positive ground

I've always wondered why years ago positive ground was used so commonly & what benefits, if any, it has over negative ground ?

It was believed that a Pos ground system was not as prone to corrosion as a neg ground system, whether there is any merit to that is doubtful as the neg system has almost completely taken over in the industry. mEl

It is still used and there are no overall benefits to either choice. There are some specific benefits to either.

Years back in elec. engineering there were two competing schools of thought on flow.

Those that favored the Hole Theory usually preferred pos. gound.

Those that favored the Electron Theory favored neg. gound.

Note they are both still theories and neither have been proven. For mass productoin using modern semi-conductors, a standard choice had to be made - and that "dart-board" choice was negative ground.

It's been discusses here before with different opinions, but I was told years ago that the engineers thought there would be less corrosion with positive ground. Jim

Had to do with electric theory that electrons flow from negative to positive, so negative was the active or hot side. The only benefit I've heard cited was less corrosion with pos. ground.

Don't want to get too technical on here as most will either get lost or plain not care but to expand on what JD said I quote the ARRL handbook. " most modern circuits employ a chassis or ground plane or bus as a common conductor, this practice reduces the wiring or printed circuitry required and simplifies the schematic diagram. When the negative terminal of the power source is connected to this "ground" system, elecrtons flow from the negative terminal through the ground system and through the circuit elements to the positive terminal. While this is certainly a correct description of the action, it is more convenient to think of the common conductor as the "return" leg. To accomodate this reasoning, electrical engineers have adopted a positive to minus convention. This convention is adhered to in most technical literature. The arrows in semiconductor schematic symbols point in the direction of conventional current and away from actual electron flow" There is much more but I hunt and peck and most won't care anyway as long as the starter works when they push the button. No one seems to care which way the electrons are going. The hole theory is a whole other matter as my understanding is that it has to do with current flow through a semiconductor.. mEl KC3EH

Similar to other postings, I read that Ford and Chrysler, I believe, thougth there was less corrosion where metal frame members met if Pos ground was used. At good ol Purdue wayyyyyyy back in the sixties (if memory serves me no warranty lol) we were taught electrons, negatively charged particles, flowed from - to + while the "holes" (openings where electrons just moved out) flowed + to -. Something like that, its been too long ago.

John T Too long retired EE

OK, my meager little brain is starting to put two and two together.

About the only modern electrical systems I'm familiar with is on the modern combines. (harvesters). And have I ever done some head scratchig trying to figure out why something electrical isn't working on a combine!

Anyway, it seems like the systems I've worked with control the ground to make something work or activate, rather than control the 'hot' side of the circuit. This way we are flowing from negative to positive. Am I right? Please correct me.

I've gotta go to a concert. See ya later.Jim

There two ways to use the chassis as part of a DC electric system. Positive ground and negative ground. They both work and history has not shown one to work better than the other. In the more recent solid state electronics era, more loads are polarity sensitive and so the auto industry has settled on negative ground. Much of the world's electronics in all areas is planned negative ground, except for telephone offices where positive ground is the standard. Yet the same transistors and integrated circuit devices are used, just with care about which side of the supply is grounded.

I think the choice about corrosion went back to DC trolleys and corrosion of buried metal water and sewer pipes. The problem there was that a considerable portion of the ground current flows in the ground instead of the rail and the ground conductivity is improved by the pipe. And somewhere along the pipe, different for every pipe, the current may enter or leave in a small area and that current density either corrodes or protects the pipe. So for each pipe and rail line there was a polarity that minimized the local electrical corrosion of the pipe. The motors, lights, and controls in the trolleys didn't care what the polarity was and worked the same on low frequency AC.

I think that trolley/pipe experience argument was carried over the vehicular electric systems where before radios and before solid state it made little difference in performance or life which side was grounded. The ignition coil works best when its polarity matches the battery though, and its important to flash the generator when changing polarity so it charges with the right polarity. Some voltage regulators were polarity sensitive because of the choices of contact point materials. Today's solid state regulators and alternators are absolutely intolerant of reversed polarity, as are radios and engine control computers. Some gas gauges don't work well with reversed polarity. And the connections to an ammeter need to be reversed when the polarity is changed so it reads right. Otherwise it reads backwards, but its not harmed.

Gerald J.

I believe the reason most components are now being controlled from the ground side is to protect the computers or controllers that activate them. Most are controlled by relays and those are equipped with a diode across the coil to quench the induced voltage generated when the magnetic field collapses across the that coil. That is why in newer equipment it is dangerous to substitute relays unless one is sure the substitute is identical electrically. Nothing like flashing a $500.00 controller with an induced current when the device is turned off and the relay opens. Hope others add to this discussion. mEl KC3EH

About the Hole Theory - it was the work of Paul Dirac long before the use of modern semiconductors. Dirac's Hole Theory and equation was recognized around 1930.

It has a lot to do with the choice of postive-ground in some systems.

Ah c'mon Joe, I said theory, and a lot of things that can't be seen can be proved. Gravity ? Magnetic force ? The little electrical stuff I think I know came from physics and USAF.

Joe,
For a little demo of current flow try a little electrolysis experiment with rusty iron. APPEARS that the rust moves from the negative to the positive. But maybe U of Illinois and the USAF are wrong.

JD as you stated in your first post, both are theories and have never been proven. My info came from the ARRL handbook and these discussions were presented with the basics. mEl

gmc truck division of gm felt so strongly about the negative to positive flow that the 40's and early 50's gmc trucks were positive ground. they felt it gave a stronger cranking for the 6 volt system, one of their reasons for it being a better truck than the chevrolet.

Joe,
No need to call me Mr., I'm just a working man. Google: Cern, or Argonne National Lab, electron, particle theory, atomic collider, quantum physics, etc. people way smarter than me have define electrons, given them a mass(weight), AND photographed them MOVING. Or is this becoming a abundant/conservative discussion where neither of us will be able to recognize the validity of the others arguement ?

(quoted from post at 06:51:09 02/02/09) Now Mr SKI your talking (( Polarity )) -- don't get that mixed up with the way electrons move -- they don't Move,
IF it was possible to look into a wire and see them move, then you would see the way they go, but no one can do that,

now --- DID you Know that the Earth Polarity has the possibility to change, and it has,, Many times,, but has not changed for the last 5000 years or so, but when it does change, and it will --- then your rust movement will go from Positive to Negative

YES -- U of Illinois and USAF are Wrong --- and I will be happy to tell them there Wrong, I am also a SKI ... Mr SKI....

Click to expand...

Here are a couple of takes: (definitely not factual)

1) Model T Ford had it right with Negative ground, then Ford "fixed" it with the Model A (Pos gnd), then Ford "fixed" it again in 1956 (back to Neg Gnd).

2) Ford was almost ready to go into production with the Model A & discovered that spark was positive...investigation revealed that the coil was manufactured wrong! Henry, being the frugal man that he was, said," take too much time & money to scrap/re-manufacturer all those coils...just reverse the battery cables". Finally fixed that mistake in 1956.

3) Had it wrong with Model T, fixed it with Model A, then made it wrong again in 1956.

4) Had it right with the Model T, messed it up with the Model A, couldn't admit mistake until all the guilty players were dead & then fixed it in 1956.

5) When lightening strikes, it is an electrical discharge from a Negative cloud to a Positive Earth, so if it was good enough for God, then it was good enough for machines. Of course the main current is in the return discharge from Earth to cloud…but the Earth is still the Positive end of it.

And FINALLY,

5) It doesn't make any difference, like left/right hand threads on lug nuts, as long as user knows how it is set up, either work just fine. It is just a convention necessary to facilitate communication.

the bottom line here is electricity could care less - as long as it has a path to follow it'll be as happy as a tornado in a trailer park. :lol:

Oh, and I forgot to mention, the engineers over at the 'green' tractor company either couldn't make up their minds, wanted to be sure they were at least half right, or covered all bases.........some of their tractors actually have BOTH Positive AND Negative grounds, at the same time and on the same tractor! And it works, too.