NEMA 2000 Fittings

[MarcHall]

The NEMA 2000 hardware is based on DeviceNet.

DeviceNet was developed by Allen-Bradley (Rockwell Automation) based on the CAN and is now overseen by ODVA.

DeviceNet is used at industrial sites largely for motor controls, sensors, etc.

It is not uncommon for connections to devices to be done with terminal strips althought the connectors are also seen. Mixing does not have an impact.

What seems to be important is that wire is consistent and that terminators at the end of the backbones are in place. Not exceeding the overall specified length of cabling in the system is also important. Since the network can have several branches, layout of the network can impact the overall length and where the terminators should be placed.

With DeviceNet one of the issues was the speed at which the network ran as longer cable length could be supported with slower speeds. Making sure the cable length would support the desired speed and that all devices are configured to run at the desired speed can be an issue. With NMEA 2000 this is not an issue.

On a sailboat with a wind instrument the logical placement of one of the terminators would be at the wind instrument at the top of the mast due to the
length of the run up to the top of the mast.

Maretron NMEA 2000 cabling can be purchased for under $2.00/foot and Micro Fittings for around $15 a piece.

Currently I am in the process of installing a NMEA 2000 network on Crazy Fish using B&G components and a mixture of B&G and Maretron cabling and connectors. My one issue is the run up the mast. Current cabling originally installed for a Datamarine consists of a shielded cable with 6 additional wires. I am going to splice the NMEA 2000 cabling into this at each end, attached the B&G wind instrument and then scope it to see how clean the signals are. If not good I will need to step the mast and run new cable. Being based in San Diego its fairly rare to step the mast.

Regards

Marc Hall
Crazy Fish, Crealock 37, Hull 207

[Charlie]

I can not even understand all the network terminology that you guys use. Perhaps what would be best is if I made up a diagram of my system and then you can make comments about it. Is there some primer where I could learn about BUS systems. I seem to be running into them a lot between newer cars and boats.

[MarcHall]

Originally Posted by Charlie

I can not even understand all the network terminology that you guys use. Perhaps what would be best is if I made up a diagram of my system and then you can make comments about it. Is there some primer where I could learn about BUS systems. I seem to be running into them a lot between newer cars and boats.

Charlie

You might want to download the Maretron N2KBuilder and check out some of their sample layouts and maybe even build your own. The instruments and displays are limited to Maretron componets but you could substitue theirs for whatever you are using and still get an idea of what your system would look like, what connectors might be necessary and do a first level check on the lenght of the cable runs, voltages at each device and placement of the 2 terminating resistors.

Software if freely availabe at Maretron's website under the Support/Software Tools Menu. Maretron : N2KBuilder

Regards
Marc Hall
Crazy Fish, Crealock 37, Hull 207
Currently slipped in San Diego.

[Charlie]

Thanks Marc. I'll have a look.