DC Ring Circuit

Hi all

I was wondering if there is such a concept of a DC ring circuit. I know this is done in AC. I have a canbus project around a boat which involves running power in 12V DC around the boat and taking spurs off it for each node. I was thinking of cable sizing as the loads are not evenly distributed. If I run one positive cable clockwise and another anticlockwise around the boat I was wondering if I could just join them and thus balance the 12V rail.

The below is a crude illustration with a couple of loads drawn in

What does "canbus" have to do with 12V power?

A power bus with two branches could make sense. The above illustration doesn't, at least to me. Use wire size large enough to avoid significant voltage drop with the maximum anticipated load, and you will not have a problem.

Each canbus node will control power to local devices. The 12v and GND rail will have a spur off it to each node which will power the uC and associated loads for that node. I will need to run cable down both sides of the boat and they will essentially meet so I was wondering if there are pros and cons to connecting them in a ring. The bottom of the diagram above should be labeled battery with 2 12v supplies and 2 GND.

In AC it is common as it saves cable rather than a radial circuit with a separate cable to each load or series of loads.

The con is fuses at the source will not keep your boat from catching fire.

Paul

Your concept looks good to me but make sure it is fused at the point the power is fed in.

Should I fuse both ends of the positive rail I.e. the two connections to the battery distribution.

One fuse feeding both ends, the same as a house ring main.

Perfect

PerryBebbington:
One fuse feeding both ends, the same as a house ring main.

Interesting. We don't have those here.

You don’t have ring mains? Which country? What do you have?

PerryBebbington:
You don’t have ring mains? Which country? What do you have?

Most countries still have the primitive radial system Perry. We were one of the few enlightened ones. :wink:

AJLElectronics:
Most countries still have the primitive radial system Perry. We were one of the few enlightened ones. :wink:

I was aware that some countries are stuck in the past in this regard! About time they caught up! I first learned of ring mains in about 1970, maybe before that, they must have been in existence long before then!

PerryBebbington:
I was aware that some countries are stuck in the past in this regard! About time they caught up! I first learned of ring mains in about 1970, maybe before that, they must have been in existence long before then!

To be quite fair, the ring circuit was an answer to the metals shortage after the war. It increases diversity and reduces the amount of copper cable required.

That makes sense but it's still a good idea, however it came into existence.

Why do you never see it in DC? It seems like a particularly good use when the low voltage means that cable sizes are large.

PerryBebbington:
You don't have ring mains? Which country? What do you have?

Canada. The electrical codes only allow a star topology, AFAIK. One breaker can only have one feed. That's domestic, I'm not sure about commercial/industrial.

aarg:
Canada.

Ok, well, I'll have a word with Lizzie next time I see her and get her to nip over with her sword, chop off a few heads and sort you lot out . I was only saying to Charlie the other day: "your old mum needs a visit to the colonies" :slight_smile:

I doubt any countries mandate a "star" distribution of mains power. :roll_eyes: My house is wired with power points chained with occasional branches.

In my house, the circuit breaker panel is the start of the star distribution. Walls or maybe rooms are wired in series. Might be some branching after leaving the breaker as well.

Paul__B:
I doubt any countries mandate a "star" distribution of mains power. :roll_eyes: My house is wired with power points chained with occasional branches.

Yes, I just mean that circuits are not allowed to reconnect with one another once they leave the breaker panel. There is only one path allowed between the load and the supply. A ring has two paths.