Design and Analysis of Intelligent Electricity Meter Based on 80C51 Single Chip Microcomputer

　　The promotion and use of smart meters is a livelihood project that benefits the people. It has greatly improved the electricity conditions of rural residents, improved the automation level of distribution networks, and has great significance for reducing the consumption of electric energy. The single-chip microcomputer 80C51 is used as the core, and the power metering chip CS5460A, LCD display 1602, Wifi communication circuit, SD memory card and other chips are added to realize the functions of power measurement and display, wireless communication, data storage, etc. Users can use the buttons on the meter to choose whether to display the user's current power consumption or the power consumption in a certain period of time.
　　
　　With the development of computer technology and communication technology, the degree of building intelligence is getting higher and higher. The intelligent meter reading system of the residence is indispensable in the building intelligence. In China, the user's meter is still read manually. This primitive meter reading method not only causes a waste of manpower and material resources, disturbs the normal life of residents, but also has poor accuracy, and the power data needs to be read manually and cannot be transmitted in real time. In order to fundamentally solve this problem, a smart meter based on a single-chip microcomputer is designed. If the electric meter uses a single-chip microcomputer as the main body to replace the conventional mechanical and electronic circuits of traditional instruments and meters, it can easily combine computing technology with measurement and control technology to form an intelligent measuring instrument. This instrument consists of a metering circuit, a microprocessor, an LCD display, a real-time clock, a communication interface and a power supply, and has functions such as electric energy metering, information storage and processing, real-time monitoring, automatic control, and information interaction.
　　
　　1 Working principle of smart electric meter
　　
　　The hardware scheme block diagram of the smart electric meter is shown in Figure 1. The electric energy meter is mainly composed of seven parts: metering, power management, storage, display, key processing, pulse output and communication unit. The smart electric meter in this article uses 80C51 as the core processor. In addition, the electric energy metering chip CS5460A and the LCD display chip 1602 are added to measure and display the user's electricity consumption. However, since the CS5460A chip can only measure instantaneous electricity, it is also necessary to use the time chip DS1302 to segment the time, so that the electric meter can display not only the user's instantaneous electricity consumption, but also the electricity consumption in a certain period of time through the key. The use of WiFi communication circuit can realize the wireless communication of smart meters. In this way, the staff who check the meters no longer need to go door to door to check, but directly receive WiFi signals to understand the user's electricity consumption, which is more convenient and time-saving. For the storage module, this paper uses a small and large-capacity SD card. Compared with the general storage module, the SD card can be disassembled and replaced at any time, which is convenient and practical. For the power module, this paper adopts an external power supply method.
　　
　　2 Hardware Design of Smart Meter
　　
　　2.1 Electric Energy Metering Circuit Design
　　
　　The electric energy metering chip uses CS5460A. Its main functions are as follows: it has a special automatic pin mode function, which can make the chip work independently and automatically initialize when powered; it has an on-chip watchdog timer and an internal power monitor; it can accurately measure the instantaneous value of voltage , instantaneous value of current , voltage effective value , current effective value, power and energy in both positive and negative directions; it provides an external reset pin; the bidirectional serial interface and the internal register array can be easily connected to the microprocessor; the maximum frequency of the external clock can reach 20 MHz ; it has a power direction output indication.

    2.2 WiFi communication module design

    The meter uses WiFi wireless communication, and the WiFi communication circuit uses BCM8000. WiFi communication technology has the advantages of high data transmission rate, flexible networking, and good mobility. WiFi communication uses a wireless network, which makes the installation of smart meters not limited by communication lines and has the advantage of convenient installation. The connection between the WiFi communication circuit and the microcontroller 80C51 only requires connecting the RXDH and TXDH pins of BCM8000 to the TXD and RXD pins of 80C51 respectively, as shown in Figure 3.

    3. Software Design of Smart Meter

    The software design of the smart meter includes the following parts: data transmission of the energy metering chip CS5460A, LCD 1602 display subroutine, key function processing program, WiFi wireless communication program, read/write operation program of the clock chip DS1302, and software design of the SD card storage module. The flow chart of its main program is shown in Figure 4. The CS5460A software block diagram is shown in Figure 5.

    4 Conclusion

    The smart meter designed this time integrates multiple functions such as measuring and displaying electricity, data storage, and data communication. After experimental verification, it was confirmed that the meter has stable performance, accurate calculation, small error, and can communicate wirelessly. However, the meter designed this time may have some deficiencies in fault self-diagnosis, which needs to be improved in the future.