Electronics notes/Ground

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⚠ 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 notes: See avnotes

Platform specific

Arduino and AVR notes · (Ethernet)
Microcontroller and computer platforms ··· ESP series notes · STM32 series notes

Less sorted: Ground · device voltage and impedance (+ audio-specific) · electricity and humans · power supply considerations · Common terms, useful basics, soldering · landline phones · pulse modulation · signal reflection · Project boxes · resource metering · SDR · PLL · vacuum tubes · Multimeter notes Unsorted stuff

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 main symbols are:

  • signal common symbol 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 symbol Chassis
if the outside of a device is metal, that's this.
  • earth symbol Earth
classically a conductive pole hammered into the literal earth

However, people use earth symbol loosely. When only it appears in a circuit, it could refer to almost any concept mentioned around here.

When chassis symbol and/or signal common symbol are also present in the same circuit dagram, those specific distinctions are made, yet earth may sometimes still refer to any of the remaining. (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 distinctions between the above and some 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 ends up being a balance of design considerations
in antenna theory: a large surface, comparable to the relevant wavelength. Earth is an easy choice.

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
a subject in itself
a strategy to alleviate some sorts of coupling

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.

Also typically to a house's neutral, exactly once. It depends your country where that connection is. It may be at your power board, or that may be specifically disallowed and will happen at the transformer nearby. My guess is for practical reasons: corrosion of that ground pole will increase resistance and lower protection, and particular with underground wiring this is easier to deal with in one place rather than at every house(verify) - but this makes less difference around sparser housing, and around overground wiring

The main purpose of this pole is (mainly/only) to discharge static electricity, avoiding buildup of it.

That is, the earth rod is not necessary for safety grounding (of metal chassis via earthed wallsockets) to work - 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.

For context: 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.

Note that static discharge includes dealing with lightning. And then seemingly mainly lightning from outside(verify), in that the ground pole should be lower resistance than your house (there beinh very regular ground poles also implies lighting can never spread over the grid much(verify), which is nice design city-wise)

Earth/ground as in wallsocket wiring
Earth/ground as in the return path for current

Ground as in (not) making noise go elsewhere

On resistance of wires in sensitive signals

On sharing ground

Safety discussions (mostly) related to ground

Insulation faults and Protective Earth
Earthing as lightning protection
Residual-current breakers (and ground)
Other device safety
On floating and safety

More safety and/or noise stuff

"Ground loop"

See Ground loop

More terms: Floating things (and galvanic isolation)

Further reading