Common circuit diagram symbols (US ANSI symbols)

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.

Standards for symbols

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  • Australian Standard AS 1102 (based on a slightly modified version of IEC 60617; withdrawn without replacement with a recommendation to use IEC 60617).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 number of standards leads to confusion and errors.[2] Symbols usage is sometimes unique 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

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

Traces

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

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

Sources

Resistors

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

Capacitors

Diodes

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

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

Inductors

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

Transformers

Transistors

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

Unipolar

Vacuum tubes

Switches

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).

Relays

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.

Lamps

LED is located in diode section.

Current limiters

Electro-acoustic devices

Speaker symbols sometimes include an internal inductor symbol.

Antennas

Cables

Connectors

There are numerous connector symbol variations.

ICs

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

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.

OpAmps

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

Oscillators

Miscellaneous devices

Historical electronic symbols

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)

All of the following are obsolete capacitor symbols.

See also

References

  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. ↑ 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). The envelope or enclosure symbol may be omitted from a symbol referencing this paragraph, where confusion would not result

Further reading

Wikimedia Commons has media related to Electrical symbols.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.