A Guide Through the World of Electronic Circuitry Symbols

Any robot relies on electronics to control its parts, relay data, and basically define and handle its function. Electronic modules are practically electrical circuits of varying complexity, interacting with each other at certain levels. Electrical circuits are based on diagrams, which are graphical representations that specify physical components required for the circuit to perform certain functions. Electrical symbols are used as abstract representations of physical electronic components that are used in the circuit, and each such representation should be simple in order to be recognized in any circumstances with no ambiguity. These circuit diagrams are not only useful in prototyping circuits, they can also be a great help in understanding and detecting errors that may occur in the circuit operation.

Printed circuit board (PCB) and probe

Printed circuit board (PCB) and probe

In time graphic representations of the physical components were standardized, each of these symbols having a certain logic behind its design. This compendium does not aim at exhaustively covering every possible component and representation, it should rather provide a pretty good coverage of the most common electronic components employed in robotic electronic circuitry, and maybe familiarize the reader with electrical schematic symbols and their purpose. Below you can find electrical symbols for common components, logic gate symbols as well as brief explanations of each element. This article is under continuous development.

Physical component representations

Electrical symbols corresponding to physical components in circuit diagrams.

AC current (source)

AC current
AC power source

Antenna

Antenna
Radio antenna

Fixed attenuator

Attenuator fixed
Attenuates a signal with fixed amount with minor distortion of waveform

Variable attenuator

Attenuator Variable
Attenuates a signal with variable amount with minor distortion of waveform

Battery

Battery
Battery power source

Capacitor

Capacitor
Element that can accumulate and release a certain amount of energy

Circuit breaker

Circuit breaker
Opens or closes a circuit

Diode

Diode
Allows for current flow in a single dirrection

Light-emitting diode (LED)

Diode light emitting
Emits light when correct polarity current passes through it

Photosensitive
(photovoltaic) diode

Diode Photosensitive
Current is generated when light hits the surface of the diode

Electrical wire

Electrical wire
Electrical liaison between elements

Flashing LED

Flashing LED
Function of LED

Chassis ground

Ground chassis
Chassis ground or earth, negative terminal

Inductor

Inductor
Or coil, induces voltage into the conductor when current fluctuates

Integrated circuit (IC)

Integrated circuit
Or simply chip, small module holding a circuit performing specific functions, as simple as a logical gate or as complex as a CPU

Coaxial jack

Jack coaxial
Electric coupling with coaxial terminals, exterior is usually ground (-), aids in shielding

Mercury switch

Mercury switch
Opens or closes a circuit based on its position

Microphone

Microphone
Generates a voltage when sound waves hit the surface

Motor

Motor
Electric motor

Laser diode

Laser diode
Laser light emitting diode

Phono plug

Plug Phono
A type of coaxial jack for signal-to-noise critical applications

Positive voltage connection

Positive voltage connection
Designates positive (+) input lead of circuit

Potentiometer

Potentiometer
Or variable resistor, variable reduction of current flow and voltage

Resistor

Resistor
Reduces current flow and voltage

Resonator

Resonator
For filtering or generating certain frequencies in a signal

SAW filter

SAW Filter
Analog filter for signal processing

Solar cell

Solar cell
Solar cell power source, circuit is powered when light hits surface

Speaker

Speaker
Transforms signals into sound waves

Tactile sensor

Touch sensor
A switch or connection normally-open or normally-closed, changes state only as long as mechanical action is present

Bipolar NPN transistor

Transistor Bipolar npn
Current flows between (C)ollector and (E)mitter when (B)ase is set high relative to C and E, i.e. B connected to power source

Bipolar PNP transistor


Complement of NPN, current flows between (C)ollector and (E)mitter when (B)ase is set low relative to C and E, i.e. B connected to ground

Unspecified component

Unspecified Component
Component to be defined

Logic gates

Logic gates are basically integrated circuits — silicon chips — containing a small number of transistors used to perform certain logical operations (Boolean functions) on signal — i.e. combine signals with respect to certain rules. Below are some electrical symbols used for representing such components.

AND gate

And Gate
Logical symbol of transistor module output high or true if signal inputs are identical

XOR gate

Exclusive Or gate
Logical symbol of transistor module output high or true if only one signal is true

NAND gate

NAND gate
Logical symbol of transistor module output high or true if either one or no signal is true. Complement of AND gate

NOR gate

NOR gate
Logical symbol of transistor module output high or true if no signal is true. Complement of OR gate

OR gate

OR gate
Logical symbol of transistor module output high or true if either one or both signals are true

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