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A multifunctional smart robot car capable of operating in three independent modes: Obstacle Avoidance, Line Following, and Bluetooth Manual Control.
The project combines an Arduino Uno for real-time motor and sensor control with an ESP32 DevKit for Bluetooth communication, creating a modular embedded system capable of both autonomous and manual operation.
Developed by Vishal and Nitish as part of the Value Added Course (VAC) – Arduino Microcontroller.
Watch the complete working demonstration of the robot on YouTube.
This project demonstrates the implementation of a multi-functional smart robot car capable of switching between three operating modes using dedicated rocker switches.
The robot combines autonomous navigation and wireless manual control into a single platform.
A common question regarding this project is:
Why use both an Arduino Uno and an ESP32 when the ESP32 alone is capable of handling the entire project?
This project was developed as part of a Value Added Course (VAC) focused on Arduino Microcontrollers, where the Arduino Uno served as the primary controller for implementing the robot's logic.
Instead of using a dedicated Bluetooth module such as the HC-05, an ESP32 DevKit was integrated to provide Bluetooth connectivity. The ESP32 receives commands wirelessly from a smartphone and forwards them to the Arduino Uno through UART serial communication.
Note: From a hardware perspective, this project can be implemented using only an ESP32, since it provides sufficient GPIO pins along with built-in Bluetooth and Wi-Fi capabilities. The dual-controller architecture was intentionally chosen to satisfy the course objectives while also demonstrating UART communication between two microcontrollers in an embedded system.
- 🚧 Obstacle Avoidance
- ➖ Line Following
- 📱 Bluetooth Manual Control
The Arduino Uno performs all real-time control operations including motor control, sensor processing, servo control, buzzer control and operating mode selection.
The ESP32 DevKit acts as a Bluetooth communication bridge by receiving commands from a smartphone and forwarding them to the Arduino Uno through UART serial communication.
- 🚗 Three independent operating modes
- 📡 Bluetooth manual control
- 🚧 Autonomous obstacle avoidance
- ➖ Automatic line following
- 🔄 Servo-mounted ultrasonic scanning
- 🔔 Buzzer alerts
- 🎛 Four rocker-switch controls
- ⚡ Battery-powered portable design
- 🤖 Arduino + ESP32 modular architecture
| Specification | Details |
|---|---|
| Main Controller | Arduino Uno |
| Bluetooth Controller | ESP32 DevKit |
| Programming Language | C++ |
| Framework | Arduino Framework |
| Motor Driver | L298N |
| Communication | Bluetooth (UART) |
| Power Supply | 7.4V (2×18650 Li-ion Batteries) |
| Drive System | 4WD DC Gear Motors |
| Sensors | HC-SR04 + 3 IR Sensors |
| Operating Modes | 3 |
| Component | Quantity | Purpose |
|---|---|---|
| Arduino Uno (CH340 Square Chip Version) | 1 | Main controller |
| ESP32 DevKit | 1 | Bluetooth communication bridge |
| L298N Motor Driver | 1 | Drives four DC motors |
| HC-SR04 Ultrasonic Sensor | 1 | Obstacle detection |
| Ultrasonic Sensor Holder | 1 | Mounts the ultrasonic sensor |
| SG90 Servo Motor | 1 | Rotates the ultrasonic sensor |
| IR Sensors | 3 | One center IR for obstacle assistance and two side IR sensors for line following |
| Active Buzzer | 1 | Audible feedback |
| Robot Chassis | 1 | Mechanical frame |
| DC Gear Motors | 4 | Robot movement |
| Robot Wheels | 4 | Locomotion |
| 18650 Li-ion Batteries (3.7V) | 2 | Power source |
| Dual 18650 Battery Holder | 1 | Provides ~7.4V |
| Rocker Switches | 4 | Power and mode selection |
| Breadboard | 1 | Power distribution |
| Jumper Wires | Multiple | Electrical connections |
| Hook-up Wires | As required | Component wiring |
The robot is powered using two 3.7V 18650 Li-ion batteries connected in series, providing approximately 7.4V.
The battery output is distributed through the breadboard power rails and supplied directly to the VIN pin of both the Arduino Uno and the ESP32 DevKit.
The breadboard serves as a centralized power distribution board for the motor driver, sensors, servo motor, buzzer and other peripherals.
The robot uses four rocker switches mounted on the chassis.
| Switch Position | Function |
|---|---|
| Left-most | Main Power ON/OFF |
| Second from Left | Bluetooth Manual Control |
| Middle | Obstacle Avoidance |
| Right-most | Line Following |
NOTE: Only one operating mode should be enabled at a time. If two or more operating mode switches are turned ON simultaneously, the Arduino intentionally places the robot in a STOP state to prevent conflicting control logic and ensure safe operation.
The Arduino continuously monitors the ultrasonic sensor and center IR sensor.
When an obstacle is detected, the robot:
- Stops and activates the buzzer.
- Moves backward briefly.
- Rotates the ultrasonic sensor using the servo motor.
- Scans both directions.
- Chooses the direction with greater clearance.
- Turns accordingly.
- Continues moving forward.
The left and right IR sensors detect the line beneath the robot. The Arduino adjusts motor movement to keep the robot aligned with the path.
The ESP32 receives Bluetooth commands from a smartphone and forwards them to the Arduino through UART serial communication for movement and buzzer control.
| Sensor | Function |
|---|---|
| HC-SR04 | Obstacle distance measurement |
| SG90 Servo | Ultrasonic scanning |
| Center IR | Obstacle assistance |
| Left IR | Line detection |
| Right IR | Line detection |
| Command | Action |
|---|---|
| F | Forward |
| B | Backward |
| L | Turn Left |
| R | Turn Right |
| S | Stop |
| H | Horn / Buzzer |
Smartphone
│
Bluetooth
│
ESP32 DevKit
│
UART Communication
│
Arduino Uno
│
┌────────┼────────┐
│ │ │
L298N Sensors Servo
│
4 DC Gear Motors
| Arduino Pin | Connected Device |
|---|---|
| D2 | L298N IN4 |
| D4 | L298N IN3 |
| D6 | ENA & ENB (Common PWM) |
| D7 | L298N IN2 |
| D8 | L298N IN1 |
| D11 | Servo Motor |
| D12 | Obstacle Mode Switch |
| D13 | Line Following Mode Switch |
| A0 | Left IR Sensor |
| A1 | Center IR Sensor |
| A2 | Right IR Sensor |
| A3 | Active Buzzer |
| A4 | Ultrasonic Echo |
| A5 | Ultrasonic Trigger |
Note: The ENA and ENB pins of the L298N motor driver are electrically connected together and driven by Arduino pin D6 due to a hardware issue with the ENB channel.
When uploading firmware to the ESP32 DevKit, temporarily disconnect the UART communication wires between the ESP32 and the Arduino Uno (ESP32 TX ↔ Arduino RX and ESP32 RX ↔ Arduino TX).
Keeping both boards connected during programming may interfere with the ESP32 bootloader, resulting in upload or synchronization errors.
After successfully uploading the firmware, reconnect the TX and RX wires before operating the robot.
Note: The Arduino Uno firmware can be uploaded normally without disconnecting any peripherals.
- Arduino IDE
- C++
- Serial Monitor
.
├── Arduino_Code/
│ └── Arduino_CarCode.ino
│
├── ESP32_Code/
│ └── ESP32_BluetoothCar_Code.ino
│
├── Images/
│ ├── Chassis.jpg
│ ├── Side view.jpg
│ ├── Top view(Turned on).jpg
│ ├── Top view(Turned off).jpg
│ ├── Wiring_Diagram.png
│
├── Video/
│ └── 3 Mode Smart car.mp4
│
├── README.md
└── LICENSE
Responsible for:
- Motor control
- Obstacle avoidance
- Line following
- Servo control
- Sensor processing
- Buzzer control
- Operating mode selection
Responsible for:
- Bluetooth communication
- Receiving commands from a smartphone
- Forwarding commands to the Arduino Uno through UART
The project was developed as part of a Value Added Course (VAC) focused on Arduino Microcontrollers. The Arduino Uno serves as the primary controller, while the ESP32 replaces the need for a separate Bluetooth module by providing built-in Bluetooth communication.
Yes.
The ESP32 has sufficient GPIO pins along with built-in Bluetooth and Wi-Fi capabilities to control the motors, sensors, and Bluetooth communication on a single microcontroller.
The dual-controller architecture was adopted primarily to satisfy the course objectives while demonstrating UART communication between two embedded systems.
Since the ESP32 already provides integrated Bluetooth functionality, it was used instead of adding an external HC-05 Bluetooth module.
Each operating mode uses different control logic.
Allowing multiple modes to run simultaneously would result in conflicting commands to the motors.
To avoid this, the software automatically places the robot in a STOP state whenever multiple operating mode switches are enabled simultaneously.
During hardware testing, the ENB enable channel of the L298N motor driver board was found to be faulty.
To ensure reliable operation, both enable pins were electrically connected together and controlled using a single PWM signal from Arduino Pin D6.
This allows both motor channels to operate correctly using the same speed control signal.
The ESP32 bootloader uses its UART interface during programming.
If the ESP32 remains connected to the Arduino Uno through the TX/RX lines, the serial communication may interfere with the upload process and cause synchronization errors.
Temporarily disconnecting the UART connections resolves this issue.
- PID-based line following
- Wi-Fi control using ESP32
- Mobile application
- Camera module integration
- Battery voltage monitoring
- Autonomous path planning
- T S Vishal Babu
- Nitish M A
Developed as part of the Value Added Course (VAC) – Arduino Microcontroller.
If this project helped you or inspired your own work, consider giving the repository a ⭐ on GitHub. It helps others discover the project and supports future development.
This project is licensed under the MIT License.