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### Topic: BEGINNERS: What is GROUND ? (Read 10893 times)previous topic - next topic

#### lastchancename

##### Oct 18, 2019, 05:16 amLast Edit: Dec 16, 2019, 06:38 am by lastchancename
GROUND is the dirt you're standing on. aka EARTH.
Nothing you do is going to change it's potential significantly.

So we use that as a reference for other +/- voltages
Usually (95% of cases) GROUND will be regarded as +/-0Vdc
but to make sure, we 'tie' the two together with low resistance (cable)

see also Why is GROUND so important ?
Experienced responders have a nose for laziness, (they were beginners once)... Sure, there are trolls, chest-beaters, and pretenders - but the help you'll get here is about as good as it gets - if you try to help youself!.

#### rtek1000

#1
##### Oct 21, 2019, 08:53 amLast Edit: Oct 21, 2019, 08:54 am by rtek1000
Please avoid private messages, your question may be someone's answer in the future!

#### lastchancename

#2
##### Oct 21, 2019, 11:37 am
Experienced responders have a nose for laziness, (they were beginners once)... Sure, there are trolls, chest-beaters, and pretenders - but the help you'll get here is about as good as it gets - if you try to help youself!.

#### RuskinF

#3
##### Oct 21, 2019, 02:04 pm
Ground literally means connecting the circuit to the ground to prevent users from getting a shock
Ground also means the threshold reference that is used to measure the +/- current flowing through the circuit.

#### Grumpy_Mike

#4
##### Oct 21, 2019, 04:28 pmLast Edit: Oct 21, 2019, 04:31 pm by Grumpy_Mike
Quote
Are you actually suppose to connect your circuit to the earth?
It depends on what you are doing but generally no.

In the UK ground and earth are two separate things. Ground is a common reference point and earth is the soil that surrounds you.

Engineers often use the word ground when the actually mean "common signal reference". Because the earth is an example of a common signal reference beginners often think you should connect your common signal reference to earth.

All mains plugs in the UK have an earth pin but I would only recommend connecting the common signal reference to that under very specific circumstances which is outside what any beginner should be doing. It is not something you should do as a matter of course. If you did then there is a real danger of tripping a mains earth leakage trip in your distribution box.

#### lastchancename

#5
##### Oct 21, 2019, 10:49 pmLast Edit: Oct 22, 2019, 07:29 am by lastchancename
Some of these replies are confusing Ground with insulation and isolation  !

Having Ground present doesn't stop you getting a shock !

If you don't know stuff, don't try to teach others !
Experienced responders have a nose for laziness, (they were beginners once)... Sure, there are trolls, chest-beaters, and pretenders - but the help you'll get here is about as good as it gets - if you try to help youself!.

#### ballscrewbob

#6
##### Oct 22, 2019, 06:55 am
Is somebody wants to work something up out of all this cluster.
Decent mind you in pics etc. and also make it Arduino relevant none of this IEEE stuff.

Right now I am as cunfuzed as anyone else as to which is what and why.

If its OK I will sticky it.

Bob.
It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google (who would have thunk it ! ) or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

#### lastchancename

#7
##### Oct 22, 2019, 07:27 am
I'd tidy it up as the OP, but I'm working mobile from hospital with one finger for a couple of weeks!

If someone does clean it up I'd really appreciate it !
Experienced responders have a nose for laziness, (they were beginners once)... Sure, there are trolls, chest-beaters, and pretenders - but the help you'll get here is about as good as it gets - if you try to help youself!.

#### PerryBebbington

#8
##### Nov 03, 2019, 11:19 am
This comes up in one form or another over and over and ....

Ground / earth / 0V
These are confusing as 'ground' and 'earth' are used both interchangeably and as to mean 2 different things, made worse by differences in English between different English speaking countries.

There is a connection to the muddy stuff outside.

There is a plane on a PCB, or in past times the chassis of the electronic system, the plane or chassis being the common connection for everything.

There is a point in the circuit designated by the designer as 0V, from which everything else is measured.

In the UK (I don't know about other countries) the earth connection in mains wiring used to be connected literally to earth with a stake in the ground outside the property, or often to the (then) lead incoming water pipe. More recently PME (protective multiple earth) was introduced. Now the earth connection is to the incoming neutral, with the connection made before any meter, switchgear or other equipment.

More than one 0V
There is the repeated misunderstanding by people new to electronics where they have 2 separate power supplies but don't see the need to connect the 0V of one to the 0V of the other. For some reason they are blind to the need for there to be a circuit back to each respective power supply and this includes for signals from the part of the circuit fed from one PSU to parts of the circuit fed by the other. Maybe this needs a tutorial all of its own, I don't know.

The need for pull up (or down) resistors
In my mind this is also part of the same discussion, and something I have been thinking of writing about for ages.

How to proceed
If this is going to be a tutorial and a joint effort, then I suggest refining the above list to one we all agree on, then writing the text and producing diagrams and schematics, then, when we are happy everything is good putting it into one complete tutorial which can be pinned somewhere.

Thoughts?

#### Grumpy_Mike

#9
##### Nov 03, 2019, 04:38 pmLast Edit: Nov 03, 2019, 04:40 pm by Grumpy_Mike
Quote
Nothing you do is going to change it's potential significantly.
Well not that you can do but there is a potential between different points in the soil.

This can be very large if the earth connection is taken from two points in the order of half a mile away. You can get potentials in the order of hundreds of volts.

You can even demonstrate sending signals through the earth.
If you don't believe me then take an amplifier and attach two kitchen forks to the input and prod in the soil about two feet apart. You can here signals.

If you connect an amplifier's output to two more points you can here the sound with you amplifier. Depending on the amplifier's output power you can get a range of over 100 feet.

Quote
Having Ground present doesn't stop you getting a shock !
It can in the event of a short to chassis that is earthed, the idea is that it blows the fuse and stops the chassis becoming live.

But a ground can be as lethal as a high voltage, because you have to touch both to get a shock. If a chassis is not earthed then that can prevent you getting a shock.

There are no easy answers to this question, like most electronics a lot depends on context.

#### PerryBebbington

#10
##### Nov 03, 2019, 05:15 pm

Quote
This can be very large if the earth connection is taken from two points in the order of half a mile away.
As is the case with the UK mains earth being taken from the incoming neutral. The neutral is earthed at the local distribution transformer, meaning it's connection to earth could well be at a different potential to an earth stake to the ground outside your house. In the event of a lightning strike on or near your local transformer there could be tens or hundreds of thousands of volts between the earth connection in your mains plug and the ground outside, well, at least until the insulation in the cable fails.

#### Grumpy_Mike

#11
##### Nov 03, 2019, 07:09 pm
Quote
As is the case with the UK mains earth being taken from the incoming neutral.
No.

Wiring regulations state a local earth bonding must be used. Usually taken from the gas supply pipes. Gas in the meaning of the word of domestic combustible gas not the stuff that goes into cars.

There is a potential of about 5 to 12V AC between neutral and ground. You can, if you like, rectify this and use it as free power because it doesn't go through the meter. But this is illegal.

#### PerryBebbington

#12
##### Nov 03, 2019, 08:53 pm

Quote
No.

Wiring regulations state a local earth bonding must be used. Usually taken from the gas supply pipes.
I beg to disagree Mike. PME brings out the neutral conductor from the incoming mains to a terminal which provides the building electrical earth connection. The connection is made before any fuse, meter or switch gear so it cannot be interrupted. It is also mandated that the gas and water pipes be bonded to each other and to this earth, not to get an earth from those pipe but to ensure that all the plumbing and electrical wiring in the property is at the same potential and has a route back to the supply in the event of a fault.

Quote
There is a potential of about 5 to 12V AC between neutral and ground. You can, if you like, rectify this and use it as free power because it doesn't go through the meter
I had a torch bulb in my bedroom powered this way when I was a boy. Never got much light out of it.

#### Grumpy_Mike

#13
##### Nov 04, 2019, 07:06 am
Quote
and has a route back to the supply in the event of a fault
That is not correct. In one house I had the mains was on a spur along our row of houses. One day the neutral developed a fault and got disconnected. The result was that we experienced twice the mains voltage in our houses.

This caused lights to fail and also electronic items like the Hi-Fi amplifier which was being used as a baby monitor at the time.

We got twice the voltage because the return was then coming from one of the other phases. If the neutral had been connected to the ground this would not have happened.

Quote
I had a torch bulb in my bedroom powered this way when I was a boy. Never got much light out of it.
Good for you.    Although a torch bulb does take a lot of current, I was thinking more of a transistor radio.

#### PerryBebbington

#14
##### Nov 04, 2019, 09:12 amLast Edit: Nov 04, 2019, 06:13 pm by PerryBebbington
Quote
That is not correct. In one house I had the mains was on a spur along our row of houses. One day the neutral developed a fault and got disconnected. The result was that we experienced twice the mains voltage in our houses.

This caused lights to fail and also electronic items like the Hi-Fi amplifier which was being used as a baby monitor at the time.

We got twice the voltage because the return was then coming from one of the other phases. If the neutral had been connected to the ground this would not have happened.
To be clear, I didn't mean just any fault, I meant something like live on contact with a water pipe for example. Your experience with loss of neutral is what I'd expect in the circumstances. Maximum possible voltage would be phase to phase, so on a nominally 230VAC system 230 * 3^0.5 = 398VAC (or in my house more like 250VAC * 3^0.5 = 433VAC)

In the UK the method of earthing generally used now is TNCS, which is what I was describing. It used to be common practice to take an earth FROM the incoming lead water pipe. Now incoming water pipes are plastic an earth is taken TO the water and gas plumbing from the electricity supply company's earth terminal. I have no doubt that not all properties are wired this way, especially if they have not been upgraded recently.

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