Design of hardware circuits for Programmable switch systems in LAN

Program-controlled switches are quite commonly used. So I studied the network monitoring system design of the power supply of program-controlled switches for LAN. I would like to share it with you here and hope it will be useful to you. The Application of program-controlled switch power supply network monitoring system has been paid more and more attention by people in this field. Currently, the commonly used power monitoring system is generally a large-scale monitoring system. This system uses 2 Mbit/s ports to transmit information, which has high requirements on transmission lines and occupies optical fiber resources. Because it comprehensively monitors the power supply of the programmable switch, the signal collection volume is very large and its structure is complex, high investment costs.

System hardware circuit design

The monitoring system consists of field monitor, transmission network and center monitor. The field monitor provides functions such as signal collection, Judgment, sending, alarm, and receiving control. The center monitor is the control center of the system, and the transmission network uses the lines and exchange devices of the telecommunication network.

The field monitor is the most important and basic unit in the Communication Power Network Monitoring System in this article. Each monitored data center must have one. The field monitor is composed of a single-chip microcomputer control system and various sensors and control components. The operation parameters and status of all monitored objects are monitored, recorded, judged, and warned by the field monitor. On-site monitor alarms are transmitted over telephone lines. They can actively dial, send alarm information to the monitoring center, and call the responsible person for voice alarms. Therefore, the on-site monitor can also work independently without relying on the central monitor. The field monitor is a single-chip microcomputer control system, which consists of DC/DC power module, dialing and DTMF code receiving and sending circuit, voice circuit, General collector, control circuit, etc. The transmission network between the monitoring system's central monitor and various on-site monitors is connected by dialing through the existing Telecom telephone network.

The Central Monitor consists of a host, a display, a speaker keyboard, a mouse, a printer, and an interface circuit. The central monitor function is to receive alerts from the on-site monitor, form screen display, sound alarm, and store fault information; send control information to the on-site monitor; set parameters of the On-Site Monitor; view power parameters of the programmable switch, it also provides management functions such as querying, counting, printing, and reporting historical faults.

Single Chip Microcomputer System Design

The on-site monitor is controlled by MCS51 series single-chip microcomputer. The CPU chip uses 8032 single-chip microcomputer, and the peripheral expansion circuit uses 74HC373 as the address lock memory. The program chip uses 27C256 and the external memory uses 62256. The 74HC138 decoder is used as the address decoding. One 74LS374 and two 8255 and 74LS374 are selected as the control indicators respectively. 82551) as analog input control, 82552) as Switch Input and Output Control.

AC/DC current acquisition

AC/DC current acquisition, first through the AC/DC Transformer to convert the current signal to 0 ~ 5 v dc voltage signal, and then converted to A voltage signal that meets the requirements of A/D converter AD574A) 0 ~ 10 V ).

Digital Signal Acquisition Circuit

The digital signal is collected by a variety of sensors, such as smoke detectors, infrared detectors, water immersion detectors, etc. The measured physical quantity is converted into a switch electrical signal, then the isolation and level conversion are performed, and the output is 8255A, it is then read by the microcontroller.

System Software Design

The system software mainly includes the software design of the center monitor and the software design of the single chip microcomputer of the field monitor. The host software of the central monitor adopts Delphi programming and runs in Windows 98, 2000, XP, and NT operating systems. The program adopts modular design and uses dynamic link library programming, multiple Threads are used for serial communication), and SQL database is used for databases.

The software function of the center Monitor interface circuit mainly completes the communication process with the microcomputer of the center monitor. The interface circuit of the central monitor communicates with the microcomputer through the RS232 interface. If there is an on-site monitor alarm, the interface circuit sends the alarm information to the microcomputer; if the center monitor sends the command to the on-site monitor, the interface circuit receives the command information from the microcomputer; if neither of the above conditions occurs, the interface circuit sends the handshake information to the microcomputer.

The on-site monitor software is compiled by MCS51 assembly language and consists of the initialization program and the interrupt service program. In the initialization program, the timer T0 is defined as a Ms interrupt, that is, the interrupt service program is executed every ms, and all operations are placed in the interrupt service program, after the initialization of the main program is complete, no actual operation is performed. The interrupt service program of timer T0 mainly contains the following subprograms: indicator timing subroutine, signal collection subroutine, fault judgment subroutine, fault alarm subroutine, control function subroutine, parameter setting subroutine, parameter reading subroutine, active monitoring subroutine, automatic inspection subroutine.

System Reliability Design

In the actual field environment where the power supply of a Programmable switch runs, various kinds of interference such as fluctuations, impacts, and electromagnetic interference often occur. In order to ensure that the single-chip microcomputer program does not crash, an automatic reset circuit is used to design the single-chip microcomputer system. In this circuit, DS1232 is the "watchdog", which can automatically reset CPU8032 when the program is not running.

To detect various functions of the system, simulate the actual environment in the lab, test the centralized monitoring function, parameter setting function, parameter reading function, automatic test function, query statistics function, and distributed notification function. The results show that all the functions designed by the system can be implemented. In addition, an extreme case test was conducted. For example, when 10 on-site monitors trigger alarms at the same time, the system can ensure that the alarms are sent to the monitoring center in sequence, so that the information is not lost; the two on-site monitors continuously trigger alarms for more than 12 hours, and the system works normally. When the alarm information library reaches 20 thousand alarm messages, the system still works normally and the query time is less than 30 seconds.

Conclusion

The system features high reliability, convenience, and low cost. The overall cost of each data center at each monitoring site is about 0.1 million RMB, while that of a large monitoring system is about RMB, this solves the problem that the power monitoring of a Programmable switch in a small data center cannot be implemented due to a large investment.