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Help with ground wiring? Answered

Ok, I am extremely new to doing anything with electronics. I'm working on a project where I am connecting some LEDs and some toggle switches. On some instructables I was looking at it mentions having a ground wire. What do I use for a ground wire? Is it a special type of wire? Anything specific I need to know? Thanks for your help in advance.

6 Replies

orksecurity (author)2011-05-05

There are several different things called ground.

One is the reference voltage -- whatever you're calling "zero volts" in your circuit. This sometimes takes the form of a "ground plane", especially in higher frequency circuitry; that's generally a layer of the printed circuit board which is at the ground voltage everywhere, to help shield the circuit. It may also be "signal ground", when you're talking about connections between circuits; that may or may not be the same as ground for each individual circuit.

Another -- more properly referred to as "earth" -- is a connection to actual dirt. This is generally relevant only for house-current power and some kinds of radio circuits. The safety grounds in your house are examples of this. It may, or may not, be connected to the zero-volts reference ground.

There are a few other uses of the term derived from these ("ground plane", for example), but those don't apply to your case.

So: "Ground wire" means a wire connected to one of those definitions of ground. Which one depends on context. If you're talking about LEDs, it _probably_ means a wire connected to the negative terminal of the battery, but you need to look at the circuit diagram to be sure.

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iceng (author)orksecurity2011-05-05

If you are an electrician wiring buildings,
Ground is a green insulation copper wire
( 0 Volt tied to a metal rod driven into the local earth )
used as the safety third wire in USA.

If you are an electronics type,
Ground is black insulation mostly copper wire
( 0 Volt measuring reference ) and return for DC power supplies.
I don;t know how its done in the UK..


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frollard (author)2011-05-05

It all amounts to what direction the electrons are flowing. Electrons flow from 'more negative' to 'more positive'. They flow from negative, to ground, and from ground, to positive.
Conventional current is the opposite, and originates from when it was thought that positive charge 'flowed' (which is true in some cases). In a regular circuit it will be electrons that flow, but any diagram will show the direction of conventional current as an arrow (diode, transistor, etc).

In the case of *most* electronic circuits (not your house wiring, but circuits 'like in electronics') -- ground is negative, and is the 'common connection' in your circuit, where everything else is referenced at +x volts.

I.e. in a flashlight, the negative battery terminal (at the back of the flashlight) is connected to the housing of the flashlight, and the power passes through the metal casing up to the front. ALL of that metal casing is ground. In this example, anything touching the positive terminal of the battery is at +x volts, and anything connecting to that, and forming a circuit to ground will pass electricity.
Another example of the same setup is 99% of all cars on the road. They have a 'negative ground' system, Everything metal in the car is connected to the battery's negative terminal and is considered ground -- every other wire in the car runs a circuit to the positive terminal on the battery, and then connects back to ground.

Where does this go for led circuits? If you see a ground symbol, hook that wire up to negative, and if you see a +x volts "up arrow" then hook those connections up to the positive terminal on your source.

***there are always exceptions to the rule. Some circuits have a ground at 0v, and a positive AND negative voltage. Others still have a positive ground and the circuit operates on the negative voltage.

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payne.kj (author)frollard2011-05-05

I think I figured out my current project. My next one is this instructable... https://www.instructables.com/id/Kids-Spaceship-control-panel-Prop/

what kind of wire would I use for grounding wire? Its hard to tell exactly how it is all connected (atleast for me) in the pictures and I can't read the schematics yet.

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NachoMahma (author)payne.kj2011-05-05

. That ground is a zero volts/negative power ground, not an Earth ground (although you could connect it to an Earth ground if you wanted to). I'm not sure what you mean by "what kind of wire". Any wire, as long as the gauge (cross-sectional area) of the wire is large enough for the current it has to carry, will work.

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FoolishSage (author)2011-05-05

I have little experience with electronics myself but as far as I know LEDs operate on Direct Current (DC) which has a positive and a negative but no ground. Alternating Current (AC) systems (such as wall sockets, have Live Neutral and Ground (or something like that). From my understanding the ground serves as an escape route for the electricity in case of a short or something.

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