How to Read and Create PCB Schematics

Printed Circuit Board (PCB) design is the backbone of modern electronics, and at the heart of PCB design lies the schematic diagram. Electronics design depends much on creating schematics since they show how to assemble circuits and systems. A schematic map illustrates the connections between several components of an electronic system by means of the electrical cables. This helps engineers overall design process vision and planning. Making schematics guarantees that everything is right, aids with troubleshooting, and facilitates communication between manufacturers and engineers, whether you are working on a basic circuit or a complex electrical system.

And when we have to keep it simple then the only name that comes to mind is EasyEDA, a powerful and user-friendly online PCB design tool. It simplifies the process of reading and creating schematics. In this guide, we'll walk you through understanding and creating PCB schematics in EasyEDA, step by step. This article will cover the reasons for the need for creating schematics, the key actions to be done, the instruments you can use, and the best approaches to ensuring your designs function.

What is a PCB Schematic?

A PCB schematic is a graphical representation of an electronic circuit. It uses standardized symbols to represent components such as resistors, capacitors, and integrated circuits, and it shows how these components are interconnected with wires or nets. The schematic acts as a blueprint for the physical PCB layout.

Unlike a real wiring diagram, a schematic does not physically depict where the parts are placed. Rather, it reveals how logically connected and interconnected they are inside the circuit.

Standard symbols enable schematics to simplify even the most complex systems, therefore facilitating engineers and designers in communicating their ideas. In electronics design, schematic drawings are also rather crucial since they enable the identification of issues before they become evident during the assembly process.

Common Components in a Schematic Design:

1. Schematic Symbols

Before diving into a schematic, familiarize yourself with the common symbols:

● Resistors: A zigzag line or a rectangle.

● Capacitors: Two parallel lines (polarized capacitors include a positive and negative marking).

● Diodes: A triangle pointing to a line, with polarity indicated.

● Integrated Circuits (ICs): Rectangles with labeled pins.

● Ground and Power Symbols: Symbols like “GND” for ground and “Vcc” for power.

2. Following Nets (Connections/wires)

Nets are lines that connect components. Each net may have a label, like “Vcc” or “GND,” to identify its function. Use these labels to understand how power and signals flow through the circuit.

3. Component Values and Designators

Each component has a designator (e.g. R1 for a resistor or C1 for a capacitor) and a value (e.g., 10kΩ for a resistor or 100µF for a capacitor). These details are essential for identifying the part and its role in the circuit.

How to Read and Interpret a Schematic Diagram

Schematics may contain multiple circuit blocks, read from left to right or top to bottom. Circuits often have repetitive patterns. Once you understand the basic symbols and their functions, you can recognize these patterns, simplifying the interpretation of complex schematics.

It is divided into 4 sections, every section is labelled properly as per its application. This circuit is for the charging purposes of a 3.7 lithium ion battery with a 1.5 ampere of max current rating.

Section 1: Input

A 2 PIN Connector is connected to 2 different capacitors, this connector is used to connect the battery charge to the external power supply unit. VIN net label is used to connect one block with another without wiring it. In this way a clean schematic can be designed which is easy to read, modify and saves overall time.

Section 2: Main IC

It is a 17 pin IC, all the connections can be made as per given in the datasheet of IC, 2 LEDs are used for charge indication purpose. The grounding, net labels and wires can be properly seen. Mostly while designing a big circuit it is recommended to divide the whole circuit in these types of small blocks and use net labels for connections.

Section 3: Charge Control

The charge control circuit is used to control the IC, designed as per the values and connections given in the datasheet of IC. Inductor and capacitor with diode here acts as buck conversion. Other capacitors are used to keep the output voltage stable, and R10_CC_CTRL resistor to set the max current to 1.5Ampere.

Section 4: Output

Two connectors are used here, one for the output and connected with the battery to charge it. Second, to select between two batteries(1S/2S) one cell or two cells.

Sometimes more than one input and output capacitors of different values are used, because of the power supply noise issues. These capacitors bypass any noise to ground and make the circuit EMI(electromagnetic noise) free.

Steps to Create a PCB Schematic in EasyEDA

Step 1: Sign Up and Start a New Project

● Go to EasyEDA’s website and sign up for an account.

● Click on “New Project” to create a blank schematic design workspace.

Step 2: Place Components

● Open the “Library” panel and search for the components you need. EasyEDA has an extensive library of symbols for commonly used parts.

● Drag and drop the components onto the schematic workspace.

Step 3: Connect Components

● Use the “Wire” tool to draw connections (nets) between component pins.

● Ensure you label critical nets like power and ground for clarity.

Step 4: Annotate the Schematic

● Use the “Annotation” tool to assign unique designators (e.g., R1, C2) to all components automatically.

● Add text notes or comments if necessary to explain complex parts of the circuit.

Step 5: Perform Electrical Rule Check (ERC)

● Run an ERC to detect issues like unconnected pins or short circuits.

● Fix any errors highlighted by the tool.

Step 6: Save and Share

● Save your schematic to the cloud or export it as a PDF or image.

● Share the project with collaborators or export it for PCB layout.

Tips for Efficient Schematic Design

Wires are the heroes of a schematic diagram, because wires are used to connect components together. Readability and reproducibility of a clean and properly labelled circuit is more than a random circuit. Some key aspects of wires and connections in schematics:

Organization: Organize wires logically and label them appropriately to indicate their functions, ensuring that electric current follows the intended paths.

Colours: In some electronic schematics, wires may have colour codes representing specific attributes. Such as power, ground, or signal connections, aiding in quick identification.

Terminations: Connections between wires and components, often represented by dots or junctions, are vital points in the circuit where current joins or divides.

Net label Routing: It  identifies and names specific electrical connections or nodes, simplifying the diagram by reducing the number of drawn wires. It helps in clearly indicating which points are electrically connected without visually cluttering the schematic.

Use Grid Snap: Enable grid snapping for precise alignment of components and connections.

Troubleshooting with Schematics

Isolate Sections: When troubleshooting, isolate specific sections of the circuit using the schematic. This helps narrow down the potential issues and locate faulty components more efficiently.

Check Connections: Examine the connections between components. Look for breaks in the circuit, loose connections, or components that might have failed.

Voltage and Current Measurement: Use the schematic to understand the expected voltage and current values at different points in the circuit. This information is invaluable when diagnosing problems.

Conclusion

A well-designed schematic diagram is the foundation of a successful PCB design, serving as a blueprint for circuit functionality, troubleshooting, and manufacturing. By clearly illustrating component connections, power distribution, and signal flow, schematics streamline the development process, reduce errors, and enhance collaboration among engineers.

With tools like EasyEDA, creating and managing schematics has become more intuitive, enabling both beginners and professionals to design efficient and error-free circuits. Properly structured schematics, with labeled nets, modular design blocks, and clear annotations, ensure readability and ease of modification. Additionally, performing an Electrical Rule Check (ERC) before proceeding to PCB layout helps detect and correct potential issues early.

Ultimately, mastering schematic design is essential for developing high-quality electronic systems. Whether working on a simple circuit or a complex multi-layer PCB, a well-organized schematic ensures accuracy, efficiency, and seamless transition from design to production.