what is ground?

[xjackal]

i am new to electronics but when i see a ground connection i think of the circuits that we draw.they had only sources in lessons so what is ground for practical circuits.or did we omit that in theories? :roll:
so please tell me the ground funciton and vcc funciton in circuits.also what is the wire that is on the riht side of the ground in foppy drive supply?my friend said it is calibbration?!

 

[Nostrafus]

Ground is something you should have learned in high school, basic wiring, basically grounding a circuit provides protection to the user/circuit in case of a power spike, it is usually attatched to a metal part of the circuit like in light switches the case is the ground meaning that if there is too much power going to the circuit it'll just discharge over the case instead of blowing up the light bulb.

Or like a lightning rod, they're mounted on top of a house and travel to the ground, so that if lightning strikes the house, it will most likely strike the lightning rod, and travel down the wiring into the ground.

Also, in some schematics, ground can also mean negative, depends on the circuit, if there's no negative in the schematic, it's best to suspect that ground is the negative, it's pretty much guestimation when it comes to other peoples circuits.

 

[Nostrafus]

Also, if you're new to electronics, I'd definately say put testing/building/reverse engineering of floppy drives aside, they're a bit too advanced for a beginner, as is working with high voltage, such as power supplies.

I'd say work from the basics until you get a good feel for what you're doing.

Trust me, if you hop right into floppy drives, you'll go through quite a few hundred dollars trying to experiment with them.

 

[1997 GA16DE]

in automotive, the ground is the same as the negative battery terminal. The negative terminal on a car's battery is almost always directly connected to the car's metal chassis making the entire body and engine block a grounding or negative power source.

 

[Mosfet]

floppies have 12vdc, 5vdc & two grounds

my 1949 Ford has 6 volt positive ground

 

[mod_critical]

Ground as far as it has ever concerned me is the base voltage that all others in your circuits are relative to. This is why your Ford would have a +6 ground. +12 Vdc in a circuit only means +12 from your base voltage, so if you have a power supply providing 30v and 42v, you can run 12v circuits between those taps. your ground is the +30 and the +42 is simply +12 from your ground. It should be noted though, that it is really easy to make the mistake of reverse biasing components when using a non 0v ground. This happened to some collegues of mine once that powered an 18v system that they added to their DAQ using the -5v and +12v taps on the power supply. The meter read +18v, but there was potential at the - side of the tantalum capacitors on the addon boards. Needless to say that whole crate of DAQs lasted about a week :lol:

 

[Mosfet]

the base voltage that all others in your circuits are relative to

Your right there.
Ground can be a lot of different things.
Even earth ground can rise several thousand volts
relative to power line neutral during a lightning strike.
Best to think in terms of potential.

 

[pebe]

Think of ground as a fixed voltage point to which all other voltages in the circuit are referred.