Wikipedia

Electronic symbol

(Redirected from Schematic symbol)

An electronic symbol is a pictogram used to represent various electrical and electronic devices or functions, such as wires, batteries, resistors, and transistors, in a schematic diagram of an electrical or electronic circuit. These symbols are largely standardized internationally today, but may vary from country to country, or engineering discipline, based on traditional conventions.

Common circuit diagram symbols (US ANSI symbols)

Standards for symbols

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The graphic symbols used for electrical components in circuit diagrams are covered by national and international standards, in particular:

  • IEC 60617 (also known as BS 3939).
  • There is also IEC 61131-3 – for ladder-logic symbols.
  • JIC JIC (Joint Industrial Council) symbols as approved and adopted by the NMTBA (National Machine Tool Builders Association). They have been extracted from the Appendix of the NMTBA Specification EGPl-1967.
  • ANSI Y32.2-1975 (also known as IEEE Std 315-1975[1] or CSA Z99-1975).
  • IEEE Std 91/91a: graphic symbols for logic functions (used in digital electronics). It is referenced in ANSI Y32.2/IEEE Std 315.
  • Australian Standard AS 1102 (based on a slightly modified version of IEC 60617; withdrawn without replacement with a recommendation to use IEC 60617).

The standards do not all agree, and use of unusual (even if standardized) symbols can lead to confusion and errors.[2] Symbols usage is sometimes idiosyncratic to engineering disciplines, and national or local variations to international standards exist. For example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics.

Common electronic symbols

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Symbols shown are typical examples, not a complete list.[3][4]

Traces

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Wire crossover symbols for circuit diagrams. The CAD symbol for insulated crossing wires is the same as the older, non-CAD symbol for non-insulated crossing wires. To avoid confusion, the wire "jump" (semi-circle) symbol for insulated wires in non-CAD schematics is recommended (as opposed to using the CAD-style symbol for no connection), so as to avoid confusion with the original, older style symbol, which means the exact opposite. The newer, recommended style for 4-way wire connections in both CAD and non-CAD schematics is to stagger the joining wires into T-junctions. The large dot signifies an electrical connection.

Grounds

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The shorthand for ground is GND. Optionally, the triangle in the middle symbol may be filled in.

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    General ground (IEC‑style)
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    Signal/low-noise ground (the asterisk is not part of the symbol)
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    Chassis ground (IEC‑style)

Sources

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    DC voltage source
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    Controlled DC voltage source
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    Current source
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    Controlled current source
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    AC voltage source

Resistors

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See also: Resistor

It is very common for potentiometer and rheostat symbols to be used for many types of variable resistors and trimmers.

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    Photoresistor (ANSI)
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    • Thermistor (ANSI).[5]
    • Use -t for NTC symbol.
    • Use +t for PTC symbol.
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    Varistor (ANSI)

Capacitors

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See also: Capacitor
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    General capacitor (IEC‑style); sometimes drawn with one plate curved[2]
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    Variable capacitor
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    Ganged (co‑moving) variable capacitors (IEC‑style)
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    Trimmer variable capacitor
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    Polarized capacitor (American‑style), such as electrolytic and tantalum capacitors

Diodes

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See also: Diode

Optionally, the triangle in these symbols may be filled in. Note: The words anode and cathode typically aren't part of the diode symbols.

Bridge rectifiers

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See also: Bridge rectifier

There are many ways to draw a single-phase bridge rectifier symbol. Some show the internal diode circuit, some don't.

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    Bridge rectifier
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    Bridge rectifier
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    Bridge rectifier
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    Bridge rectifier
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    Three-phase bridge rectifier

Inductors

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See also: Inductor

An inductor can be drawn either as a series of loops, or series of half-circles.

Transformers

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See also: Transformer
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    Transformer
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    Transformer with center tap on secondary winding (right side)
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    Transformer with two secondary windings (right side)
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    Current transformer
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    Zero-sequence current transformer (ZSCT) (also known as a window-type current transformer)
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    Bushing-type current transformer
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    Voltage transformer

Transistors

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See also: Transistor

Optionally, transistor symbols may include a circle.[6] Note: The pin letters B/C/E and G/D/S aren't part of the transistor symbols.

Bipolar

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See also: Bipolar junction transistor

Unipolar

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See also: Field-effect transistor

Vacuum tubes

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See also: Vacuum tube

Switches

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See also: Switch

For multiple pole switches, a dotted or dashed line can be included to indicate two or more switch at the same time (see DPST and DPDT examples below).

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    Pushbutton, normally open, push-to-make (horizontal line on top)
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    Pushbutton, normally open, push-to-make (IEEE-style)
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    Pushbutton, normally closed, push-to-break (IEEE-style)
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    Pushbutton, normally closed, two circuits (IEEE-style)
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    Switch, 1P1T, SPST (single-pole single-throw)
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    Switch, 1P2T, SPDT (single-pole double-throw)
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    Switch, 2P1T, DPST (double-pole single-throw)
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    Switch, 2P2T, DPDT (double-pole double-throw)
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    Slide switch, 1P3T,
    break-before-make, nonshorting style
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    Slide switch, 1P4T,
    break-before-make, nonshorting style
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    Slide switch, 1P4T,
    make-before-break, shorting style
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    Rotary switch, 1P3T,
    break-before-make, nonshorting style
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    Rotary switch, 1P4T,
    break-before-make, nonshorting style
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    Rotary switch, 1P4T,
    make-before-break, shorting style

Relays

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See also: Relay

Relays symbols are a combination of an inductor symbol and switch symbol.

Note: The pin letters in these symbols aren't part of the standard relay symbol.

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    SPST, SPDT, DPST, DPDT relays (American‑style)
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    SPDT relay (IEC‑style)

Lamps

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LED is located in diode section.

Current limiters

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Electro-acoustic devices

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Speaker symbols sometimes include an internal inductor symbol.

Antennas

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See also: Antenna (radio)
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    General antenna
    (IEC-style)
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    Dipole antenna
    (IEC-style)
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    Loop antenna
    (IEC-style)
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    Loop antenna
    (IEEE-style)

Cables

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See also: Electrical cable
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    Cable, Shielded 1 conductor
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    Cable, 2 conductor
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    Cable, Shielded 2 conductor with shield connected to ground
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    Cable, 5 conductor
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    Cable, Shielded 5 conductor

Connectors

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See also: Electrical connector

There are numerous connector symbol variations.

ICs

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See also: Integrated circuit

Logic gates

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See also: Logic gates

For the symbols below: A and B are inputs, Q is output. Note: These letters are not part of the symbols.

There are variations of these logic gate symbols. Depending on the IC, the two-input gates below may have: 1) two or more inputs; 2) infrequently some have a second inverted Q output too.

The above logic symbols may have additional I/O variations too: 1) schmitt trigger inputs, 2) tri-state outputs, 3) open-collector or open-drain outputs (not shown).

Flip-flops

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See also: Flip-flops

For the symbols below: Q is output, Q is inverted output, E is enable input, internal triangle shape is clock input, S is Set, R is Reset (some datasheets use clear (CLR) instead of reset along the bottom).

There are variations of these flip-flop symbols. Depending on the IC, a flip-flop may have: 1) one or both outputs (Q only, Q only, both Q & Q); 2) one or both forced inputs along top & bottom (R only, S only, both R & S); 3) some inputs may be inverted.

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    Simple SR flip-flop (inverted S & R inputs)
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    Gated SR flip-flop
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    Gated D flip-flop (Transparent Latch)
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    Clocked D flip-flop
    (Set & Reset inputs)
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    Clocked JK flip-flop
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    Clocked T flip-flop

OpAmps

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Note: The outside text isn't part of these symbols.

Oscillators

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See also: Electronic oscillator

Miscellaneous devices

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Historical electronic symbols

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The shape of some electronic symbols have changed over time. The following historical electronic symbols can be found in old electronic books / magazines / schematics, and now considered obsolete.

Capacitors (historical)

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All of the following are obsolete capacitor symbols.

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    Obsolete capacitor (very old style)
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    Obsolete capacitor
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    Obsolete capacitor
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    Obsolete capacitor
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    Obsolete capacitor

See also

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References

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  1. ^ "IEEE Standard American National Standard Canadian Standard Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters)," in IEEE Std 315-1975 (Reaffirmed 1993), vol., no., pp.i-244, 1993, doi:10.1109/IEEESTD.1993.93397.
  2. ^ a b Sobering, Tim (April 2008). Guidelines for Drawing Schematics.
  3. ^ Circuit Symbols for all Electronic Components. Talking Electronics, 2013. Retrieved 01 Apr 2015.
  4. ^ Electrical Symbols & Electronic Symbols. RapidTables, 2012. Retrieved 17 April 2016.
  5. ^ "Standards for Resistor Symbols". EePower. EETech Media. Retrieved September 13, 2021.
  6. ^ "A4.11 Envelope or Enclosure". ANSI Y32.2-1975 (PDF). Archived from the original (PDF) on 2022-10-09. Retrieved 2020-12-29. The envelope or enclosure symbol may be omitted from a symbol referencing this paragraph, where confusion would not result

Further reading

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Standards
Books
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Wikimedia Commons has media related to Electrical symbols.
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