NMEA 0183 VWR Sentence

[Kurrawong_Kid]

Our boat has an Autohelm/Raymarine 7000 autopilot but no windvane input because we have a B&G Hornet windvane which uses a different protocol. The manual indicates that I need a ST 50 windvane input or any other windvane that outputs VWR sentence. Any suggestions as to what other windvane transducers might work? I can find no output specifications for ST 60 series, for example. I know AT instruments will make up a pc board to change Hornet outputs to NM 0183 but I do not wish to disturb a working system. I was thinking of adding a second wind vane transducer at an alternative site.
Thanks in advance for any info.

 

[tillergirl]

It has on the ST60

Here is a sample on the bus:

$IIMWD,046.5,T,046.5,M,9.3,N,4.8,M*42
$IIVLW,3897.3,N,3.61,N*4F
$IIVTG,104.5,T,104.5,M,8.1,N,15.0,K*64
$IIBWC,050003,,,,,,T,,M,,N,*07
$IIDBT,31.5,f,9.60,M,5.25,F*2B
$IIGLL,5144.793,N,00100.028,E,050002,A,D*50
$IIHDG,106.5,,,0,W*2C
$IIHDM,106.5,M*20
$IIHDT,106.5,T*20
$IIRMC,050003,A,5144.792,N,00100.031,E,8.1,105.0,070616,0,W,D*03
$IIMWV,315.0,R,12.6,N,A*0F
$IIMWV,291.5,T,9.5,N,A*38
$IIVHW,108.0,T,108.0,M,5.40,N,10.00,K*65
$IIVPW,1.98,N,1.02,M*51
$IIVWR,045.0,L,12.6,N,6.5,M,23.3,K*52
$IIVWT,068.5,L,9.5,N,4.9,M,17.6,K*6B
$IIBWC,050003,,,,,,T,,M,,N,*07
$IIDBT,31.3,f,9.54,M,5.21,F*2E
$IIGLL,5144.792,N,00100.031,E,050003,A,D*58
$IIHDG,107.5,,,0,W*2D
$IIHDM,107.5,M*21

I only have an ST60 on the bus for wind.

 

[Martin_J]

Be careful if you spend money and just buy the masthead unit.

I thought the masthead units just output variable voltages for both wind speed and direction..

Confirmed here.
Testing a ST50/ST60 Masthead Transducer

It's the display part that then translates to a protocol and I thought that the ST50 and ST60 wind displays only had Seatalk connections, so would then need a Seatalk to NMEA0183 converter of some sorts.

Tillergirl - Where are you reading those NMEA0183 sentences?

Back to the original question - I seem to think the NASA wind MHU does actually output NMEA0183..

 

[prv]

The manual indicates that I need a ST 50 windvane input or any other windvane that outputs VWR sentence. Any suggestions as to what other windvane transducers might work? I can find no output specifications for ST 60 series, for example.

The manual's stipulation would be better expressed as "either NMEA0183 with VWR sentence, or Seatalk". The ST60 outputs Seatalk so that will be fine, no NMEA involved.

Here is a sample on the bus:

$IIVPW,1.98,N,1.02,M*51
$IIVWR,045.0,L,12.6,N,6.5,M,23.3,K*52
$IIVWT,068.5,L,9.5,N,4.9,M,17.6,K*6B

What bus? That's a sample from an NMEA0183 link, not a bus, and most ST60 instruments don't have an NMEA output.

The ST60 Multi does, older Raymarine autopilots do, and there's a standalone Seatalk to NMEA converter box, but it obviously doesn't make sense for the OP to fit any of these when he could just connect to the Seatalk bus directly.

Pete

 

[Martin_J]

The ST60 Multi does, older Raymarine autopilots do, and there's a standalone Seatalk to NMEA converter box, but it obviously doesn't make sense for the OP to fit any of these when he could just connect to the Seatalk bus directly.

Pete

Sounds good keeping the wind information all in Seatalk... But it would still need the display unit (that the masthead unit wires into) in order to get the variable voltages onto the Seatalk wires..

 

[prv]

Sounds good keeping the wind information all in Seatalk... But it would still need the display unit (that the masthead unit wires into) in order to get the variable voltages onto the Seatalk wires..

Of course. You need the whole instrument, not just part of it.

Interestingly I think even the newest Raymarine range doesn't have a self-contained N2k wind instrument available, it's still analogue wiring down the mast and a box at the bottom (or a dedicated wind instrument).

Pete

 

[Martin_J]

Of course. You need the whole instrument, not just part of it.

Interestingly I think even the newest Raymarine range doesn't have a self-contained N2k wind instrument available, it's still analogue wiring down the mast and a box at the bottom (or a dedicated wind instrument).

Pete

Off topic - but you're right.. Strange - Although for Simrad to make their 508 wind transducer connect direct to the NMEA200/SeatalkNG network, it has to incoporate the termination resistor within the MHU itself.. so not exactly N2k compliant. Perhaps Raymarine didn't like the idea of taking the backbone to the top of the mast.

Back to the OP.. Nasa wind MHU appears to output NMEA0183
NASA Marina tactical-wind-mast-sensor/

 

[Martin_J]

Just noticed it outputs the MWV sentence. In order to get the VWR (apparent wind) sentence, the source device would need access to Speed through water data....

 

[earlybird]

Just noticed it outputs the MWV sentence. In order to get the VWR (apparent wind) sentence, the source device would need access to Speed through water data....

Despite what NASA say, I'd expect true wind needs speed through water and apparent wind from the MHU, not vice-versa.
In other words, I can't see how a MHU can output true wind without supplementary data.

 

[Martin_J]

Despite what NASA say, I'd expect true wind needs speed through water and apparent wind from the MHU, not vice-versa.
In other words, I can't see how a MHU can output true wind without supplementary data.

That's more like it.. I wasn't thinking straight. Thinking more about the coming weekend and struggling in the UK summer heat

 

[tillergirl]

Be careful if you spend money and just buy the masthead unit.

I thought the masthead units just output variable voltages for both wind speed and direction..

Confirmed here.
Testing a ST50/ST60 Masthead Transducer

It's the display part that then translates to a protocol and I thought that the ST50 and ST60 wind displays only had Seatalk connections, so would then need a Seatalk to NMEA0183 converter of some sorts.

Tillergirl - Where are you reading those NMEA0183 sentences?

Back to the original question - I seem to think the NASA wind MHU does actually output NMEA0183..

I collect NMEA from the Autohelm converter. Seatalk comes into the converter and inter alia it sends NMEA via RS232 into my laptop. I use it for surveys in the Estuary. Obviously I only use the DBT, time and lat long codes for that but everything on the bus is sent over. PS I have a simple and effective NMEA logger programme.

 

[prv]

Although for Simrad to make their 508 wind transducer connect direct to the NMEA200/SeatalkNG network, it has to incoporate the termination resistor within the MHU itself.. so not exactly N2k compliant. Perhaps Raymarine didn't like the idea of taking the backbone to the top of the mast.

Ah, of course, that makes slightly more sense.

The length of an N2k drop cable is limited; can’t remember the figure off-hand but it’s probably less than the height of a typical mast, hence only the backbone can get up there and still be compliant. I think a device that’s part of the backbone and incorporates a terminator is not technically allowed, but it’s electrically identical to a layout that would be legal so pragmatically it’s ok. Nobody wants a bundle of loose T-pieces and cable and terminators at their masthead.

Given this wrinkle the Raymarine approach looks a little more sensible.

Pete