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Topic: BEGINNERS: Why is GROUND so important? (Read 4153 times) previous topic - next topic

lastchancename

Apr 15, 2018, 11:08 am Last Edit: Dec 16, 2019, 06:37 am by lastchancename
There is no secret to 0V / GROUND.

Your power supplies (except in quite unusual situations beyond Arduino) should all have their 0V / GND wires tied together - no other topology makes sense.

This basic understanding of voltages (potential difference) is critical to wiring up *any* electrical circuit.

GROUND is a potential that is  nominally equal to the surrounding electrical 'environment'.
POSITIVE voltages are those 'above' ground.  +12V, +5V and +3V3 are the common positive voltages.
NEGATIVE potentials are those voltages *below* ground potential.

In virtually every 'standard' Arduino project, there are no negative voltages exposed to the developer/user.
Custom boards and interfaces may add 'other' voltages needed by the application.

So the take-away is : BEFORE you burn out boards, or start programming, make sure you have your hardware worked out.
There's no point putting fuel in your car if it doesn't have tyres!

see also What is ground?
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!.

Grumpy_Mike


LMI1

Weirdest things I have seen happen when someone forgets to connect grounds together.

SnacksDaily

What do you mean by "connecting grounds together"?

Grumpy_Mike

What do you mean by "connecting grounds together"?
You take the ground off one system and wire to to the ground off another system.

Clearly you have not read the link I posted.

lastchancename

#5
May 04, 2018, 10:54 pm Last Edit: May 10, 2018, 05:25 am by lastchancename
The two separate systems - the grounds should be connected together with the lowest resistance path available.

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!.

Grumpy_Mike

Number 3 is not a type of ground but a type of connector.

Number 2 is any point you decide to be ground is ground, it is no different from any other sort of ground apart from mains ground which is soil or dirt under your feet.

dochawk

Weirdest things I have seen happen when someone forgets to connect grounds together.
I managed to do this, leading to much head scratching, replacing the starting motor on a '72 Cadillac with a 500cid (8.2L) engine.

Gosh, it spins, but not hard enough . . . somehow, I managed to not attach an inch wide flat woven connecter that (for good reason) goes from the negative battery terminal to the chassis on a starter bolt . . .

It drove home ground issues in a way no hobby circuit ever could have managed!

lastchancename

Don't worry, smoke works just as well in cars as it does electronics  :D
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

Thank goodness for "limp mode" had that just before xmas on my silverado.
My mech knew right away what the issue was eve without plugging anything in.

10 minutes and no charge and I was on my way both grinning and feeling sheepish.

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

dochawk

Don't worry, smoke works just as well in cars as it does electronics  :D
It wouldn't be the first car I let the magic smoke out of . . . but in this case, it merely meant that not enough current got delivered from the battery's local connection to group, and the starter just spun weakly.

As for limp modes . . . I had a truly interesting drive home in an '02 Deville DHS the day I bought it.   The prior owner having set all kinds of stuff putting in the wrong plugs, it did 0-30 in, roughly, 30 seconds.

Yet it could reach freeway speed (albeit slowly).   

New ignition banks for each side (I forget what they're called) and the right plugs, along with a couple hours of my time, and all was good . . .

LMI1

10 minutes and no charge and I was on my way both grinning and feeling sheepish.


That is very familiar feeling. I once? searched a fault on mains powered machine. I started from the sensors, very methodically I went through whole machine until I noticed the mains lead was unplugged.

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