The research of electrical parameters of threshold detectors

Introduction and problem statement

The security and fire system (hereinafter OPS) is an important means of protecting an object, providing timely detection and response to threats. Important parameters of the OPS are the reaction time and the probability of false positives. It includes subsystems: fire alarm (hereinafter SPS) and burglar alarm (hereinafter SOS) ^[1].

The SPS notifies people about a fire-hazardous situation and organizes evacuation. It includes light and sound sirens, and also sends an alarm signal to the central control point (hereinafter referred to as the control center). It can also include fire extinguishing and smoke removal systems.

There are three types of automatic fire alarm: threshold system, address-polling system and address-analog system ^[2]. The threshold system determines the triggering by changing the electrical characteristics of the communication line, which complicates the precise determination of the source of the triggering. The address-polling system polls each device for a fire signal, which allows you to accurately determine its location. The address-analog system transmits information about the signals to the control panel, providing a high level of security.

The SOS detects unauthorized entry into the object ^[3]. When triggered, an alarm is sent to the control center. It monitors the safety of the facility and the operability of the detectors on the security loop.

The security alarm system performs the following tasks: detection of an intruder, formation of an information notice, transmission of a notice and procedures for arming and disarming ^[4].

There are three main types of security alarm systems: wired, wireless and address systems ^[5].

1. A wired system uses wired connections to communicate between components. It consists of a receiving and control unit and various sensors, such as acoustic, magnetic contact and motion sensors. Wired systems are reliable and stable, although they require wires to connect.
2. The wireless system provides communication without the use of wires. It has an addressability, which allows you to accurately determine the location of the signal. The wireless system is easy to install, but may be affected by external factors such as interference.
3. Address system Each device has a unique address, allowing you to accurately determine the location of the signal. It has the function of self-testing of sensors and transmitting information about operability. Address systems provide a high level of security, but require more installation and maintenance costs.

The alarm loop (SS) is a wired line connecting the detectors and the receiving and control device. It transmits alarm and service signals, and can also be used to power detectors. The SHS can be two-wire and contain remote elements for proper operation of the system. It is characterized by electrical parameters such as current, voltage and resistance. The loop states include "normal" (flowing current), "breakage" (no current) and "short circuit" (increased current) ^[6].

Threshold detectors are activated when environmental parameters reach certain threshold values, for example, temperature or smoke concentration. The article discusses in detail the connection schemes of such detectors, as well as the "norm" and "alarm" states. The main difference between threshold detectors is their simplicity and reliability, but at the same time they may be less sensitive to the initial stages of a fire compared to other types of alarms.

In Russia, threshold detectors are widely used in various facilities, from residential buildings to large industrial complexes. Their simplicity, reliability and relatively low cost have made them a popular solution. However, there are also certain problems associated, for example, with frequent false positives or reaction delays. Threshold detectors are also popular abroad, but in a number of countries new technologies are being actively developed and implemented to increase the sensitivity and accuracy of operation, as well as reduce the number of false alarms.

One of the main problems of threshold detectors is the high level of false alarms. This may be due to incorrect configuration or poor isolation of the device. Therefore, it is necessary to ensure regular maintenance and calibration of devices, as well as the use of modern models of detectors with improved characteristics. Some threshold detectors may respond to changes in conditions with a delay, which is critical in the rapid development of a fire.As a solution, we recommend the use of combined systems, including threshold and other types of detectors.

Threshold detectors play a key role in ensuring safety at various facilities ^[7,8]. Despite their advantages, they also have a number of disadvantages. It is important to conduct regular research and modernization of the system to improve its efficiency and reliability. Such a comprehensive solution will ensure a high level of security and fire safety of facilities in any conditions.

A specially designed stand for the study of threshold detectors can play a key role in solving the problems of studying and analyzing their electrical parameters. With the help of the stand, it is possible to provide standardized conditions for all experiments, which reduces the likelihood of errors due to variable external factors. This ensures the repeatability and reproducibility of the experimental results. The stand can be configured to simulate various real operating conditions: changes in temperature, humidity, light level and other parameters. This will reveal the specific features of the detectors in various scenarios. Modern stands can be equipped with automatic registration and data analysis systems. This ensures fast and accurate data collection without the human factor. The stand can be configured to work with different models of threshold detectors, which will allow for a comprehensive comparative study of various devices on the market. Instead of conducting separate experiments in different conditions and with different tools, the stand allows you to centrally manage the entire process, while saving time and resources of researchers. The stand can serve not only as a tool for scientific research, but also as a training platform for students and specialists. In addition, it can be used to demonstrate to potential customers or partners the features of the operation of various detectors.

Stand for monitoring and analysis of threshold detectors

Clamp connectors are available on the developed stand ^[9], which allow connecting the detector wires to the loop. We have the opportunity to choose the number of connected detectors from one to three. In addition, there are pin connectors with a diameter of 4 mm on the input and output contacts of the loop. These connectors are designed to connect various monitoring and analysis devices, such as a voltmeter and an ammeter. By connecting such devices, we will be able to measure the voltage characteristics of the loops in real time in various operating modes of the system. This will allow monitoring and analysis of the operation of the loops using appropriate devices.

Figure 1. Training stand OPS ASTRA – 812

The laboratory stand consists of the following components (Fig. 1):

1. The Astra-712/0 power supply, which supplies all the components of the stand.
2. Receiving and control device Astra-812 pro.
3. The Astra-713 expander.
4. Matrix-II card key reader.
5. The Astra-10 light security and fire alarm system.
6. Sound security and fire alarm Oriole.
7. Optical-electronic detectors IO 409-26.
8. Security surface sound detectors IO 329-5.
9. Smoke smoke detectors optoelectronic IP 212-45.
10. Fire detectors thermal IP 103-5/4.
11. Doors with magnetic contact security detectors IO 102-16/2.
12. Devices for monitoring loops USK-01.
13. Electronic voltmeter, for measuring the voltage of the loops.
14. Analog ammeter, for measuring loop currents.

To study the current-voltage characteristics of the OPS, we will consider in detail each of the alarm loops on the stand.

The loop of magnetic contact detectors IO 1-2-162. Figure 2 shows a serial connection diagram of the detectors connected by a common loop "power" and "ground", where at the end of the loop there is a terminal resistor R _approx. The detectors consist of a reed switch mounted on a stand and a permanent magnet on the door leaf. When the doors are closed, the permanent magnet keeps the reed contacts closed, a constant current flows through the loop, when the door is opened, the permanent magnet is diverted from the reed switch, which causes the contacts to open and the loop opens.

Figure 2. Connection diagram of magnetic contact detectors

Consider the characteristics of the loop in various modes of operation and events (Fig. 3).

Figure 3. Voltage characteristics of a loop with magnetic contact detectors

In the "guard" mode, when all reed switches are closed, a voltage of 15.4 volts and a current of 4 mA is set on the loop. The alarm modes in the "security" mode range from 2.9 to 5.8 mA. If it falls higher or lower, then the alarm gives an alarm. If there is an opening of the flap or a break in the loop, then the current drops to 0 and the voltage rises to 19.4 volts, while the control panel cannot accurately identify whether it is a break in the loop or the opening of the door leaf.

The loop of fire thermal detectors IP 103-5/4. Figure 4 shows a serial connection diagram of the detectors connected by a common loop "power" and "ground", where at the end of the loop there is a terminal resistor R _approx. These detectors are normally closed in the normal state and have a conductivity with a minimum resistance (no more than 0.5 ohms), when exposed to a temperature of more than 60 ° C, the contact of the detector opens, which leads to the breakage of the loop.

 
Figure 4. Connection diagram of fire-fighting heat detectors

Consider the characteristics of the loop in various modes of operation and events (Fig. 5).

Figure 5. Voltage characteristics of a loop with fire-fighting heat detectors

The loop of fire thermal detectors IP 103-5/4. Figure 4 shows a serial connection diagram of the detectors connected by a common loop "power" and "ground", where at the end of the loop there is a terminal resistor R _approx. These detectors are normally closed in the normal state and have a conductivity with a minimum resistance (no more than 0.5 ohms), when exposed to a temperature of more than 60 ° C, the contact of the detector opens, which leads to a break in the loop.

The plume of fire smoke detectors IP 212-45. Figure 6 shows the connection diagram of the detectors connected by a common loop "power" and "ground", where at the end of the loop there is a terminal resistor R _approx. In the detector there is a camera with a pair of LED – photodiode. The principle of operation is based on the scattering of the light stream as it passes through the smoke particles entering the chamber. The LED creates a luminous flux, which is captured by a photodetector. For signal processing, a microprocessor is used, which is configured for the threshold parameters of the luminous flux and, when they change, closes the loop on the internal resistance R _vn, which is of a lower nominal value than R _ok ^[10].

 
Figure 6. Connection diagram of fire smoke detectors

Consider the characteristics of the loop in various modes of operation and events.

Figure 7. Voltage characteristics of the loop with fire smoke detectors

In the "protection" mode, when all detectors are not exposed to smoke, the detectors are activated through a loop and a voltage of 15.4 volts and a current of 4 mA is set, just as in the detectors considered in the previous loops. The alarm modes in the "security" mode range from 2.9 to 5.8 mA. An "alarm" signal will be issued outside this range. If smoke is exposed as a result of a fire, then the detector closes the loop circuit through the internal resistances, the current rises to 10 mA and the voltage drops to 8 volts. Perhaps another condition is a loop break, while the current drops to 0, and the supply voltage is set to 19.4 volts.

A loop of passive acoustic detectors IO 329-5, designed to detect glass breakage in the characteristic frequency range of sound (about 12 kHz). Figure 8 shows the connection diagram of the detectors connected by a common loop "power", "ground", input "SHS1" and output "SHS2". Through the "power" and "ground" contacts, the detectors are powered, which contain: microphones, microcontrollers, sound recording and amplification circuits ^[11,12]. The information output "SHS1-SHS2" passes through each of the detectors, after the last detector in the loop, the output "SHS2" is closed to the ground line through the terminal element R _approx. In different modes of operation and events, there are changes in the voltage characteristics of the loop.

Figure 8. Connection diagram of passive acoustic detectors

Consider the characteristics of the loop in various modes of operation and events. The voltage characteristic between "power supply" and "ground" is shown in Fig. 9.

Figure 9. Voltage characteristics of the power-ground loop with acoustic detectors

In the "normal" mode, the consumption current is 75 mA and the supply voltage is 13.4 volts. When the detector is triggered, the current and voltage do not change. When the loop breaks, the current drops to 0 and the voltage rises to 19.4 volts. Another relationship is between "SHS1" and "earth", shown in Figure 10.

Figure 10. Voltage characteristics of the SHS1-ground loop with acoustic detectors

When arming, 15.4 volts and a current of 4 mA are set between "SHS1" and "ground", while the current threshold is from 3.8 to 5.1 mA. When the signal breaks, an alarm is issued, the current becomes 0, and the voltage at the contacts is 19.4 volts.

A loop of passive acoustic detectors IO 409-26, designed to detect the presence of people in the viewing area of the detectors by thermal radiation of the body in infrared (IR) radiation. Figure 11 shows the connection diagram of the detectors connected by a common loop "power", "ground", input "SHC1" and output "SHC2". Through the "power" and "ground" contacts, the detectors are powered, which contain: IR receivers, microcontrollers for signal processing and decision-making, a Fresnel lens and light filters to protect against false alarms of the detector. The information output "SHS1-SHS2" passes through each of the detectors, after the last detector in the loop, the output "SHS2" is closed to the ground line through the terminal element R _approx. In different modes of operation and events, there are changes in the voltage characteristics of the loop.

 
Figure 11. Connection diagram of passive optoelectronic detectors

Consider the characteristics of the loop in various modes of operation and events. The voltage characteristic between "power supply" and "ground" is shown in Fig. 12.

Figure 12. Current-voltage characteristics of the power-ground loop with optoelectronic detectors

In the "norm" mode, the "power" and "ground" contacts have 13.4 volts, the current consumption is 34 mA. When an alarm is triggered, the current drops to a value of 26 mA for the period of exposure of the violation object to the detector – t _v, the voltage does not change.

The relationship is between "SHS1" and "earth", shown in Figure 13.

Figure 13. Voltage characteristics of the SHS1-ground loop with acoustic detectors

When arming, 15.4 volts and a current of 4 mA are set between "SHS1" and "ground", while the current threshold is from 2.9 to 5.8 mA. When the signal breaks, an alarm is issued, the current becomes 0, and the voltage at the contacts is 19.4 volts.

Development of a program for the study of threshold detectors

A program in the C# programming language has been developed to collect and analyze the electrical parameters of threshold detectors. The choice of C# as a programming language for developing a program for studying the electrical parameters of threshold detectors was due to a number of advantages of this language and the .NET platform. These advantages include reliable integration with the Windows operating system, high performance, access to modern libraries and opportunities for further expansion of the project. C# is the key language of the platform.NET, which provides many tools for application development. Most threshold detectors and other equipment are integrated with the Windows operating system, which makes C# and .NET is an ideal choice for creating programs designed to work with such equipment. C# combines the expressiveness of modern programming languages with the rigor and reliability of typing. This allows you to quickly develop complex applications with reliable error control at the compilation stage, which is critical for hardware-related tasks. Platform.NET provides developers with access to a variety of libraries and frameworks, which simplifies integration with various equipment, including threshold detectors. C# programs are characterized by high performance due to Just-In-Time compilation, as well as optimizations provided by the .NET platform. For tasks related to rapid data collection and analysis, this can be critical. Creating a program in C# makes it easy to scale a project by adding new functions or integrating with other systems. This provides a long-term perspective for the developed application.

The developed program consists of three main components: user interface (Windows Forms), data collection module (SerialPort), data analysis module.

Let's give a simplified representation of the developed components in the form of fragments of program source codes, while the real application has more advanced functionality and description, which is beyond the scope of this article.

Let's analyze the code related to the user interface on Windows Forms:

using?System;
using?System.Windows.Forms;
public?class?MainForm?:?Form
{
private?Button?analyzeButton;?//?Объявляем?кнопку?для?анализа
private?Label?resultLabel;?//?Объявляем?метку?для?отображения?результатов
//?constructor of the main form of the application
public?MainForm()
{
analyzeButton?=?new?Button();?//?Инициализируем?кнопку
analyzeButton.Text?=?"Start";?//?Задаем?текст?на?кнопке
analyzeButton.Click?+=?OnAnalyzeButtonClick;?//?Подписываемся?на?событие?нажатия?кнопки
resultLabel?=?new?Label();?//?Инициализируем?метку
resultLabel.Text?=?"Подключите?извещатель?и?нажмите?'Start'";?//?Задаем?начальный?текст?метки
Controls.Add(analyzeButton);?//?Добавляем?кнопку?на?форму
Controls.Add(resultLabel);?//?Добавляем?метку?на?форму
}
//?Обработчик?события?нажатия?на?кнопку?analyzebutton
private?void?OnAnalyzeButtonClick(object?sender,?EventArgs?e)
{
//?cod?analysis
}
//?ТочТочвходввходприприпри Application
public?static?void?Main()
{
Application.Run(new?MainForm());?//?Запускаем?главную?форму?приложения
}
}

In this code, we create a simple graphical interface based on Windows Forms. The key elements are a button to start the analysis process and a label on which the results or messages for the user will be displayed.
1) MainForm inherits from the Form class, which makes it a window form in Windows.
2) In the MainForm constructor() we initialize the button and label, set them the appropriate properties and add them to the form.
3) The OnAnalyzeButtonClick method is a handler for the button click event.
4) In the Main method, the main form of the application is launched, which is the entry point to our application on Windows Forms.

Next, we will analyze the code that relates to the data collection module via the SerialPort interface:

using?System.IO.Ports;
public?class?DataCollector
{
public?string?CollectData()
{
using?(SerialPort?port?=?new?SerialPort("COM3",?9600))
{
port.Open();?//?Открываем?соединение?с?COM port
string?data?=?port.ReadLine();?//?Читаем?строку?данных?из?COM port
port.Close();?//? Closing the? connection
return?data;?//We return the calculated data
}
}
}

1) using System.IO.Ports; – a directive that connects a namespace containing classes for working with serial ports, such as COM ports.
2) The DataCollector class is designed to collect data from a COM port. It has one method – CollectData.
3) The CollectData method performs the following operations:

• • using (SerialPort port = new SerialPort("COM3", 9600)) – creates a new SerialPort object for communication via a COM3 port with a transmission rate of 9600 baud. The using keyword guarantees that the resources occupied by the port will be correctly released after the completion of work with it (that is, closing the port).
  • port.Open(); – opens a connection to a COM port. If the connection cannot be opened (for example, because the port is already being used by another program), an exception will be generated.
  • string data = port.ReadLine(); – reads a string of data from the COM port. This method will wait for data to appear on the port until it encounters a newline character or a timeout expires.
  • port.Close(); – closes the connection to the COM port. This is an important step that frees up the port for other processes or programs.
  • return data; – returns data read from the port.

This code provides basic functionality for reading data from a COM port. In a real application, additional port settings, error and exception handling, as well as more complex data reading mechanisms are used.

And in conclusion of this paragraph of the article, we will analyze the details of the implementation of the data analysis module in a simplified scenario.

public?void?OnAnalyzeButtonClick(object?sender,?EventArgs?e)
{
DataCollector?collector?=?new?DataCollector();
string?rawData?=?collector.CollectData();
//?conversion of? and?analysis of? Data
string?analyzedData?=?rawData;
resultLabel.Text?=?$"Results of the analysis:?{analyzedData}";
}

This method responds to the event of clicking the analyze button, and that's what happens step by step:

• • public void OnAnalyzeButtonClick(object sender, EventArgs e) – declaration of the method that will be called when the button is clicked. Two parameters are passed here: sender (the sender of the event, in this context it is a button) and e (the arguments of the event, which, in this case, are not used).
  • DataCollector collector = new DataCollector(); – creates a new instance of the DataCollector class, which is responsible for collecting data from the COM port.
  • string rawData = collector.CollectData(); – the CollectData method of the created collector instance is called to collect data from the COM port. The received data is stored in the RawData variable.
  • resultLabel.Text = $"Analysis results: {analyzedData}"; – displays the results on the resultLabel label, which is presented on the GUI.

In general, this method demonstrates the basic logic of collecting and displaying data from the COM port.

Conclusion

In conclusion, it can be noted that the results of the study of threshold detectors using a stand and developed software demonstrate the principles of operation of security and fire alarm systems based on monitoring of currents and voltages of the alarm loop. It was found that during the normal operation of the system, when the SHS is closed, the current strength is maintained at a certain level. When a loop break occurs, the current drops to zero, which signals a violation in the system. Similarly, with a short circuit of the SHS, the current increases, which leads to disconnection of the loop and activation of the alarm signal.

The results of this study not only provide valuable information about the characteristics and operating modes of alarm loops, but also emphasize the importance of maintaining currents and voltages within the set parameters. Going beyond these limits may indicate potential violations or malfunctions in the system.

In the light of these results, we see significant potential for further development of this field, especially with the use of high-performance computing systems ^[13,14]. These systems will allow you to quickly and efficiently process a large amount of data on the state of the SHS, as well as use advanced algorithms to predict and prevent possible malfunctions. As a result, such an approach can significantly increase the reliability and efficiency of security and fire alarm systems, providing a higher level of security at protected facilities.