Design of UPS Monitoring System Based on SMS Communication

In recent years, communication methods based on public networks have been widely used in industrial remote monitoring. These remote communication means include public telephone networks, Internet networks, and wireless networks. Wireless communication networks do not require transmission lines and can communicate anywhere in the coverage. Obviously, these advantages are unmatched by wired networks.

The GSM (Global System for Mobile Communications) network is currently the most widely used and widely used wireless communication network in China. Therefore, when constructing a remote transmission system, it is possible to fully utilize the existing GSM wireless network without rebuilding the base station.

At present, there are many applications for remote monitoring using SMS (short message service), such as power remote meter reading system, remote hydrological monitoring system, remote monitoring system for remote station, remote environmental monitoring system, remote power distribution monitoring system and other remote information query systems. . SMS is suitable for occasions where data traffic is low, while UPS (uninterruptible power supply) has less status information and fault information data, and SMS transmission is very suitable.

The remote monitoring system introduced in this paper is mainly used to monitor UPS. Because there are fewer UPS faults, if each UPS is equipped with duty personnel, it is obviously a waste of manpower, material resources and financial resources. If it is left alone, if there is a problem, it will not be obtained. Dealing with it in a timely manner can have serious consequences. With the existing wireless network, as long as there is a person on duty in the monitoring center, all UPSs can be monitored, not only can the status information of the UPS be queried at any time, but also the fault information of the UPS can be obtained in time, saving manpower, Material and financial resources.

1 system composition principle and system realization function

1.1 System Composition Principle

The system consists of a monitoring center, on-duty personnel, and remote monitoring points. The monitoring center consists of a PC and a GSM communication module, and only one monitoring center is needed. The remote monitoring point consists of the monitoring object and the monitoring module. The UPS is the monitoring object. The system uses more than 10 monitoring objects. The monitoring module consists of a GSM communication module and a single-chip microcomputer, and each monitoring object requires a monitoring module. The system schematic is shown in Figure 1.

1.2 System implemented functions

The monitoring center has four main functions:

a) Remotely set the monitoring module, such as setting the monitoring module to return data to the SIM card number of the monitoring center;

b) Send a command to remotely query various information of the UPS and receive the returned data;

c) automatically receiving the alarm information returned by the remote monitoring point;

d) Store status information and alarm information of the UPS.

The role of the duty officer is: in the event of a UPS failure, the monitoring module will send the data information to the duty officer in addition to sending the data to the monitoring center. The duty officer can rush to the site in time to repair the UPS and minimize the loss.

The two functions of the remote monitoring point are:

a) Receive the query command sent by the monitoring center and query the UPS, and then send the data returned by the UPS to the monitoring center;

b) The idle time constantly queries the working status of the UPS to determine whether a fault has occurred. If a fault occurs, the fault information is sent to the monitoring center and the duty officer.

1.3 GSM communication module

At present, many GSM communication equipment manufacturers produce GSM communication modules, such as Wavecom's WM02 series and two subsidiaries' TC35 series. The functions and usages of these modules are basically the same. The system used Wavecom's Wismo2c module in the early development, and used Siemens' TC35I module when it was put into use later. Both modules are second-generation wireless dual-band communication modules that comply with the E-GSM900/GSM1800 (or E-GSM900/GSM1900) standard and comply with the AT control commands of GSM 07.07 and 07.05.

2.2 Software Design of Monitoring Center

2.2.1 Frame structure of data transmission

Data transmission needs to follow a certain protocol, that is, to specify the frame structure of the communication. The data frame structure used by this system has the following two categories:

a) The data frame structure of the monitoring center sending data to the remote monitoring point, as shown in Figure 3. Among them: the command type is used to distinguish whether the command sent to the remote monitoring point is a setting command or a query command. If it is a setting command, the start word and the check word are not necessary.

b) The data frame structure of the remote monitoring point to send data to the monitoring center and the duty officer, as shown in Figure 4. Among them: there are 3 types of data returned: the first type is the status information of the returned query; the second type is the confirmation information of the return setting command, there is no start word and check word; the third type is to return the alarm information, if it is an alarm The information is sent to the monitoring center and sent to the duty officer.

2.2.2 Programming of the monitoring center

In this system, the monitoring center is programmed in VB language, and the PC communicates with the GSM communication module through AT commands. Figure 5 is a flow chart of the monitoring center program.

The main program is divided into four parts: an initial setting subroutine, a sending query subroutine, a receiving data subroutine, and a modified user information subroutine by button selection.

The initialization setting subroutine first sends an AT command through the serial port to initialize the GSM communication module of the monitoring center, and then initializes the remote monitoring point. After the initial remote monitoring point command is sent, the program will automatically switch to the receiving data subroutine module, waiting to receive the confirmation message. If the confirmation message is wrong, the initialization command can be resent. The setting of the remote monitoring point is only required once, and it is not necessary to set the software every time.

The send query command subroutine is divided into the query single input and single output UPS subroutine according to the type of the UPS, the three-input and single-out UPS subroutine, and the three-in and three-out UPS subroutine. The main function is to send a query command to the remote monitoring point to obtain the required status information. Similarly, after sending the command, it goes to the receive data subroutine and waits for the data to return.

The Receive Data subroutine is mainly used to receive data returned by the remote monitoring point. The UPS may malfunction at any time. Therefore, the receiving data subroutine is always running without other operations, so that the alarm information returned by the remote monitoring point can be obtained in time. The Receive Data subroutine stores the received useful information into the database as a history.

The Modify User Information subroutine is mainly used to set the user name and password for opening this software to prevent unscrupulous personnel from logging in for destructive operations.

Since each UPS is equipped with a SIM card, the system uses a SIM card to identify the UPS. In this system, the SIM card number is stored in the database in advance, and the UPS can be set and sent to query commands simultaneously by means of a loop, which brings great convenience to the management. The system uses a single byte to read the serial port buffer. If the short message arrives and the system is transmitting data, the short message number is first stored in the array, and when the idle time is received, the short message is automatically read according to the short message number, thereby Achieve the function of group sending and receiving. Since the number of short messages stored by the SIM card is limited, once the data is stored in the database, the program automatically sends a command to delete the short message on the SIM card.

3 System design of remote monitoring points

3.1 Hardware design of remote monitoring points

The remote monitoring point is mainly composed of GSM communication module, single chip microcomputer and UPS. The MCU mainly has two functions: one is to control the GSM communication module to send and receive short messages; the other is to query the working status of the UPS. Since the MCU transmits the TTL level, and the GSM communication module and the UPS transmit the RS-232 level, the level conversion is performed between the MCU and the GSM communication module, and between the MCU and the UPS with the chip MAX232. The hardware schematic is shown in Figure 6.

As can be seen from Figure 6, two serial ports are used in this system, and the AT89S52 has only one serial port. How to solve it? In this system, P3.2 and P3.3 are used to simulate the function of the serial port to solve the problem.

Since the UPS is in doubt when it is idle, it is necessary to store a command for querying the working status of the UPS. Different types of UPS have different commands. If these commands are stored in the program memory, different types of UPS will use different monitoring modules, which reduces the versatility of the monitoring module. In this system, an AT24C04 E2PROM is used. As long as the monitoring center sends a command to query the UPS working status, the remote monitoring point stores these commands in the AT24C04. In this way, the MCU can take these commands from the AT24C04 to query the UPS. That is, the monitoring module can be used for different types of UPS. As for which UPS is used by the monitoring module, it is only necessary to set it through the monitoring center. Obviously, this solution improves the versatility.

The MCU communicates with the AT24C04 via I2C. In addition to the command to query the working status of the UPS, the AT24C04 is also used to store the SIM card number of the monitoring center and the duty officer.

3.2 Software design of remote monitoring points

The remote monitoring point is mainly MCU programming, using assembly language. Assembly language has the advantages of high speed and high efficiency, which can improve the response speed of the system. This system programming is more complicated.

After the program runs, the GSM communication module is first initialized, and then it is determined whether the telephone number of the monitoring center and the command for querying the working state of the UPS have been stored in the AT24C04. If it has already been stored, the information is read out. If there is no such information, no operation is performed, and the monitoring center is sent to send the command settings.

The monitoring center may send commands to the remote monitoring point at any time. Obviously, it is a waste of resources to use the query method to judge whether the short message arrives. Therefore, the system adopts the interrupt mode, that is, when a short message arrives, an interrupt occurs, and the flag is set. Bit. Therefore, after entering the main loop after initialization, the flag bit is first used to determine whether a new short message arrives. If there is a new short message, the short message header is used to determine the short message type; if the short message is set, the corresponding setting is made, and the confirmation information is sent to the monitoring center, and then returns to the main program; if it is the monitoring center The incoming query command queries the UPS status and sends the data returned by the UPS to the monitoring center, and then returns to the main program.

Most of the time, the monitoring center will not send commands, and then there is no need to process new short messages, but turn to query the working status of the UPS. If the UPS has not failed, the returned data is normal. At this time, the MCU does not perform any operation and returns to the main program. If the UPS fails, the MCU controls the GSM communication module and sends the fault information to the on-duty personnel and the monitoring center, so that the on-duty personnel can go to the site to repair the UPS in time to minimize the loss, and the monitoring center puts all the fault information. And the status information is stored in the database.

4 Conclusion

The existing GSM network technology is mature, stable, and has a wide coverage. For data acquisition systems with small data traffic and scattered monitoring points, SMS using GSM network to transmit data has the advantages of always online, no dialing, and low price, which can greatly save manpower, material resources and financial resources. The system can be used for other remote monitoring systems with appropriate modifications, and has certain promotion value.