1 Introduction In the past two years, with the development of power supply technology, the continuous improvement of the reliability and intelligence of various power supply equipment, and the rapid development of computer technology, the technical foundation for realizing centralized monitoring and unmanned management has been improved. The specific research content of the system designed and developed in this paper is to use computer hardware and wireless communication technology to develop a new type of remote power supply monitoring system, which has the characteristics of low cost, simple use, convenient maintenance, and convenient management. Since the system reflects the operating status of the equipment by monitoring the power supply operation status, the system can form a complete monitoring network of the equipment that needs to be monitored. The system can be implemented in a one-to-one communication mode or a one-to-many communication mode, which is flexible and practical. 2 System Composition and Working Principle 2.1 System Composition Overview The system is divided into two parts: a monitoring center station and remote monitoring substations. The monitoring center station mainly consists of a monitoring center station server, a GSM wireless communication module, a database system and its application software. The remote monitoring substations mainly consist of an AT89S52 microcontroller and peripheral circuits, a temperature sensor and a GSM wireless communication module (TC35i). The monitoring center controls the GSM wireless communication module to send and receive short messages, receives temperature data collected by each monitoring substation, and then displays, processes, and prints the data. Remote monitoring substations collect, process, and display temperature data. They also control the GSM wireless communication module to send and receive short messages. Wireless remote communication is achieved between the monitoring center and remote monitoring substations via the GSM network. This realizes a remote monitoring system based on the GSM network. 2.2 Hardware Circuit Composition The MCU of this system uses the AT89S52 microcontroller manufactured by Atmel. It is a low-power, high-performance CMOS 8-bit microcontroller with 8K in-system programmable Flash memory. Manufactured using Atmel's high-density non-volatile memory technology, it is fully compatible with the instructions and pins of industrial 80C51 products. The on-chip Flash allows the program memory to be programmed in-system and is also suitable for conventional programmers. With a powerful 8-bit CPU and in-system programmable Flash on a single chip, the AT89S52 microcontroller provides a highly flexible and efficient solution for many embedded control applications. The temperature sensing module uses the DS18B20 sensor. The DS18B20 is an improved intelligent digital temperature sensor launched by DALLAS Semiconductor in the United States after the DS1820[22]. It has the following features: a 3-pin TO-92 small package; a temperature measurement range from -55℃ to +125℃, with an accuracy of ±0.5℃ in the temperature range of -10℃ to +85℃; a resolution of 9 to 12 bits can be achieved by programming according to actual requirements, and the conversion of 9-bit and 12-bit temperature information can be completed in 93.75 ms and 750 ms respectively; a unique single-wire bus interface, which only needs to occupy one general-purpose I/O port to complete the communication with the microprocessor. Therefore, using the DS18B20 can save a lot of ports and logic circuits, making the system structure simpler and more reliable. The microcontroller peripheral circuit is shown in Figure 1. Figure 1 Microcontroller peripheral circuit The GSM module selected in this design is the Siemens TC35i from the TC35 series. This is the latest wireless module launched by Siemens, which is compatible with the TC35 and has a compact design, greatly reducing the size of the user's product. The TC35i has 40 pins, brought out through a ZIF (Zero Insertion Force) connector. These 40 pins can be divided into 5 categories: power, data input/output, SIM card, audio interface, and control. Pins 1-14 are the power section, with pins 1-5 being the power input (Vbatt+), pins 6-10 being the ground (GND), pins 11 and 12 being the charging pins, pin 13 being the output voltage (for external circuitry), pin 14 being the AUUU-IEMP pin for connecting a negative temperature coefficient thermistor, pins 24-29 being the SIM card pins (UCIN, UCRSI, UCIU, UUCLK, CCVCC, and CCGND respectively), pins 33-40 being the voice interface for connecting a handset, and pins 15, 30, 31, and 32 being the control section, with pin 15 being the ignition pin (IGT). When the TC35i is powered on, a low level of more than 100ms must be supplied to the IGT for the module to start. Circuit 30 is RTC backup, circuit 31 is Power down, circuit 32 is SYNC, and circuits 16-23 are data input/output, namely DSRO, RINGO, RxDO, TxDO, CTSO, RTSO, DTRO, and DCDO, respectively. The peripheral circuit of the TC35i is shown in Figure 2: Figure 2 TC35i peripheral circuit 2.3 System Software Working Principle The software design of this system mainly includes two parts: the program design of the monitoring end and the program design of the central server end. These two parts perform different functions respectively, and cooperate with each other to complete the remote monitoring function of the power supply. The design idea of ​​the monitoring end program is: under normal circumstances, the microcontroller automatically completes the cyclic detection of the power status of the device. If an abnormality in the power supply current is detected, the microcontroller controls the GSM modulation module to send an alarm SMS to the central server or mobile terminal via AT commands. Users can also send corresponding control commands via mobile phones or the Internet, which are transmitted to the module through the GSM network. The AT89S52 microcontroller receives and interprets these commands, and performs corresponding actions, such as modifying parameter settings, querying the current device operating status, and setting the user center number. The embedded system program is designed using C language and, after successful debugging on a development platform with a simulator, the target code is written into the microcontroller. The server-side program design consists of two parts: a data processing section, including serial communication, SMS sending and receiving processing programs, system interface design, and the function of storing processed data in the database; and a database section, which stores various power supply data for future querying and management. The main functions of the monitoring program are information reception, processing, and transmission. Since the monitoring system continuously sends real-time power supply status data to the target device and receives parameter settings from the target device, a query-based approach is clearly unsuitable. Therefore, the software design of this system places the entire SMS processing module within the MCU's interrupt service subroutine to improve MCU efficiency and response timeliness. The 52 series microcontroller supports C language programming on the MPLAB platform. Due to the complexity of the monitoring program involving numerous encoding and decoding operations and the need to implement complex functions, the high-level language features of C are fully utilized. A structured programming approach is adopted, following a top-down, step-by-step refinement principle, dividing each function into different modules for implementation. This facilitates segmented debugging and future modifications to certain functions. The system main program flowchart is shown in Figure 3. Figure 3 System Main Program Flowchart 3 Conclusion This paper describes the hardware and software design of the GSM remote temperature monitoring system. Temperature detection uses the DS18B20, which is highly suitable for temperature monitoring systems operating in multi-point, harsh environments. The GSM module facilitates system integration, has low cost, stable and reliable operation, is suitable for long-distance monitoring, is not limited by terrain conditions, and has broad application prospects. References: [1] Li Deling, Ma Chao. Implementation of real-time processing of short messages in embedded systems [J]. Microcontrollers and Embedded Systems Applications, 2006.01:33-39 [2] Li Shulin, Zhang Ying, Li Xiuping. Sending and receiving short messages using GSM wireless module [J]. Computer and Digital Engineering, 2005.07:79-84 [3] Guo Hongxia, Pan Bin. Design of wireless terminal for controlling TC35i using Cygnal C8051F020 [J]. Instrumentation User, 2004.04:75-78 [4] Yan Jingbin, Zhou Yongqin, Yang Gang, Yu Changsheng. Design of remote monitoring system for heating network based on GSM [J]. Measurement and Control Technology, 2005.03:33-35 [5] Chang Xudong, Hong Li, Wang Zhifu. Remote alarm and control system based on short message [J]. Jiangxi Science, Vol.24 (2006), No.2:191-194