A Guide Through the World of Electronic Circuitry Symbols • Smashing Robotics

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.

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 power source

Antenna

Radio antenna

Fixed attenuator

Attenuates a signal with fixed amount with minor distortion of waveform

Variable attenuator

Attenuates a signal with variable amount with minor distortion of waveform

Battery

Battery power source

Capacitor

Element that can accumulate and release a certain amount of energy

Circuit breaker

Opens or closes a circuit

Diode

Allows for current flow in a single dirrection

Light-emitting diode (LED)

Emits light when correct polarity current passes through it

Photosensitive
(photovoltaic) diode

Current is generated when light hits the surface of the diode

Electrical wire

Electrical liaison between elements

Flashing LED

Function of LED

Chassis ground

Chassis ground or earth, negative terminal

Inductor

Or coil, induces voltage into the conductor when current fluctuates

Integrated circuit (IC)

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

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

Mercury switch

Opens or closes a circuit based on its position

Microphone

Generates a voltage when sound waves hit the surface

Motor

Electric motor

Laser diode

Laser light emitting diode

Phono plug

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

Positive voltage connection

Designates positive (+) input lead of circuit

Potentiometer

Or variable resistor, variable reduction of current flow and voltage

Resistor

Reduces current flow and voltage

Resonator

For filtering or generating certain frequencies in a signal

SAW filter

Analog filter for signal processing

Solar cell

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

Speaker

Transforms signals into sound waves

Tactile sensor

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

Bipolar NPN transistor

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

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

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

XOR gate

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

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

Logical symbol of transistor module output high or true if no signal is true. Complement of OR gate

OR gate

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

Resources

Electronic symbols, Wikipedia
Electronic symbols, Electronics Club
Electronic symbols, Clker.com
Circuit symbols, Talking Electronics
Circuit symbols, Oracle ThinkQuest Foundation