Heading input for 1815 RADAR

[Aquarius]

I have just installed a new Furuno GP-39 GPS and 1815 RADAR. I have been trying to figure out the NEMA wiring connection from the GPS to the RADAR.

Right now, I have the GPS Blue wire connected to the RADAR Grey with one Red dot wire. The GPS White wire is connected to the Grey with one Black dot wire. On my RADAR display I have the correct position and speed for "OWN SHIP" and, if I have a waypoint entered into the GPS, BRG, RNG and TTG to that waypoint.

My heading still reads all asterisks, as does my cursor position. According to my GP-39 manual I should be getting an output that includs COG (course over ground). That seems an ideal heading input. I am getting SOG (speed over ground) so I must assume that I have the wiring almost correct.

Can someone help me with the rest of the wiring? I have three NEMA inputs on the RADAR and a total of 4 wires from the GPS (I have not connected the Green or Yellow wires to anything.) Do I need something else for heading input and how must it be connected.

Thank you.

 

[C-Bass]

Good morning Aquarius,

Thank you for your inquiry. Heading is a different data sentence than COG, they are not the same thing. Heading requires a dedicated sensor like a PG700 compass, SC30 Satellite Compass, or in larger ships a gyro compass.

So what other equipment do you have on the vessel? Do you have an autopilot? Autopilots generally need a dedicated heading compass to function so if you have one we might be able to pick the HDG or HDM data sentence from it to use in the 1815 radar?


C-Bass

 

[Aquarius]

I have a Simrad RFC35NS Fluxgate Compass connected to a Robertson AP 2500 Autopilot.

 

[Aquarius]

Hello Gentlemen,

I have not seen a reply to this recently. I am wondering if there is a way to get heading input from my existing fluxgate compass. Is there anyway you might know how to wire it up?

 

[C-Bass]

Good morning Aquarius,

I don't know if the compass itself can provide NMEA0183 heading without a secondary junction box like the N2500.

Do you have the n2500 box?

What i could not find out is the output speed of this NMEA0184 interface box. I don't know if it provides fast heading at 10hz or if it is just at 1hz. I also don't know what baud rate it works at or what the NMEA0183 heading sentence it provides.

 

[Aquarius]

Thank you for the reply. I have never seen that diagram before. It is not in any of the manuals that I have. My heading sensor and autopilot are connected to a J1000B Junction Unit.

The RFC250 was the original heading sensor. I installed a (supposedly) upgraded unit, the RFC35NS Fluxgate Compass, a few years ago. The tech data I have on the unit is as follows:

Heading Output...........Serial and analogue
Output Format.............NMEA183 10x/sec. and sine/cosine
NMEA data..................$IIHDM,x.x,m*hh<cr><If>x.x=heading, hh=checksum
Analogue data.............Sine/Cosine +- 2V, 2.5VDC reference
Accuracy..................... <1.25 deg rms
Repeatability...............<0.2 deg rms
Calibration..................automatic

and a few other things that are equally meaningless to me.

I hope this helps.

 

[C-Bass]

Thank you for the information.

The j1000b does not appear have an NMEA0183 output.



You will have to contact Simrad to find out if it is possible to get NMEA0183 heading from the compass. In your post it does mention the correct heading sentence. I just don’t know how to get it out of the autopilot system.

If you can find the NMEA transmit wire pair and their colors for polarity we can assist further.

C-bass

 

[Aquarius]

Thank you for the info. I have not seen the documents that you have posted. Those pages are not in any of the manuals that I have. I looks like I have to search for that Splitter Box.

One possible option is to buy a heading sensor totally dedicated to the radar input. I am over budget right now with my new GPS and RADAR so an entire new auto pilot system is out of the question.

Could you advise which FURUNO heading sensor would be suitable for the 1815 RADAR input and perhaps a future upgrade to a new autopilot system?

It does seem a shame that all the advanced features of this RADAR depend on a single input from a single sensor that reads magnetic heading. For collision avoidance, a calculation of CPA would be much more accurate with Course Over Ground rather than heading. COG is the actual direction the vessel is travelling. Heading is merely where the bow is pointing and is not always the direction of travel due to set and drift. A COG input from a GPS would not be subject to magnetic deviation. On my boat, on some courses, that is 12 degrees. Typical for a small boat with a big diesel right in the middle. The only real necessity of heading input is to convert apparent wind to true wind. Most small boats, except sail boats, do not have an anemometer so that capability is not used anyway.

As a last shot at something simple, is there anyway that the 1815 can be "tricked" into using COG from a GPS so I can get the "True Tails" and the tracking functions to work? I imagine you would have mentioned that if such a thing were possible.

 

[Aquarius]

Update.

Feeling a little dumb right now. My autopilot does in fact have the N2500 junction box as well as the J1000b.

So it looks like this might have a happy ending for me. I have two terminals on the N2500, one labeled NMEA Ret and on labeled NMEA Out. On the RADAR I have a Grey wire with a series of 3 red marks and a Grey wire with a series of 3 black marks.

If you could tell me which goes where it sounds like I will have a heading input for my RADAR.

 

[C-Bass]

Thank you Aquarius,

The was not able to find out information on what the High and Low signal coming out of the N2500 so it may take a little experimenting on your part. We typically want to connect the Transmit High with the Receive High and Transmit Low with Receive Low. This is not labeled very well on the Simrad unit, it says NMEA Out and NMEA RET. Nothing else.

So the Furuno Wires you mentioned are for Port 3 of the Radar:
Grey/Black (3) Is the Receive High
Grey/Red (3) Is the Receive Low


Try to connect Grey/Black (3) to the Simrad NMEA Out
Try to connect Grey/Red (3) to the Simrad NMEA Ret.

If that does not work you will have to switch the polority and try again.

The manuals that i could find on the Simrad did not indicated any Baud Rate setting either so you may need to try both 4800 baud or 38,400 baud.

Also there is a chance this may not work at all. The Talker ID of the Simrad NMEA Output is HC. That is a really old Talker ID. But it is worth a shot.

 

[Aquarius]

When the weekend comes I will give this a try.

There are only two possible wiring combinations. I have a 50/50 chance of getting it right the first time.

Is there any danger of damaging the equipment if I get it backwards?? That is really the only thing that concerns me at this point.

 

[C-Bass]

Good morning Acquirius,

No you should be fine. I have not seen an NMEA0183 polarity reversal damage an NMEA port.

Good luck!

 

[Aquarius]

Success!!! Thank you for all the help!

I hooked up the wires as suggested. Grey/Black to NMEA Out and Grey/Red to NMEA RET.

I now get heading input and it looks like I will have True Trails and Tracking functions. I only did a dock trial as weather kept me in on Saturday and other commitments kept me off the boat on Sunday.

I did notice one issue. I turned my autopilot on and set a course different from the direction my boat was facing. The electric pump went on to move the rudder and I got some interference on the radar display. It was most visible at below the half mile scale. The interference sort of "smeared" across the screen blocking everything out. When the pump stopped, it took several sweeps for the interference to go away. Like I said, this was at the dock without the engine running. I did not get the interference when I used the auto pilot at sea before I got the heading sensor hooked up. Any ideas??

 

[C-Bass]

Good morning Acquarius,

It sounds like you have introduced some noise into the radar after interfacing it with the Autopilot. You will want to make sure the the Radar display is grounded to the ships ground if it is not already. You may have to use some additional EMI cores on the NMEA Interface cable as well to try and choke it off.

Could you take a photo so we can see what the extent?

 

[Aquarius]

I am going to attempt to send two pictures. One shot when my autopilot is off, and the other with it on and me changing the desired course so that that the pump runs. This was done at the dock with the engine/alternator off. (It looks like it loaded in the reverse order that I intended, but I think you can see the difference.)

 

[C-Bass]

If you turn off target trails and you run the test again does the interference show up?

 

[C-Bass]

Good afternoon Aquarius,

After further review can you please check the following:

1.) It appears the noise is electrical in nature and we need to find the cause. So we know the noise did not show up on the radar display until the compass was interfaced. Please disconnect the compass wires at the compass and leave the interconnect cable in the same path to see if the noise is coming from the compass or compass interface wires.
2.) Can tell if the autopilot pump power wires are thoroughly twisted. Pumps can create an electrical field that may be jumping from the pump power wires into the radar display or a cable that is feeding the radar display.
3.) Do you know when the last time the brushes on the autopilot pump were cleaned? Dirty brushes could lead to a larger field, it may be time to clean them?
4.) Is the radar display properly grounded? Is the autopilot processor properly grounded? Is the compass properly grounded? If all three units are not grounded a suggestion would be to ground the units.

5.) What is the source of power? 12vdc/24vdc straight from the battery? Is there a inverter on the vessel? Does the vessel have a battery charger? Are there any power conditioners on the vessel? Do you hear noise on the VHF radio or SSB? How about noise on an AM/FM radio?

C-Bass

 

[Aquarius]

Sorry for my late response. I did turn off Target Trails and I do still get the interference. I did not have the opportunity to try any of the other suggestions.

The boating season is now over for me here in the North East. I will have to wait for the spring to look into this again.

Thank you so much for the help. Back on this in a few months. Have a good winter.