NMEA 2000 network - testing in the office

[pjp1]

I'm attempting to set up a NMEA 2000 network for some custom software development but I do not currently have access to a boat nor is it convenient for me to test on one. So I'm doing this in the office.

I'll be using an actisense starter kit (e.g. Actisense NMEA2000 Starter Kit 1 - A2K-KIT-1) with one or two NMEA 2000 sensors.

My question is, from what I've read, NMEA needs to be powered by 12V or 24V DC (or close to). However, since I'll be testing in an office, I'll be using AC power so will need to transform down to DC. The voltage side of things is fine but can someone tell me what range of current/amps I would need for the backbone?

[smac999]

it must be 12v. not 24.

generally nmea 2000 is fused at 3a. not much draw. you may need the 12v power supply to power other devices though as well. like a screen. so you may need more power.

[pjp1]

Thanks! Would a normal 12V <3amp charger be suitable so?

[odonnellryan]

Originally Posted by pjp1

Thanks! Would a normal 12V <3amp charger be suitable so?

Buy a DC power supply. https://www.amazon.com/Lab-Power-Sup...node=318022011

That will also be useful for other projects you may do down the line.

[Dave Lochner]

Another vote for a 12v power supply. I have this one from Amazon:

https://amzn.to/2Guj99Y

As for power consumption, my 9" Zeus display and 2 low power N2K devices draw under 1 amp total at 12.7 v.

[guyrj33]

Originally Posted by pjp1

Thanks! Would a normal 12V <3amp charger be suitable so?

Battery chargers require a restive load to produce 12v and probably won't work if hitched directly to you MNEA 12v wiring. You'll need to include a battery in the circuit or get a 12v power supply as others have suggested.

[Mirage35]

Rereading the original post - probably just a question of wording, but for clarity: You don't need to just "transform down" to 12 VDC, you need to transform, rectify, and regulate.

Which is exactly what the suggested power supplies do.

[Mr O]

If you have a 12v battery handy, that will work. It doesn’t matter if its a small motorcycle battery or car battery. An automatic battery charger may be needed for long term use. Alternatively, a 12v power supply will do the job.

[odonnellryan]

12v power supplies for routers, modems, etc.. do work in a pinch but a DC power supply is a much nicer solution.

[OldChris]

Do you have one of those 12VDC jump boxes many people have for their cars/smaller boat engines? They will power low draw devices for hours and then can be recharged easily from a wall outlet for their next use.

[pjp1]

Thanks everyone for the replies. A fountain of great information there!

[Coventina]

Related question - what is the minimum number of NMEA devices to make a network viable? I've read "2 x NMEA 2000 certified devices (at least 1x TX and 1x RX) and a means to connect them" is the minimum requirement, is that correct? Many thanks!

[transmitterdan]

The minimum system is one “device” and one “system controller” plus two terminators. Use a 12V lab supply to power the network. The amount of current depends on the number and type of devices. For a minimal network even 1A may be sufficient.

For software development you may need to use extra long cables that push the distance between devices to the maximum rated length. Also, for a proper test of collision detection you need multiple devices at various distances along the network. NMEA2000 is based on the CAN standard. Software has to respect certain CAN constraints such as response time. CAN is a real-time network.