PCB Design for Micromouse Using Eagle CAD

PCB (Printed Circuit Board) design is one of the most important stages in embedded systems and robotics development. In projects such as Micromouse robots, motor controllers, sensor modules, and STM32-based systems, a well-designed PCB improves reliability, signal quality, and overall performance.

Autodesk EAGLE is a widely used PCB design software that combines schematic capture, board layout, and routing tools in a single environment. It is popular among students, hobbyists, and professional engineers because of its relatively simple workflow and extensive component libraries.

Basic PCB Structure for Micromouse

Most Micromouse robots use a 2-layer or 4-layer PCB.

2-Layer PCB

Advantages:

Low manufacturing cost
Easier to design
Good for beginners

Disadvantages:

Harder routing
More noise sensitivity
Limited ground plane quality

4-Layer PCB

Advantages:

Better grounding
Cleaner signal routing
Reduced EMI
Improved power stability

Disadvantages:

Higher cost
More complex design

Typical 4-layer stack:

Top Layer — Components and signals
Inner Layer — Ground plane
Inner Layer — Power plane
Bottom Layer — Signals

For high-speed Micromouse robots, 4-layer boards are strongly recommended.

What is Eagle CAD?

Eagle CAD stands for:

Easily Applicable Graphical Layout Editor

It is used to:

Draw electronic schematics
Create PCB layouts
Route electrical connections
Generate manufacturing files such as Gerber files
Design single-layer and multi-layer boards

Typical applications include:

Micromouse robots
STM32 development boards
Motor driver circuits
Sensor interfaces
IoT devices
Arduino-compatible shields

Main Sections of Eagle CAD

1. Schematic Editor

Circuit design

The schematic editor is used to create the electrical diagram of the circuit.

Functions include:

Adding electronic components
Connecting wires and nets
Naming signals
Adding power symbols
Electrical rule checking

A schematic should clearly represent how the circuit operates before PCB layout begins.

2. Board Editor

PCB Design

The board editor converts the schematic into a physical PCB layout.

Features include:

Component placement
PCB dimension definition
Copper routing
Via placement
Ground plane creation
Design rule checking

The board editor is where electrical connections become actual copper traces.

3. Library Manager

Libraries contain:

Symbol & Footprints
Symbols
Footprints
3D package information

Common components available in Eagle libraries include:

Resistors
Capacitors
STM32 microcontrollers
Connectors
MOSFETs
Sensors
Motor drivers

Custom libraries can also be created for specialized components.

PCB Design Workflow in Eagle CAD

Step 1: Create a New Project

Start by creating a new project directory.

Recommended project organization:

/schematic
/board
/libraries
/gerber

Keeping files organized simplifies future modifications.

Step 2: Draw the Schematic

Use Clear Signal Names

Examples:

MOTOR_L_PWM
ENCODER_A
BATTERY_5V
GYRO_SCL

Proper naming improves debugging and routing.

Separate Functional Blocks

Organize the schematic into sections:

Power supply
Microcontroller
Sensors
Motor driver
Communication interface

This improves readability and maintenance.

Add Decoupling Capacitors

Every microcontroller power pin should include nearby capacitors.

Typical values:

0.1µF ceramic capacitor
10µF bulk capacitor

These reduce voltage noise and improve stability.

Step 3: Generate the PCB Board

After schematic completion:

Run ERC (Electrical Rule Check)
Switch to board editor
Eagle automatically creates airwires

Airwires represent unrouted electrical connections.

Component Placement Techniques

Good placement is critical for PCB quality.

Place Important Components First

Priority order:

Microcontroller
Power supply
Motor driver
Sensors
Connectors

Keep Related Components Close

Examples:

Crystal oscillator near MCU
Driver IC near motors
Sensor filter capacitors near sensors

This minimizes electrical noise.

Separate Analog and Digital Areas

Sensitive analog sensors should be isolated from:

Motor drivers
PWM traces
High-current switching circuits

This reduces interference.

Component Placement Strategy

PCB layout should begin with component placement before routing traces.

Microcontroller Placement

The microcontroller is the brain of the robot.

Examples include:

STM32F411CEU6
STM32F405RG

Placement guidelines:

Place near the center of the PCB
Keep traces short
Position close to sensors and motor drivers
Separate from noisy power circuits
Provide easy SWD programming access

Crystal oscillators should be placed very close to the MCU.

Motor Driver Placement

Motor drivers handle large current flow and generate electrical noise.

Common drivers:

DRV8833
TB6612FNG

Placement rules:

Place close to motors
Use thick power traces
Keep away from analog sensors
Add sufficient copper area for heat dissipation
Place bulk capacitors nearby

Motor current loops should be as short as possible.

Sensor Placement

Micromouse commonly uses infrared wall sensors.

Typical parts:

SFH 4550
TEFT4300

Placement considerations:

Front sensors should align symmetrically
Side sensors should face maze walls accurately
Avoid obstruction by wheels or chassis
Keep analog signal traces short
Avoid routing near motor lines

Sensor matching and symmetry are extremely important for stable wall following.

IMU Placement

Gyroscope and accelerometer modules such as:

MPU6050

should be:

Positioned near the center of gravity
Far from motor magnetic fields
Mounted away from vibration sources
Connected with short I2C traces

Ground noise around the IMU should be minimized.

Battery Placement

Battery placement strongly affects robot balance.

Common batteries:

LiPo 2S
Li-ion packs
9V rechargeable

Placement rules:

Place low and centered
Keep weight balanced left-to-right
Use wide power traces
Keep battery current loops short

Poor battery placement may reduce turning stability.

Voltage Regulator Layout

Micromouse commonly uses:

Buck converters
LDO regulators

Important guidelines:

Place regulator near power input
Keep switching loops small
Use short feedback traces
Separate analog and motor power

Switching regulators generate noise, so routing is very important.

Connector Placement

Important connectors include:

Battery connector
SWD programmer
UART debugging
Sensor connectors

Recommendations:

Place near PCB edges
Ensure easy access
Label clearly

Good connector placement simplifies debugging and maintenance.

Ground Plane Design

Grounding is one of the most important PCB concepts.

A solid ground plane:

Reduces noise
Improves return current flow
Stabilizes sensors
Reduces EMI

Recommendations:

Use uninterrupted ground planes
Avoid splitting grounds unnecessarily
Connect analog and digital grounds carefully
Add multiple ground vias

Ground bounce can seriously affect encoder and sensor readings.

Routing Rules in Eagle CAD

Routing creates copper traces between components.

Trace Width

Different signals require different widths.

Typical values:

Signal Type	Recommended Width
Logic signals	0.2–0.3 mm
I2C / UART	0.2–0.3 mm
PWM motor signals	0.3–0.5 mm
Battery power	1.0 mm or larger
Motor current paths	1.5–3.0 mm

Higher current requires wider traces.

Keep Traces Short

Shorter traces reduce:

Resistance
EMI noise
Signal delay

This is especially important for:

Encoder signals
SPI communication
High-speed clocks

Avoid Sharp Angles

Use:

45° bends

Avoid:

90° corners

Sharp corners may cause impedance issues and acid trapping during manufacturing.

Ground Plane Usage

A ground plane improves:

Noise reduction
Current return paths
Thermal performance

In Eagle CAD:

Use the POLYGON tool
Draw around the PCB
Name polygon as GND
Run RATSNEST

The polygon fills unused space with copper connected to ground.

Via Usage

Vias connect different PCB layers.

Guidelines

Minimize unnecessary vias
Avoid vias in high-current paths
Keep via count low for easier manufacturing

For beginner projects, a 2-layer PCB is recommended.

Design Rule Check (DRC)

DRC verifies manufacturing safety.

Checks include:

Minimum clearance
Trace width
Drill sizes
Overlapping copper

Always run DRC before manufacturing.

PCB Design for Micromouse Robots

Micromouse robots require compact and reliable PCB layouts.

Motor Driver Section

Requirements:

Thick power traces
Short motor paths
Large ground return

Sensor Section

IR sensors and amplifiers should be:

Isolated from motors
Protected from switching noise
Connected with stable ground references

STM32 Section

For STM32F411 designs:

Place decoupling capacitors close to VDD pins
Keep crystal traces short and symmetric
Route SWD debugging pins clearly

Common PCB Mistakes

Poor Component Placement

Bad placement causes:

Long routing paths
Excessive vias
Increased noise

Thin Power Traces

Thin traces may:

Overheat
Drop voltage
Reduce motor performance

Missing Ground Plane

Without proper grounding:

Noise increases
Sensors become unstable
Communication errors occur

Improper Decoupling

Missing capacitors may cause:

Random MCU reset
ADC noise
Unstable communication

Generating Gerber Files

Gerber files are used for PCB manufacturing.

In Eagle CAD:

Open CAM Processor
Load Gerber template
Generate files

Common generated files:

Top copper
Bottom copper
Solder mask
Silkscreen
Drill files

These files are uploaded to PCB manufacturers.

Limitations of Eagle CAD

Library Management

Custom component creation can require additional work.

Complex Projects

Very large multi-layer designs may be easier in advanced tools such as:

KiCad
Altium Designer

Conclusion

PCB design using Autodesk EAGLE is an essential skill for electronics and robotics development. A successful PCB requires:

Clean schematic organization
Good component placement
Proper routing rules
Solid grounding techniques
Careful power design

For Micromouse robots and STM32 systems, proper PCB layout directly affects speed, sensor accuracy, and controller stability. By understanding Eagle CAD tools and PCB design fundamentals, developers can create compact, reliable, and high-performance electronic systems.