Electronics notes/Ground

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This is for beginners and very much by a beginner.

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 · Ground · batteries · resistors · changing voltage · transistors · fuses · diodes · varistors · capacitors · inductors · transformers · baluns · amplifier notes · frequency generation · skin effect

And some more applied stuff:

IO: Input and output pins · wired local IO · wired local-ish IO · · · · Shorter-range wireless (IR, ISM RF) · RFID and NFC · bluetooth · 802.15 (including zigbee) · 802.11 (WiFi) · cell phone

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Actuators: General actuator notes, circuit protection · Motors and servos · Solenoids

Some stuff I've messed with: Avrusb500v2 · GPS · Hilo GPRS · JY-MCU · DMX · Thermal printer ·

Audio notes: microphones · device voltage and impedance, audio and otherwise · amps and speakers · basic audio hacks · digital audio · noise reduction · multichannel and surround ·

Less sorted: Common terms, useful basics, soldering · Arduino and AVR notes · ESP series notes · PLL · signal reflection · pulse modulation · electricity and humans · resource metering · Microcontroller and computer platforms · SDR · Project boxes · Unsorted stuff

See also Category:Electronics.

Yes, ground.

The basic concept so simple, the practical details both interesting, but also a conflated mess that means a lot of semi-experts (and smartarses like me) don't fully grasp.

And on larger scales things become more interesting - yet most of us deal with smaller scales, where other engineers have spent time making things simple and safe for you.

...yet even then you may care when you care about common mode noise, ground loops, and such.

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

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

The main symbols are:

  • Earth.png Earth
classically a conductive pole poking into the literal earth
practically any of these
  • Chassis.png Chassis
if the outside of a device is metal, that's this.
  • Signal common.png 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

People use Earth.png loosely. When only it appears in a circuit, it could refer to almost any concept mentioned in this section.

When Chassis.png and/or Signal common.png are also present, 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.)

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

  • 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 surface large, comparable to the relevant wavelength. Earth is an easy choice.

  • Safety ground/earth
our main intuition in house wiring

a subject in itself

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
  • Guarding
a strategy to alleviate some sorts of coupling

Earth/ground as in 'pole in the earth'

Earth can refer to a conductive pole in the earth near your front door.

Usually it isn't visibly exposed, but you have one. (And usually exactly one - if you have multiple, electrical code often says they must be connected to the main utility earth with a beefy cable, so there's usually little point to more) (One reason to have more is lightning rods, to ensure it conducts enough for a strike(verify), but there are more significant footnotes to this, electrical-code-wise)

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

Which includes dealing with lightning. Seemingly mainly lightning from outside(verify), because your house is a higher-resistance path than the ground pole in front of it. (this setup also implies lighting can never spread over the grid much, which is nice design city-wise)

Earth is not for safety grounding of chassis. that safety measure would work without the pole (because it's the job of the wallplug wiring and main breaker - see notes below).

It is however required to detect ground faults, e.g. with an RCD.

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

Grounded sockets supporting chassis safety
Earthing as lightning protection
Residual-current breakers (and ground)
Other device safety
On floating and safety

More safety and/or noise stuff

More terms: Floating things (and galvanic isolation)