Electronics notes/Ground

⚠ This is for beginners and very much by a beginner / hobbyist It's intended to get an intuitive overview for hobbyist needs. It may get you started, but to be able to do anything remotely clever, follow a proper course or read a good book. Some basics and reference: Volts, amps, energy, power · batteries · resistors · transistors · fuses · diodes · capacitors · inductors and transformers · ground Slightly less basic: amplifier notes · varistors · changing voltage · baluns · frequency generation · Transmission lines · skin effect And some more applied stuff: IO: Input and output pins · wired local IO · wired local-ish IO · ·  Various wireless · 802.11 (WiFi) · cell phone Sensors: General sensor notes, voltage and current sensing · Knobs and dials · Pressure sensing · Temperature sensing · humidity sensing · Light sensing · Movement sensing · Capacitive sensing · Touch screen notes Actuators: General actuator notes, circuit protection · Motors and servos · Solenoids Noise stuff: Stray signals and noise · sound-related noise names · electronic non-coupled noise names · electronic coupled noise · ground loop · strategies to avoid coupled noise · Sampling, reproduction, and transmission distortions Audio and video notes: See avnotes Platform specific: : Microcontroller and computer platforms ·· Arduino and AVR notes · ESP series notes · STM32 series notes · Teensy series notes Less sorted: USB notes · Ground · device voltage and impedance (+ audio-specific) · electricity and humans · Soldering · landline phones · pulse modulation · PLL · multimeter notes · signal reflection · Project boxes · resource metering · Radio and SDR · vacuum tubes · Unsorted stuff · 'E-fuse' Some stuff I've messed with: Avrusb500v2 · GPS · Hilo GPRS · JY-MCU · DMX · Thermal printer · See also Category:Electronics.

Terms: Earth, ground, common, signal, chassis, shield, guard, virtual ground, etc.

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

The symbols you see mainly include:

  Signal common  

the reference used for a signal

in PCBs there may be dedicated trace(s) (or not)

in cabling this is often one of the wires in the cable

 Chassis       

if the outside of a device is metal, that's this.

 Earth             

classically a conductive pole hammered into the literal earth

In practice, however, people use loosely. When only it appears in a circuit, it could refer to almost any concept mentioned around here.

When and/or also appear in the same circuit diagram, those specific distinctions are made.

Even then, earth may sometimes still refer to any of the remaining, not specifically mentioned ones. (Even when the physical design is very well considered (isolation, shielding, trace weight, order of connections, ground planes), the circuit diagram may not show each, as it may be considered a simplified functional summary.)

For a wider view, you want to know about the existance, and distinctions, between the above, plus further related concepts (most of which have no symbols):

• common current return path

many components on a PCB that draw power tend to return it via a trace, often shared by many

which we tend to call ground. This our main intuition in circuit design

...though it has no direct relation to earth (e.g. not all wired ones connect it to ground, no portable devices do)

Even when this is connected to ground, it is not at quite the same potential, which becomes important in some cases with noise

• Safety ground/earth

our main intuition around house wiring

• Ground plane

in PCBs design: ground is often made as a large area of copper.

This is a PCB design thing, and a nontrivial topic in itself, as it relates to coupling and more (and shielding and grounding), and ends up being a balance of design considerations

in antenna theory: a large surface, comparable to the relevant wavelength. Earth is an easy choice.

• Shielding

a subject in itself

• Guarding

a strategy to alleviate some sorts of coupling

• virtual ground

itself a bit of a confusing one / misnomer.

Also not often relevant to noise or safety discussions, because it's by nature internal to a circuit, so often there by design

Earth/ground as in 'pole in the earth'

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Earth can refer to a conductive pole hammered into the ground, near your house (usually near your breaker panel - seems to vary with a country's electrical code(verify)), connected via a chunky bit of wire.

Usually it isn't visibly exposed, but you almost certainly have one. (And usually exactly one - if you have multiple, your electrical code will probably say they must be connected to the main utility earth with a beefy cable, so there's usually not much point point to having more)

The earth in your wallplugs will be wired to that pole, the main purpose of which is to avoid buildup of static electricity by always discharging it.

That is, the earth rod is not necessary (or sufficient) for safety grounding to work (of metal chassis via earthed wallsockets) - that works based on the circuit going through a trippable breaker (basically both wires go to the local transformer with thick enough wires), and this pole is not involved in that circuit.

So yes, safety grounding, residual current faults (see RCD), and static discharge are in effect three different protections -- that happen to share wiring, because it can, but only two of them use this pole.

More safety and/or noise stuff

"Ground loop"

See Ground loop