Go Down

Topic: Understanding Grounds (Read 670 times) previous topic - next topic

arduinobeginner101

Hello,

I am having a difficult time understanding grounds. Take a basic LED for example. Say you have it attached to some arbitrary pin on the Arduino board and you attach the ground the GND pin. The LED lights up. Why then can't the LED's ground wire attach to some piece of metal elsewhere. That piece of metal has no potential, so why wouldn't it work. I thought the ground is something with no voltage coming out of it that the electrons can flow into.
Can someone explain this to me, please.

Thanks!

Grumpy_Mike

Quote
I thought the ground is something with no voltage coming out of it that the electrons can flow into.

No it is not.
A ground is short for common signal ground. It is the reference point. If it is not connected it is as we say floating.
See:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

Would you expect the flashlight to light up in this circuit?

arduinobeginner101

I see from your battery analogy that it wouldn't work. Why though?

Grumpy_Mike

Because there is no path for the current to flow round. You need a circular path, that is why it is called a circuit.
No path no current.

arduinobeginner101

But on an atomic level what is the reasoning? Why then do some grounds connect to the Earth itself then?

Grumpy_Mike

On the atomic level it is still the same no path no current.
Electrons do not just leave their atoms they just shuffle along at about 30 mph. Think of it as a very long train with the carriages bumping into each other. The bump travels much faster than the carriages. So while electrons travel slowly the effect is at the speed of light.

An electron can slip it's atom but is not wrenched from it so unless there is an electron to take its place they do not move. Current is the slipping of electrons round a circuit, no circuit no electron movement.

Go Up