Problems with GROUND. (Two grounds?!)

[cibonato]

Hello ... first of all: what  is the fuction of the ground?

and second: sometimes I see some projects with two "separeted" schematics - like in amp´s project, I mean: in one hand there is the schematic of the amp itself and in the other hand there is the schematic of the power-supply (with needed, of course) - and, the question is: can I connect the grounds of these two circuits togheter?

Thanks! Bye

[R.G.]

You not only can, but must if the two ground symbols are the same graphically. Otherwise, it won't work properly.

Sometimes there are two ground symbols, one like a downwards-pointing triangle, another like a rake. The triangle is usually signal ground, the rake earth/AC safety ground. These are usually connected at one and only one point for hum reduction and safety reasons.

[bwanasonic]

Aside from the distinction between ground symbols RG made, you can think of ground as a line or *rail* that that all components marked ground connect to, as shown in the diagram below:



This can also be applied to other symbols (i.e. +9v, Vcc+, +4.5v, etc.)

Kerry M

[niftydog]

ground is meerly a single point in a circuit where many component connect together.  Hence why it is sometimes called "common" - owing to the fact that it's common to many components.

It's generally the "zero" point of the circuit, but it may not necessarily be at zero volts (depending on your point of reference!)

I like to call it either ground or common.

RG was refering to the "the rake earth/AC safety ground" which I tend to call EARTH.  Simply because the earth connection in the power points on the walls of your house are literally connected to the earth!

The two need not always be connected, but as RG points out, it's sometime good safety practise to do so.