Author Topic: GND for Dummies.  (Read 2462 times)

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Offline AMSDOS

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GND for Dummies.
« on: 12:17, 20 February 16 »
I'm sticking this here because it's not Amstrad related, but an Amstrad topic prompted me to write about it.


As part of an electronics kit I purchased some time ago to put together some electronic projects (from 2 x AA Batteries), some of those make use of GND.


The Manual suggests ramming a metal rod into the Ground will give you GND or alternatively a "Dunny" Down-pipe will do the same thing, but prefer to construct indoors, where I don't see anything going into the ground, our home is on a Concrete Slab, so is GND, GND as long as it touches the floor, or does it need to go into the Ground to make it fully GND?
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Offline 1024MAK

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Re: GND for Dummies.
« Reply #1 on: 12:41, 20 February 16 »
In this sense of the meaning, they mean at "Earth potential", or "ground potential".
By putting a metal rod into an area of earth / dirt in the ground, you are creating a "clean" earth rod. By clean, this means electrically clean, as it is free of any other electrical current flow. It does mean it will not get muddy  :laugh: .

With an earth rod, normally it is important to put it in the ground so that it makes really good contact with lots of damp soil. In dry countries that can be difficult to achieve.

In your case, you cannot do this inside a building. And in built up urban areas, it also may not be possible. Not as good, but it still sometimes works, is to run a wire to the main electrical earth terminal of your property. Not to be confused with the Neutral (or return) phase wire/terminal. Do not disconnect any of the existing earth wires/terminals. Just find a non-destructive way of attaching your wire to the terminal. If you have to unscrew any terminal. Switch off the main supply isolating switch (or switches if more than one) to prevent any risk of a spark when you are working on the wiring (in some systems the earth connections may carry some current).

Or if you live in a house that is supplied by a metal water pipe (meaning the pipe that enters your property), tightly wrap a wire around that. Be aware, water companies now use plastic pipe, and that does not work so well...

I presume you have a radio kit or a weather detector or something similar?

Good luck  :D

Mark
Looking forward to summer in Somerset :-)

Offline SRS

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Re: GND for Dummies.
« Reply #2 on: 18:13, 20 February 16 »
I don't want you to grill yourself, so ask some australian electrician before doing smthg ->

Your AS/NZS 3112 have a earth plug - so you maybe can construct a  "One pin" - lead
 for having your electronic grounded with help of an outlet ?



Offline Fessor

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Re: GND for Dummies.
« Reply #3 on: 18:57, 20 February 16 »
Earthing system - Wikipedia, the free encyclopedia

Quote
In Australia, New Zealand and Israel the TN-C-S system is in use; however, the wiring rules currently state that, in addition, each customer must provide a separate connection to earth via both a water pipe bond (if metallic water pipes enter the consumer's premises) and a dedicated earth electrode. In Australia and New Zealand this is called the Multiple Earthed Neutral Link or MEN Link. This MEN Link is removable for installation testing purposes, but is connected during use by either a locking system (locknuts for instance) or two or more screws. In the MEN system, the integrity of the Neutral is paramount. In Australia, new installations must also bond the foundation concrete re-enforcing under wet areas to the earth conductor (AS3000), typically increasing the size of the earthing, and provides an equipotential plane in areas such as bathrooms. In older installations, it is not uncommon to find only the water pipe bond, and it is allowed to remain as such, but the additional earth electrode must be installed if any upgrade work is done. The protective earth and neutral conductors are combined until the consumer's neutral link (located on the customer's side of the electricity meter's neutral connection) - beyond this point, the protective earth and neutral conductors are separate.

Offline AMSDOS

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Re: GND for Dummies.
« Reply #4 on: 23:35, 20 February 16 »

Sounds quite serious  :o 


Sorry folks, it looks like I didn't explain myself properly.  :(


@Fessor I looked at that Wikipedia page earlier before coming here with this thread and I couldn't nut head or tail of it.


@SRS I've found an image of the kit I'm using, it's an Electronics Lab, which allows you to build 30 different things & some of those projects need a GND. According to the box it's safe, so I didn't want to waste some money an Electricians time in case I get a shock.  :)





Still GND is GND, I'm still unsure what that meant for something like this, when I got the kit initially, I thought I could use the leg on the side of the kit, but the manual doesn't say that.
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Offline 1024MAK

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Re: GND for Dummies.
« Reply #5 on: 00:29, 21 February 16 »
Still GND is GND.
As I said, in this sense of the meaning, they mean at "Earth potential", or "ground potential".
By putting a metal rod into an area of earth / dirt in the ground, you are creating a "clean" earth rod. By clean, this means electrically clean, as it is free of any other electrical current flow.
The radio circuits in the kit need a clean ground connection in order for the radio to receive a good signal. There are alternatives if there is no way to get a ground connection. But they are not very practical.

If you are not bothered about the radio sections of the kit, you do not really need a ground connection.

BTW, the link to the picture does not work.
This link takes you to a list of the images: Index of /electronics-lab/maxitronix-30-in-1-electronics-lab

Mark
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Offline AMSDOS

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Re: GND for Dummies.
« Reply #6 on: 03:04, 21 February 16 »
As I said, in this sense of the meaning, they mean at "Earth potential", or "ground potential".
By putting a metal rod into an area of earth / dirt in the ground, you are creating a "clean" earth rod. By clean, this means electrically clean, as it is free of any other electrical current flow.
The radio circuits in the kit need a clean ground connection in order for the radio to receive a good signal. There are alternatives if there is no way to get a ground connection. But they are not very practical.


I had a chat to @SRS just now in a PM, and what I brought up in that, was if I could use the GND which is on the back of my Hi-Fi System, which is there for a Turntable (if I had one), or if that would be dangerous?

Quote
If you are not bothered about the radio sections of the kit, you do not really need a ground connection.

Well it was one of the reasons I got the Electronic Lab, I wasn't looking for anything fancy, just some basics, if you guys think that using the GND on the back of my Hi-Fi could be bad, I'll just take my Lab outside and use an iron Stake.

Quote
BTW, the link to the picture does not work.
This link takes you to a list of the images: Index of /electronics-lab/maxitronix-30-in-1-electronics-lab

Mark


No, I just posted an image of the Kit I have, wasn't meant to be a Link to anything.  :)
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Offline Bryce

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Re: GND for Dummies.
« Reply #7 on: 11:56, 25 February 16 »
I'm not up to speed on Australian earthing systems, but here's a few alternatives:

1 - The earth pin of any 230V socket.
2 - If you have central heating in your house, your radiators will be earthed, so you can use them.
3 - Any metal water pipes.
4 - If all of these aren't available, a sheet of metal on the concrete floor should give you enough ground-plane.

However, I'd build the circuit and see how well it works without a ground before I went looking for one.

Bryce.

Offline 1024MAK

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Re: GND for Dummies.
« Reply #8 on: 13:19, 25 February 16 »
I had a chat to @SRS just now in a PM, and what I brought up in that, was if I could use the GND which is on the back of my Hi-Fi System, which is there for a Turntable (if I had one), or if that would be dangerous?
A GND connection on a Hi-Fi system should not be dangerous if the mains plug is correctly fitted (wired correctly) and the mains socket is correctly wired. Does this Hi-Fi system have metal case parts? If yes and you have had no problems with it, I see no reason why you should not try this.

Of course, just because it is labelled as GND does not necessarily mean it is earthed. If you can open up the plug to look inside, does it have two or three wires connected inside?

Mark
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Offline AMSDOS

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Re: GND for Dummies.
« Reply #9 on: 08:21, 26 February 16 »
@SRS gave a different answer regarding the GND connector on my Hi-Fi System, suggesting it's used to connect to an GND and not for connecting another GND to it. I've got out the Manual for my Hi-Fi system which states it's there to connect an earth lead from the Turntable to the GND, which I presume is different from connecting a GND to GND?


I'll just set it up in the Garage and use a Steel Railing that goes into the Ground & do what @Bryce suggests a test it with & without. just didn't want to blow anything up just because something wasn't connected (even though it's only 3v).
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Offline Bryce

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Re: GND for Dummies.
« Reply #10 on: 10:19, 26 February 16 »
@SRS gave a different answer regarding the GND connector on my Hi-Fi System, suggesting it's used to connect to an GND and not for connecting another GND to it. I've got out the Manual for my Hi-Fi system which states it's there to connect an earth lead from the Turntable to the GND, which I presume is different from connecting a GND to GND?


I'll just set it up in the Garage and use a Steel Railing that goes into the Ground & do what @Bryce suggests a test it with & without. just didn't want to blow anything up just because something wasn't connected (even though it's only 3v).

If the GND on the HiFi is for grounding the turntable, then it is the correct ground that you need, as long as your HiFi has a 3 pin power plug.
You definitely won't blow something up anyway. The 3V circuit is floating and the GND is just to improve reception of the reciever, there's no power going to ground, it's just a reference.

Bryce.

Offline AMSDOS

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Re: GND for Dummies.
« Reply #11 on: 11:08, 26 February 16 »
If the GND on the HiFi is for grounding the turntable, then it is the correct ground that you need, as long as your HiFi has a 3 pin power plug.
You definitely won't blow something up anyway. The 3V circuit is floating and the GND is just to improve reception of the reciever, there's no power going to ground, it's just a reference.

Bryce.


The Hi-Fi Power Plug only has 2 pins, guess that's bad, not that I may not blow anything up in that respect.








@Audronic PMed, suggesting to test my GND connection without and with a connection to the shed Railing, so I guess that's something. :)
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Offline Bryce

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Re: GND for Dummies.
« Reply #12 on: 12:30, 26 February 16 »

The Hi-Fi Power Plug only has 2 pins, guess that's bad, not that I may not blow anything up in that respect.

@Audronic PMed, suggesting to test my GND connection without and with a connection to the shed Railing, so I guess that's something. :)


Ok, then the HiFi is floating too. Go for the rail solution (after you've checked whether it works without GND).

Bryce.
« Last Edit: 13:32, 26 February 16 by Bryce »

Offline 1024MAK

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Re: GND for Dummies.
« Reply #13 on: 12:32, 26 February 16 »
The Hi-Fi Power Plug only has 2 pins, guess that's bad, not that I may not blow anything up in that respect.
In that case, the Hi-Fi GND connection is not mains earth. So is no good to you.

So, we are back to using the steel railing, or a metal water pipe.


BTW "floating" when used in the electrical sense means a circuit has no direct intended electrical connection to earth.

Mark
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Offline Bryce

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Re: GND for Dummies.
« Reply #14 on: 13:35, 26 February 16 »
BTW "floating" when used in the electrical sense means a circuit has no direct intended electrical connection to earth.

Mark

Yeah, I should have probably explained what floating means. I'd remove the word "intended" from your definition though. Even if the earth connection is unintended, the device is then no longer floating!

Bryce.

Offline 1024MAK

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Re: GND for Dummies.
« Reply #15 on: 14:46, 26 February 16 »
Yeah, I should have probably explained what floating means. I'd remove the word "intended" from your definition though. Even if the earth connection is unintended, the device is then no longer floating!

Bryce.
In the industry where I work, we use the term "earth free" to describe floating supplies. These electrical supplies are tested at regular intervals to see if they are still "earth free". If they are found to have an unintended connection (due to a partial or complete failure of insulation, or due to water ingress) they are then described as earthy, or more formally as having an "earth fault".

But yes, floating only applies if there is no earth connection, intended or otherwise.

Mark
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Offline Bryce

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Re: GND for Dummies.
« Reply #16 on: 14:51, 26 February 16 »
That's much the same as in electronics, but I haven't heard the term "earthy" before? Sounds like something a gardener would say :D

In electronics some things are deliberately floating and some deliberately earth referenced, so you always need to know (and confirm) the DUTs (Device under Test) status before you go hooking up a scope to it. The smoke that comes out of a scope is expensive smoke.

Bryce.

P.s. Look, this time I explained the technical jargon (although you most likely knew this) :)

Offline Gryzor

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Re: GND for Dummies.
« Reply #17 on: 21:06, 26 February 16 »
That's much the same as in electronics, but I haven't heard the term "earthy" before? Sounds like something a gardener would say :D


Or a wine tester.

Offline Audronic

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Re: GND for Dummies.
« Reply #18 on: 23:55, 26 February 16 »
I used to belong to a Group Called "Down to Earth" I wonder if they are "Grounded"   ;)


Ray 
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Offline AMSDOS

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Re: GND for Dummies.
« Reply #19 on: 03:35, 27 February 16 »

Yes I was able to understand what floating meant.


I got around to wiring up both projects, I couldn't hear a thing from the radio which draws current from the Antenna, either my hearing isn't good enough & there was too much noise for me to hear.


So I went onto the Second Radio which uses 2 AA Batteries and had success with that one, though was surprised how quiet that one was, though the Lab doesn't have any Volume, guess that's more advanced Electronics. I tried that radio with GND Floating and connected, though it didn't seem to make much difference funnily enough.
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Offline Audronic

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Re: GND for Dummies.
« Reply #20 on: 03:53, 27 February 16 »
@AMSDOS


Try tuning into 774 (My old work) this would be the strongest station in Victoria.




Ray
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Offline AMSDOS

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Re: GND for Dummies.
« Reply #21 on: 10:21, 27 February 16 »
@AMSDOS


Try tuning into 774 (My old work) this would be the strongest station in Victoria.




Ray


Yes, it was the only station I could hear.  :D
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Offline Bryce

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Re: GND for Dummies.
« Reply #22 on: 10:53, 27 February 16 »
Don't expect too much from those radio projects. The volume will also depend on what speaker you are using. They've probably only used a tiny single stage amplifier with enough power to drive a headphones.

Bryce.

Offline 1024MAK

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Re: GND for Dummies.
« Reply #23 on: 12:07, 27 February 16 »
Yes I was able to understand what floating meant.


I got around to wiring up both projects, I couldn't hear a thing from the radio which draws current from the Antenna, either my hearing isn't good enough & there was too much noise for me to hear.


So I went onto the Second Radio which uses 2 AA Batteries and had success with that one, though was surprised how quiet that one was, though the Lab doesn't have any Volume, guess that's more advanced Electronics. I tried that radio with GND Floating and connected, though it didn't seem to make much difference funnily enough.
For these low tech radios, you normally need three things:-
1) as large an aerial as possible if the aerial is just a wire, plus a good noise free earth connection to provide a "ground plane",
2) either a nearby transmitter for a radio station, or a high power main transmitter that does not have to be local, but which you get a strong signal on a normal domestic radio,
3) high impedance earpiece. For the powered circuit, a set of 32 ohms stereo headphones.

But results do vary. In the UK many, many years ago, I got better results from an audio power amp when the input was not connected to a source than a low tech radio receiver :D

Mark


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