A guide to Common Electrical Schematic Symbols

When you first see an electrical schematic, the mixture of lines, dots, and shapes may seem odd. After you are aware of what it all means, you can begin to see the logic and flow of any circuit. Electrical schematic symbols are how engineers talk about electronic systems when designing, building, and communicating.

In this article, we will help you identify some commonly used electrical symbols in the industry, like wires, switches, batteries, and motors, so that you may read and design your own schematics with some confidence.

1.    Why Electrical Symbols Matter

Every circuit diagram is built upon electrical symbols. These shapes are essential for engineers, technicians, and manufacturers to express designs with ultimate accuracy.

Here is why standardized symbols are essential in the world of electronics and PCB design:

⦁ Clarity: Symbols enable engineers to provide electricians with a visual reference showing exactly what to wire and how to wire it.

⦁ Safety: It’s always best to be able to see any potential danger areas in a circuit before wiring anything.

⦁ Shared Language: This language is independent of the written word and allows people across the globe to understand handiwork of other mechanisms.

⦁ Troubleshooting: If a problem occurs within said system, the technician always starts with the diagram. Clear indicators facilitate quick troubleshooting of circuits.

⦁ Business Communication: Merchants and suppliers also depend on established symbols to communicate components unambiguously in catalogs and datasheets.

At JLCPCB, maintaining consistent schematics is crucial for reliable PCB manufacturing and assembly, so that every trace and component footprint matches the original circuit design.

2.    How to Read Electrical Symbols

Even though electrical circuit symbols may seem unusual at first, there is a common logic that applies to all of them. Here are some important ideas to remember:

⦁ A single dot at a joint means that the wires are connected.

⦁ Plus (+) and minus (−) symbols show DC polarity.

⦁ A wave symbol (~) represents AC voltage or current.

⦁ Arrows along a wire indicate the direction of current flow.

⦁ A diagonal arrow over a component shows adjustability (e.g., a variable resistor).

⦁ A letter in a circle (V, A, Ω) indicates a measuring instrument.

⦁ Triangles (i.e., in diodes or op-amps) show you which way current is flowing.

You will be able to read wiring diagrams and suss out the details if you understand how these types of symbols work.

Common Electrical Symbols and their purpose

Below are some standard schematic symbols and their purpose.

3.    Wire and Connection Symbols

⦁ Wire: A straight line connecting one component to another.

⦁ Connected Wires (●): A dot at the junction means the wires are electrically connected.

⦁ Unconnected Wires: A line “jumping” over another indicates no connection.

⦁ Fuse: Protects the circuit from excessive current. It’s shown as a small symbol with a breakable filament between two lines.

4.    Source Symbols

These represent how electrical energy enters a circuit.

⦁ Single-Cell Battery: Two unequal lines; the longer line marks the positive terminal.

⦁ Multi-Cell Battery: Multiple pairs of unequal lines for multiple cells.

⦁ Voltage Source:  A circle with + and – marks; provides constant voltage.

⦁ Controlled Voltage Source: A diamond-shaped symbol that shows adjustable voltage.

⦁ AC Voltage Source: A circle with a wave symbol (~) for alternating current.

⦁ Current Source: A circle with an arrow showing constant current flow.

⦁ Controlled Current Source: A diamond symbol with an arrow for variable current.

5.    Ground Symbols

Grounds are crucial for circuit safety and stability.

⦁ Earth Ground: Three diminishing lines showing discharge to physical ground.

⦁ Chassis Ground: This component is connected to a metal structure that is ultimately grounded.

⦁ Digital/Analog Grounds: This refers to a technique used in electronic circuits to decouple the analog signals from the digital signals in order to minimize noise.

6.    Switch and Relay Symbols

These symbols represent the current control devices.

⦁ SPST (Single Pole, Single Throw): The system only utilizes one on/off switch.

⦁ SPDT (Single Pole, Double Throw): A switch that isolates one of two circuits.

⦁ Normally Open (N.O.) Push Button: This device only conducts when pushed.

⦁ Normally Closed (N.C.) Push Button: This switch opens up when the circuit is pressed.

⦁ DIP Switch: A group of miniature switches in a row.

⦁ SPST Relay: Current flows when the electromagnet closes the relay.

⦁ SPDT Relay: Switches between two outputs when activated.

7.    Inductor Symbols

When the current flows through an inductor then the energy is stored as a magnetic field.

⦁ Simple Inductor: Segments that resemble a coil.

⦁ Iron-Core Inductor: A coil with two parallel lines representing an iron core.

⦁ Variable Inductor: Includes a diagonal arrow to show adjustable inductance.

8.    Electromechanical Device Symbols

These transform electric power into motion, light, sound, or heat.

⦁ Motor: Transforms electric power to mechanical motion.

⦁ Speaker: Produces sound waves.

⦁ Buzzer: Emits a buzzing tone.

⦁ Bell: Activates a mechanical ringer.

⦁ Lamp or Light Bulb: Produces light when powered.

⦁ Heater: It transforms electric power into heat.

9.    Combining Everything

Once you have a grasp of these symbols, you can open the  door to building circuits for all sorts of projects from LED driver circuits to home automation. Schematic designing is relatively simple using CAD tools such as EasyEDA (integrates with JLCPCB). With built-in libraries of standard symbols, you can design your circuit visually and generate your PCB layout directly.

At JLCPCB, our fabrication and SMT assembly services ensure your schematics are turned into professional-quality printed circuit boards with accuracy and reliability.

Conclusion

Electrical schematic symbols are more than just drawings. They are the visual language of modern engineering. Every project starts with these fundamental components, whether it's a simple wire or a complicated microcontroller circuit. Whether you are a beginner learning your first schematic or an industry designer developing your next prototype, it doesn't matter - the first step to effectively communicating your ideas and putting them into action is to understand these symbols. At JLCPCB, we translate your schematic into a high-quality PCB ready for testing and experimentation.