Ground
From BEAM Robotics Wiki
The term Ground is typically applied the common return path to the negative side of the power supply. It is used as a common reference point when making voltage measurements and is therefore typically considered to be at zero volts.
There are three types of ground referenced in electronics:
- Chassis Ground: generally refers to using the chassis or frame of a device as a common return path and reference point for a circuit or circuits mounted on and electrically connected to that chassis or frame.
- Signal Ground: A return path for signals and power within a circuit and/or a connection between separate but circuits and/or circuit boards. Also called “Circuit Ground” or “Circuit Common”
- Earth Ground: not generally used in BEAM robotics, it refers to a common return path with a direct physical connection to the Earth. Also called “Earth Return” An Earth Groundis used for equipment that uses household line (Mains) power and is done for safety purposes to protect people from the effects of faulty insulation. It is also used in radio communications but that is beyond the scope of this page.
NOTE: The schematic symbol for Earth Ground is often used as a generic ground symbol. Though this is probably not a good practice.
[edit] Comments from Wilf
The following is from a post to the alt-beam mail list:
Grounding???, Alt-beam Message #9415, Thu Jan 20, 2000
Original Message-----
From: Ian Bushong Sent: Wednesday, January 19, 2000
I am beginning in electronics, and I am stuck on the concept of grounding. Exactly what is its purpose and what do the connection indications on schematics connect to? From what I can make of it, it seems to be a part of a circuit with no electrical potential. Is this right? How is that possible? Could you maybe explain it further.
Somewhere I read that the ground is sometimes connected to a metal chassis. And why are there sometimes more than one of them and sometimes none at all (like in smaller BEAM circuits). I have also noticed that there are also sometimes resistors or caps in between the circuit and ground (??). As you can see, I am VERY confused and would really appreciate a simple explanation. I can't seem to find anything about it anywhere.
-Ian Bushong
Wilf's Response:
I'm not surprised you are confused. It's a matter of history and personal taste what name is used for the common measurement reference point. Ideally we should use a standard name but throughout the electronic world different naming conventions have come and gone or live side by side.
BEAMERS (myself included) have not been very consistent in using terms like 0V, GND, COMMON, Vss, RET and sometimes NEG, -V, -xV (ie -5V), and V- In BEAM designs the terms GND, 0V , COM all mean more or less the same thing: a common bus of all connections to the negative terminal of a single positive power supply. Unless otherwise indicated this bus is the reference point for all voltage measurements and voltages shown on the schematic. My preference is for 0V since it is the shortest and most explicit label.
The other common bus is the positive terminal of the positive powersupply which is called +V, V+, Vcc, Pos, or xV (ie 5V).
NOTE: The chip power supply connections, the termination of unused inputs and the typical power supply bypass capacitors are not always shown in schematics on the assumption that everyone know these are required. Just the thing to make life interesting for newbies of course.
Shielding and grounding for safety have a number of different meanings and should be explicitly explained when used.
