Design of environmental detectors in outdoor cabinets

With the advancement of smart city information construction, as the hardware carrier of information equipment, the outdoor cabinet has also developed from the past small box, single device, extensive management to the direction of large-scale, highly integrated, fine intelligent management, the number of installations is also increasing, and the difficulty of outdoor cabinetoperation, management and maintenance has also increased. At present, the operation and maintenance management of outdoor cabinets in cities mostly relies on inspection and repair, and managers are faced with various problems such as different types of outdoor cabinets, many management items, complex supervision contents, delayed problem discovery, and insufficient management personnel. This management mode is not only inefficient in dealing with problems, but also ignores the monitoring and management of the most important cabinet for outdoor equipment.

To solve this problem, this paper designs a set of multifunctional detector suitable for outdoor cabinets, which can dett environmental variables such as power supply voltage, current, temperature, humidity, smoke and water level inside the cabinet, and alarm and automatically adjust abnormal situations. The equipment provides an excellent operating environment to ensure equipment safety, and also has the function of Internet of Things data transmission. Internet platform services, so as to achieve the fine monitoring and management of outdoor equipment at the micro level, to provide an efficient management means for maintenance personnel. The system application topology is shown in Figure 1 below:

Through the combination of Internet of Things technology and Internet + technology, integrating detection system, alarm system, remote data transmission system, automatic regulation system, positioning system, and expanding AI fault prediction technology, forming a set of independent and highly intelligent outdoor cabinet monitoring system, so that managers can view the operating environment of outdoor IT equipment in real time, and timely alarm when encountering abnormal conditions. It can automatically adjust abnormal phenomena and upload operating environment data in the cloud. Through AI analysis of environmental data, it can predict the abnormal state of equipment in advance, and make equipment maintenance "unpredictable", so as to realize the progress of managers from passive maintenance to active predictive maintenance.

The detector is mainly composed of STM32 processor, measurement module, communication module, self-regulating output module, alarm positioning module and human-computer interaction module. The system composition is shown as follows:

ST's STM32F105 microprocessor takes ARM Cortex-M3 as the core, uses 32 as the internal bus architecture, integrates rich resources, easy to use architecture and low power consumption characteristics, and has outstanding power efficiency. In standby mode, when the reset circuit is opened, the typical power consumption is only 2μA. The power supply voltage range of 2.0 to 3.6V is suitable for battery powered applications, and has first-class peripheral interfaces including UART interface, IIC interface, Ethernet interface, USB interface, SPI interface, ADC interface, CAN interface, etc. In addition, it also has the advantages of fast processing speed, cheap price, low power consumption and powerful function, which is suitable for this design.

2.1. Measurement module

2.1.1. Design of electrical parameter acquisition circuit

The detector can support 12 AC(0 ~ 220V/0 ~ 40A) AC signal acquisition, 3 DC(0 ~ 100V/0 ~ 10A) DC signal acquisition, designed to use 30 A/D channels, but the STM32 ADC pin is limited, the digital to analog conversion chip AD1556 to perform electrical data scanning acquisition. The AD1556 sends the collected data STM32 through the IIC serial port.

2.1.2. Design of environmental parameter acquisition circuit

The detector can support 4 channels of 0 ~ 100℃ temperature signal acquisition, 4 channels of 0 ~ 100RH% humidity signal acquisition, choose the Swiss Sensirion temperature and humidity digital sensor SHT20, its core uses CMOSens® technology, semiconductor technology and sensor technology integration. The designed temperature and humidity probe has the advantages of high precision, high reliability, high digitalization and high cost performance.

The detector can support smoke detection, multi-stage water level detection, and up to 70 level water level detection. The design adopts smoke sensing maze as the sensor module for smoke detection. Due to its internal infrared tube and optical maze structure, it has the advantages of strong anti-interference, high reliability and low cost, which is very suitable for application in this design. The water level detection using reed tube, float ball and other mature magnetic sensing technology, at the same time has low price, accurate detection, reliable performance and many other advantages.

2.2. Alarm positioning module

By GB/GPS dual-mode positioning module, GPRS module, loudspeaker warning module together constitute detector alarm positioning function, the SKC111 GSM/GPRS+GNSS integrated integration module produced by the well-known domestic manufacturer Tiangong measurement and control SKYLAB, the module is based on MTK2503 scheme design, the function is very powerful, with 4 frequencies: GSM850 / GSM900 / DCS1800 / PCS1900 GSM/GPRS functionality, support GPS/GLONASS/beidou/GALILEO, support the speaker output, developing a simple, cost-effective, suitable for this design.

2.3. Communication output module

The detector can support a variety of external wireless communication means, which uses the characteristics of electromagnetic wave signal can spread in free space for information exchange, with the advantages of no need to erect lines and strong flexibility, the design adopts the mature technical solutions in the industrial Internet of things, including: Le Xin ESP8266 WiFi chip, NORDIC nRF52832 BLE chip, four letter F8913D ZigBee module, simcom SIM7100X 4G module together.

2.4. Adjust the output module

After detecting smoke, water leakage, high or low voltage, high or low current, and high or low temperature and humidity, the detector can protect and adjust the detected cabinet by signal output control, which is designed in the form of isolation circuit + drive output circuit. To achieve this function, the cooling fan, LED warm light, AFG fire bomb, electric control reclosing, anti-countercurrent drainage pump are controlled.

STM32 can be embedded in a total of three common operating systems: μC/OS-II, μClinux, eCos. μC/OS-II is developed on the basis of μC/OS. It is a compact and preemptive multi-task real-time kernel written in C language. It has the characteristics of high execution efficiency, small occupied space, excellent real-time performance and strong expansibility. Compared with Linux, μClinux has the advantages of small kernel, good stability, good portability and powerful network function. eCos is more suitable for deep embedded applications, and its characteristics are flexible configuration, modular design, rich scheduling methods, etc. According to the specific needs of this design, more attention is paid to the compact and real-time operating system, so the choice of μC/OS-II as the operating system is the most appropriate.

The system software design part mainly includes seven important parts: the transplantation of μC/OS-II operating system in timing adjustment, environment detection and collection in cabinet, fault alarm, abnormal self-recovery adjustment, Internet of Things data interaction, Internet data cloud transmission, asset management data platform development and user interface graphic design.

System program design mainly collects the data of multiple sensors inside the cabinet, and compares the data with reasonable environmental indicators. If there is an anomaly, the fault alarm module will alarm, and the abnormal self-recovery adjustment part will control the corresponding adjustment module according to the abnormal situation, and the collected data will be sent through the communication module Internet + technology subcontract. Establish Socket connection with fixed asset management platform data center, and use TCP/IP protocol to exchange data. The real-time data content of the system program will also be transmitted through the Internet of Things technology. WIFI hotspots, BLE ibeacon and ZigBee networking as sub-threads embedded in the system will be connected to the mobile terminal used by the administrator, and maintenance workers can check the user monitoring interface of the APP on the mobile terminal. The outdoor cabinet can be inspected and maintained without opening the cabinet door, and the manager can monitor all outdoor cabinets in the metro area by simply clicking on the platform page, and perform AI analysis and fault prediction for outdoor cabinet faults, so as to achieve centralized and efficient management of outdoor cabinets.

4.1. Monitoring the signal outdoor cabinet

The fixed asset management platform monitors the voltage, current, temperature, humidity, smoke, water level and other information inside the signal machine respectively, and alarms the abnormal situation. Figure 4 shows the environmental data of the equipment at the intersection. According to the system analysis results, the voltage and current result is 0, indicating that the intersection is abnormal in power failure

4.2. Maintenance and management of signal outdoor cabinets

When the data management center predicts that a fault will occur or a fault has already occurred through the detector network data and AI calculation, the fixed asset platform will push the accurate cabinet geographical location information and fault type to the inspection and repair personnel to achieve efficient and refined protection of outdoor cabinets.

As the core controller, this paper realizes a set of outdoor cabinet environment detection equipment through measurement sensor, communication module, alarm module, adjustment output module, etc., combining the Internet of Things technology and Internet + technology, expounds the design process of the system from two parts: hardware and software. Combined with the application of the fixed asset management data platform, the outdoor environment detector in the cabinet can not only monitor the micro-environment parameters such as current and voltage, temperature and humidity, and smoke level in the cabinet, but also give real-time alarm to abnormal situations. It can also control and adjust the output module to self-adjust the internal environment variables, providing a stable operating environment for the equipment. Through the communication module, the data can be uploaded to the fixed asset management data platform, so as to achieve centralized monitoring of the metropolitan outdoor cabinet, efficient management, accurate equipment maintenance, and predictive fault judgment, providing users with a set of low-cost and efficient outdoor cabinet management products, and protecting the safety of the construction of intelligent transportation infrastructure. At the same time, the detector can also be used in building room, security home, smart city and other fields, and has a wide range of application prospects.