Summary: Effective application of electrical fire systems significantly reduces the occurrence of electrical fires within buildings, while ensuring safety and quality. With the advancement of related technologies in our country, an increasing number of complex electrical technologies and equipment are being applied in building circuits, raising the probability of electrical fires and having a profoundly negative impact on the positive function of buildings and the safety of users. The application of LoRa wireless communication technology in electrical fire monitoring systems can significantly reduce the probability of electrical fires and achieve the goal of preventing them. This wireless communication technology has a long transmission distance, good wall-penetrating capabilities, and due to its low power consumption, it can be effectively used in electrical fire monitoring systems. Therefore, the main focus is on the composition, principles, and internal hardware and software design of electrical fire systems, further elaborating on the design measures for electrical fire monitoring systems.
Keywords: LoRa; Wireless Communication Technology; Electrical Fire Monitoring System
I. Introduction
With the advancement of science and technology in our country, the electrical wiring inside buildings has become increasingly complex, and the complexity of the equipment within the electrical circuits has also significantly increased. On one hand, this complex electrical wiring provides convenience for both residential and production activities. On the other hand, it has notably increased the likelihood of electrical fires. Therefore, the application of electrical fire monitoring systems is crucial. These systems can monitor the temperature, leakage, and magnitude of leakage current in the electrical circuits, thus issuing early warnings for potential fire hazards. Traditional electrical fire monitoring systems often employ CAN bus communication technology, which, under the current complex electrical circuit conditions, faces challenges such as difficult wiring, high construction costs, and limited hardware performance. Therefore, during the subsequent development of electrical fire monitoring systems, it is important to prioritize wireless communication technology and communication distance requirements. This approach will enhance the operational quality of the systems and reduce the likelihood of electrical fires.
II. Composition and Principle of Electrical Fire Monitoring System
The electrical fire monitoring system based on LoRa wireless communication technology primarily consists of temperature sensors, leakage current sensors, electrical fire detectors, wireless transmission systems, and the main monitoring system. The main application principle of this electrical fire system is that if there is a short circuit or leakage in the electrical circuit, the electrical fire detector can collect data on the temperature and leakage current in the circuit through temperature and current sensors. After processing the data, it is transmitted to the main electrical fire monitoring system. If the temperature or leakage current of the circuit exceeds the system's preset warning threshold, the main control chip in the detector can transmit the alarm information to the main control system and display the alarm value in real-time. During the design of the electrical fire monitoring system, it is advisable to place good wireless transmitter chips inside the detector and within the main monitoring system, allowing the detector to also transmit alarm information to the on-duty personnel via LoRa wireless communication technology, and clearly display the warning location and data, thereby laying a solid foundation for the on-duty personnel to implement effective control measures. Moreover, under the background of China's development in information technology and the internet, the application of big data technology and intelligent control devices in electrical fire monitoring systems is possible. The application of big data technology can collect and comprehensively analyze data on frequently occurring parts exceeding the warning threshold, enabling the on-duty personnel to consider the lifespan and quality of the equipment through data analysis, and to replace and repair equipment that does not meet monitoring requirements in a timely manner. This not only improves the operation quality of the electrical fire monitoring system but also effectively reduces the probability of electrical fires. The application of intelligent devices in electrical fire monitoring systems can effectively ensure the intelligent processing of abnormal data, thereby significantly enhancing the application quality and value of the electrical fire monitoring system.
Internal hardware design measures for electrical fire monitoring system
Microcontroller Unit
During the hardware design process of electrical fire monitoring systems, the main content includes microcontroller units, signal acquisition paths, communication interfaces, and wireless communication circuits. The primary goal of these hardware devices is to ensure that data signals are accurately collected and promptly transmitted to the main electrical fire monitoring system, thereby reducing the probability of electrical fires and minimizing the negative impacts on production and life after an electrical fire occurs. When designing the microcontroller units for electrical fire monitoring systems, the main choice is 32-bit microcontrollers based on the ARM Cortex-M core, featuring a 64KB internal system memory. Their advantages include high-speed operation memory, which enables the rapid transfer of data information, and the ability to store certain warning messages. The chip operates at a voltage of 2-6V and can work below 85°C, thus requiring a low working environment, low power consumption, fast computation speed, and high stability due to its simple structure. Designers can use this microcontroller unit to set different control modes according to actual living and working needs, thereby meeting the diverse operational requirements of electrical fire monitoring systems. However, there are certain drawbacks to the application of this microcontroller unit, such as the inability to store data for a long time. Therefore, during the data collection and transmission process using this microcontroller unit, technicians can set up certain information storage units around the microcontroller unit to better play the positive role of data anomaly monitoring and the operation of the electrical fire monitoring system. In the information storage units set, a regular data cleaning mode should be set, which can effectively extend the service life of the information storage unit, typically setting it for every three months or six months.
Signal Acquisition Circuit
The main contents of the signal acquisition circuit include signal sampling loops, operational amplifiers, reference power supplies, voltage followers, and signal filtering circuits, among others. Different circuits operate in various modes and with different objectives. For instance, the main operating mode of the temperature measurement sampling loop circuit is to measure the internal circuit's operating temperature through circuit design, thereby transmitting the relevant temperature data to the microcontroller unit to enhance its control and early warning capabilities over temperature. The current sensor primarily operates to monitor the magnitude of short-circuit or leakage currents in a timely manner, passing the monitored data to the signal acquisition circuit to quickly transmit abnormal data to the main control unit, achieving timely early warning. The specific operating mode involves forming a sampling loop with voltage dividers, switching transistors, and temperature sensors, followed by the voltage follower implementing the buffering and isolation stages. This not only achieves high input resistance and low output resistance but also ensures that the circuits between stages do not interfere with each other, while also reducing the interference of voltage on the temperature signal acquisition, positively impacting the accuracy of signal collection and transmission. During data collection, the microcontroller unit controls the switching transistor to allow the voltage signal generated by the temperature sensor to directly enter the filtering circuit. After reducing interference and amplification, the signal is connected to the microcontroller unit for data processing, fully monitoring the temperature. The working principle of the signal acquisition circuit is to collect information technology and then filter the data based on predefined operating modes. Abnormal data is transmitted using amplification methods, and during transmission, efforts are made to reduce interference from external factors to ensure the accuracy and reliability of the data received by the microcontroller unit. This maximizes the application advantages of data while reducing the computational space occupied during data collection, improving the quality and efficiency of the microcontroller unit's control. In addition to applying temperature-measuring electrical fire detection sensors, during system design, technicians can also use arc-type electronic fire detection sensors. These sensors can prevent fires caused by arc energy and provide comprehensive monitoring of arcs. When using these detectors, technicians can install them at the end of distribution lines, effectively improving the monitoring of arc occurrences and thus reducing the probability of fire accidents. Currently, the quality and level of arc-type electrical fire detection sensors in China are relatively low and cannot fully meet the fire prevention requirements of most buildings. Therefore, when selecting arc-type electrical fire detection sensors, it is essential to introduce detection methods and sensors to improve the quality of arc detection, strengthen auxiliary monitoring, and ensure the effective operation of arc-type electrical fire detection sensors.
(3) Communication Interface
Data processed by the microcontroller unit is transmitted via communication interfaces to wireless communication devices. During the design of communication interfaces, attention should be given to the connection between the wireless communication device and the microcontroller unit, and the design of impedance matching functions should be considered to effectively reduce and eliminate signal reflections during data transmission. For example, pins can be set as reset pins to initialize parameters and ensure that low level is effective. A good synchronous serial interface should also be set up to ensure the quality and efficiency of data transmission between the wireless communication device and the microcontroller unit. The design process of the communication interface mainly consists of the chip resistor array and the connection part between the wireless communication and control units. Therefore, the application of the communication interface is not only for data transmission but also to mitigate the adverse effects of external factors on data quality. The use of the chip resistor array can effectively reduce high-frequency signal reflections and lower the distortion of transmitted data, thus better achieving the goal of data transmission between the microcontroller unit and the wireless communication circuit.
(4) Wireless Communication
The design of wireless communication circuits for electrical fire monitoring systems can be divided into transmission and reception circuits. The communication between the fire detection device and the main monitoring system utilizes LoRa-based wireless data transmission technology. Compared to wired communication circuits, wireless circuits have higher requirements for data transmission integrity, as they are more susceptible to interference. Any negative impact on data transmission could lead to misjudgment by on-duty personnel regarding the equipment's status, ultimately increasing the likelihood of electrical fires and adversely affecting the quality of work. When selecting data transceivers, attention should be given to integration, low power consumption, and multi-frequency bands to achieve long-distance communication while reducing external interference during transmission, thereby ensuring data quality and efficiency. The crystal oscillator circuit provides timing signals to the system, forming the transceiver circuit through a dual-matching loop, thereby enhancing the wireless communication's interference resistance and reliability. In the design of the transmission circuit, data must be filtered to reduce the interference from external high-frequency signals, thereby lowering the signal-to-noise ratio. The C28 and L8 form a series resonance circuit, while other resistors form two parallel resonance circuits, allowing for adjustment of internal electronic component parameters based on different communication frequencies during information transfer, ensuring optimal data transmission. In designing the reception circuit, emphasis should be placed on filtering out signals outside the communication frequency range. During operation, the input wireless signals are converted to acoustic signals for transmission on the medium surface, and at the output, these acoustic signals are converted back to wireless signals for reception and transmission. The design process can utilize the SX1278 transmitter chip, which offers high integration, low power consumption, multiple frequency bands, enabling long-distance transmission tasks while maintaining strong interference resistance. This chip also has high sensitivity, meeting the vast majority of requirements for electrical fire monitoring systems' operation and data transmission. During its use, attention should be given to the application of accompanying equipment to ensure stable power supply, enabling the chip to fully exert its positive effect in actual operation, enhancing data transmission interference resistance and stability.
Four: Internal Software Design Measures for Electrical Fire Monitoring System
(1) Data Collection Software Design
The design goal of the data collection software is to enable hardware devices to collect data. Currently, a variety of programming languages can be applied in data collection software design, such as C, Java, and web scraping languages. Generally, C language is better suited to meet the design requirements of electrical fire monitoring system software. During the operation of the electrical fire monitoring system, the data collection software can affect devices like temperature sensors, current sensors, and electrical fire detectors. It collects relevant data and signals through sensors, while the software should also have good data storage capabilities. After powering on, the software should first perform initialization operations, adjusting data and parameters to the optimal data collection state, such as resetting the microcontroller and the detector. Additionally, clear the screen. After initialization, send start commands to various sensors. Once the sensors collect the relevant data, compare it with the internal early warning values of the detectors. If it doesn't exceed the threshold, repeat the data collection and comparison. If it does exceed the threshold, issue an alarm, display the current values, and upload the data. During data upload, send data bundled together to significantly reduce transmission volume, which is highly beneficial for data reception and usage. Throughout the software design process, ensure the software maintains the accuracy of the monitored current information. Besides hardware approaches, technicians can set up data detection on the software level, checking data packets sent at the same time at least three times. This method effectively improves the accuracy of the software's alarm function, positively impacting the reduction of operational errors in the electrical fire detection system and significantly enhancing the quality of the electrical fire monitoring system's application.
(2) Data Transmission Software Design
Data transfer software should be designed with three operating modes: wake, sleep, and normal. The sleep mode corresponds to the mode before the data collection software starts working, while wake and normal modes are activated when the relevant data information exceeds the preset threshold. The corresponding operating mode is selected through specific instructions in the software, and the data transfer software should initialize timers and system time to ensure synchronization with the data collection software. After selecting the operating mode from the registered parameters, the software sends data wirelessly, enters a sleep mode after each successful send to wait for the next command, significantly reducing power consumption. The design goals of the data transfer software mainly include three points: the quality of data transfer, the speed of data transfer, and the application of data after transfer. In the design process, in addition to ensuring the application quality of the data transfer software through register settings, to improve the quality of data transfer, data encryption and decryption, bundling, or sub-packaging modes can be set at both ends of the data transfer software using inverse reaction. This not only significantly enhances the integrity and high quality of data transfer but also effectively increases the speed, playing a positive role in meeting data transfer objectives. Moreover, during the operation of the data transfer software, there may be issues where the operating mode does not match the data collection mode, so a well-set software auto-start mode should be established to restart promptly when discrepancies are found, effectively improving the matching degree between the data transfer software and the data collection software, ensuring the stable and high-quality operation of the overall electrical fire monitoring system.
(3) Monitoring System Software Design
Designers should ensure a robust design for both monitoring software and the main system, allowing for data transmission and reception via LoRa technology through customizable communication protocols. Additionally, the system should directly employ LoRa technology for data reception and transfer. For instance, the monitoring host can utilize modular design to ensure real-time display of alarm and fault information on the surveillance screen. The human-machine interface should incorporate a touchscreen to enhance interaction between staff and the monitoring system, facilitating smooth setup, entry, and exit functions. Moreover, designers can set up portable electrical fire monitoring systems, which can promptly alert staff on their information terminals if monitored parameters exceed thresholds during system operation. This also enables the system to play a positive role in electrical fire monitoring. The main monitoring system, in addition to supervising and transmitting alarm information and functioning as an alarm, should also have a comprehensive inspection capability. By analyzing historical data records, it can adjust alarm thresholds to ensure they remain within reasonable intervals, thereby improving the system's predictive ability regarding electrical fires and enhancing the overall quality and efficiency of the fire monitoring system. Since implementing big data technology within the electrical fire monitoring system is challenging, it should be integrated into the main monitoring system or portable management devices for staff. Big data technology can then conduct large-scale data analysis and calculations on abnormal data points, such as detecting overheating in a specific location within the electrical fire monitoring system. After big data analysis reveals a high frequency of overheating incidents at that location, indicating that traditional electrical wiring no longer meets safety requirements, the analysis results can be promptly transmitted to on-duty managers. Following an inspection, the managers can replace the electrical wiring in that area, significantly reducing the likelihood of electrical fires and positively impacting the quality and efficiency of the fire monitoring system.
(4) Wireless Communication
Design Considerations for Electrical Fire Monitoring Systems First and foremost, it is crucial to avoid any negative impact on residents' normal lives from the application of the monitoring system. Therefore, during the design process of a wireless communication-based electrical fire monitoring system, technicians should treat the overall fire warning and alarm system as an independent subsystem, which also aims to reduce interference factors in wireless communication signal transmission. The electronic signals emitted by the electrical fire monitoring system can only represent potential hazards within the electrical system and cannot directly determine the occurrence of an electrical fire. Therefore, during the design process, the electrical fire monitoring system should be integrated with the automatic fire alarm system to achieve the early warning goal and assist staff or residents in properly handling fire situations, thereby improving the quality and efficiency of fire prevention work. It is essential to ensure the stability of power supply during the alarm of the electrical fire monitoring system; otherwise, residents' lives may be affected due to false triggering. Therefore, it is necessary to ensure the stable operation of wireless communication and the electrical fire monitoring system. Secondly, during the design process of wireless communication-based electrical fire monitoring systems, it is important to pay attention to the rational application of protective devices. To ensure that wireless communication devices can play a positive role in both fire situations and early warnings, the wireless communication devices should be protected, which includes sufficient protection of the wireless communication interfaces, microcontrollers, and data transmission modules. Insulating, waterproof, and fire-resistant materials should be set externally to ensure that the wireless communication function can operate normally even in harsh conditions. This not only effectively improves the quality and efficiency of electrical fire early warnings but also significantly enhances the stability of wireless communication, playing a positive role in reducing factors affecting signal transmission. Lastly, it is necessary to set up good emergency response software functions. This software is primarily used in cases where there are failures in wireless communication devices or microcontrollers, ensuring that both software and hardware devices can be restarted promptly. The software needs to implement the disconnection of communication connections between sensors and related equipment to reduce the occurrence of abnormal or erroneous phenomena after restart. By considering these precautions, the application quality of the electrical fire system can be effectively improved, playing an extremely positive role in enhancing building usage experience, ensuring the health and safety of residents, and maintaining the normal rhythm of residents' lives.
Ankorree Electrical Fire Monitoring System
(1) Overview
The Acre1-6000 Electrical Fire Monitoring System is a fully digital, independently-operated system developed by Ankoer Electrical Co., Ltd. in accordance with the current national standards. It has passed the fire product testing certification by the National Fire Product Quality Supervision and Inspection Center and has also successfully undergone rigorous EMC electromagnetic compatibility tests. This ensures the safe and normal operation of the series in low-voltage distribution systems. The system is now in mass production and widely used across the country. By collecting and monitoring signals such as residual current, overcurrent, overvoltage, temperature, and fault arcs, it achieves early prevention and alarm of electrical fires. It can also disconnect the distribution circuits with excessive residual current, temperature, and fault arcs upon necessity. Additionally, it can meet the needs of data exchange and sharing with the AcreIEMS corporate microgrid management cloud platform or fire automatic alarm systems, as per user requirements.
Application Scenarios
Applicable to intelligent buildings, high-rise apartments, hotels, restaurants, commercial buildings, industrial and mining enterprises, key fire protection units of the state, as well as the fields of petrochemical, cultural and educational health, finance, and telecommunications.
(3) System Architecture
(4) System Functions
Monitoring devices can receive residual current and temperature information from multiple detectors. When an alarm is triggered, it emits sound and light alarm signals, with a red "ALARM" indicator light on the device and the display indicating the location and type of the alarm. It records the time of the alarm. The sound and light alarm continues until the "RESET" button on the device or the "RESET" key on the touch screen is pressed remotely to reset the detector. The sound alarm signal can also be manually eliminated using the "Mute" key on the touch screen.
When the monitored loop triggers an alarm, the control output relay closes to control the protected circuit or other equipment. Upon alarm clearance, the control output relay releases.
Communication Fault Alarm: When a communication failure occurs between the monitoring equipment and any connected detector, or when the detector itself fails, the corresponding detector on the monitoring screen will display a fault alert, and the yellow "FAULT" indicator on the device will light up, along with an alarm sound. Power Supply Fault Alarm: In the event of a failure in the main power supply or the backup power supply, the monitoring equipment will emit an audible and visual alarm signal, display fault information, and allow access to a specific interface for detailed information and to deactivate the alarm sound.
In the event of residual current, over-temperature alarms, communication, or power failures, the alarm location, fault information, and alarm time are stored in the database. Similarly, records are made when alarms are lifted and faults are rectified. Historical data provides multiple convenient and rapid search methods.
(5) Configuration Solutions
Six, Conclusion
In summary, applying LoRa wireless communication technology to electrical fire monitoring systems significantly enhances the quality and efficiency of the monitoring operations. This approach boasts low construction costs, long data transmission distances, and low energy consumption. Consequently, it not only meets the requirements for the construction and operation of electrical fire monitoring systems but also satisfies users' needs for both living and production. Tests have shown that the signal transmission performance of such systems is reliable, with accurate data display within the monitoring systems. This enables practical application in both production and daily life, thereby positively promoting the quality of life and production for our nation's residents.
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