Multi Cable Connections

[Dave S]

Need to connect NMEA-0183 Auto Pilot and Flowscan. Manual and tag on cable shows White is TD-A and Blue is TD-B, which would indicate two output ports. Unclear what is NMEA ground, so I contacted Furuno Support and got the following, which contradicts the manual:

White (TX+)
Blue (TX-) also referred to Common or Ground

White (TX+) will connect (RX+)
Blue (TX-) will connect to (RX-) also referred to Common or Ground

I'm inclined to believe Tech Support over the manual and cable tag since in the marketing material specs they mention 1 NMEA-0183 output.

Has anybody made these connections and confirm? The manual is a bit lacking in the description of these connection functions like the power switch functions (purple & brown) and I just want to be sure.
Thanks!

 

[Johnny Electron]

Hello Dave,

Here is the decoder ring for the Furuno interconnection diagrams.

TD = Transmit Data
RD = Receive Data
A = +
B = -
H = Hot/High/+
C = Cold/Common/-
SD = Send Data
SG = Signal ground
FG = Frame ground

The TZT3 has one NMEA 0813 output per display. As you pointed out the output is White (+) and BLUE (-) and connects to the receiving unit(s) on their receive lines. (matching + to + and - to -) .

You have to be careful with NMEA 0183. By NMEA standard it is RS422 not RS232. RS422 has signal on both the positive and negative. (called a differential signal) The negative is NOT ground. It has active information on it and shouldn't be grounded. Some older units from cheaper made products saved money by using NMEA 0183 at an RS232 signal level. With RS232 the negative is indeed ground. RS422 is more expensive to build but much more robust and hence why NMEA.ORG will no longer allow manufacturers to certify 0183 unless it is at the RS422 standard. People get into trouble when connecting some of the older cheaper devices.

When connecting units NMEA 0183 is not always the full picture. If the receiving unit has both +/- input wires then it is most likely RS422 and safe to connect. If the unit has a shared ground (like the ground is shared for both input and output) then it is RS232 and should NOT be connected to your Furuno without proper interfacing. (RS422/RS232 converter) You must match signal levels. RS422 goes to RS422 and RS232 goes to RS232. You get people who unknowingly mix them. When they connect an RS232 receiving unit to an RS422 output, they are shorting out the negative signal line. This results in intermittent data and over time damage to your output port which is being shorted out. If both your Pilot and Flowscan use RS422, then no big deal. Connect them both to the single output and they both can drink from the same output data stream. (You can have up to three standard listeners on one NMEA output) Be careful of VHF radios using 0183 because they pull more than typical current so we always count them as two listeners.

Hopefully that makes some sense and you find it helpful.

 

[Dave S]

OMG, thank you so much! This is suitable for framing :respect . I'm learning the only thing standard with 0183 is the message protocol. I actually read some of the NMEA history and specs last night and there were to be standardized wire colors and naming conventions that nobody ever followed. I think Furuno was the most "creative"

I think I'll be okay, the AP is an old Simrad AP20 (like the Vikings used on their conquests :sail ). It has dedicated TD & RD (+/-) ports. Even has little LEDs on the junction box that show message transmission. And here's the part your really going to like, uses PROMs for software upgrades.

The Flowscan also has (+/-) wires and they call (-) ground. But there is only RD. It simply uses GPS output for SOG to calculate MPG from the fuel flow rate (GPH). Nothing back to the GPS so not a shared ground. Here is what the Flowscan says about NMEA connection:

This unit conforms to NMEA 183, Version 1.5 and 2.0 interface standards and requires a message that includes “GPRMC” or “LCRMA”.

That's all that will be connected to the TZT3 NMEA 1083 port.

There will be a radio connected, and its an AIS capable but NMEA 0183, so that one will utilize the Furuno IF-NMEA-2K2 configured for 34,800 bps so all of it's coms will be on N2k. Your decoder ring helped me figure that one out!

Previous boat I upgraded everything to all N2k with only one NMEA 0183 connection (same model AIS radio as above) and was sooo much easier. Everything just plugged together and it worked. This one is old (obviously) but new to me and I'm just need to get everything functional before the 350 mile ride to bring it home. Remaining Furuno upgrades to follow.

Thanks again, awesome!

 

[Johnny Electron]

I think I'll be okay, the AP is an old Simrad AP20

Yes that is okay for use.

It seems you are well on your way to a great install. :sail

 

[Dave S]

Hi just wanted to follow up on the installation integration and all the helpful connection guidance:
We finally got out of the yard last week and began the 140 mile first leg of our trip home.
- 0183 integration for AIS to Standard Horizon radio worked, have AIS targets
- 0183 integration to Simrad AP20 worked, able to Navigate follow route
- 0183 integration to Flowscan worked, have total MPG and GPH per engine
- scx20 installation worked was able to select functions for that or internal GPS
- BBWX4/ Sirius XM is visible on network, not endpoint yet (future).
- transducer connection next and more components / upgrades next season

Planned rather complex route using time zero, and as soon as connected to internet, I had route on TZT3 and followed it flawlessly with autopilot - awesome feature. Only issue I had was couldn't make screen bright enough, not sure why.

So it was a happy pre-planned and successful install, integration and maiden voyage. We broke a shaft about 13 miles from destination but that't another story... We came in on one engine without having to worry about navigation issues.

 

[Johnny Electron]

We broke a shaft about 13 miles from destination but that't another story... We came in on one engine without having to worry about navigation issues.

That doesn't sound like fun. Thanks for the follow up.