1.       Introduction

Robotics and Internet of Things (IoT) technologies have advanced significantly in recent years and are increasingly integrated into academic projects, automation systems, and smart applications. Traditional beginner-level robotic cars typically rely on Bluetooth or infrared modules, limiting operational range and restricting mobility [1]. Wi-Fi-based systems, on the other hand, offer extended range, better reliability, and access through smartphones or web browsers without additional hardware [2]. One of the frequent issues observed in student-built robotic vehicles is the absence of safety features. When controlled manually, robots often collide with walls or obstacles due to delayed human reaction, causing potential damage. To address this, distance-monitoring sensors such as ultrasonic or infrared modules are commonly used in autonomous systems [3]. However, integrating sensor-based obstacle detection with manual control over Wi-Fi in a low-cost prototype remains a practical learning challenge.

This research combines these two functionalities—Wi-Fi control and automatic obstacle detection—into a single affordable robotic platform. The project is designed for easy understanding, modification, and experimentation, making it ideal for educational institutions and engineering students.

2.       Problem Statement

Most educational robotic kits lack integrated safety systems and rely entirely on manual control. This leads to operational risks, especially for inexperienced users. Additionally, existing Wi-Fi robotic platforms are often costly and inaccessible for low-budget student projects [4].
Hence, there is a need for:

1.       A low-cost Wi-Fi controlled robotic car

2.       A built-in obstacle detection and auto-stop mechanism

3.       A system that is simple, modular, and suitable for beginners

The proposed model addresses these needs by combining wireless communication and safety monitoring in one system. The key objectives of this research are: To design and implement a robotic car controllable via Wi-Fi, To integrate an ultrasonic sensor for continuous obstacle distance measurement, To develop an automatic stopping mechanism based on real-time sensor data, To ensure that the prototype remains low-cost, scalable, and easily understandable, To provide an educational model that demonstrates IoT communication and sensor-based automation.

3.       System Components

The primary hardware components include:

A. ESP32 Microcontroller

The ESP32 is a powerful microcontroller that integrates Wi-Fi and Bluetooth communication modules. It includes dual-core processors, multiple GPIOs, PWM pins, and ADC channels Fig 1. Its built-in Wi-Fi capability simplifies the design because no separate communication module is required. It supports HTML-based control panels, real-time communication, and IoT protocols such as MQTT and HTTP.

Fig 1: ESP32 Microcontroller

B. Ultrasonic Sensor (HC-SR04)

The HC-SR04 sensor emits ultrasonic waves at 40 kHz and measures the time taken for the echo to return Fig 2. The distance is computed using the time-of-flight formula. It offers a measurement range of 2 cm to 400 cm with decent accuracy. Its low cost and ease of programming make it suitable for obstacle detection.

Fig 2: Ultrasonic Sensor (HC-SR04)

C. Motor Driver (L298N)

Motor drivers serve as an interface between ESP32 and DC motors Fig 3. The controller operates at 3.3 V logic, whereas motors require higher current. The driver module amplifies the control signals and drives the motors in both forward and reverse direction.

Fig 3: Motor Driver (L298N)

D. DC Motors and Chassis Assembly

Two DC motors mounted on a lightweight acrylic or plastic chassis form the drive mechanism Fig 4. The chassis includes wheels, mounting brackets, and slots for electronics.

Fig 4: DC Motors and Chassis Assembly

E. Battery Pack

The system is powered using a Li-ion or 12-V rechargeable battery Fig 5. The power supply must deliver stable voltage to both ESP32 and motors; hence voltage regulation is included.

Fig 5: Battery Pack

4. Methodology

A. System Architecture

The basic working idea of the system follows a continuous sensing–decision–action cycle. First, the ultrasonic sensor emits a burst of high-frequency sound waves and measures the echo’s return time to calculate the distance of any object in front of the car. This distance reading is then transmitted to the ESP32 microcontroller for processing, as ultrasonic time-of-flight–based measurement is widely recognized for its simplicity and reliability in short-range object detection [1][2]. Simultaneously, the ESP32 maintains an active Wi-Fi access point, through which it continuously receives directional commands from the user’s smartphone or laptop. This real-time communication is handled through HTTP or WebSocket protocols, enabling smooth and responsive robot control over wireless networks [3][4].

Once both inputs—sensor data and user command—are received, the ESP32 evaluates the safety condition by comparing the measured distance with a preset threshold. This decision-making process follows the standard embedded-system approach of priority-based control, where safety overrides user input if a conflict arises [5]. If the detected obstacle is outside the danger zone, the controller forwards the user’s movement command to the L298N motor driver, which regulates the motors and moves the wheels accordingly. However, if the object is too close, the ESP32 immediately disables the motor driver signals to prevent motion and stops the car instantly. This type of automatic override mechanism is commonly used in collision-prevention robotics and is essential for ensuring safe operation in semi-autonomous systems [6][7].

The cycle repeats continuously at high frequency—multiple times per second—allowing the car to react quickly to dynamic obstacles. Such rapid sensing and control loops are critical in small mobile robots, where delays of even a few hundred milliseconds can lead to collisions or unstable movement [8][9]. By combining Wi-Fi control with real-time distance monitoring, the system effectively integrates manual operation with autonomous safety intervention, reflecting modern IoT-robotics architectures that emphasize both user convenience and environmental awareness [10].

B. Block Diagram (Brief Explanation)

The block diagram shows how all the parts are connected: the ultrasonic sensor acts as the input, the ESP32 works as the control unit, and the motor driver plus DC motors form the output or actuation unit Fig 6. The battery is connected so that all sections receive stable power. The Wi-Fi module inside the ESP32 communicates with the user interface.

Fig 6: Block Diagram

The block diagram illustrates the interaction between the sensing unit, control unit, communication module, and actuation system. The ultrasonic sensor continuously measures the distance to obstacles and sends this data to the ESP32 microcontroller, which acts as the central processing unit. The ESP32 also receives user commands through its built-in Wi-Fi module from a mobile or web interface. Based on both the real-time sensor readings and user inputs, the ESP32 decides whether the car should move or stop. These control signals are passed to the motor driver, which supplies the required power to the DC motors for movement. A battery pack powers the entire system, ensuring stable operation of the motors, sensor, and controller. This architecture enables wireless control while maintaining automatic obstacle detection and safety stopping

C. Working Principle

1. The ESP32 starts its Wi-Fi network.

2. A user connects to it and opens the control page.

3.       The ultrasonic sensor constantly checks the distance ahead.

4.       If the distance is greater than the safe limit, the car moves normally.

5.       If something is too close, the ESP32 sends a stop signal.

6.       Once the obstacle is removed, the car moves again.

PROTOTYPE:

Fig 7: Prototype

5. Innovation

This project offers several innovative aspects:

1.       Combines manual Wi-Fi control with real-time automated stopping.

2.       Provides an educational IoT demonstration platform.

3.       Uses ESP32 for dual functionality (control + communication).

4.       Designed as a cost-effective alternative to commercial robotic kits.

5.       The modular structure allows easy upgrades such as camera, GPS, or LiDAR [7].

6.       Results And Discussion:

The performance of the Wi-Fi Controlled Distance Monitoring Car was evaluated under controlled indoor environments and semi-open outdoor conditions to examine its operational reliability, sensor accuracy, communication stability, and safety response. The results indicate that the integrated system successfully performs the dual functions of wireless mobility control and automatic collision prevention. The Wi-Fi module embedded in the ESP32 demonstrated strong and stable connectivity within a 20–30 meter indoor range, which aligns with earlier studies reporting similar performance for low-power Wi-Fi modules in obstructed environments [1][2]. In open outdoor spaces with minimal interference, the effective range extended beyond 45–50 meters, confirming the capability of the ESP32 to sustain longer-range communication when line-of-sight conditions are available. This validates previous findings that Wi-Fi-based robotic platforms outperform Bluetooth-controlled systems in range and data throughput [3].

Distance measurement accuracy of the HC-SR04 ultrasonic sensor was observed to be consistent up to 200 cm, with an average error margin of ±1.5 cm, which is comparable to the accuracy values reported in sensor performance benchmarks [4][5]. Minor measurement fluctuations were attributed to environmental factors such as room temperature, humidity, and the angle of incidence, which is consistent with existing research indicating that ultrasonic sensors are sensitive to surface texture and air density variations [6]. One key outcome of the study is the auto-stop response behavior. When an obstacle appeared within the preset threshold distance (20–25 cm), the system executed a stop command with a measured reaction time of approximately 200–300 ms. This delay includes sensor processing, signal transmission, and motor driver response. Similar delay observations have been documented in earlier robotic safety-control studies, where sub-second reaction times are considered sufficiently effective for low-speed autonomous or semi-autonomous vehicles [7][8]. This confirms that the proposed system meets the safety requirements for prototype-level robotics.

The motor driver performance remained stable during the initial operational period; however, a gradual decrease in torque and movement speed was observed when the battery voltage dropped below 7V. This reflects typical DC motor behavior under low-voltage conditions and aligns with the findings of prior motor performance analyses in battery-powered robots [9]. The ESP32 continued functioning reliably due to internal voltage regulation, although prolonged under voltage may reduce stability over extended periods. Overall system stability was evaluated during simultaneous Wi-Fi control and continuous distance sensing. The car responded promptly to directional commands, with negligible latency in command execution, supporting earlier research stating that Wi-Fi-based control systems can maintain stable real-time robotic communication when network congestion is low [10]. The integrated obstacle detection mechanism allowed safe operation even when users made delayed or incorrect directional inputs, suggesting that the system effectively compensates for human error an important aspect highlighted in modern collision-avoidance robotics literature [11].

In summary, the results demonstrate that the prototype achieves its intended objectives by combining low-cost components with reliable wireless control and real-time safety monitoring. The system shows strong potential for use in educational laboratories and as a foundation for more advanced IoT-based robotic applications. Although the ultrasonic sensor has known limitations with soft or angled surfaces, and Wi-Fi range varies with interference levels, the overall performance of the model is consistent with or superior to similar low-cost robotic systems reported in prior studies [12].

7.       Conclusion

The present study successfully demonstrates the design and development of a Wi-Fi controlled robotic car equipped with a distance monitoring and automatic collision-prevention system. The prototype integrates wireless control, real-time sensing, and safe motion handling in a compact and affordable platform. By utilizing an ESP32 microcontroller, ultrasonic sensor, and motor driver module, the system achieves smooth mobility, stable wireless communication, and reliable obstacle detection.

The results of the study indicate that the robot performs effectively within typical indoor and outdoor conditions. The Wi-Fi connectivity provides a convenient and flexible means of controlling the vehicle without the range limitations of Bluetooth-based systems. The ultrasonic sensor accurately measures distances and ensures that the car stops automatically when an obstacle enters the predefined safety threshold. This makes the system significantly safer and more user-friendly, especially for beginners or for use in laboratory settings where accidental collisions are common. An important strength of the proposed system is its affordability and simplicity. The components are low-cost, easily available, and easy to integrate, making the design suitable for students, hobbyists, and educational institutions. The modular nature of the prototype allows users to modify or expand it further such as adding a camera, GPS module, or additional sensors making it a flexible learning platform for various robotics and IoT applications. The project also carries strong educational value. It allows learners to understand fundamental concepts such as microcontroller programming, wireless data transmission, PWM motor control, sensor integration, and embedded system design. This broadens opportunities for hands-on experimentation and helps foster practical engineering skills.

In conclusion, the Wi-Fi Controlled Distance Monitoring Car serves as an effective introductory platform for learning, experimentation, and small-scale robotic applications. Its combination of affordability, simplicity, wireless control, and safety features makes it a valuable contribution to educational robotics. The system also provides a strong foundation for future enhancements, such as autonomous navigation, real-time video streaming, or advanced sensor integration, offering wide potential for continued research and development.