The penguin's motorcycling and Jeep blog

Saturday, July 12, 2008

Motorcycle wiring, Part 1

In which the penguin talks about wiring up accessories on motorcycles (and which will work on pretty much anything else too)...

Okay, first, why am I talking about wiring stuff up in the first place? Well, here's the deal. I have the following electrical gear that needs juice from my motorcycle:

  1. GPS
  2. Voltmeter/Thermometer/Clock
  3. Air pump
  4. Cruise control
  5. Heated jacket liner
  6. Heated grips
Of all the above, the only thing my bike has a spare connector and fuse set up to drive is the heated grips. Everything else I'm going to have to set up an auxiliary fuse panel wired to my battery and run them off of that.

Now, lots of folks, they get sorta panicky around electricity. They don't understand it, they don't want to understand it, so they won't. But really, it's pretty much bog simple. Your battery in your motorcycle or car has two poles on it, marked "+" and "-". Consider electricity to be a buncha little elves that march around in circles (we'll just call these elves "electrons", okay). You can imagine these elves marching out of the "+" pole on your battery, marching through your gizmo where they then spin the handles to make your air pump pump or whatever, then once they're all tired out they march out the other side of your gizmo to the "-" side of the battery. (Actually the electrons march from the "-" to the "+" but for historical reasons we pretend they march the other way, sorta like we pretend that we're civilized and shit like that).

So anyhow, everything electrical in a car or boat or motorcycle looks like this:

+ ------------GIZMO---------- -

Every gizmo has two wires. You got a wire from the "+" on your battery to the gizmo for your little energized ("voltage") elves to march through, then another wire from the gizmo to the "-" on the battery for the tired out elves, tired out from doing all that work in your gizmo, to march back out of until they can get re-energized in your battery. (Now note that this is not exactly how it works, but this is close 'nuff for your purposes :-).

Now I hear you saying, "but I have this gizmo that has only one wire going into it!" Well, if that's the case, that one wire goes to the "+". Then there's some stud or something which has to be hooked up to the "-" for the electron elves to march back out of. Because see, on older cars and motorcycles, rather than spend money running two wires, they just ran a wire from the "-" on the battery to the steel frame of the car or motorcycle. Then the tired elves just marched out of the tail light or whatever through the mounting bolts that held it to the back of your old Rambler, and marched through the steel frame of your car until they got back to the "-" on the battery. So there was two wires, but one was sorta implied, the second wire was the frame of your car or motorcycle.

But you definitely do not want to do that with any gizmo on a modern motorcycle that has an aluminum frame, because then you set up a galvanic current that causes corrosion where the aluminum hits steel (such as the steel of the bolts holding the engine to your frame, duh!). The result is that your frame rots to death. Instead, you want to run a wire all the way back to the "-" on your battery. So we need a way to distribute both the "+" and "-" to gizmos without having a jillion wires hooked to the battery. Something like, say, this Blue Sea fuse panel: See, you can run the "+" on the bottom to the "+ on the battery, and the "-" on the top to the "-" on the battery, then you can hook your gizmos up to the respective "+" terminals (on the bottom) and "-" terminals (on the top) of this fuse block, and voila! And aside from distribution, you get protection from short circuits also. Which is good. Because short circuits are bad.

So what's a short circuit? Well, remember, we had a wire that went like this:

+ ----------GIZMO--------- -

Our little electron elves marched out of the "+", did some work in the gizmo, then marched out to the "-". But a short circuit is when something melts down or connects so we end up with this instead:

+ ------------------------- -

Now our little electron elves march out of the "+", and lookie! Nothing to do! But they're just so full of energy and just want to work their little elve fingers off, so what do they do? Why, they make heat, that's what, as they march their merry little ways from point A to point B. Enough heat to make the insulation of the wiring melt and make things catch on fire. And remember, the battery of your motorcycle and a lot of its wiring is under your seat. Which, remember, is what your butt is sittin' on. OUCH! So anyhow, short circuits starting a fire is something we want to avoid just to preserve our butts, if ya know what I mean. Toasty buns are good only if yer eatin' hamburgers, not when you're riding your motorcycle!

So anyhow, that's what fuses are there to handle. Our little elves melt the fuse wires before they manage to heat up the rest of the wiring, the fuse wire breaks the circuit, our little electron elves no longer have a path to use to march from "+" to "-", so they don't. They just kinda stand around doing nothing, sorta like the five construction workers you see standin' around the one guy down in the hole diggin' like a mole. Which is fine and dandy, if we can't get any work from them by shippin' them through the GIZMO, they can stand around all they want, dig?

So anyhow, now you have the basics of motorcycle wiring. Yes, you do. It ain't rocket science, no matter what folks tell ya! So tomorrow I'm going to introduce you to the major tools needed for motorcycle electrical work, and then maybe we'll even get to play with some of those new toys I introduce you to. Don't worry, it'll be fun! For some definition of fun. That definition being more like, "damned tedious". It ain't rocket science, but it is a lot of fiddly work with skinny little wires, connectors, scissors, shrink-tubing, cranky crimpers, and so forth, all of which are put to the task at hand, which is getting those electrons to march from the "+" on the battery, through our gizmo, and finally to the "-" of the battery on the other side of the gizmo. So tune in for Motorcycle Wiring, Part 2 tomorrow!

-- Badtux the Electrifying Penguin


Gordon said...

As a practical matter, you are correct, sir, and that is the way to wire it.

The way you stated it is called Conventional Flow Theory, and was the reason for Positive Ground automotive electrical systems, discontinued in the U.S. sixty years ago, and clung to by English motorcycles until the late '70s because the tooling and design for the few electronic parts which they had reluctantly begun using in the late '60s was paid for.

According to Electron Flow Theory, in general use for sixty years, electrons flow 'up' from ground (negative) through whatever to the positive post of the battery.

Electrons behave the way they always have. It is simply the way we think about them that has changed, and it didn't matter until electronic parts had to be designed for a particular direction of flow.

Be sure to tell your readers that there are exactly TWO things that can go wrong with an electrical circuit, though some technerds will say three. An ongoing and extremely dull argument.

BadTux said...

Well, Gordon, my discussion of the volt-ohm meter is going to go into the business of short circuits vs. breaks in the wiring.

As for the rest of it, I had a minor in Electrical Engineering in college, so I think I know a bit about the underlying mechanisms of electricity, but the deal is that I was trying to put it in terms that most folks could understand and that would suffice for most folks to do their own electrical work on their motorcycles and cars. Because frankly, it ain't brain surgery, no matter how much folks get freaked out about the whole notion of electricity!

- Badtux the Electrifying Penguin

Gordon said...

You're absolutely right - brain surgery it ain't.

I ain't got no degree, but I had 36 weeks of electronics schools in the service to become a radio repairman. If I wanted to be uppity I could say I was an electronics technician, which I was.

Stuff ya learn in the service sticks with ya. Here's the resistor color codes and tolerances: Bad Boys Rape Our Young Girls But Violet Gives Willingly. Get Some Now.

I learned about vacuum tubes as well, though I don't use that knowledge much anymore for some reason.

Gordon said...

Please read this as well.

BadTux said...

Crap, you probably know about practical electrical shit than me, then. All they taught us up there in the ivory tower was theory. Everything else was learned in the school of hard knocks, heh.

-- Badtux the Schooled Penguin