Incredibly Newbie Question (i have to clear this up!)

[bazzwazzle]

Is Ground the - of the power source? Or is it just a place where the connections go and you just like to call it ground? :lol: apparently i'm new to this.

[GreenEye]

from one newbie to another:

Have you read the DIY FAQ link on this site?  First two items deal with ground.

[bazzwazzle]

i think i read one, not sure i'll recheck, but i don't think i understood. Whatever I'll read it again  thanks

[Peter Snowberg]

That's a good question.

It doesn't have a 100% consistant answer either which makes it a good question for sure.

Most of the time, yes, the negative side of the power supply and the "ground" connection are the same. When you get outside of radios, ground changes a little in meaning. In radios the ground is the other end of the signal path from the antenna. In guitars it's the other end of the pickup signal path, but it's also usually paired with the more traditional "radio ground" that's a connection to the earth to reduce AC hummmmmmmm and provide shock protection. Now by adding a powered signal processor we intoduce a third "ground" but this time it's the other end of the effect's power supply from the +.

Some effects (few, but there are some) use "split" power supplies that have +, -, AND ground connections. In that case the ground is usually 1/2 way between the + and the -.

Most effects internally translate the + and - power into something more like the "split" supply described above. In that case you end up with +, -, and Vref. The power supply minus is now connected to guitar ground, and the Vref serves the same purpose that the guitar ground does in the split supply. I know some of this will probably sound really odd right now but it will sink in once you see enough examples.

The short answer.....
Yes over 99% of the time when the effect is 9V powered and it's not a PNP fuzzface or a couple other fuzzes.  

[bazzwazzle]

k i understand, because i have mine setup with the battery connected to the other part of the stereo jack for plug n play.  thanks man

[niftydog]

in my way of thinking, it's just

a place where the connections go and you just like to call it ground

In fact, more correctly it's called "common".

It's generally considered to be the return path for current to the power source. (I'm talking conventional current flow here, not electron flow!)

It is not necessarily the negative of the battery, but most commonly it is.


Mini-rant follows;
This is because conventional current flow is deemed to be easier to understand than the "correct" electron flow method. If people like Volta, Ampere, Ohm and Farday got it right first time, we'd all be used to electron flow, and the positive of the battery would be the common! Strange but true.

[Paul Perry (Frostwave)]

If people like Volta, Ampere, Ohm and Farday got it right first time, we'd all be used to electron flow, and the positive of the battery would be the common! Strange but true.

Give them credit, without them everything would be acoustic. By candle light.  (shudder!)

[R.G.]

If people like Volta, Ampere, Ohm and Farday got it right first time, we'd all be used to electron flow, and the positive of the battery would be the common! Strange but true.

Actually, I believe it was Benjamin Franklin that made the positive/negative guess wrong.

Is Ground the - of the power source? Or is it just a place where the connections go and you just like to call it ground?

Historical note: Once, "ground" meant literally that - the presumably constant voltage you got when connecting a wire into the dirt under your feet. It turns out that electrical utilities still use that definition, and electrical power "ground" for AC power is developed and maintained by a conductive wire running down the poles into the dirt they're set on.  The use of the planet itself as a reference voltage made a lot of sense when all electricity was generated by static-electricity and static-charge means.

Once people developed batteries (and to a lesser extent condensers or capacitors as we call them in the USA now) they could have a source of voltage that did not depend on having one terminal connected to the planet. It gets harder to call something "grounded" when it is clearly isolated from the dirt. But the idea persisted that whatever you wanted to use as a reference voltage was "ground" in your particular frame of electrical reference.

And that's what ground has come to mean - a reference voltage, nominally assigned zero volts and the potential against which all other pertinent  voltages are measured. Ground is not necessarily a battery positive or negative, although modern semiconductors often require that the negative wire be considered to be at 0V for simplicity. We encounter positive ground circuits often when using vintage germanium devices in effects.

It would be better if we had a different term. Like the rant about getting conductor quantum flow right from niftydog, the slightly more experienced electronicist could rant that using "ground" for a reference voltage is at best misleading, and often downright wrong and/or obstructive.

Case in point: hum from ground loops.

Huh? If ground is the reference, how can it have loops? Obviously, not all grounds are equal. There are no perfect conductors, so any current passing through any conductor will cause some voltage loss, so if you hook a 12V car battery from one iron stake in the ground to another iron stake in the ground, it is possible to measure a voltage difference between the two iron rods even though both are "grounded" in the original sense. The current passing through the dirt causes one terminal to be elevated in voltage and the other lower in voltage than the dirt at some large distance from either one. "Ground' actually has three voltages in this situation.

Likewise, any wire used for "ground" will have some voltage across it. If your circuits are not well designed to ignore this voltage, you can get induced power line hum, oscillation, or noise and crosstalk.

"Voltage reference" or "Common reference potential" is a better term for what we commonly call ground.  And we won't (here) get into the fact that you simply must have two or more grounds in some circuits to keep things working right.

Think "reference voltage" when you see "ground".

[remmelt]

thanks RG, for this great reply.

[brett]

Really great explanation RG. Thanks.
And thanks Aron and Peter for the the informative and educational forum.

[bazzwazzle]

double quote

[Transmogrifox]

good coverage.  Thought I'd throw in my 2 cents worth since the concept of "ground" totally threw me when I was first learning about electronics.  I would say it was the biggest obstacle to overcome: "how can so-and-so just randomly draw a ground symbol on a schematic and call it ground?"


Most of us understand that to have a voltage we need a difference in charge.  What's the reference? From what to what?

In the case of lightening,  the ground and the sky accumulate charges.  Does one charge stay the same and the other change?  Do they both change?  

The answer is that it can't be determined without a reference.  Therefore we arbitrarily pick some point, say, my finger as a reference.  I stick one probe of a DMM on my finger and one on the ground and there is a 1V potential difference between my finger and ground.  Therefore the ground is at, say "-1 V" with respect to my finger.  Then I stick that probe into the sky and I measure 10V difference between my finger and some object in the sky(keep in mind this is not physically possible, it's just an illustration that will hopefully make sense).  Therefore, there is 11V difference between that certain point in the sky and the ground.  

Then a storm comes along and there is hundreds of mega-volts potential between the sky and the ground and my finger.  Therefore my DMM burns up and I turn into a charcoal briquette because current flows from the ground to the sky or from the sky to the ground, depending on the polarity of the charge difference.

Anyway, I have established my finger as "ground".  Therefore, I can go jump in the air and grab a 440 kV power line without being electrocuted.  As long as anything I touch is at 0V with respect to me (for instance, another 440 kV line in phase with the one I'm touching), no current will flow and I will not be zapped.  

If somebody brings a 100kV line near me (in phase) there is a potential difference of 340 kV to my arbitrary ground (finger), and I will be toast if I touch it.

If that utterly confused you, go back to the other posts and get your mind set straight again.  This was all just for taking the concept a level further to see if it would help solidify or inspire deeper understanding of what has already been established.

[bazzwazzle]

i.. sort of got it... lol :mrgreen:

[Transmogrifox]

Yeah, I re-read that and I must admit it's pretty scatter-brained.  Stick to RG's explanation and you're pretty safe.

I think the main point, to summarize, is that ground as we use it is a common connection in a circuit that is a reference to define all other voltages and currents.

It is also important that ground ideally has no impedance to the source of charge, which is why we generally use a + or - terminal of a voltage source.

[Thomas P.]

If people like Volta, Ampere, Ohm and Farday got it right first time, we'd all be used to electron flow, and the positive of the battery would be the common! Strange but true.

Give them credit, without them everything would be acoustic. By candle light.  (shudder!)

...and please don't forget Maxwell. He was a true genius!
Anyway I think in most 'practical' cases it doesn't matter that the 'true' current are flowing electrons (and not positrons or whatever you want to call it).

[bazzwazzle]

just because we're on topic... how could i determine (if i happened to make my own circuit) where to put ground?

here we goooooooooooo! lol

[GreenEye]

Small Bear's Tweak-O layout diagram shows the ring of the (stereo) input jack going to the ground and the sleeve going to the battery.  Some of the layouts on GGG (in the tech area) show the sleeve going to the ground and the ring going to the battery (I think the 2 parts are just mislabelled):

http://www.generalguitargadgets.com/diagrams/switch_lo_3pdt_tb_battery.gif

What's the golden rule here?  How does it vary with positive or negative ground?

[niftydog]

What's the golden rule here?

Either way works. There's no right or wrong.

this whole "positive or negative ground" thing is confusing. Just call it ground and be done with it. It matters not.

What MATTERS is whether it's positive or negative SUPPLY!!!

[quote"bazzwazzle"]how could i determine (if i happened to make my own circuit) where to put ground?[/quote]

That's the beauty of it, you can put it wherever you like. But convention is that you put it in a sensible place. If you have to ask this question, you have a lot to learn before making your own circuit, I'm sorry to say!

It's usually connected to the negative of the battery... if that helps!