Negative ground advantage?

[MexicoMike]

I know some folks have converted their Commandos to neg ground but I have to admit that I don't really see the operational advantage. I know there are some components that won't work on Pos ground unless you take steps to isolate it but, TBH, I can't think of any components offhand that I would install that fall into that category. But I admit I haven't thought seriously about it and maybe I'm missing some important issues/components that would be useful.

Can someone maybe explain what advantages they have seen in changing from pos to neg ground.?

 

[tomspro]

Excellent question Mike.
I have been considering a changeover to negative ground when I re-do my wiring but not sure it worth the trouble.
One obvious reason is lack of positive ground compatible electronic parts.
Some Norton suppliers (Smiths, TriSpark, etc.) make allowances for either polarity, but many generic components are negative ground only.
Another minor reason is that the 'exposed' terminal on my battery charging pigtail will fry the fuse (or worse) if it touches the frame. Sparks have briefly flown in the past!

 

[kommando]

There more reasons in the past when alarms etc grounded through the steel cover, in these days of plastic enclosures and isolated internals less need.

 

[850commando]

12v pos ground is archaic. i guess so is the bike, but it really only is a benefit for people who can't remember or don't know about the pos gnd. In my past life i had a lot of failures of the pos gnd bits, including assimilators, and rectifiers, so i went to a more modern V+ box to fire the charge bulb. this (http://www.aoservices.co.uk/data/lvs.htm) is neg gnd. and then added leds... the rest of the system doesn't really care.

 

[baz]

The reason I went to negative earth was solely because I wanted to fit an 02 sensor that is negative grnd (no doubt someone will tell me I didn't need to!)
But for me it was simple I had a 3 phase 180w alternator and a Honda regulator so it didn't cost anything to just swap the wires over
With the added benefit of LED headlight bulb and tail light /indicators
But if you don't need to swap over don't bother there's not much to gain

 

[lcrken]

The reason I went to negative earth was solely because I wanted to fit an 02 sensor that is negative grnd (no doubt someone will tell me I didn't need to!)
But for me it was simple I had a 3 phase 180w alternator and a Honda regulator so it didn't cost anything to just swap the wires over
With the added benefit of LED headlight bulb and tail light /indicators
But if you don't need to swap over don't bother there's not much to gain

Same for me. I'm doing a MK3 restomod project, and the O2 sensor display and data logger I want to use require a negative ground system, so I converted. I'm doing a complete new wiring harness anyway, so it is no big deal to go negative ground. I also like the idea of being compatible with any future electronics I might want to install. On the other MK3, which I share with my grandson, we stuck with the original positive ground system when we rebuilt it, just because it was simpler to do so, and we didn't have any reason to change. On my Commando-engine featherbed landspeed racer, I also converted to negative ground for compatibility with instrumentation systems. Like you said, if you don't have a definite reason to convert, it's not worth the effort and expense.

Ken

 

[Fullauto]

The reason I went to negative earth was solely because I wanted to fit an 02 sensor that is negative grnd (no doubt someone will tell me I didn't need to!)
But for me it was simple I had a 3 phase 180w alternator and a Honda regulator so it didn't cost anything to just swap the wires over
With the added benefit of LED headlight bulb and tail light /indicators
But if you don't need to swap over don't bother there's not much to gain

You didn't need to.

 

[MexicoMike]

Hmm...a related question: Why put an O2 sensor on an engine that cannot make any use of it? What can you do with an O2 sensor on it's own?

 

[kommando]

The heater does not care which way the electricity goes as its just an element and the earth is not through the body as it is isolated and you have the Signal wire (+ve) and the earth is the negative wire.

Now if you go for digitally switched ignitors (fed a 5V signal which is then stepped up) and COP (coil on plug) coils then you have a problem as that system grounds through the spark plug and expects a -ve ground.

 

[kommando]

Hmm...a related question: Why put an O2 sensor on an engine that cannot make any use of it? What can you do with an O2 sensor on it's own?

To feed the 0 to 1V signal to an LED or gauge to show the mixture ratio in the exhaust for tuning purposes.

 

[baz]

You didn't need to.

I thought someone would say that but after spending £130 on a Koso narrow band o2 system that says "negative earth only" from memory
And having a limited knowledge of electronics I didn't want to break it
So for me the easiest solution was to change polarity changing a couple of wires

 

[baz]

Hmm...a related question: Why put an O2 sensor on an engine that cannot make any use of it? What can you do with an O2 sensor on it's own?

It's a narrow band koso O2 sensor /guage
It was a great help to me getting my carbs tuned how I want them
I marked the throttle drum and watched the gage ,it showed me the adjustments I needed
IE needle position and slide cutaway etc etc

 

[JimC]

Reason being the whole aotomotive world uses a negative ground. Anything that is polarity sensitive will be a negative ground device today.

Question: What is the benefit of a positive ground? None, that I can think of.

This all goes back to the early theories of electron flow. Conventional theory versus electron theory. One posited electrons flowed from positive to negative, the other theory stated electrons flowed from negative to positive. The British chose the latter, whereas the Americans chose positive to negative.

 

[baz]

If your bike is good on possitive earth then why change?

 

[Triton Thrasher]

Reason being the whole aotomotive world uses a negative ground. Anything that is polarity sensitive will be a negative ground device today.

Question: What is the benefit of a positive ground? None, that I can think of.

This all goes back to the early theories of electron flow. Conventional theory versus electron theory. One posited electrons flowed from positive to negative, the other theory stated electrons flowed from negative to positive. The British chose the latter, whereas the Americans chose positive to negative.

I’ve read that there were American +ve earth vehicles.

 

[Yakatak]

Fords (American) from the Model A till the mid 50's were positive ground.

 

[Fullauto]

I thought someone would say that but after spending £130 on a Koso narrow band o2 system that says "negative earth only" from memory
And having a limited knowledge of electronics I didn't want to break it
So for me the easiest solution was to change polarity changing a couple of wires

Just kidding Baz. I have an O2 sensor and AFR gauge fitted. Bought it off the interweb. It fitted and worked with positive earth. I also have LED head and tail lights. No problem with either. It seems that people only have a problem when they buy cheap stuff which isn't compatible.

 

[Fullauto]

Hmm...a related question: Why put an O2 sensor on an engine that cannot make any use of it? What can you do with an O2 sensor on it's own?

I have an O2 sensor fitted with an air/fuel ratio gauge. It tells you the air/fuel ratio so that you have accurate information with which to work with tuning and jetting changes. It has taught me a lot about tuning and is far more accurate than seat of the pants testing. Nortons will run quite well over a wide range of carburettor settings. These little gadgets enable you to get optimum results fairly easily.

 

[JimC]

GPS, cell phones both use negative ground.

 

[Whiterabbit]

All this talk about Pos earth vs Neg earth has me wondering if my my bike is wired up Flat earth. I can't get any damn light bulb to come on!!