Wiring a switch box

Okay I started buying a bunch of rubbish because I want to do this properly, unlike days past where there are random wires everywhere. I have two questions since I don't want this to be a fire hazard or anything if I happen to be running everything at once.



Where the number 1 is. Where is a good place to get a signal (ignition? whatever its called, the one that turns on with the key) The only one I know readily is on the back of the stereo. Can i tap that to use as a main line into my box, then split that up to each switch?

Then number 2, can I do the same thing with the ground? Can I combine all my grounds from my switches, then run a larger guage to my main ground in the engine compartment?

Thanks in advance, and i'll take any other advice since I pretty much hate electrical. I'm running a 4 or 6 gauge wire from the battery with a 30a inline fuse. The fuse panel has 6 30 amp fuses as well.

look up fitch box

If you're running a 30A master supply fuse (you really should fuse circuits separately, for various reasons, but we'll stick to this basic assumption,) then you can actually make things easier on yourself:

1) Find a Hot in ACC lead somewhere - the radio supply is usually a good source. You can tap it at the fuse box.

2) Use the lead you just found to "trigger" a relay (DIN relays are cheap, common, and pretty much the same thing your vehicle uses anyhow - so stick to them.) This will become your main power supply. A DIN relay is good for 30A, which is why I did the fuse assumption above (if you go with a fuse on each circuit - you should - then just add up the fuse ratings to get the total supply current. Easier to just use a fuse panel, fed via a relay, for distribution.)

3) This will give you a relatively high-current source, without compromising an extant circuit, and it will automatically turn off when you turn the key OFF. All good things.

The relay may then be split to feed the various switches and such.

As far as grounds - you can easily use a convenient spot on the chassis for a ground. Preferably, something right near the accessory you need the ground for (this allows you to effectively feed a circuit with a minimum of wire.) Use a ring lug and a sheetmetal screw, and strip the contact patch for the ring lug down to bare metal and apply corrosion inhibitor when you assemble.

For a 30A supply, a 10AWG wire will serve. The distribution fuses (for the accessories) should be sized according to the accessory - if it came with a specific rating of fuse (most electronics,) use that rating and no higher! For lighting, it's simple to calculate - take the wattage and the number of lights on a circuit (say, two 55W lamps,) and divide by nominal voltage. Example:


While this will actually give a slightly higher current value than you'd actually use, it also gives a bit of "headroom" that comes in handy for startup loads and the like - and it's easier to remember a nominal 12VDC than it is to remember to measure system voltage each time (and it varies anyhow.)

If you want to understand the maths, look up Ohm's Law and Watt's Law. Both govern the mathematical relationship between voltage (V), current (A), resistance (ohms), and power (W) - and the relationship is both very simple and quite critical. Even if you don't go into major electrical design work, it's still something that you should know - and know cold.

Oh - and I edited your post as well. Please, keep it cool - we try to maintain a "family-friendly" atmosphere. Dis ain't Pirate, y'know...:wave:.

JeepFreak21 said:

LOL @ "rubbish". You beat me to it.

Oh, and I added that "]" for ya
Billy

Click to expand...

Gah - thanks. Still recovering from last week (family knee-knockers are typically tiring as Hell for me. I keep waiting for the meltdown. Fortunately, this year, I was disappointed...)

I run one ground wire straight to the battery and tie in to that main wire from my other accessories. In my head doing this eliminates any chance of a bad ground(or a connection coming loose(I always solder my electrical connections and then heat shrink them)