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 symbolsEdit
The graphic symbols used for electrical components in circuit diagrams are covered by national and international standards, in particular:
- IEC 60617 (also known as British Standard 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 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- Australian Standard AS 1102 (based on a slightly modified version of IEC 60617; withdrawn without replacement with a recommendation to use IEC 60617).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. 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 symbolsEdit
The large dot signifies an electrical connection.
The shorthand for ground is GND. Optionally, the triangle in the middle symbol may be filled in.
It is very common for potentiometer and rheostat symbols to be used for many types of variable resistors, including trimmers.
IEC-style: (a) Resistor, (b) Rheostat,
(c) Potentiometer / Trimmer
Optionally, the triangle in these symbols may be filled in. There are multiple ways to draw a bridge rectifier symbol.
Light-emitting diode (LED)
Diac (may be a varistor in older schematics)
Opto-isolator: LED (left), photo transistor (right)
There are many ways to draw a single-phase bridge rectifier symbol. Some show the internal diode circuit, some don't.
Optionally, these symbols may include a circle.
Optionally, these symbols may include a circle.
LED is located in diode section.
Incandescent light bulb (as an indicator)
Moulded-case circuit breaker (MCCB)
TRS phone jacks
For the symbols below: A and B are inputs, Q is output.
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.
Buffer gate with schmitt trigger input
Buffer gate with tri-state output control.
(B is the tri-state control)
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.
Operational amplifier (opamp)
Historical electronic symbolsEdit
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.
All of the following are obsolete capacitor symbols.
- "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.
- Guidelines for Drawing Schematics.
- Circuit Symbols for all Electronic Components. Talking Electronics, 2013. Retrieved 01 Apr 2015.
- Electrical Symbols & Electronic Symbols. RapidTables, 2012. Retrieved 17 April 2016.
- "Standards for Resistor Symbols". eePower. EETech Media. Retrieved September 13, 2021.
- "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
- Beginner's Guide to Reading Schematics; 4th Ed; Stan Gibilisco; McGraw-Hill, 224 pages; 2018; ISBN 978-1260031119.
- How to Read Electronic Circuit Diagrams; 2nd Ed; Brown, Lawrence, Whitson; Tab Books; 214 pages; 1988; ISBN 978-0830628803.
- How to Read Schematic Diagrams; 4th Ed; Donald Herrington; Sams Publishing; 160 pages; 1986; ISBN 978-0672224577. (2nd Ed in 1967)
|Wikimedia Commons has media related to Electrical symbols.|
- IEEE Standard American National Standard Canadian Standard Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters)
- IEC 60617 : Graphical Symbols for Diagrams (2012) - International standard
- MIL-STD-806B : Graphical Symbols for Logic Diagrams (1962) - U.S. DoD standard
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