58914444 System modules

POther module circuits
EEPROM: The CPU accesses the EEPROM device 24C25624C256 through the I2C bus. The webpage is stored in EEPROM. The webpage content in EEPROM can be browsed, re downloaded, and updated through the read and write operations of the main CPU. Due to capacity limitations, it is impossible to store a large number of pages.
Clock module circuit: The clock chip DS12B887DS12B887 is selected. It can generate seven time scales, including seconds, minutes, hours, days, weeks, months, and years. These timestamps can be read and modified through programming, and timed interrupts can also be generated through programming. By using a hard clock, it can save the timer resources of the microcontroller and reduce software design workload.
Watchdog circuit: The working environment of power grid monitoring instruments usually has strong electromagnetic interference. In order to prevent interference in extremely high working requirements, a watchdog circuit is introduced. Using MAX813LMAX813L chip. This chip has a monitoring circuit. If the program does not provide a “dog feeding signal” to MAX813L within 1.6 seconds, it will generate a watchdog output and reset the system.

The Ethernet interface module uses RealTek’s RTL8019AS full duplex Ethernet controller, whose main function is to handle Ethernet protocols. It comes with a 16KB SRAM and communicates with Ethernet through the RJ45 interface. The flow of data is: the request information comes from Ethernet and is sent to RTL8019AS through RJ45. The processed data packet is sent to the SX52BD protocol stack, which analyzes the data packet to obtain the original request information. The request information is processed by SX52BDSX52BD to generate a reply message. The process of replying to messages to Ethernet is exactly the opposite of the above process.

58914444 System modules

The Structure and Function of Embedded Power Grid Monitoring Instrument
The power grid monitoring instrument samples and processes voltage and current signals on the power grid, and saves data for a certain period of time. The specific functions are as follows:
(1) Real time monitoring of three-phase voltage Va, Vb, Vc, and four phase current Ia, Ib, Ic, and I0;
(2) Monitor the three-phase power factors of A, B, and C;
(3) Communicate with Ethernet through RJ45 interface;
(4) Save voltage, current data, and power factor at the hour of the hour, and save monthly statistical data;
(5) Using a digital display, users can view and set the operating parameters and historical records of the instrument on site. The structure of the power grid monitoring instrument is shown in Figure 2. It mainly consists of a microcontroller, voltage and current sampling module, power factor monitoring module, Ethernet interface module, etc. Complete the monitoring of power grid parameters, achieve functions such as signal processing, data display, and display of power grid operation status.
2.1 Microcontroller
The microcontroller module is the core of the entire power grid monitoring instrument. Mainly completes two major functions:
(1) Data collection and processing;
(2) Implement Ethernet access.
Process the real-time three-phase voltage, real-time three-phase current, and neutral current obtained through the voltage and current monitoring module; Real time monitoring data can be transmitted to Ethernet through the RJ45 interface, enabling the monitoring center to timely obtain relevant parameters of the power grid; At the same time, the power grid monitoring software determines the operation status of the power grid and whether the voltage is beyond the limit or too low based on the test parameters. The microcontroller uses UBICOM’s 8-bit ultra high speed microcontroller SX52BD, with a data processing capacity of 100 million times per second. Because UBICOM MCU has a very high speed and can realize real-time multitask operation, it can package and transmit data to the Internet while MCU performs data acquisition and control functions.

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