Smart Automatic Door System

Course: Electronic Devices and Circuits (CE124.Q14)

Institution: University of Information Technology (UIT) - VNU-HCM

Instructor: Dr. Tran Quang Nguyen

📸 Final Product Showcase

Below are the images of the completed system, highlighting the circuit assembly and mechanical structure:

Figure 1: The complete system setup including the sensor unit, control circuit, and actuator mechanism.

📖 Overview

This project focuses on the analysis and application of Electronic Devices to construct a Smart Automatic Door System. Unlike purely software-based projects, this study emphasizes the electrical characteristics, component specifications, and circuit design required to drive a high-power DC motor using low-voltage logic control signals from the STM32 microcontroller.

🛠 Tech Stack & Methodology

• Design Methodology:
  • Circuit Analysis: Calculating current/voltage requirements for the Motor and Driver.
  • Component Selection: Choosing the H-Bridge driver based on power dissipation and peak current ratings.
• Hardware Components:
  • Controller: STM32F407VET6 (ARM Cortex-M4).
  • Power Stage: L298N Dual Full-Bridge Driver (Bipolar tech).
  • Sensor: HC-SR04 (Ultrasonic Transducer).
• Tools:
  • Altium Designer / Proteus: For circuit design and simulation.
  • STM32CubeIDE: For firmware implementation.

⚡ Component Specifications & Analysis

The system consists of three main stages with specific electrical parameters:

1. Control Stage (STM32F407VET6)

• Operating Voltage: $3.3V$ DC.
• Clock Frequency: $168 \text{ MHz}$.
• Logic Level High ($V_{OH}$): $3.3V$ (Sufficient to drive L298N Logic Inputs).
• GPIO Mode: Push-Pull Output.
• GPIO Output Current: Max $25 \text{ mA}$ (Sufficient to drive L298N Logic Inputs).

2. Power Driver Stage (L298N H-Bridge)

• Device Type: Dual Full-Bridge Driver (Transistor Logic).
• Supply Voltage ($V_s$): Supports up to $46V$ (We utilize $12V$).
• Peak Output Current ($I_o$): $2A$ per channel.
• Logic High Voltage ($V_{IH}$): $2.3V \le V_{in} \le V_{ss}$ (Compatible with STM32 3.3V logic).
• Power Dissipation: Heatsink required for currents $> 1A$.

3. Sensor Stage (HC-SR04)

• Operating Voltage: $5V$ DC.
• Operating Current: $15 \text{ mA}$.
• Frequency: $40 \text{ kHz}$.
• Range: $2 \text{ cm} - 400 \text{ cm}$.

📊 System Operation Logic

The circuit operates by switching the transistor states within the L298N H-Bridge to control current flow direction through the DC Motor.

Condition	Sensor Distance ($d$)	MCU Signal (PB0 / PB1)	H-Bridge State	Motor Action
User Approaching	$d < 15 \text{ cm}$	HIGH / LOW	Q1, Q4 ON	Forward (Open)
Holding Open	(Delay 3s)	LOW / LOW	All OFF	Stop (Coast)
User Away	$d \ge 15 \text{ cm}$	LOW / HIGH	Q2, Q3 ON	Reverse (Close)

💻 Firmware & Hardware Interface

Although this is a hardware-centric project, Firmware is essential to generate the correct Electrical Control Signals. The STM32 is programmed in Embedded C using the HAL Library to manage the state of the GPIO pins.

Control Logic Implementation

The firmware implements a Finite State Machine (FSM) to control the voltage levels at pins PB0 and PB1, determining the conduction state of the transistors inside the L298N.

/* LOGIC TABLE FOR L298N CONTROL */
// PB0 = High (3.3V), PB1 = Low (0V)  -> Current flows A to B -> Motor Opens
// PB0 = Low (0V),  PB1 = High (3.3V) -> Current flows B to A -> Motor Closes

if (Distance < 15) // Sensor Input
{
    // Action: OPEN DOOR
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_SET);   // PB0 -> 3.3V
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_RESET); // PB1 -> 0V
    
    HAL_Delay(3000); // Hold state for 3 seconds
}
else
{
    // Action: CLOSE DOOR
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_RESET); // PB0 -> 0V
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_SET);   // PB1 -> 3.3V
}

⚙️ Installation & Setup

1. Clone the Repository:

   git clone https://github.com/NguyenDinhNhatNguyen/Auto-Door

2. Hardware Wiring:
   • Connect 12V Source to L298N $V_{CC}$ and GND to common ground.
   • Connect STM32 PB0, PB1 to L298N IN1, IN2.
   • Connect STM32 PA1, PA6 to Sensor Trig, Echo.
   • Caution: Ensure common GND between 12V and 5V/3.3V sources.
3. Flash Firmware:
   • Load the .elf file using STM32CubeIDE or ST-Link Utility.

👥 Contributors & Roles

Student Name	ID	Role	Responsibilities
Le Hung Phat	23521139	System Arch	System integration, Firmware logic, Schematic design.
Nguyen Thanh Hieu	23520486	Power Electronics Eng.	L298N & Motor analysis, Power calculations, Thermal analysis.
Tran Quang Nhat	23521102	Control Circuit Eng.	STM32 interface design, Simulation (Proteus), Wiring.
Nguyen Dinh Nhat Nguyen	23521043	Sensor & Mech. Eng.	HC-SR04 signal analysis, Mechanical build, Calibration.
Ngo Tien Dat	23520254	QA & Technical Writer	Testing & Measurements, Debugging

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Ho Chi Minh City, January 2026