A compact, PCB-integrated autonomous line-following robot built on the Arduino Nano platform. This project demonstrates embedded systems design encompassing custom PCB development, sensor integration, motor control, and real-time firmware development.
This repository documents the complete design, development, and validation of an autonomous line-following robot intended for industrial and academic applications. The system uses infrared sensor arrays to detect and track a contrasting line on a flat surface, executing proportional-derivative (PD) control to maintain trajectory with minimal oscillation.
The robot is built around a custom-designed two-layer PCB that integrates power regulation, motor driving, sensor interfacing, and microcontroller hosting into a single compact board.
| Objective | Description |
|---|---|
| Sensor Integration | Interface a 5-channel IR sensor array for real-time line position detection |
| Motor Control | Implement bidirectional DC motor control with PWM-based speed regulation |
| Power Management | Design a regulated power distribution system from battery source to all subsystems |
| PCB Design | Develop a custom two-layer PCB with proper power integrity and signal routing |
| Embedded Firmware | Write efficient Arduino-based firmware implementing PD line-following control |
| System Integration | Combine all subsystems into a functional, testable autonomous platform |
- 5-Channel IR Sensor Array — TCRT5000-based reflective sensors for robust line detection across varying surface conditions
- Dual H-Bridge Motor Driver — TB6612FNG driver for independent left/right motor control with PWM speed regulation
- Regulated Power Architecture — LM7805-based 5V regulation with bulk and bypass capacitors for noise suppression
- Custom PCB Design — Two-layer board designed in Altium Designer with optimized component placement and routing
- PD Control Algorithm — Proportional-derivative control for smooth trajectory tracking with minimal overshoot
- Compact Form Factor — Single-board design reducing wiring complexity and improving reliability
graph TB
subgraph Power["Power Subsystem"]
BAT[Battery<br/>7.4V-9V]
REG[LM7805<br/>5V Regulator]
C1[100nF<br/>Bypass Cap]
C2[10uF<br/>Bulk Cap]
end
subgraph MCU["Microcontroller"]
NANO[Arduino Nano<br/>ATmega328P]
end
subgraph Sensors["Sensor Subsystem"]
IR1[TCRT5000 Ch1]
IR2[TCRT5000 Ch2]
IR3[TCRT5000 Ch3]
IR4[TCRT5000 Ch4]
IR5[TCRT5000 Ch5]
end
subgraph Driver["Motor Driver"]
TB66[TB6612FNG<br/>Dual H-Bridge]
end
subgraph Actuators["Actuators"]
ML[Left DC Motor<br/>N20 Gear Motor]
MR[Right DC Motor<br/>N20 Gear Motor]
end
BAT --> REG
REG --> C1
REG --> C2
REG -->|+5V| NANO
REG -->|+5V| TB66
REG -->|+5V| IR1
REG -->|+5V| IR2
REG -->|+5V| IR3
REG -->|+5V| IR4
REG -->|+5V| IR5
NANO -->|AIN1 AIN2 PWMA| TB66
NANO -->|BIN1 BIN2 PWMB| TB66
IR1 -->|A0| NANO
IR2 -->|A1| NANO
IR3 -->|A2| NANO
IR4 -->|A3| NANO
IR5 -->|A4| NANO
TB66 -->|Motor A| ML
TB66 -->|Motor B| MR
| Component | Part Number | Quantity | Function |
|---|---|---|---|
| Arduino Nano | ATmega328P | 1 | Main microcontroller, PD computation, I/O control |
| TB6612FNG Motor Driver | TB6612FNG | 1 | Dual H-Bridge motor driver, PWM speed control |
| TCRT5000 IR Sensor | TCRT5000 | 5 | Reflective IR sensor for line detection |
| N20 DC Gear Motor | N20 | 2 | Compact gear motors for wheel actuation |
| LM7805 Voltage Regulator | LM7805CFG | 1 | 5V linear voltage regulation from battery |
| Electrolytic Capacitor | ECEA1HKS4R7 | 1 | 10uF bulk capacitance on regulator output |
| Ceramic Capacitor | 100nF | 1 | Bypass capacitor on regulator input |
| SSQ-109-06-G-S Header | Samtec SSQ | 1 | 9-pin sensor interface connector |
| SSQ-108-X-X-S Header | Samtec SSQ | 2 | 8-pin motor driver interface connectors |
| SSQ-102-03-F-S Header | Samtec SSQ | 1 | 3-pin battery input connector |
The custom PCB was designed in Altium Designer as a two-layer board with the following considerations:
- Component Placement: Arduino Nano centrally located for short trace runs to peripherals. Motor driver positioned between Nano and motor connectors. Sensor header along the front edge for optimal sensor positioning.
- Power Distribution: Dedicated power traces routed with adequate width for motor current. Separate +5V regulation section with proper input/output capacitance.
- Signal Routing: Analog sensor traces routed away from power lines to minimize noise coupling. Motor driver control signals kept short and direct.
- Board Outline: Custom polygon shape optimized for robot chassis mounting with mounting holes at corners.
See PCB Design Documentation for detailed analysis.
The firmware implements a PD (Proportional-Derivative) control algorithm:
- Sensor Acquisition — Reads 5 analog IR sensor values at defined intervals
- Position Calculation — Computes weighted average of sensor readings to determine line position
- Error Computation — Calculates error term (deviation from center position)
- PD Control — Applies proportional and derivative terms to compute motor correction
- Motor Command — Translates correction value into differential PWM signals for left/right motors
Motor_Output = Kp * error + Kd * (error - prev_error)
Left_Motor = Base_Speed + Motor_Output
Right_Motor = Base_Speed - Motor_Output
| Test Category | Description | Status |
|---|---|---|
| Sensor Calibration | Individual IR sensor threshold verification across line/surface | Verified |
| Motor Driver | PWM response validation, direction control, stall current measurement | Verified |
| Power Integrity | Regulated voltage stability under varying load conditions | Verified |
| PD Tuning | Kp and Kd parameter optimization for smooth line tracking | Tuned |
| Integration Testing | Full system autonomous line-following on standard test track | Validated |
See Testing & Validation Documentation for detailed procedures.
Autonomous-Line-Following-Robot/
├── README.md # This file
├── LICENSE # MIT License
├── docs/
│ ├── architecture.md # System architecture deep-dive
│ ├── hardware-design.md # Hardware design documentation
│ ├── pcb-design.md # PCB design methodology and decisions
│ └── testing-and-validation.md # Testing procedures and results
├── images/
│ ├── robot_photos/ # Assembled robot photographs
│ ├── schematics/ # Schematic screenshots
│ └── pcb/ # PCB layout screenshots
├── firmware/ # Arduino firmware source code
└── hardware/
├── schematics/ # Altium schematic files (.schdoc)
├── pcb/ # Altium PCB layout files (.PcbDoc)
└── track-move.PrjPcb # Altium project file
- Power Supply Decoupling — Adequate bypass capacitance near the motor driver IC is critical to prevent voltage dips during motor startup transients.
- Sensor Mounting Height — TCRT5000 sensors are sensitive to distance from the reflecting surface; consistent mounting height (5-10mm) is essential for reliable detection.
- PWM Frequency Selection — Motor driver PWM frequency must be chosen to avoid audible noise while maintaining sufficient torque at low speeds.
- Ground Plane Design — A continuous ground plane on the bottom layer significantly reduces noise in analog sensor readings.
- Connector Selection — Pin header connectors provide reliable, serviceable connections for prototyping; consider screw terminals for production.
- PID Control — Upgrade from PD to full PID control for improved steady-state error correction
- Speed Optimization — Implement adaptive speed control (slow on curves, fast on straights)
- Wireless Telemetry — Add Bluetooth module for real-time parameter tuning and data logging
- Multi-Line Detection — Extend sensor array to detect intersections, markers, and track features
- PCB Revision — Add dedicated motor driver IC footprint (TB6612FNG) directly on board instead of header-based module
- Battery Monitoring — Implement voltage divider circuit for battery level monitoring via ADC
This project is licensed under the MIT License. See LICENSE for details.
Academic Embedded Systems Project
For questions or collaboration inquiries, please open an issue on this repository.