Nasa Electronic Log - again

[doug748]

I am thinking of fitting one of the new NASA electromagnetic log transducers, inputting it into an existing instrument (Echopilot):

https://www.nasamarine.com/product/electromagnetic-log/

So what I really need is fresh sets of eyes to foresee any problems that I have missed.

There will be no assistance from Echopilot, the existing display was probably designed 20 years ago and has not been made for maybe 10.

There are three problems with this sort of adventure:

1) Will the new transducer physically fit into the existing hull fitting?
This should be no problem I have a standard 42mm I/d tunnel on the boat

2) Will the existing wiring be ok?

From the transducer to the control unit is fine, both are part of the new package.

From the control box to the existing display. Now then:

The display has three wires in:
White – labelled signal ground.
Orange – labelled Log Sig In
Red - labelled 5v Out
The Nasa box has three connections:
Silver - labelled Neg
Blue - labelled NMEA
Red - labelled Pos +

So I connect,,,,,,, Signal Ground (on Display) to Neg ….....Signal In (on display) to NMEA........5v Out (on display) to Pos + And all will be well? What do you think?


3) Will the new box output be compatible with the old display instrument?
The existing display is said to accept NMEA 0183 ver 2 (2.3 I think) and accept input sentences: VHW and VLW. The Nasa box is said to dish these out, see:

https://www.nasamarine.com/wp-content/uploads/2018/12/EML-2-User-manual.pdf

So I should be ok what do you all think?
I will, of course be speaking to Nasa when the time is ripe.

Thanks for any input.

 

[PaulRainbow]

I'll bet no-one has ever carried out such an installation Doug

I've fitted a couple of the NASA units though, one was to a very old Simrad system and that worked fine. The NASA unit is straight forward enough, connect the transducer to the "box". Next to impossible that the transducer will fit the existing through hull though.

If the Echopilot display acepts standard NMEA sentences i can't see why it won't work.

The display has three wires in:
White – labelled signal ground. -12v
Orange – labelled Log Sig In NASA blue
Red - labelled 5v Out Doubt this is conencted anywhere

The Nasa box has three connections:
Silver - labelled Neg -12v
Blue - labelled NMEA Display orange
Red - labelled Pos + +12v

Where does the display get its power from ?

 

[doug748]

"Where does the display get its power from ?"

It is a sounder as well so gets it's power independently from the main board.

However..

"Next to impossible that the transducer will fit the existing through hull though."

You are quite correct, missed the most obvious thing, the transducer is based on a 50mm hull opening. So that's torn it. Don't think I want the bother of taking out my nice bronze through hull and putting in that plastic item.

I knew it was worth asking on here, cheers Doug :-[

 

[Gwylan]

Why do you want a log?

With GPS and all that they do not tell you very much and what they do tell you needs to be interpreted.

Or have I missed something when I gave up trying to keep all the little mussels from making their home in the whirly wheel thing?

 

[pvb]

Or have I missed something when I gave up trying to keep all the little mussels from making their home in the whirly wheel thing?

You missed the fact that the electronic log doesn't have a "whirly wheely thing", although, on the other hand, it is made by Nasa.

 

[MikeCC]

I believe the orange wire input on Echopilot is for a wheel-type log pulse input. The NMEA connection is the black and white pair (assuming you have a Bronze Trio). If you already have a GPS or other NMEA device hooked up, then you won't be able to use both without a multiplexer.

 

[doug748]

I believe the orange wire input on Echopilot is for a wheel-type log pulse input. The NMEA connection is the black and white pair (assuming you have a Bronze Trio). If you already have a GPS or other NMEA device hooked up, then you won't be able to use both without a multiplexer.

I was thinking the point of the Nasa box was that it mimicked the conventional paddle wheel but I see it now. So that is another potential spanner in the works.

It is a Bronze Trio, and I do have a plotter connected. It's excellent so I won't be changing, that puts the final capper (as they say in Cornwall) on the project. Thanks for pitching in

 

[GHA]

I was thinking the point of the Nasa box was that it mimicked the conventional paddle wheel but I see it now. So that is another potential spanner in the works.

It is a Bronze Trio, and I do have a plotter connected. It's excellent so I won't be changing, that puts the final capper (as they say in Cornwall) on the project. Thanks for pitching in

You probably could do it with a little arduino turning nmea into pulses if you had the datasheet. Though, hard to believe, not every boat has a box of arduinos and a fascination to suit

 

[Stemar]

Why do you want a log?

With GPS and all that they do not tell you very much and what they do tell you needs to be interpreted.

Or have I missed something when I gave up trying to keep all the little mussels from making their home in the whirly wheel thing?

To me, it's a nice to have, rather than a must have, useful when trimming sails, as it reacts quicker than the GPS. OTOH, mine hasn't worked all season, and I haven't bothered to fix it