Hoping to understand Raymarine ST60 and ST60+ Tridata instrumentation.

[prv]

Does this mean that your paddle-wheel simulator thing won't work on my system Nigel?

Why on earth would it mean that?

Nigel's box will work fine, it just takes GPS data (I assume NMEA0183) and outputs a stream of pulses that look like a paddlewheel spinning round. It doesn't care what is or isn't on your seatalk bus.

Pete

 

[RichardS]

Why on earth would it mean that?

Nigel's box will work fine, it just takes GPS data (I assume NMEA0183) and outputs a stream of pulses that look like a paddlewheel spinning round. It doesn't care what is or isn't on your seatalk bus.

Pete

The input could be either Seatalk or NMEA but I need a gizmo that outputs Seatalk like my RS125 rather than NMEA as my NMEA port is now set to high speed and Nigel's gizmo might need a low speed input.

Richard

 

[nigelmercier]

To clarify. My device takes an NMEA 0183 input at 4800 Baud and produces a 12V square wave at 5.5Hz per knot. This plugs directly into the paddle-wheel input on the ST60 Speed (or Tridata). It is this instrument puts the speed data on the SeaTalk bus, it thinks the square wave is coming from a paddle-wheel.

 

[PabloPicasso]

You're missing something about apparent wind. The apparent wind is a vector of true wind and water speed/ direction. The boat is sailing in the water not driving over the ground. So GPS speed data will be inaccurate for calculating apparent wind.

Perhaps that is why they have invented ground wind from GPS data.

 

[pvb]

You're missing something about apparent wind. The apparent wind is a vector of true wind and water speed/ direction. The boat is sailing in the water not driving over the ground. So GPS speed data will be inaccurate for calculating apparent wind.

Apparent wind isn't calculated, it's measured by the wind transducer.

 

[RichardS]

To clarify. My device takes an NMEA 0183 input at 4800 Baud and produces a 12V square wave at 5.5Hz per knot. This plugs directly into the paddle-wheel input on the ST60 Speed (or Tridata). It is this instrument puts the speed data on the SeaTalk bus, it thinks the square wave is coming from a paddle-wheel.

Ah I see .... many thanks Nigel. I think I've got it now. I'd missed the vital bit about the Tridata converting the analogue signal to Seatalk and sending it to the chartplotter and the Wind display.

I see that you can buy a commercial converter http://www.cruzpro.com/sog1.html so I guess that this does the same as your gizmo? It's rather expensive (probably £100 when postage included) so I would be interested in building one as a "project".

It says 22,000 pulses per nautical mile and doesn't seem to need any calibration to achieve 0.01 knot accuracy. Presumably if the Tridata receives those 22k pulses over 12 minutes it calculates a speed of 5 knots, although that looks like a frequency of 4.4 KHz per knot which would be variable depending upon speed so that looks different to your gizmo?

Richard

 

[RIBW]

I have a C80 Classic plotter, ST60 Wind Instrument and ST60+ Tridata speed and depth display. All the speed data comes from the GPS as I have no speed paddle through-hull on this boat. The first thing which puzzled me was that the wind instrument has a button for Apparent Wind or True Wind ..... but True Wind doesn't work. Having read this forum and others over the years, I know that the ST60 will only make the True Wind calculation from paddle wheel speed and not from GPS speed so I can forget about that. Richard

When faced with that same issue a few years ago, I disconnected the paddle wheel and bought the Gadgetpool converter to fake 'Boat Speed'. I use it with an old cheapo Garmin GPS. This combination with a separately powered ST60 set up means that I don't need to turn on the C80 unless I need a radar in fog/mist. (I prefer my stand alone SH chartplotter for fair weather sailing).

Cheers
Bob

 

[RichardS]

When faced with that same issue a few years ago, I disconnected the paddle wheel and bought the Gadgetpool converter to fake 'Boat Speed'. I use it with an old cheapo Garmin GPS. This combination with a separately powered ST60 set up means that I don't need to turn on the C80 unless I need a radar in fog/mist. (I prefer my stand alone SH chartplotter for fair weather sailing).

Cheers
Bob

Thanks Bob

I also looked at the Gadgetpool.de device a couple of years ago but it looks like a mini-computer running a program so I was a bit put off by the complexity. The Cruzpro box http://www.cruzpro.com/sog1.html which I didn't find until today looks like simple "plug and play" but I don't know if this 22k pulses per nautical mile exactly reproduces the Raymarine / Airmar paddlewheel output or not?

I'll try and do some Googling to find out.

Richard

 

[RIBW]

I also looked at the Gadgetpool.de device a couple of years ago but it looks like a mini-computer running a program so I was a bit put off by the complexity.
Richard

Richard,
I see how you came to that feeling but the gadgetpool was simple to install and has been reliable. The designer is also very helpful. Personally, I find the Raymarine 'mind set' far more difficult for my brain - I ended up writing my own interpretation of their operating manual to even stand a chance of getting sense out of the radar!

Good luck with what you decide.
Cheers
Bob

 

[pvb]

...but I don't know if this 22k pulses per nautical mile exactly reproduces the Raymarine / Airmar paddlewheel output or not?

If you look at Airmar's website, it gives the pulse data for various transducers. I think your ST60+ would normally have an ST800 transducer, which outputs 17000 pulses per nm. The instrument has sufficient calibration range to use 22000 pulses per nm.

 

[RichardS]

If you look at Airmar's website, it gives the pulse data for various transducers. I think your ST60+ would normally have an ST800 transducer, which outputs 17000 pulses per nm. The instrument has sufficient calibration range to use 22000 pulses per nm.

Thanks PVB. I just did the Googling and typed exactly what you have said only to find that this huge storm we are having had taken out the internet around here and it has only just come back. My words were lost forever somewhere! Anyway, thanks for confirming ST800 and 17000 and for the calibration latitude.

What I don't understand is how this 17000 p/nm is equivalent to 4.8 Hz per knot. I clearly did entirely the wrong calculation above but never mind, it is what it is.

Richard

 

[nigelmercier]

All I know is that my Raymarine ST60 Service Manual says 5.5Hz per knot, and that feeding a reset ST60 Wind with such a signal produces the correct speed. I guess that per nm there would be 60 x 60 x 5.5 pulses, 19,800.

The ST60 actually uses a rolling average, so if you change instantly from 5.5Hz to 55Hz it takes about 10 seconds to display 10kn (after a reset), this latency is adjustable.

 

[RichardS]

All I know is that my Raymarine ST60 Service Manual says 5.5Hz per knot, and that feeding a reset ST60 Wind with such a signal produces the correct speed. I guess that per nm there would be 60 x 60 x 5.5 pulses, 19,800.

The ST60 actually uses a rolling average, so if you change instantly from 5.5Hz to 55Hz it takes about 10 seconds to display 10kn (after a reset), this latency is adjustable.

So that's how you do it! 4.8 x 60 x 60 = 17k. Thanks

I'm going to see if I can persuade the family that the ideal Father's Day present would be a SOG-1. Wish me luck

Richard

 

[AngusMcDoon]

Apparent wind isn't calculated, it's measured by the wind transducer.

Fred drift I know, but in top end B&G systems apparent wind is calculated from measured wind, take into account pitch, roll & yaw and mast height.

 

[RichardS]

Fred drift I know, but in top end B&G systems apparent wind is calculated from measured wind, take into account pitch, roll & yaw and mast height.

But why would it need to calculate anything when apparent wind is what the spinny-pointy thing at the top of the mast actually measures directly?

Richard

 

[sailaboutvic]

And what if there some crap on it so it's not spinning as it should .?

 

[AngusMcDoon]

But why would it need to calculate anything when apparent wind is what the spinny-pointy thing at the top of the mast actually measures directly?

Richard

Apparent wind is relative to the boat. The wind measured by the transducer is also measuring the wind created by the pitch & roll of the boat. If you want apparent wind with the pitch & roll induced elements taken out then you need to do a calculation. This doesn't happen for the likes of us here but does in big boats fitted with top end kit.

 

[RichardS]

Apparent wind is relative to the boat. The wind measured by the transducer is also measuring the wind created by the pitch & roll of the boat. If you want apparent wind with the pitch & roll induced elements taken out then you need to do a calculation. This doesn't happen for the likes of us here but does in big boats fitted with top end kit.

Or perhaps just slow down the response setting of the masthead unit (range of 1 -15 on my basic ST60) so you get a longer average reading which will remove the pitch and roll effects?

Richard

 

[nigelmercier]

New thread started: Raymarine ST60 Paddle Wheel Simulator

 

[RichardS]

So that's how you do it! 4.8 x 60 x 60 = 17k. Thanks

I'm going to see if I can persuade the family that the ideal Father's Day present would be a SOG-1. Wish me luck

Richard

Father's Day present arrived today ..... and it's the tinyiest and lightest boaty thing I've ever seen. I won't have any problems finding somewhere to fix it.

Here it is standing on a standard beer mat.

Just in time for next week's Med cruise.

I'll report back in due course.

Richard