Creating custom symbols in PCB Design - Why You Should Know This

The Big Idea

What if you could design your own symbols once and never redraw them again?

The Scenario

Imagine you are designing a complex circuit board and need a unique symbol that isn't available in your software's library. You try to draw it manually every time you use it, copying and adjusting shapes pixel by pixel.

The Problem

This manual approach is slow and frustrating. Each time you redraw the symbol, small mistakes creep in. It's hard to keep the symbol consistent across different projects, and updating it means redoing all your work.

The Solution

Creating custom symbols lets you design your unique parts once and save them. You can reuse these symbols easily, ensuring consistency and saving time. Updates to the symbol automatically apply everywhere it's used.

Before vs After

✗ Before

Draw symbol from scratch each time; adjust shapes manually

✓ After

Create and save custom symbol; insert symbol from library

What It Enables

It enables fast, consistent, and error-free circuit designs by reusing your own custom symbols across projects.

Real Life Example

A hardware engineer designs a new sensor symbol once, saves it, and uses it in multiple circuit boards without redrawing or risking mistakes.

Key Takeaways

Manual drawing wastes time and causes errors.

Custom symbols save time and keep designs consistent.

Updating a symbol updates all its uses automatically.

Practice

1. What is the main purpose of creating custom symbols in PCB design?

easy

A. To make schematics clearer and tailored to specific components

B. To increase the size of the PCB board

C. To automatically route PCB traces

D. To generate 3D models of the PCB

Solution

1. Step 1: Understand the role of symbols in schematics

   Symbols represent components visually in schematics to improve clarity.

2. Step 2: Identify why custom symbols are used

   Custom symbols help tailor the schematic to specific or unique components, making it clearer.

3. Final Answer:

   To make schematics clearer and tailored to specific components -> Option A

4. Quick Check:

   Custom symbols improve clarity [OK]

Hint: Custom symbols improve schematic clarity and fit unique parts [OK]

Common Mistakes:

• Confusing symbols with PCB size or routing
• Thinking symbols create 3D models
• Assuming symbols automatically route traces

2. Which step is essential when creating a custom symbol in a PCB design tool?

easy

A. Running the autorouter to connect pins

B. Exporting the PCB layout as a PDF

C. Adding pins to represent electrical connections

D. Changing the board thickness settings

Solution

1. Step 1: Identify key elements of a custom symbol

   A symbol must have pins to show where connections happen.

2. Step 2: Recognize irrelevant steps for symbol creation

   Autorouting, exporting layout, or board thickness are unrelated to symbol creation.

3. Final Answer:

   Adding pins to represent electrical connections -> Option C

4. Quick Check:

   Pins are essential in symbols [OK]

Hint: Pins define connections in symbols, always add them [OK]

Common Mistakes:

• Confusing symbol creation with routing or export steps
• Skipping pin placement
• Changing unrelated board settings

3. Consider this symbol creation process:
1. Draw rectangle shape
2. Add 4 pins at edges
3. Save symbol as 'MyIC'
What will happen if you reuse 'MyIC' in multiple schematics?

medium

A. The symbol cannot be reused once saved

B. Each schematic shows a different random symbol

C. The symbol loses pins when reused

D. The symbol appears consistently with 4 pins in all schematics

Solution

1. Step 1: Understand symbol saving behavior

   Saving a symbol stores its shape and pins for reuse.

2. Step 2: Predict reuse effect

   Reusing the saved symbol inserts the exact same symbol with all pins intact.

3. Final Answer:

   The symbol appears consistently with 4 pins in all schematics -> Option D

4. Quick Check:

   Saved symbols reuse consistently [OK]

Hint: Saved symbols keep pins and shape consistent when reused [OK]

Common Mistakes:

• Thinking symbols change randomly on reuse
• Assuming pins disappear after saving
• Believing symbols cannot be reused

4. You created a custom symbol but when placing it in the schematic, pins do not connect to wires. What is the likely cause?

medium

A. The symbol shape is a rectangle

B. Pins were not assigned electrical pin numbers or names

C. The PCB board size is too small

D. The schematic grid is turned off

Solution

1. Step 1: Check pin properties in custom symbols

   Pins must have electrical numbers or names to connect properly.

2. Step 2: Identify why pins don't connect

   Without pin numbers/names, the tool cannot recognize pins for wiring.

3. Final Answer:

   Pins were not assigned electrical pin numbers or names -> Option B

4. Quick Check:

   Pin numbering enables connections [OK]

Hint: Always assign pin numbers/names to enable wire connections [OK]

Common Mistakes:

• Blaming symbol shape for connection issues
• Ignoring pin numbering importance
• Thinking grid affects pin connectivity

5. You want to create a custom symbol for a new sensor with 6 pins arranged in two rows. Which approach best ensures clarity and reusability?

hard

A. Draw the symbol shape, add 6 pins with correct numbers, group pins logically, then save as a reusable symbol

B. Draw the symbol shape only and add pins later in each schematic

C. Use a generic symbol with fewer pins to simplify the schematic

D. Create separate symbols for each pin and place them individually

Solution

1. Step 1: Plan symbol layout with correct pins

   Arrange all 6 pins logically in two rows with correct numbering.

2. Step 2: Save the complete symbol for reuse

   Saving the full symbol ensures consistent use and clarity in schematics.

3. Final Answer:

   Draw the symbol shape, add 6 pins with correct numbers, group pins logically, then save as a reusable symbol -> Option A

4. Quick Check:

   Complete, numbered, reusable symbol [OK]

Hint: Complete and save symbols with all pins for clarity and reuse [OK]

Common Mistakes:

• Adding pins later in each schematic causing inconsistency
• Using generic symbols missing needed pins
• Splitting pins into separate symbols causing confusion