Converting a Hand-Drawn Circuit to a Professional Schematic

Electrical schematics designing and interpretation is the basic requirement to understand and troubleshoot the electrical systems. Whether you're an aspiring electrician or an engineering student, learning how to read electrical schematics is a valuable skill. In this guide, we will break down the essential elements of electrical schematics and provide practical tips for deciphering these diagrams.

What is an Electrical Schematic?

An electric schematic, also known as circuit diagram, is a graphical representation of an electrical circuit. It uses standardised symbols to depict the various components and their connections in the circuit. The purpose of a schematic is to convey the design and function of the circuit, making it easier to understand how the circuit operates and how the components are interconnected.

The symbols are the primary component of the circuit diagram, and without these symbols, the circuit diagram can never be completed. These symbols allow engineers, electricians, and technicians to easily understand the functions of a designed circuit without any documentation. The schematic symbols are adopted internationally such that a schematic diagram can be interpreted across different languages and regions. A simple schematic of the rectifier is given above with an inductor, capacitor and zener diode based filter section, designed to output stable DC voltage.

Understanding the Basics of a Circuit Schematic:

Ways to Represent a Circuit Graphically:

There are two methods to represent a circuit, one with the help of a block diagram and second with the help of a schematic diagram. Both have their advantages and disadvantages, in schematic diagram all the circuit components their connection and arrangement is shown clearly but in block diagram method internal circuit is unknown. Block diagrams help in understanding the function of a circuit in a general not in specific manner.

Block Diagram:

Engineers and technicians employ block diagrams in various ways. Commonly, block diagrams indicate the interconnections between small circuits in a larger device, or between diverse devices in a large system. Bock diagrams can also be called functional diagrams because they reveal the basic functioning of the electronic circuit. The functional diagram offers a simplistic explanation of how the device operates, it can lead to more detailed information provided by a schematic diagram.

Schematic Diagram:

Let’s open the audio amplifier block of the above given block diagram and see what’s inside it. According to standard schematic drawing practice, every component should bear a unique alphabetic/numeric label to designate it. The components are identified only by their schematic symbols along with value designations or industry standard part designations.

Using the example shown, we know that the transistor is a 2N2222 type, and that the resistors have values of 470, 33k (33,000), 330k (330,000), and 680 ohms. The input capacitor has a value of 0.01 microfarad (μF) and the output capacitor has a value of 0.1 μF. The emitter capacitor, which goes across the 470-ohm resistor, has a value of 4.7 μF. This is only one box(one part) of the above given block diagram. Hence block diagrams are very general in nature and used to hide actual circuit connections.

How to Read a Simple Circuit:

Let me briefly tell you what this above given circuit is actually responsible for. This is an amplifier circuit in voltage divider common emitter configuration. The gain of the amplifier is set using the various resistors present in the circuit, which can be calculated as per design formulas given in the some book or datasheet.

By reading the circuit from left to right, the input signal is given to C2 which acts as a decoupling capacitor here, only allowing the AC signal to pass through it for amplification. R3, R2 set the bias point of the transistor and set it in the active amplification region, R1, C1 is feedback resistor and bypassing capacitors, used to provide stability to circuit.  Finally the transistor collector acts as output, hence amplifying the signal with some gain. R4 is loading resistance connected for loading. And finally the C3 is used to produce AC amplified output.

Designing a Professional Schematic in 7 Steps:

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.

Step 1: Getting Started with EasyEDA:

To begin your journey from paper to digital, follow these steps:

• Visit www.easyeda.com and create an account or log in.
• Navigate to the Online Editor under the Products tab.
• Create a new project and name it appropriately.

Once you've set up your workspace, you'll see a canvas in the middle of the screen. This is your schematic workspace where you'll bring your hand-drawn circuit to life.

Step 2: Importing Components

The second step in creating your schematic is to import the necessary components:

Use the component library on the left side of the screen to search for and select the components in your hand-drawn circuit. Click on a component in the library and then click on the canvas to place it. Repeat this process for all components in your circuit.

EasyEDA boasts an extensive library of components, making it easy to find what you need. If you can't locate a specific component, you can request it for free through EasyEDA's component request service.

Step 3: Connecting Components

After placing all components, it's time to connect them:

Use the wiring tool (activated by pressing 'W' on your keyboard) to draw connections between components. Click on the end of a component pin and drag to create a wire.

Add junctions where wires intersect by clicking on the intersection point. Remember to refer to your hand-drawn circuit frequently to ensure accuracy in your connections.

Step 4: Adding Power and Ground

To complete your schematic use the VCC and Ground tools from the wiring toolbox to add power and ground connections. Place these symbols appropriately according to your original design.

Step 5: Enhancing Your Schematic

To make your schematic more professional:

• Add labels to components and wires for clarity.
• Use the text tool to add notes or explanations where necessary.
• Align components neatly using the grid feature for a cleaner look.

Step 6: Verifying Your Design

Before finalizing your schematic double-check all connections against your hand-drawn circuit. Use EasyEDA's built-in electrical rules check (ERC) to identify any potential issues. Make any necessary corrections based on the ERC results.

Step 7: Making Section and Labelling

Identify functional sections of your circuit (e.g., power supply, microcontroller, sensors) and group them accordingly. Use rectangular or oval shapes to visually separate these sections.  EasyEDA provides an annotation tool to automatically assign proper component numbers. Use this tool to ensure consistency and prevent duplicate designators.

Conclusion:

Converting a hand-drawn circuit to a professional schematic using EasyEDA is a straightforward process that can significantly improve the clarity and usability of your design. With its user-friendly interface and extensive component library, EasyEDA makes it easy for both beginners and experienced designers to create high-quality schematics.

Reading electrical schematics is a fundamental skill for anyone working with electronics or electrical systems. To know how PCBs are fabricated in JLCPCB factory, see our recent blog.

By familiarising yourself with symbols, understanding the flow of circuits, and practicing with real-world examples, you can gain confidence in interpreting these essential blueprints. Remember, practice makes perfect. The more circuits you convert, the more proficient you'll become at using EasyEDA and creating professional schematics. Happy designing!