Custom 12v Breakout Box

[33driver]

First diy/tut so go easy

I bought a shift light the other day and thought to myself that with the amount of accessories and electrics I have in the cabin, something is going to fry if I keep using the existing wiring and accessories fuse lines.

Solution? Build a breakout board that would guarantee safe, fused power when and where i wanted it.

The assembly is fairly straight forward, just need to think about how basic 12V works. I'll post the finished product and give a brief step by step to build it:

Features:

12 Outputs, all 30amp fused

6 outputs are constant 12V

6 outputs are switched on when you turn on accessories

each bank of 6 is individually grounded

What you will need:

Fuse box (I chose a Narva prewired one that has two banks of 6 for input voltage part number 54426)

2 x 12 gang connector strips

1 x 12v 30amp 4 pin relay

2 x small battery lugs (normally come in a pair anyway)

Roll of black and a roll of red wire

Heatshrink (6mm stuff seemed to work fairly well)

A board to mount it all on

Electrical tape (good brand - nitto or 3m)

How it works:

The constant 12v bank of 6 is pretty straight forward, hook up the fused side to 12v off the battery and earth out the negative sice

The switched 12v bank uses a 4 pin relay i to switch the bank on and off. The relay is activated by the existing accessories wire

How to build it:

Step 1

First of all, line up where you want the fuse box to be mounted, under it drill a series of holes for the wires to run out off, I ended up drilling about 5 holes to make it neat.

Step 2

Use small pieces of heatshrink to label the outputs on the gang connector strips as positive and negative. Next, cut 12 lengths of black wire about 30cm in length. Fix these to all the negative outputs on thee gang strips (see pictures below). Then feed the negative wires though the holes you have made on the board.

Step 3

Feed the wires from the fuse box through the hoels on the board so that everythign is flat and neat. Connect the output wires from the fuse box to the postive points on the connector strip. Lay them out so that the top 6 outputs go to one side and the other 6 to the other side.

Step 4

Group the negative wires into their 2 banks and solder them to the battery lugs. These are now your grounding leads. Wrap them up in electrical tape for safety.

The above steps are fairly brief, however it is very straight forward and easy to see what is happening in the pictures below. The next few steps talk about how to hook the relay up and set up a bank for use with the accessories output in your car

Step 5

Mount the relay to the board. Take note of the diagram that is usually on top of the relay. When voltage passes through pins 86 and 85, the switch closes which allows electricity to flow from pin 30 to 87.

This means that pins 86 and 85 need to go your accessories wire and earth.

pin 30 should have constant 12volts running to it, with pin 87 going through to the bank on the fuse box. When accessories in turned on, this closes the switch and turns the bank of 6 on.

Any further questions, please don't hesitate to ask!

Cheers,

Matt

:)

[Duncan]

brilliant work. i will post a pic later of inside the race car's dash to show why i needed your help lol.

for mine I wil run similar but both from relays - one for ignition power and the other for headlight power so I can run all the gauges.

[__PhaseShiftDown]

Great Idea. But could you post up a rought electric diagram?

brilliant work. i will post a pic later of inside the race car's dash to show why i needed your help lol.

for mine I wil run similar but both from relays - one for ignition power and the other for headlight power so I can run all the gauges.

[33driver]

yeah no worries, I'll do one up this arvo. I changed my layout a little when I fitted it to the car, earthed the relay off one of the main earth leads as I had a weak earth somewhere in the car with the lead that I was tapping into.

I'll post up a few pics of it installed as well.

[Duncan]

btw, one other question

you used 54426, is 54426 the same set up but without the wiring attached? because it looks like that might be easier - just put female crimps on the end of each wire and plug straight in. or maybe 54434 which looks even better?

http://www.narva.com.au/books?id=5#page=8

[33driver]

yeah i had a look at those, i've used them before, only thing I don't like is that the terminals are exposed if you have nothing connected, easily solved by putting an empty crimp on it.

But they will work just as well, and they have a single input which is even better. I got the 54426 cause it simply had the prewired dual circuits. But any of those would work.

here is the wiring diagram, i'll pust pics of it installed this arvo

[turbo_brian]

Awesome work, but the only thing I would change would be to fuse the constant battery as well as the actual points.

Reason being, not to dis-trust your work, but if something happens between the distribution block and the battery, you still want to have the circuit fused before the box, always think of electronic safety.

But it has to be said, AWESOME DIY, well done.

B.

[33driver]

very good point!, my setup actually runs through a fused distribution block at the battery, so didn't even think about that lol.

[342Four]

actually in the diagram shouldn't the positive outputs BOTH come off pin 30 at the relay???

ur diagram seems to suggest that only one bank of outputs is switched through the relay

unless this was the intended idea that one was switched and another not???????

[Duncan]

pretty sure that's how he designed it - 6 off the relay and 6 on permanent 12v. as I said I would go 6 off 12v accessories relay and 6 off 12v lights on relay

[33driver]

yep exactly right, 6 outputs are constant 12volts the other 6 are switched. I have some accessories that require a constant 12v to store their memories etc... thats why I put it in.

[infamous_t]

I used to do this sort of stuff as my job a few years ago, you see some really dodgy & shitty setups about.

You've done a great job in this case

Just one thing Id mention tho, If i was doing this I'd separate the positive & negative from each other to separate blocks to save from accidents, maybe have the negative block separated to the rear (depending on how you decide to mount)

[33driver]

yeah i thought about that, personal preference i guess, but I figured that i'll be the only one wiring stuff into my car, I've used heatshrink to clearly identify that terminals so if i wire it up wrong its my own fault lol. there is the off chance of something conductive shorting across them, but the terminals are fairly well ressessed so it would have to be one hell of a fluke hehe

[mr moo]

went into jaycar today and they had jack sh#t except wire and clips. then went to dick smith and there store just sells computer sh#t and games. just wondering where you got the stuff from. did you go to auto one, haven't tried them yet. also tried a few electric stores they were no help.

can prob make up my on fuse box with connectors etc but stuff that.

[33driver]

jaycar is ok for the basic stuff, i get all my auto electric gear direct from the suppliers, check out a company called http://www.ashdown-ingram.com.au

they are owned by the repco group and supply about 70-80% of the auto electric stuff australia wide.

They generally only do trade sales, but will usually do over the counter cash sales. Not sure where you are but there is at least 3 or 4 in the brisbane area. Usually awesome prices compared to autobarn or normal repco shops

that said, autobarn or repco should be able to get the narva fuse boxes etc... (at a premium of course)

Edited June 17, 2008 by 33driver

[33driver]

if people are having problems sourcing parts I can certainly look at making up a few boards, with different configs if ppl were interested.

[daisu]

Only problem I see here is your fuse selection. You are using 1 30amp relay to supply 6 outputs, which are each protected by a 30amp fuse. Theoretically you could draw 25amps on each output, multiply that by 6, you would be trying to draw 150amps through the relay.

Realistically I don't think you would be drawing anywhere near 30amps on most of your outputs, so the relay is probably rated okay. Most accessories will probably draw less than 5 or 10amps. The fuse is there to protect the cable in the event of a fault. An oversized fuse may not blow out and you could end up with an electrical fire.

I would suggest removing all the fuses, (leave the fuse holders there) and install a fuse each time you use an output. Most accessories will state how much current they draw, ideally you would want a fuse that is only slightly larger than the rated current of the accessory.

Also, since the relay is rated to 30amps, I would suggest placing a single 30amp fuse just infront of the relay, in case your 6 outputs total more than 30amps.

And as the others have suggested, the supply between the fuse box and the battery should be fused as close to the battery as possible (you say you are already using a fused distribution block so that is okay).

Just have to make sure that the cable you use is capable of supplying current that is larger than your fuses.

In this case you have 12 outputs, all using 30amp fuses, that would mean the cable between the battery and the fuse box would have to be capable of supplying 360amps, otherwise you could end up with blown main fuses or even worse an electrical fire.

[33driver]

totally agree on all points there, I really like the idea of using fuses to match the outputs, i'll change that this weekend. I just chose 30amp as a default (that and i had plenty on hand lol)

I knew that the system would never work if all circuits were fully loaded, however as you mention that is very unlikely to occur. The two 12v lines into the circuit are both fused with 150amp block fuses, so inputs should be ok. Could probably uprate the relay to a higher amperage, but i'd be very surprised if I was to meet the 30amp limit.

I'm also looking at using a latching relay instead of the standard relay, I don't really like having a relay held on for long periods of time.

I'll whip up a new circuit and stuff, might even lay it down on a circuit board if i get a chance.

cheers for the input, looks like breakout box v2 is already on its way lol.

[infamous_t]

jaycar is ok for the basic stuff, i get all my auto electric gear direct from the suppliers, check out a company called http://www.ashdown-ingram.com.au

they are owned by the repco group and supply about 70-80% of the auto electric stuff australia wide.

They generally only do trade sales, but will usually do over the counter cash sales. Not sure where you are but there is at least 3 or 4 in the brisbane area. Usually awesome prices compared to autobarn or normal repco shops

that said, autobarn or repco should be able to get the narva fuse boxes etc... (at a premium of course)

Ashdowns are great.

I used to deal with them heaps at my old work, infact my workmate moved there after I left.

Anyway my old work has all gear needed as well if you want to compare prices. http://www.12volt.com.au/

This is what I used to run (very $$$ compared to your DIY), however doesn't allow for split permanent power/relay switched power...

[33driver]

who was your mate? I worked at ingram during the merge with ashdown and then at head office for a while so I know most of the ppl around the joint

12volt shop is good, worth going in to have a look. There is one in brisbane, on wynum road near tingalpa.

Edited June 17, 2008 by 33driver