NN3D MFD Heading Sensor Compatibility

Yeti

Yeti

Member
I discovered (searching here) that a heading sensor is required to allow radar overlay. It looks like the easiest way to do this is to add a Furuno PG700 heading sensor. The bad news is, is that the PG700 is ~$800. :shock

Question:
Garmin's Steady Cast Heading Sensor (also N2k) retails for ~$140. Would this Garmin unit suffice? I'm sure given the cost differential the PG700 is a superior unit in some way or form (hell, it better be), but is it necessary in this circumstance? As an aside, I'll be the first one to never mix-n-match. In fact, my boat is 100% Furuno equipped. But let's be realistic here, $800 vs $140? Am I missing something here?

Rob
 
Been researching heading sensors in great depth lately and actually went into programming one just to understand all the issues and it is a long story. But in short one could say that the cheap Garmin sensor may work for you if your area is in latitudes lower than 40 degrees, you are not tilted (heeled) other than rolling a bit and it is not a steel boat.

I have not looked at this particular sensor, but think it is a simple magnetometer only device, which may in fact work better than some of the more expensive so called 9-axis devices.

The PG-700 is a fluxgate based device with gyroscope compensation. These 'old' designs are hard to beat since the flux-gate coils are gimballed and only a 2-dimensional compensation is necessary. While the coils do swing in a seaway, their average position over a few seconds is level and so a smoothed heading is good, the short variations in heading are taken care of by the gyro component. A proven approach.

The thing with the latitude is that the earth magnetic field has an inclination that increases in higher latitudes. On a levelled device the vertical component has no influence, it just sees the horizontal force getting weaker. But a little magnetometer, fixed to a board sees a change with tilt. Correcting that take measuring acceleration forces necessary and a lot of computation that requires a powerful microprocessor and a good compensation in a 3 dimensional way. Few have mastered that, and steel boats in higher latitudes keep having problems with these types of sensors.

The low price sensor you mentioned, is very likely not trying to compensate tilt, which is better than doing it with poor 3-D compensation.

For you the radar overlay will work as soon as it sees a heading signal, you may just see that radar image moving a bit on the chart. ARPA needs a good heading to stick to a target, and if you try to display your chart heads up, the display would be nervous if your sensor isn't performing well.

You seem to not have an auto pilot, as those would require a good heading sensor to steer well.
 
Taniwani,
Thanks for that great post.

I'm still having trouble wrapping my brain around the nuts and bolts of why a heading sensor is needed in the first place to do overlay. My old 1621 MK2 stand-alone "followed" the boat heads-up, the split chart/radar screen on this new MFD, the radar follows the boat. I don't get why the two can't be overlaid without adding a heading sensor, but that's a thread for another day. I digress...

You mentioned an autopilot. I actually do have one, and in confession to my earlier comment about being 100% Furuno, the autopilot is an older (however bulletproof) Autohelm ST4000. If it was possible to get this data transferred (assuming its N0183) to N2K via converter, do you believe this would be a better option over the Garmin Steady Cast? Although my NN3D MFD still has an unused 0183 data port available, I would prefer NOT to run ANOTHER data cable (see my rant in the "Options for Wiring a DRS2D to MFD8" thread) up my old-school Edson helm pedestal, and just tie it into my N2K backbone system.

Anybody's thoughts on this would be appreciated.

Rob
 
Without a heading sensor, your radar will display just a heads up picture with all echoes relative to the boat. If you turn the radar image will rotate obviously.

When you look at the chart screen, north will remain up, regardless of your course.

Without kn owing the relation between the two, you cannot overlap the radar image on the chart. You need to know which way the boat is pointing to do that, and that is what the heading sensor tells you.

Without that information you cannot display a north up radar image and you cannot display the chart heading up. With a heading sensor you get both choices on both the radar and the chart.

The ST4000 does have a fluxgate heading sensor, but no NMEA output. You would need to pick up that information from old SeaTalk and use a gateway to bring it to either NMEA0183 or NMEA2000. I don't think it's worth going down that path, as it is not a particularly good heading sensor, having no gyro assistance. And a gateway would cost you more than the low cost sensor from Garmin .
 
Taniwani, thanks again.

In doing some more research here, it appears the Simrad GS25 GPS heading sensor may be a better approach over Garmin's Steady Cast. The GS25 is N2K network-able, and according to Simrad "... GS25 provides magnetic heading for accurate boat direction at any speed and for radar/chart overlay..." It is not however suitable for use with MARPA, which is OK with me, as radar overlay is my primary goal.

https://www.simrad-yachting.com/simrad/ ... dule-pack/

Additionally, and maybe you could confirm this, I believe all I need to do is swap out my current N2K GPS (position only) antenna with this one, and have one device for both.

Your thoughts?
 
Yes, you would just have to swap it out which makes installation easy. And that unit is probably not much different as a heading sensor as the Garmin you had in mind.
 
Got it, thanks.

For future reference, the Simrad G25, B&G ZG100, and the Lowrance Point 1 heading sensors are all identical units, just re-branded. All three units retail for around $200.

I just purchased the B&G unit (on sale at Defender for $189). I'll report back with an update on how both the chart and radar sync with one another. IMO, given the $600 savings and ease of install, it's worth the experiment.

Rob
 
OK, got the B&G ZG100 wired into my N2K system, ran the MFD Wizard, no detection. No GPS, no SOG, etc.

Ideas?

EDIT: I forgot to note, the B&G ZG100 is wired into my N2K system via the N2K port *inside* the DRS2D. Additionally, my MFD8 hasn't had a software update since new.
 
Yeti...the Furuno folks will reply and you should depend on their answer, not mine: but my understanding is that the DRS N2K port is not a 'regular' N2K port and is only designed to take (some) Furuno gear, like the 330B gps, the SC30/50 sat compass and a weather station.

You may succeed if you connect via the main N2K port/backbone.

Good luck
 
aquabelle":1zout1jh said:
Yeti...the Furuno folks will reply and you should depend on their answer, not mine: but my understanding is that the DRS N2K port is not a 'regular' N2K port and is only designed to take (some) Furuno gear, like the 330B gps, the SC30/50 sat compass and a weather station.

You may succeed if you connect via the main N2K port/backbone.

Good luck
Click to expand...
Thanks Aquabelle.

You may be correct with regards to the B&G ZG100, and that it needs to be wired directly into my N2K system (via either a backbone connection or FI-5002 junction box) for it to work.

However, when I purchased (used) the DRS2D, it came with a GP330B GPS antenna, which the previous owner had wired directly to the N2K port inside the DRS2D. When I installed the radar, I wired the GP330B the same, and in doing so, had GPS data on my other N2K instruments (SOG on my FI504, etc.). This is why I thought I could do the same with the B&G ZG100.
 
aquabelle":254q0t3v said:
Yes...I did specifically say the 330B could use connected to the DRS port
Click to expand...
Got it, thanks.

Still waiting for our expert Mods to chime in on this. Johnny?....Melville?...Calico?

In the interim, I ordered up a 6 meter drop cable in the event I need to run the B&G ZG100 heading sensor over to my junction box to make this work.
 
Yeti-
I will try and get a tech to answer your questions, but going through this thread has me confused. Your initial post had to do with radar overlay and the need for a heading sensor.

Overlay can not be displayed with out a heading message, being true or magnetic. It will NOT work with a COG (course over ground) input. It needs to know which way the "pointy" end of the boat is facing. Inexpensive GPS sensors will not output the proper message, unless they are actual satellite compasses which can be pricey.. That is why we suggest our PG500 or PG700.
 
Melville, thanks for your response.

As noted, the PG700 would have been my choice, but with a ~$800 price tag, and it being a full blown classified rate compass, it's a bit overkill IMO if I just want radar overlay. A less expensive N2K heading sensor should suffice (I don't need MARPA, and it wouldn't be used for AP). This is why I believe the B&G ZG100 heading should work. According to my research, the ZG100 incorporates a triaxial rategyro, a triaxial magnetometer, and a triaxial accelerometer.

Again, this is a bit of an experiment, but at a $600 savings (the ZG100 retails for ~$200), I'm willing to take the chance. I'll report back with my findings, but if it does work for radar overlay, hey, just more money in the beer cache, and that's more important than anything. :cool
 
Yeti-
I finally was able to find the manual and I see that the ZG100 does output PGN 127250 which according to the standards is the NMEA2000 heading output. You can go to the set up in the installation wizard and see if it shows in the port monitor. If so select it as a primary source and see if that solves the heading issue.
 
Melville":3bjk33vz said:
...I see that the ZG100 does output PGN 127250 which according to the standards is the NMEA2000 heading output. You can go to the set up in the installation wizard and see if it shows in the port monitor...
Click to expand...
Yep, however you need to go back to post #8 of this thread to read about the current issue in getting the B&G ZG100 to be recognized:

Yeti":3bjk33vz said:
OK, got the B&G ZG100 wired into my N2K system, ran the MFD Wizard, no detection. No GPS, no SOG, etc.

Ideas?

EDIT: I forgot to note, the B&G ZG100 is wired into my N2K system via the N2K port *inside* the DRS2D. Additionally, my MFD8 hasn't had a software update since new.
Click to expand...

User Annabelle, in the following post, suggested that the problem may be that I have the ZG100 wired to the N2K port inside the DRS2D, and that it may need to be wired directly into my N2k network instead, which is the question currently on the table.
 
Melville":32zkzosc said:
Did you created a small canbus backbone to go from the ZG100 into the DRS2D with terminators on each side?...
Click to expand...
Hah! That would be a big fat NO. Didn't think (or know) about needing to add terminators or a resistor (resistor shown on page 14 of the linked Installation Manual).

As stated in an earlier post, I had a GP330B wired directly to the DRS via its N2K port. The GP330B drop cable pigtail did not use any terminators or a resistor at this connection, however it provided position data to my N2K network anyway, and why I thought I could wire the ZG100 similarly. Perhaps the GP330B incorporates an internal resistor?

So, if I understand you correctly, all I need to do is add a resistor at the DRS N2K port as shown on page 14, and in theory, things should work?

Where does one find/purchase these resistors?
 
I'm not sure how you had it wired originally, but the GP330B had a small pin that was inserted into the base to create a termination. If the sensor was used as a drop to a backbone then the pin would be removed. If wired into the DRS2D then the termination resistor, our part number 000-167-746 was used in the dome to create a small backbone with limited power. So if you are trying to wire the ZG100 into the dome you would need the termination in the radar as well as a way to terminate at the ZG100.

However, I think you might want to take the advice and just run the ZG100 as a drop to your N2K backbone.
 
Melville":1pxziind said:
...However, I think you might want to take the advice and just run the ZG100 as a drop to your N2K backbone.
Click to expand...

Yup, completed just now. The 6 meter drop cable I ordered Monday came in yesterday (gotta love Amazon!). I ran the drop from the ZG100 over to my FI-5002 junction box, fired-up the MFD, ran the Wizard, and VOILA! Radar overlay, SOG, etc., etc., etc. We also went out and tested the overlay on the water, and it works beautifully. So, I can safely say that if you're just looking for the overlay function on your NN3D MFD, this less expensive alternative to a PG500 or PG700 will suffice.

Thanks to all those who contributed here.

Rob
 
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