Anatomy of a PCB Design > Projects > Schematics

Electronic circuit symbols are standardized graphical representations of electronic components used in circuit diagrams and schematics. Each symbol is designed to represent a specific type of component, such as resistors, capacitors, transistors, diodes, and integrated circuits (ICs), and indicates their electrical functionality and connections within the circuit.

These symbols are used to create schematic diagrams, which are visual representations of how components are connected in an electronic circuit. By using these standardized symbols, engineers, technicians, and designers can communicate complex circuit designs in a clear and universally understood manner.

Purpose of Electronic Circuit Symbols

Electronic circuit symbols

These are standardized graphical representations of electronic components used in circuit diagrams and schematics. Each symbol is designed to represent a specific type of component, such as resistors, capacitors, transistors, diodes, and integrated circuits (ICs), and indicates their electrical functionality and connections within the circuit.

Simplification of Circuit Design

Symbols provide a simplified way to represent complex electronic components, making circuit design and analysis more manageable.

Universal Language

Circuit symbols serve as a universal language that can be understood by engineers and designers worldwide, regardless of the specific language they speak.

Efficient Communication

They enable efficient communication of circuit designs, making it easier to convey information during design reviews, documentation, manufacturing, and troubleshooting.

Standardization

Standardized symbols eliminate ambiguity, ensuring that anyone looking at the schematic can correctly interpret the function of each component.

Categories of Electronic Circuit Symbols

Circuit symbols can be grouped into several categories based on the type of component they represent. Here are the main categories and some examples:

Passive Components

Resistor: Represented by a zigzag line or a rectangle (depending on the standard). Used to limit current or divide voltage.

•Resistor: Represented by a zigzag line or a rectangle (depending on the standard). Used to limit current or divide voltage.

•Capacitor: Represented by two parallel lines (for non-polarized capacitors) or one straight and one curved line (for polarized capacitors). Used to store electrical energy.

Inductor: Represented by a series of loops or a rectangle. Used to store energy in a magnetic field.

Power Supply and Ground

Inductor: Represented by a series of loops or a rectangle. Used to store energy in a magnetic field.

•Voltage Source: Represented by a circle with a `+` and `-` symbol or a simple line with `V`.

•Ground: Represented by a series of decreasing lines or a triangle pointing downwards, indicating the common return path.

Semiconductor Devices

Diode: Represented by a triangle pointing to a line. Used to allow current to flow in one direction only.

•Diode: Represented by a triangle pointing to a line. Used to allow current to flow in one direction only.

•Transistor: Represented by a combination of lines and circles with arrows. NPN and PNP transistors have different orientations.

Integrated Circuit (IC): Represented by a rectangle with multiple input and output pins. ICs can have custom labels for specific functionality.

Switches and Relays

Integrated Circuit (IC): Represented by a rectangle with multiple input and output pins. ICs can have custom labels for specific functionality.

•Switch: Represented by a gap in a line with a movable contact. Used to open or close a circuit.

•Relay: Represented by a switch with an electromagnetic coil symbol, indicating remote operation.

Measurement and Indicators

•Relay: Represented by a switch with an electromagnetic coil symbol, indicating remote operation.

•LED (Light Emitting Diode): Represented by a diode symbol with arrows indicating light emission.

Voltmeter: Represented by a circle with a `V` inside, indicating voltage measurement.

•Voltmeter: Represented by a circle with a `V` inside, indicating voltage measurement.

•Ammeter: Represented by a circle with an `A` inside, indicating current measurement.

Connectors and Terminals

•Connector: Represented by a rectangle or a circle with pins or lines indicating connection points.

•Terminal: Represented by a dot or small circle at the end of a wire, indicating a connection or point to interface with.

Standardization of Circuit Symbols

Electronic circuit symbols are standardized by organizations such as the International Electrotechnical Commission (IEC), the Institute of Electrical and Electronics Engineers (IEEE), and the American National Standards Institute (ANSI). These organizations provide guidelines to ensure that symbols are consistent and universally recognizable.

Some commonly used standards include:

•IEC 60617: International standard for graphical symbols for use in electrotechnical diagrams.

•ANSI Y32 / IEEE Std 315: American standards for graphic symbols for electrical and electronics diagrams.

•BS 3939: British standard for graphical symbols.

How to Read and Interpret Electronic Circuit Symbols

•Understand Basic Symbols: Familiarize yourself with basic symbols like resistors, capacitors, and power sources before moving to complex components.

•Look for Labels and Values: Each symbol is often accompanied by a label (e.g., `R1`, `C2`) and a value (e.g., 10kΩ, 1μF) that provide additional information about the component.

•Identify Connection Points: Symbols have connection points, typically shown as dots or ends of lines, indicating where electrical connections should be made.

•Follow the Flow: Trace the connections (nets) between symbols to understand the flow of signals and power through the circuit.

Applications of Electronic Circuit Symbols

•Schematic Diagrams: The primary use of electronic circuit symbols is in schematic diagrams, which serve as the blueprint for circuit design and PCB layout.

•Documentation and Manuals: Symbols are used in data-sheets, manuals, and technical documents to describe circuits and systems.

•Educational Tools: Symbols are used in textbooks, tutorials, and training materials to teach electronics and circuit theory.

Benefits of Using Standard Electronic Circuit Symbols

•Clarity and Consistency: Using standard symbols ensures that the circuit diagram is clear, easy to read, and consistent with industry norms.

•Reduces Errors: Standard symbols reduce the risk of misinterpretation, preventing design errors or incorrect assembly.

•Facilitates Collaboration: Standard symbols enable easy collaboration between engineers, designers, and manufacturers, even across different regions and languages.

Conclusion

Electronic circuit symbols are a fundamental aspect of electrical engineering and design, providing a standardized way to represent and communicate complex circuits. They serve as the building blocks of schematic diagrams, enabling clear communication of design intent, efficient documentation, and effective collaboration. Understanding these symbols is essential for anyone involved in electronics, from hobbyists and students to professional engineers.