Hello guys,
Can someone explaint to me, why do we connect most circuits to the ground? what is the purpose? when i build a simple circuit with my hands, i never connect it to the ground. I know this might be a naive question,but i am just a beginner

Thank you

 

ISO ground symbols

http://www.ni.com/product-documentation/54469/en/

Earth ground is simply a reference point for a electrical potential. For most circuits it's not a electrical energy path (for RF antennas it might be part of the electrical circuit for EM effects like a image antenna) for power or signals like the circuit 'ground/common/signal' reference point is for potentials within the circuit.

 

For a start ground isn't always ground.
Read here: https://www.allaboutcircuits.com/technical-articles/an-introduction-to-ground/

 

There's different reasons why you ground a circuit and when you don't. Different reasons WHEN you do and don't.

Grounding to the ground is generally a safety measure when dealing with higher voltages. Low voltages like 12 and 24 volts and lower don't benefit from grounding unless you're building something like a receiver. Grounding can enhance the reception of the antenna. But it's not always necessary.

When you deal with high voltages ground can be a life saver because it gives stray electrical charges a path to ground without going through your body.

There are different types of ground (and here's where a lot of people are going to get silly, but) basically there's the ground ground that's connected TO THE GROUND. There are floating grounds and chassis grounds. Chassis ground may be something designed to block stray electrical noises from affecting your circuit; whereas floating grounds are just a common point throughout the circuit. I'm not good at explaining it but I'm sure you'll get a lot of good help here.

 

Hello guys,
Can someone explaint to me, why do we connect most circuits to the ground? what is the purpose? when i build a simple circuit with my hands, i never connect it to the ground. I know this might be a naive question,but i am just a beginner

Thank you

What kind of circuits are you talking about?

What kind of ground are you talking about?

 

Grounds #5017, 5018 and 5019 are GROUND grounds. #1520 is a chassis ground symbol and the two that look like arrows pointed down are signal (floating) grounds in most cases.

 

basically there's the ground ground that's connected TO THE GROUND. There are floating grounds and chassis grounds. Chassis ground may be something designed to block stray electrical noises from affecting your circuit; whereas floating grounds are just a common point throughout the circuit.

One reason I prefer the less ambiguous British distinction in the usage of 'Earth' Wire/Conductor/Connection, wording, less confusing than the all encompassing 'Ground' used in N.A.
Max.

 

...when i build a simple circuit with my hands, i never connect it to the ground. I know this might be a naive question,but i am just a beginner.

Well, you do (if your circuits work), but don't know it. If it makes you feel any better, call your grounds "common". In the context that you are talking about, a "ground" is just a circuit return.

 

I prefer the less ambiguous ••• usage of 'Earth'

Agreed. I even thought (afterwords) of using "Earth". You know how us Yankees think. Everything we do is right no matter what.

Funny, just had a dream of powering an electric motor from a car battery. It was in a 1957 Chevy with an automatic transmission. In the dream I burned everything down including the battery and the transmission.

Don't know why I included that.

For my "Sin" George W Bush was going to execute me.

 

Don't know why I included that.

Maybe it wasn't a dream but a memory?

 

Maybe it wasn't a dream but a memory?

SHUT UP Al. ( ( ( kidding of course ) ) )

 

What kind of circuits are you talking about?

What kind of ground are you talking about?

I am learning how to analyse circuits and every time i see a circuit, i see the following symbol:

I asked a teacher once, but he didnt explain a lot about it, he just said it means that its connected to the ground.
I also read in a book called "code" that we can use earth as a conductor and the circuits in that book are all connected to th ground with the same symbol, and the circuits in that book are basic circuits and not really complicated and i dont think they have very high voltage.

 

I am learning how to analyse circuits and every time i see a circuit, i see the following symbol:

I asked a teacher once, but he didnt explain a lot about it, he just said it means that its connected to the ground.
I also read in a book called "code" that we can use earth as a conductor and the circuits in that book are all connected to th ground with the same symbol, and the circuits in that book are basic circuits and not really complicated and i dont think they have very high voltage.

And Therein lies the rub!
You should have asked him what he meant by 'Ground'!
It is actually classed as Earth Ground in the majority of symbol classifications, but is generally ignored as such and used from anything for Chassis ground to Earth ground and everything in between.
Just search this site for Earth ground and see the number of posts it brings up.!
Max.

 

I am learning how to analyse circuits and every time i see a circuit, i see the following symbol:

I asked a teacher once, but he didnt explain a lot about it, he just said it means that its connected to the ground.
I also read in a book called "code" that we can use earth as a conductor and the circuits in that book are all connected to th ground with the same symbol, and the circuits in that book are basic circuits and not really complicated and i dont think they have very high voltage.

The word "ground" has a number of meanings and so the context of usage becomes important.

For circuits of the type you might build on a breadboard, the "ground" is actually just a "common reference node". Since a voltage is ALWAYS a potential difference between two points, it only makes sense to talk about "applying 9 V" to something if it is understood what other point that 9 V is relative to. By convention, we pick one node to be our common reference node and call it the circuit's "ground" (though "common" is a better term). We indicate this choice by using a special symbol on the schematic. The one you show above is probably the most commonly used one and, as a result, it is also the one that conveys the least information and is subject to the most confusion.

Since it is very commonly the case that lots of components get tied to the common reference node (that's usually one of the things that we take into account when choosing the reference node), we can often declutter our schematics enormously by just showing components tied to that symbol with the understanding that they are actually all tied together -- almost always through wired connections of some type.

There are also more specialized symbols. One is the "chassis ground" symbol which traditionally meant that that node was physically tied to the case that the equipment was in. This was important because it showed what node a person would be connected to when touching the case. Another symbol is the "earth ground", which is a physical connection to the Earth, often through a sufficiently long rod or pipe driven into the ground.

Yes, the physical Earth CAN be used as a conductor, but that is almost never the case in the kind of circuits you are working with.

EDIT: Fix typos.

 

Example of a physical earth conductor.

The Pacific DC Intertie has a fallback (it normally runs in Bipolar mode) earth return system between California and Oregon for the HVDC transmission system.
https://www.jstor.org/stable/41265483?seq=1#page_scan_tab_contents

https://www.google.com/maps/place/4...!1s0x0:0x0!8m2!3d45.497586!4d-121.06462?hl=en
https://www.google.com/maps/@37.2768646,-120.6316687,89a,35y,39.56t/data=!3m1!1e3
The grounding system at Celilo consists of 1,067 cast iron anodes buried in a two foot trench of petroleum coke, which behaves as an electrode, arranged in a ring of 3,255 m (2.02 mi) circumference at Rice Flats (near Rice, Oregon)

http://clui.org/section/sylmar-ground-return-electrode

 

"Ground" or "Earth". I've heard the terms both used the other way around as well. Back in the 60's my brother brought home a car from - um - England I think? European nonetheless. It was termed as a positive earth electrical system. Meaning the positive was grounded (there's that word) to the chassis. Why on earth would you use the term "Earth" if it wasn't "Earth'd?" Chassis ground, common or earth - what we call it is almost irrelevant. Well, not so irrelevant. We use common terms to avoid such confusion. Unfortunately there can be confusion even in the clearest set of rules. The other day we had a meeting on "Sharpness". It was to discuss exactly what is meant when a metal edge is "Sharp". We had some wires cut through because of a sharp edge. My boss missed the meeting, and afterwords, when he caught up with us he asked "How was the meeting on sharpness?" I spoke up and said "It was rather dull."

 

Ground and earth are asked to perform many functions.
An equipotential reference (0V) for your circuit.
Be a groundplane for your antenna
Bond circuits that may have different ideas about where 0V sits.
To carry return current without complaint
To sink away fault and leakage currents
Shield against RFI and more.
Its big ask of this one thing.
"Ground" is a hangover from 19th century telegraph systems. The actual ground was used complete the signaling loop. This meant a great economy in copper wire could be achieved. Telluric currents from natural phenomena like passing thunder clouds and from human activities mean that ground is a loose idea. I once worked on telephone systems at a large power plant. It was shocking- the control room earth was 700v higher than the gate house! It changed with the weather and the MVA being put on line.
Fitting long bonding bus from the switch yard to the gate house fixed this. Wiring utp cables between adjoining buildings is no longer permitted in the uk because earth is local to the building substation. Fibre to the rescue there. In broadcast studios there are two earths made available- the fault current earth and a tech earth for analog signals.

teleprinters: signal ground, frame earth and chassis ground. go figure.

Then there's MEIGaN. Each OR, X-Ray, radiotherapy machine and its room etc has its its own local isolated supply with earth fault monitoring. Very expensive and of dubious benefit. After 30 years in medical device systems I've yet to hear of a confirmed case of microshock. Not even a tingle.
I found out the hard 120V way from the transformer. it doesn't protect against a N-E reversal at all. Helpfully ground/earth is referred to as Terra in defining various termination your power entry point "the company head". Just to clarify things I suppose.

Ralph Morrison is the Earth God. His books are enlightening and very useful.

 

Ralph Morrison is the Earth God. His books are enlightening and very useful.

There is also the book by Eustace Soares 'Book On Grounding' used by the International Assoc. of Electrical Inspectors and used as a reference for NEC,CEC and National Apprenticeship Training Institute.
Max.

 

there's some weird history.

Initially electricity to the homes was 2 wire. There were no motors. It was all lighting. Outlets were non-polarized and light bulb sockets had non-polarized female receptacles.

Then there were non-polarized receptacles.

Then polarized 2-prong.

Then the electric dryer mess. 3-wire done the wrong way. Now they are 4 wire. L1, L2, G and N.

Now you had 3 prong grounded receptacles. Still done wrong in my opinion, It provided protective ground.

You have the service entrance problem. Everything needs a ground reference, Metal pipes, appliance metal enclosures.

The ERA of tubes/valves was wierd too.

Then the double insulated craze.

Now the CATV and the telephone needs a ground. Telco for surge suppression and ground for power for princess phones.

5V logic comes around and really messes things up.

So, ground needs to be used for protection. A place for surges to go. Ground needs to be a reference too.
Daisy chining of 120 V outlets in NA violates this. So, DID dryer wiring.

Now believe it or not, the system voltage (Internal to the devices) is about 340 DC which is 120 V full-wave rectified and 240 full wave rectified. All other voltages are derived from DC-DC converters.

So, we definately have earth, chassis and signal(s), protective, reference(s).

What we don't want is different paths to ground. If you had copper water pipes but rubber hoses, that ground is broken. The protective ground from the power is used and there is only one path to the ground rod for the house.

Stuff goes sideways, but the time line does draw a logical path. It also means you hv to think differently through the different periods of time.

 

Most home ground systems are horribly inadequate for sensitive applications.
In my house home theater/media room I completely gutted the existing electrical system from wall sockets to lamp circuits. I built a separately derived system using an obsolete (used before central HVAC was installed) house 220VAC 30A baseboard heater circuit to a 5KVA split-phase transformer to a separate sub-panel where the center conductor neutral was bonded to a new ground rod system bonded outside the house to the existing ground rod system. This provided very clean AC power with a very clean and noise free earth ground for for several KW of AV equipment. Before I built this new electrical system the background hum and noise of house electrical switching was very annoying at realistic theater volumes, after, there was blissful silence between alien attacks.

https://iaeimagazine.org/magazine/2009/11/16/separately-derived-systems/

One thing to note, the interconnection of equipment grounding conductors, the grounding electrode system, or bonding conductors from one source to another does not mean there is not a separately derived system.