Design of Network Monitoring System for Power Supply of Programmable Switch for Local Area Network

The application research of program-controlled switch power network monitoring system is increasingly concerned by people in this field. At present, the commonly used power monitoring system is generally a large-scale monitoring system. This system uses a 2Mbit/s port to transmit information, has high requirements for transmission lines, and occupies optical cable resources. Due to the all-round monitoring of the program-controlled switch power supply, the signal collection volume is very large, its structure is complex, the investment cost is high, and the technical level of the staff is also high. It is suitable for large-capacity computer rooms, but not for power monitoring of many rural small-capacity computer rooms. Based on the study of the power monitoring system of large program-controlled switches, this paper proposes a new type of program-controlled switch power network monitoring system suitable for small-capacity computer rooms.

System hardware circuit design

The monitoring system consists of a field monitor, a transmission network, and a central monitor. The field monitor has functions such as signal collection, judgment, transmission, alarm, and reception control; the central monitor is the control center of the system; the transmission network uses the lines and switching equipment of the telecommunications network.

The on-site monitor is the most important and basic component of the communication power network monitoring system in this article. One unit must be placed in each monitored room. The on-site monitor is composed of a single-chip control system and various sensors and control components. The operating parameters and operating status of all monitored objects are monitored, recorded, judged and alarmed by the on-site monitor. The alarm of the on-site monitor is transmitted by telephone line. It can actively dial to transmit alarm information to the monitoring center, and can also call the person in charge to make a voice alarm. Therefore, the on-site monitor can also work independently without relying on the central monitor. The principle block diagram of the on-site monitor is shown in Figure 1. The on-site monitor is a single-chip control system, which consists of a DC/DC power supply module, dialing and DTMF transceiver circuit, voice circuit, general collector, control circuit, etc.

The transmission network between the central monitor of the monitoring system and each on-site monitor is connected by dialing using the existing telecommunications telephone network. The system networking diagram is shown in Figure 2.

The central monitor consists of a host, display, speaker keyboard, mouse, printer, interface circuit and other parts. The functions of the central monitor are: receiving the alarm information of the on-site monitor, forming screen display, sound alarm, and storing fault information; sending control information to the on-site monitor; setting the parameters of the on-site monitor; viewing the on-site power supply parameters, and also has the management functions of querying, counting, printing, and reporting historical faults.

1 Single-chip system design

The field monitor is controlled by MCS51 series single-chip microcomputer. The principle block diagram of the single-chip microcomputer system is shown in Figure 3. The CPU chip uses 8032 single-chip microcomputer, the peripheral expansion circuit uses 74HC373 as address latch, the program chip uses 27C256, and the external memory uses 62256. The 74HC138 decoder is used as address decoding to select one 74LS374 and two 8255s respectively. The 74LS374 is used as the control indicator output. 8255 (1) is used as analog input control, and 8255 (2) is used as switch input and output control.

2 AC and DC current collection For

the collection of AC and DC current, the current signal must first be converted into a DC voltage signal of 0~5V through an AC and DC transformer, and then converted into a voltage signal (0~10V) that meets the requirements of the A/D converter (AD574A) through voltage conversion. The circuit principle block diagram is shown in Figure 4.

3 Digital signal acquisition circuit

The acquisition of digital signals is firstly done by various sensors such as smoke detectors, infrared detectors, water immersion detectors, etc., which convert the measured physical quantity into a switch quantity electrical signal, and then isolate and level-convert it, output it to 8255A, and then read it by the single-chip microcomputer. The circuit schematic is shown in Figure 5.

System software design

The system software mainly includes two parts: the central monitor software design and the field monitor single-chip computer software design. The

central monitor host Software is programmed with Delphi and runs under Windows98, 2000, XP, and NT operating systems. The program adopts modular design and uses Dynamic link Library programming. The serial port communication adopts multi-threading (serial port interruption), and the database adopts SQL database system.

The software function of the central monitor interface circuit mainly completes the process of communicating with the central monitor microcomputer. The central monitor interface circuit communicates with the microcomputer through the RS232 interface. If there is an alarm from the field monitor, the interface circuit sends an alarm message to the microcomputer; if the central monitor sends a command to the field monitor, the interface circuit receives the command information from the microcomputer; if neither of the above two situations occurs, the interface circuit sends a handshake message to the microcomputer. The interface circuit RS232 serial port receiving and sending information program flowchart is shown in Figure 6.

The field monitor software is written in MCS51 assembly language, which consists of an initialization program and an interrupt service program. In the initialization program, timer T0 is defined as a 6.25ms interrupt, that is, the interrupt service program is executed every 6.25ms, and all operations are placed in the interrupt service program. After the main program is initialized, no actual operation is performed. The interrupt service program of timer T0 mainly includes the following subroutines: indicator light timing subroutine, signal acquisition subroutine, fault judgment subroutine, fault alarm subroutine, control function subroutine, parameter setting subroutine, parameter reading subroutine, active monitoring subroutine, and automatic patrol subroutine. System

reliability design

In the actual field environment where the power supply is running, there are often various interferences such as power supply fluctuations, impacts, and electromagnetics. In order to ensure that the single-chip microcomputer program does not "freeze", an automatic reset circuit is used when designing the single-chip microcomputer system. The circuit principle is shown in Figure 7. DS1232 in this circuit is the "watchdog", which can automatically reset the CPU (8032) when the program is not running, so that the single-chip microcomputer can start running again. In the figure, S1 is a manual reset button.

In order to test the functions of the system, the actual on-site environment was simulated in the laboratory, and the centralized monitoring function, parameter setting function, parameter reading function, automatic test function, query statistics function, decentralized notification function and other functions were tested. The results show that all the functions designed by the system can be realized. In addition, extreme situation tests were also conducted. For example, when 10 on-site monitors alarmed at the same time, the system could ensure that each alarm information was transmitted to the monitoring center in sequence without loss of information; two on-site monitors continuously alarmed for more than 12 hours, and the system worked normally; when the alarm information database reached 20,000 alarm information, the system still worked normally, and the query time was within 30 seconds.

Conclusion

The system is highly reliable, convenient and practical, and low-cost. The comprehensive cost of each monitoring point (computer room) is about 8,000 yuan, while a large-scale monitoring system requires about 100,000 yuan, which solves the problem that power supply monitoring in small computer rooms cannot be realized due to large investment.