-thing/android pad.

.manitu
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