Should supply rails be negative?

On Tuesday, September 3, 2013 11:18:02 AM UTC-4, Phil Hobbs wrote:
On 09/03/2013 10:25 AM, George Herold wrote:

On Monday, September 2, 2013 10:19:09 PM UTC-4, Phil Allison wrote:

snip

IIRC the switch to negative ground was to reduce galvanic corrosion.

OK that's also the answer I got from here,
http://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=nboard&th=848277

To quote from one response,

More:

explanation to this question comes from a 1978 Rolls-Royce Enthusiasts' Club service manual.

"...it has been found that cars wired positive earth [ground] tend to suffer from chassis and body corrosion more readily than those wired negative earth. The reason is perfectly simple, since metallic corrosion is an electrolytic process where the anode or positive electrode corrodes sacrificially to the cathode. The phenomenon is made use of in the "Cathodic Protection" of steel-hulled ships and underground pipelines where a less 'noble' or more electro-negative metal such as magnesium or aluminum is allowed to corrode sacrificially to the steel thus inhibiting its corrosion."...

For more information on cathodic protection, please read Roger Alexander's article, An idiots guide to cathodic protection or Chris Gibson's article What is Galvanic Erosion, is it serious and can it be prevented? for metal boat hulls. By 1956, all the North American manufactured cars and trucks, except the Metropolitan, were using negative earth [grounding].

Also:

"In most modern automobiles, the grounding is provided by connecting the body of the car to the negative electrode of the battery, a system called 'negative ground'. In the past some cars had 'positive ground'. Such vehicles were found to suffer worse body corrosion and, sometimes, blocked radiators due to deposition of metal sludge."


George H.
Cheers



Phil Hobbs



--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC

Optics, Electro-optics, Photonics, Analog Electronics



160 North State Road #203

Briarcliff Manor NY 10510



hobbs at electrooptical dot net

http://electrooptical.net
 
On 09/03/2013 10:25 AM, George Herold wrote:
On Monday, September 2, 2013 10:19:09 PM UTC-4, Phil Allison wrote:
"P E Schoen"





Another reason for the positive rail and NPN or N-channel devices being more

popular may be their closer correlation to vacuum tubes, which (AFAIK) do

not have a PNP or P-channel counterpart.





** That would be the origin of the B+ rail convention.



Early transistor radios use germanium PNP devices, so had positive ground

supplies.



Most old motor vehicles ( pre 1950s) had positive ground systems, usually 6V
too.
Yup, I wonder why? (My old tractor originally had a positive ground 6V battery, now all switched to 12V and neg. to Gnd)

Though not at all an expert, ECL also uses a positive ground 'scheme'.

To give the OP a bit of a break there does seem to be some positive bias in electronics at present. I can buy lots of positive voltage references, but negative ones are not so common.

George H.







.... Phil

IIRC the switch to negative ground was to reduce galvanic corrosion.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On Tue, 03 Sep 2013 11:18:02 -0400, Phil Hobbs wrote:

> IIRC the switch to negative ground was to reduce galvanic corrosion.

Did it?

--
"Design is the reverse of analysis"
(R.D. Middlebrook)
 
On Tue, 03 Sep 2013 08:22:50 -0400, _defaullt wrote:

If you are in electronics just think of electrons going with the arrow in
diodes and bipolar transistor symbols and you won't go far wrong.

Huh??

--
"Design is the reverse of analysis"
(R.D. Middlebrook)
 
On Tue, 03 Sep 2013 11:18:02 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 09/03/2013 10:25 AM, George Herold wrote:
On Monday, September 2, 2013 10:19:09 PM UTC-4, Phil Allison wrote:
"P E Schoen"





Another reason for the positive rail and NPN or N-channel devices being more

popular may be their closer correlation to vacuum tubes, which (AFAIK) do

not have a PNP or P-channel counterpart.





** That would be the origin of the B+ rail convention.



Early transistor radios use germanium PNP devices, so had positive ground

supplies.



Most old motor vehicles ( pre 1950s) had positive ground systems, usually 6V
too.
Yup, I wonder why? (My old tractor originally had a positive ground 6V battery, now all switched to 12V and neg. to Gnd)

Though not at all an expert, ECL also uses a positive ground 'scheme'.

To give the OP a bit of a break there does seem to be some positive bias in electronics at present. I can buy lots of positive voltage references, but negative ones are not so common.

George H.







.... Phil


IIRC the switch to negative ground was to reduce galvanic corrosion.

Cheers

Phil Hobbs

Actually, in automobiles, it seems to have occurred when radios went
transistorized. I don't know if there's a correlation or not.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Tue, 3 Sep 2013 15:59:20 +0000 (UTC), Lauri Alanko <la@iki.fi>
wrote:

In article <l03ev3$dg8$1@dont-email.me>, P E Schoen <paul@peschoen.com> wrote:
You're dealing with Jim Thompson here, and lately he has shown increasing
evidence of being a "dick",

Well, everyone deserves the benefit of doubt, even those who don't
give it to others. It was worth a shot.

But to respond on-topic to your inquiry, even if it had some validity (and
I'm not saying it does not), the conventions for circuits using a positive
rail have become so deep-rooted that only a very compelling reason would
suffice to promote the alternative.

Yes, obviously. The problems with running high-side n-channel switches
are relatively minor, and there are well-established solutions. But it
is annoying to think that there might be an easier way to do things
and only convention prevents it.

Another reason for the positive rail and NPN or N-channel devices being more
popular

The popularity of N-type transistors is understood. What I don't get
is how that associates with preferring a positive rail, when to me it
seems like N-types would be more practical with a negative rail.

I do appreciate the time and thought you put into your post, but I
think it is more of a philosophical proposition or "thought
experiment"

Yes, of course. What else?

A big part of learning about a system is studying different
configurations and trying to understand how they behave. It is
essential that the configurations are highly variable and illustrate
all aspects of the system, and not merely constrained to those
encountered in practice.

For instance, when studying physics, it is quite on par to consider
what happens when you send someone to space and back at light speed.
It doesn't matter that this sort of thing will never ever happen in
the real world: it illustrates how special relativity works, and you
_have_ to be able to explain what happens if you want to claim to
understand physics.

However, in many online discussions of electronics I have seen
something that I hesitatingly call an "engineering mindset": if a
question is not related to a practical real-world problem that someone
is trying to solve, it is not worth discussing. Those sort of people
will no doubt think that discussion of unconventional rail
configurations is a waste of time. (Those people also must think I'm
mad for getting joy from getting a circuit work purely in simulation
even if I have no intention of ever building it in practice.)

For comparison, suppose a beginning math student just learned about
numeral systems and exclaimed: "Hey, wouldn't it be better if we used
a duodecimal system? After all, we divide things into threes and fours
much more often than into fives!" A reasonable response would be
something like: "Probably, yeah. It's not going to happen, of course,
but you are right that it would have advantages." Even though the
proposal is utterly unrealistic, making it demonstrates that the
student has grasped something essential about the purpose of numeral
systems and the tradeoffs in their design, and that is to be
commended.

People with an "engineering mindset" would respond: "You're not
experienced enough to challenge such basic practices. Keep on using
the decimal system like everyone else."

Usenet may be on the road to extinction, and it will only survive
by the influx and proper use of this resource by younger or newer
people with electronics.

Indeed. Thanks for your reply, the first decent one I got in this
thread.


Lauri

Of course. Paul Schoen has been long known to be a nutcase. You and
he should pair up >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On 09/03/2013 11:36 AM, Fred Abse wrote:
On Tue, 03 Sep 2013 08:22:50 -0400, _defaullt wrote:

If you are in electronics just think of electrons going with the arrow in
diodes and bipolar transistor symbols and you won't go far wrong.

Huh??

;)

The best reasons to keep the current convention are that it works
satisfactorily, everybody uses it, and it confuses nobody AFAICT.

Changing would break all three of those fine properties, as well as
requiring all the textbooks to be rewritten and all the classical papers
changed. That earthquake would make ROHS look like a small bump in the
road.

Apart from the Hall effect, there's really nothing going on in solid
state circuits that depends on the polarity of the carriers anyway.
Electron mobility is higher, but that won't even enter the consciousness
of somebody who's likely to have trouble with conventional current flow.

If we were still using tubes, where there's a much more substantial
asymmetry, the argument would be a bit stronger but not much.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On Tue, 3 Sep 2013 15:59:20 +0000 (UTC), Lauri Alanko <la@iki.fi> wrote:

In article <l03ev3$dg8$1@dont-email.me>, P E Schoen <paul@peschoen.com> wrote:
You're dealing with Jim Thompson here, and lately he has shown increasing
evidence of being a "dick",

Well, everyone deserves the benefit of doubt, even those who don't
give it to others. It was worth a shot.

But to respond on-topic to your inquiry, even if it had some validity (and
I'm not saying it does not), the conventions for circuits using a positive
rail have become so deep-rooted that only a very compelling reason would
suffice to promote the alternative.

Yes, obviously. The problems with running high-side n-channel switches
are relatively minor, and there are well-established solutions. But it
is annoying to think that there might be an easier way to do things
and only convention prevents it.

Another reason for the positive rail and NPN or N-channel devices being more
popular

The popularity of N-type transistors is understood. What I don't get
is how that associates with preferring a positive rail, when to me it
seems like N-types would be more practical with a negative rail.

I do appreciate the time and thought you put into your post, but I
think it is more of a philosophical proposition or "thought
experiment"

Yes, of course. What else?

A big part of learning about a system is studying different
configurations and trying to understand how they behave. It is
essential that the configurations are highly variable and illustrate
all aspects of the system, and not merely constrained to those
encountered in practice.

For instance, when studying physics, it is quite on par to consider
what happens when you send someone to space and back at light speed.
It doesn't matter that this sort of thing will never ever happen in
the real world: it illustrates how special relativity works, and you
_have_ to be able to explain what happens if you want to claim to
understand physics.

However, in many online discussions of electronics I have seen
something that I hesitatingly call an "engineering mindset": if a
question is not related to a practical real-world problem that someone
is trying to solve, it is not worth discussing.

Well, we're in the business of building things. Lots of things. 95% of what we
do works fine without a lot of introspection. The sort of thing that you're
talking about, related to the reverse electron current flow convention, most EEs
have thought about and got over long ago.



Those sort of people
will no doubt think that discussion of unconventional rail
configurations is a waste of time. (Those people also must think I'm
mad for getting joy from getting a circuit work purely in simulation
even if I have no intention of ever building it in practice.)

Most of us will use any power supply arrangement that works. But given that
nearly all digital logic chips have multiple positive rails, and the most
convenient power switches are low-side n-types, most supplies tend to be
positive against common. 74 series TTL exploited fast NPN transistors and pretty
much solidified positive logic levels and rails.

Simulation is fun, but so is soldering. Copper as art:

https://dl.dropboxusercontent.com/u/53724080/Protos/LDP2.JPG


For comparison, suppose a beginning math student just learned about
numeral systems and exclaimed: "Hey, wouldn't it be better if we used
a duodecimal system? After all, we divide things into threes and fours
much more often than into fives!" A reasonable response would be
something like: "Probably, yeah. It's not going to happen, of course,
but you are right that it would have advantages." Even though the
proposal is utterly unrealistic, making it demonstrates that the
student has grasped something essential about the purpose of numeral
systems and the tradeoffs in their design, and that is to be
commended.

People with an "engineering mindset" would respond: "You're not
experienced enough to challenge such basic practices. Keep on using
the decimal system like everyone else."

More likely we'd say "bases of 2^n, like hex, are more useful in practise."
Nobody (that I know of) does logic or signal processing, in uPs or FPGAs, in
decimal. We do lots of - signed and unsigned - binary integer, fixed-point, and
fractional formats, and occasionally floats [1]. We'll use 18 bit signed
fractional data paths in an upcoming signal processing app. Engineers aren't
(all) as inflexible as you seem to suggest. But we've got past most of the basic
issues.

[1] somebody semi-famous said "If you absolutely have to use floating point, you
don't understand the problem."


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
 
On Tue, 03 Sep 2013 12:19:03 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 09/03/2013 11:36 AM, Fred Abse wrote:
On Tue, 03 Sep 2013 08:22:50 -0400, _defaullt wrote:

If you are in electronics just think of electrons going with the arrow in
diodes and bipolar transistor symbols and you won't go far wrong.

Huh??


;)

The best reasons to keep the current convention are that it works
satisfactorily, everybody uses it, and it confuses nobody AFAICT.

It really confuses people who learned "electron flow" in the military or in
certain trade schools.

--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
 
On Tue, 03 Sep 2013 08:36:30 -0700, Fred Abse
<excretatauris@invalid.invalid> wrote:

On Tue, 03 Sep 2013 08:22:50 -0400, _defaullt wrote:

If you are in electronics just think of electrons going with the arrow in
diodes and bipolar transistor symbols and you won't go far wrong.

Huh??

Put a plus voltage on the cathode and you get a plus voltage on the
anode - that arrow thing pointing to where the plus voltage goes..

But then if you cut your teeth on vacuum toobs, it seems unreal that
electrons boil off the heated cathode and travel to the anode (or
plate) against the logical flow.

But today we are faced with some people using "pins" when they don't
mean physical pins but IO ports, or storage drives that are physical
or virtual.

In balance the whole concept would seem to strengthen the idea of
thinking outside the box, or thinking with no box.

Never argue with empirical results. Adapt.
 
On Tue, 03 Sep 2013 12:44:21 -0400, _defaullt wrote:

Put a plus voltage on the cathode and you get a plus voltage on the anode
- that arrow thing pointing to where the plus voltage goes..

That's not what you said. You said:

"If you are in electronics just think of electrons going with the arrow
in diodes and bipolar transistor symbols and you won't go far wrong."

In diodes and bipolar transistors, *conventional current* "goes with the
arrow", NOT electrons.

Voltage does not "go" anywhere, it just sits.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)
 
On Tue, 03 Sep 2013 09:28:18 -0700, John Larkin wrote:

It really confuses people who learned "electron flow" in the military or
in certain trade schools.

That's just to keep "other ranks" "in their place" ;-)

--
"Design is the reverse of analysis"
(R.D. Middlebrook)
 

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