DEVELOPMENT OF A SMART SECURITY SYSTEM BASED ON MOTION SENSORS

ABSTRACT

This paper discusses the development of a smart security system based on motion sensors. The primary objective of the system is to detect movements within a secured area, analyze them, and provide appropriate alerts or signals in real-time. The paper covers the operational principles of motion sensors, their types, and the architecture of a microcontroller-based management system.

Furthermore, the integration of software and hardware components of the smart security system is analyzed, alongside methods to reduce false alarms and improve system reliability and efficiency. The proposed solution can be applied to ensure security in residential, office, and industrial facilities, serving to create an automated control system based on modern information technologies.

АННОТАЦИЯ

В данной статье рассматривается разработка интеллектуальной системы безопасности на основе датчиков движения. Основная задача системы — обнаружение движений в охраняемой зоне, их анализ и предоставление соответствующих оповещений или сигналов в режиме реального времени. В статье рассматриваются принципы работы датчиков движения, их типы и архитектура системы управления на базе микроконтроллера.

Кроме того, анализируется интеграция программных и аппаратных компонентов интеллектуальной системы безопасности, а также методы снижения ложных срабатываний и повышения надежности и эффективности системы. Предложенное решение может быть применено для обеспечения безопасности в жилых, офисных и промышленных помещениях, создавая автоматизированную систему управления на основе современных информационных технологий.

Keywords: Motion sensor, Arduino, alarm system, pyroelectric element (PIR), infrared, area of light distribution, sensitivity range, microcontroller.

Ключевые слова: Датчик движения, Arduino, система сигнализации, пироэлектрический элемент (PIR), инфракрасное излучение, зона распределения света, диапазон чувствительности, микроконтроллер.

Introduction

A motion sensor allows you to track the movement of heat-emitting objects (humans, animals) in an enclosed space. Such systems are frequently used in residential buildings, for example, to turn on lights in corridors. In this article, we will look at connecting PIR sensors—Passive Infrared sensors or pyroelectric sensors—that detect motion to Arduino projects. Their small size, low cost, ease of use, and simple wiring make these sensors suitable for use in various alarm systems [1, р.9].

Figure 1. A motion sensor consists of a cylindrical crystalline component at the center of the pyroelectric element (PIR)

The design of the PIR motion sensor is not very complex. It consists of a pyroelectric element (a cylindrical component with a crystal at its center) that is highly sensitive to the presence of a certain level of infrared radiation within its range. The higher the temperature of the object, the larger the radiated field. A hemisphere is installed over the PIR sensor, which is divided into several sections (lenses), each directing heat energy to different segments of the motion sensor. A Fresnel lens is often used as the lens, expanding the sensitivity range of the Arduino infrared motion sensor by concentrating the thermal radiated field.

Structurally, the PIR sensor is divided into two parts. The reason for this is that the alarm system is sensitive not to the level of the radiation itself, but to movement within the detection zone. Therefore, the parts are installed such that when one part detects a high level of radiation propagation, a high or low signal is sent to the output [2, p.15].

Materials and methods

The main technical characteristics of the motion sensor:

• Detection range of moving objects: 0 to 7 meters;
• Viewing angle range: 110°;
• Supply voltage: 4.5–6 V;
• Operating current: up to 0.05 mA;
• Temperature range: -20°C to +50°C;
• Adjustable delay time: from 0.3 to 18 seconds.
• The module with the built-in infrared motion sensor includes additional electrical wiring with a fuse, resistor, and capacitor.

The operational state of the motion sensor is as follows:

• When the device is installed in an empty room, the radiation received by each element remains constant, as does the voltage;
• As soon as a person appears in the room, the first thing they do is enter the field of view of the first element, where a positive electrical impulse is generated;
• As the person moves in the room, the radiated field moves with them and reaches the second sensor. This PIR element generates a negative impulse;
• These multi-directional impulses are recorded by the electronic circuit of the sensor, which leads to the conclusion that a person is present in the viewing field of the PIR sensor.

The motion sensor works as follows: Let’s assume the sensor is installed in an empty room. Each sensor element can continuously radiate, meaning the voltage in them remains constant (Figure 2) [3, p.5].

Figure 2. The motion sensor operates in the following state (a, b, c).

As soon as a person enters the room, they enter the field of view of the first element, causing a positive electrical impulse to appear in it (Figure b).

As the person moves, their radiated field passes through the lenses to the second PIR element, which generates a negative impulse [10,p.530]. The electronic circuit of the motion sensor records these oppositely directed impulses and concludes that a person has entered the sensor's field of view. The output of the sensor generates a positive impulse (Figure c).

In this paper, we utilize the HC-SR501 module. This module is very common and used in many projects due to its low cost [8, p.65].

The sensor features two variable resistors and a jumper for mode adjustment. One of the potentiometers adjusts the sensitivity of the device. The higher the sensitivity, the further the sensor can detect. Sensitivity also affects the size of the detected object; for instance, you might see it trigger from the movement of a dog or a cat [4, p.3].

Figure 3. Names of the input and output ports of the motion sensor

Connecting the HC-SR501 to an Arduino Uno:

The HC-SR501 has three pins for connecting to a microcontroller or directly to a relay. Connect them to the Arduino using the following diagram:

Schematic Diagram

Figure 4. Diagram

Connecting the PIR Sensor:

«Ground» – to any GND connector on the Arduino;

Digital output – to any digital input or output on the Arduino;

Power supply – to +5V on the Arduino [5, p.3].

Results and discussion

Circuit diagram of the smart security system using an Arduino motion sensor:

Figure 5. Scheme

Algorithm of the smart security system of the Arduino motion sensor:

Figure 6. Scheme

Code of the smart security system of the Arduino motion sensor:

// PIR sensor pin (motion sensor)

int pirPin = 7;

// LED lamp pins

int ledRed = 9;      // red LED

int ledGreen = 8;    // green LED

// Passive buzzer (signaling device) pin

int buzzerPin = 11;

void setup() {

pinMode(pirPin, INPUT);      // PIR — input

pinMode(ledRed, OUTPUT);     // red LED — output

pinMode(ledGreen, OUTPUT);   // green LED — output

}

void loop() {

// Read signal from PIR: HIGH = motion detected

int motion = digitalRead(pirPin);

if (motion == HIGH) {

// -------------------------

// Light indication

// -------------------------

digitalWrite(ledRed, HIGH);    // red LED turns ON

digitalWrite(ledGreen, LOW);   // green LED turns OFF

// ------------------------------------

// POLICE SIREN SOUND

// Frequency gradually increases and decreases

// ------------------------------------

for (int i = 0; i < 10; i++) {

tone(buzzerPin, 700);

delay(400);

tone(buzzerPin, 1200);

delay(400);

}}

else {

// -------------------------

// No motion

// -------------------------

digitalWrite(ledRed, LOW);      // red LED turns OFF

digitalWrite(ledGreen, HIGH);   // green LED turns ON

noTone(buzzerPin);              // buzzer turns OFF

}}

Conclusion

In conclusion, this work provided a detailed analysis of both theoretical and practical aspects of a smart security system built on the HC-SR501 PIR Motion Sensor and Arduino Uno. The results of the research showed that motion sensors based on PIR technology are highly efficient in detecting human or animal movement in enclosed areas, and are characterized by their energy efficiency and simplicity.

During the project, the hardware (sensor, microcontroller, signaling devices) and software (Arduino code) components of the system were integrated to create a real-time functioning security mechanism. The developed system ensures rapid warning by providing visual (LED) and audio (buzzer siren) signals when motion is detected. At the same time, the capabilities to adjust sensitivity and manage delay time allow the system to be adapted to various conditions.

The analysis indicated that correctly selecting the sensor's placement, sensitivity parameters, and external environmental factors is crucial to reducing false alarms. The proposed solution serves as an affordable, reliable, and scalable platform for enhancing security in homes, offices, and industrial facilities [9, p.150].

Overall, this project demonstrates an effective approach to creating smart security systems based on modern microcontroller technologies and serves as a solid foundation for developing even more functional systems through future integration with IoT (Internet of Things) technologies.

References:

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