Linking Navman wind instrument to Raymarine ST4000+ via NMEA?

[Rob_Webb]

Does anyone know with certainty (like they've done it before) how to link a Navman 3150 wind instrument to an Raymarine Autohelm ST4000+?

I've already got all the Navman isntruments happily talking to each other via their proprietary Navbus system - beautifully easy (simply bundle all the orange wires together and all the blue wires together). Done.

But now I want to feed wind speed and angle data from my Navman 3150 instrument to the ST4000+ so I can use it in windvane mode to sail an apparent wind.

I've attempted to insert pics from the manuals (apologies for the blurring). In essence they suggest it is easy. Firstly, the Navman manual says it can send and receive NMEA data. And the NMEA out is the white wire.

And secondly the autohelm book says clearly that it can receive NMEA wind data from a wind instrument. But from the pic it seems to require two wires, Data In +ve and Data In -ve, which themselves must come from two NMEA outputs from the wind instrument (Data Out +ve and Data Out -ve).

So in effect the autohelm seems to require 2 NMEA input wires but I only seem to have one wire coming from Navman wind instrument?

Any ideas?

Navman Manual
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Autohelm ST4000+ Manual
[image]

[/image]

 

[Talbot]

your confusion is possibly cause some people use + and -, whereas others use in and out. Navan manual is clearly showing 2 nmea signals:
yellow - in
White - out

These 2 get connected to the + and - input on the st4000 . Cant remember which goes to which, but only one way will work so use a temp connnection to prove it.

 

[Rob_Webb]

Thanks. So if I experiment with the yellow & white outputs from the Navman and get them the wrong way around initially, could I do any damage to either instrument?

 

[Malcb]

[ QUOTE ]
So if I experiment with the yellow & white outputs from the Navman and get them the wrong way around initially, could I do any damage to either instrument?

[/ QUOTE ]

As far as I know, No you will not do any damage because there is no 'current' being transferred, only data.

 

[tome]

Sorry to be contrary but info is wrong here and the setup won't work either way you connect it

Only the white NMEA Out should be connected to the NMEA In + on the ST4000+. The NMEA In - on the ST4000+ should go to 12V negative

The yellow wire is provided on the Navman to allow you to feed in external NMEA

 

[tome]

Sorry Mark, hope you don't think my correction ill mannered

 

[fluffc]

I agree with this.

'NMEA +' is signal
'NMEA -' should be connected to ground.

Technical Reason:

Sometimes the input stage of an NMEA port uses a differential amplifier : it is looking at the <u>difference</u> in potential (ie voltage) between the 'NMEA +' and 'NMEA -' connections. Since most devices transmit the signal referenced to ground, then the correct potential difference is obtained by connecting 'NMEA -' to ground.

The reason that this is done is so that any external interference that is induced into the wire (and by using twisted wire is induced by the same amount in both the + and - wires) is effectively ignored by the amplifier, since the amplifier is only measuring the difference in potential between the two wires, and doesn't see the interference that has been induced (equally) into both wires.

Make sense? It's late; I'm babbling.

 

[Talbot]

Happy to be corrected. I wish companies would use the same protocol.

 

[pappaecho]

is the NMEA signal anything like current loop or Rs 323? Does for example it have a software flow control Xon/Xoff or similar, or does it rely on short data words and lowish baud rate?

 

[tome]

Re: Broken Forum

I saw a few responses here before the forum broke! Hope it wasn't us that caused it

 

[Talbot]

its RS232 - hence most GPS connections are serial.

 

[Rob_Webb]

Navman Manual

Autohelm Manual

 

[Rob_Webb]

Thanks Tome. That makes much more sense. I tried the first recommendation and not surprisingly (with hindsight) it didn't work. I did wonder about the earth connection option but didn't try it. I look forward to giving it another go tonight - let you know how it goes.

Cheers
Rob

 

[Rob_Webb]

It worked!

Thanks

 

[tome]

Re: It worked!

/forums/images/graemlins/smile.gif

 

[FullCircle]

I think, and I stand to be corrected, that you can only input one NMEA device to Raymarine. Therefore if you have GPS inputting to ST4000, then you cant add a Navman 3150. You will need the extra NMEA to Seatalk conveerter junction box, about 135 quid.
I have this issue, as I connect a JRC1800 Chartplotter into ST4000+ Wheelpilot, and want to put my Navman 3150 wind input to it.

 

[tome]

[ QUOTE ]
is the NMEA signal anything like current loop or Rs 323

[/ QUOTE ]

Strictly speaking it's meant to be rs422 but is often fudged. It's close enough to rs232 so that you can connect it to a pc serial port. The data is serial at 4800 baud and consists of short sentences of up to 80 characters (plus CR/LF terminators), there is no handshaking so no flow control

It's possible to look at the data using hyperterminal - this is a useful tool for troubleshooting. Connect the NMEA to pin 2 of the PC and connect pin 5 of the PC to instrument ground

All NMEA inputs should go through an opto-isolator according to the NMEA spec, but often they use a differential input instead as fluffc says. An opto isolator is just an LED with a series resistor which means if you connect the wires the wrong way round it simply won't work but no damage done which is good news

When current flows through the LED it illuminates - this is detected by a photo transistor which switches on in sympathy. Thus you have signal flow without any electrical connection, simple and clever

NMEA is pretty robust unless you do anything really daft

I've pasted some NMEA wind sentences below so you can see what they look like

These sentences are taken from a Raymarine ST60 system via an NMEA bridge. Because the vessel was stationary the true and apparent winds are equal.


$IIMWV,084.0,R,10.4,N,A
$IIMWV,084.0,T,10.4,N,A

Field

1 $IIMWV II Talker, MWV Sentence
2 084.0 Wind Angle 0 - 359
3 R Relative (T = True)
4 10.4 Wind Speed
5 N Wind Speed units Knots (K = KPH, M = MPH)
6 A Status (A= Valid)

$IIVWR,084.0,R,10.4,N,5.4,M,19.3,K
$IIVWT,084.0,R,10.4,N,5.4,M,19.3,K

1 $IIVWR II Talker, VWR or VWT Sentence
2 084.0 Wind Angle 0 - 180
3 R Right of vessel heading (L = Left)
4 10.4 Wind Speed
5 N Wind Speed units Knots
6 5.4 Wind Speed
7 M Wind Speed units Metres per second
8 19.3 Wind Speed
9 K Wind Speed units Km/Hr

The subsequent True Wind sentence VWT is similar. These sentences are older NMEA not recommended for new designs

 

[tome]

Quite correct, you'll need the interface and connect one device via Seatalk bus which is multi-drop

 

[shamrock]

An alternative to the Raymarine NMEA / Seatalk bridge, is to use a multiplexer, which takes multiple NMEA feeds and combines them into one single NMEA feed out.

Brookhouse do one with a Seatalk input, so you can put e.g. Seatalk + up to 3 NMEA feeds in, get a single NMEA feed out for lots of devices, and a serial or USB of the same info for the laptop. 115 pounds for serial, 135 for USB

Although looking again at the Raymarine box it's probably almost the same thing.