Help with nmea 0183 interface of units with standard horizon plotter

[PaulRainbow]

Hi, apologies..what do you mean by ground plane? I was referring to the 12V negative as my ground. By the way its a Storebro and is fully bonded throughout with metal strap bonded in the grp acting as conduits...not that I planned using this for nmea.

Are you saying connect the plotter nmea reference/ground wire to 12V negative and then all four other instruments to the same?....using the 12V neg to link them all together.

I think the VHF MT500 has also a + nmea wire to go to ground according to instructions i have found.

Thank you for the guidance...its all new to me nmea interfacing.

Do not use the galvanic bonding circuit.

The use of the word "ground" in the Standard Horizon manual is misleading, it's the NMEA - connection and is common to any NMEA equipment interfaced with the plotter So let's forget about "ground".

With regard to NMEA data connection, each device will have NMEA + for each input/output port. These obviously need connecting together. The talker "OUT" goes to the listener "IN".

As for the NMEA - connections, these vary. The plotter has a single, common, connection, all NMEA "IN" and "OUT" - connection should be joined here. Some equipment will have NMEA + and - connections, so these obviously go the the + and - connections on the plotter. Others have no - connection, they use the 12v - internally. Some have a - wire that has to be connected to the 12v -.

You need to look at the wiring diagram for each piece of equipment to see which method they employ for the - connection.

VHF MT500 has also a + nmea wire to go to ground

That makes no sense, you cannot connect a + wire to anything other than another NMEA + connection. If the VHF connection is for GPS data for DSC then the VHF will be a listener and the NMEA + will need to be connected to the NMEA "OUT" of the GPS. The NMEA - may need connecting to the NMEA - on the GPS or to 12v -.

Again, avoid the use of the word "ground" for this.

 

[PaulRainbow]

Mine has nmea grounds connected through 12v neg and all works fine.

This is normally the case, there are odd exceptions though. Some will even work without connecting the NMEA -.

No ground in NMEA data connections

 

[petrolhead63]

Thanks again , i am nearly there and it is understood now. To the VHF, MT500.

There are 8 data wires and 5-8 are for programming/flash so ignored?

1) nmea rx(+) connect to output nmea of plotter.
2) nmea(-) connect to 12v neg on boat.
3) nmea TX(+) connect to input nmea on plotter
4) Ground/TX (-) connect to 12v neg on boat as well.

also as i read it, if i connect all 5 units nmea (-) to 12v neg on boat they will likely work fine. The plotter has a cable nmea (-) as do two listeners which could in theory be connected to this cable. The other two listeners have to use 12neg on boat according to manuals....but just join them all together using the 12v neg.