Abstract: Since the traditional socket can not achieve more than the rated current power-off function, this paper starts from the RFID wireless radio frequency technology and the electrical plug structure, and uses the STC12C5A60S2 single-chip microcomputer as the processor, combined with the current transformer, LCD1602 display module and electronic label. An intelligent security socket based on RFID is used in conjunction with an electrical plug with an electronic tag that records the rated current. When the current of the electric appliance exceeds the rated current of the electric appliance, the automatic power-off treatment is realized to realize the protection of the household line.
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In recent years, huge economic losses have been caused by fire accidents caused by household appliances. According to the statistics of the Public Security Fire Bureau, there are more than 30,000 accidents caused by electrical fires in China each year, and fires caused by household appliances failures account for more than 20% of the total number of fire accidents. However, the automatic power-off effect of domestic sockets is not obvious. For example, the automatic disconnection of the traditional socket relies on the fuse inside the socket. When the appliance exceeds its rated current and does not exceed the fuse's fuse current value, the appliance is short-circuited. Self-ignition; the timing socket relies on setting the time of automatic power-off, so that the socket can realize the automatic power-off function within the set time, but does not realize the current value of the real-time detecting electrical appliance; the power measuring socket can be used for real-time power of the electrical appliance. The measurement is performed and the current value of the automatic power-off can be set, but the real-time current value of the detection appliance cannot be realized. The socket cannot perform real-time monitoring and automatic power-off according to the rated current of various electrical appliances.
In response to the above problems, an intelligent security socket based on RFID is designed in this paper. The electronic tag is embedded in the plug of each electrical appliance. The rated current value of the electronic tag is read by RFID radio frequency technology, and the AC current value is measured in real time by the current transformer module. In turn, the automatic power-off function is realized.
1 System Overview and Structure
When the electronic tag of each appliance enters the read/write area of ​​the socket RFID reader, the RFID reader feeds back the signal to the microcontroller STC12C5A60S2, and the microcontroller displays the rated current value of each component of the electronic tag through the LCD1602 display module, and passes in real time. The A/D conversion and current transformer module reads the current value of the current real-time electrical appliances. When the real-time current value of the electric appliance exceeds the rated current value on the electronic tag, the automatic power-off function is realized, thereby realizing the protection function for the home circuit and effectively preventing the occurrence of fire. Figure 1 is a diagram showing the overall structure of the system.
Micro-control circuit: It consists of STC12C5A60S2 microcontroller, RFID reader, current transformer module, LCD1602 display module and relay.
Electrical plug structure: Various electrical plugs are attached to the electronic tags that indicate the rated current of various electrical appliances.
2 micro control hardware circuit design
2.1 Microcontroller
The microcontroller is the core of the micro-control circuit. The micro-control circuit requires low power consumption and strong anti-interference ability. At the same time, it can read the current transformer module in real time through A/D conversion. This article uses Hongjing's STC12C5A60S2, the normal working voltage is in the range of 3.5 ~ 5.5 V, to meet the low power requirements.
2.2 RFID reader module
This article uses NXP MFRC522 highly integrated non-contact IC card reader chip, the normal working voltage is in the range of 2.5 ~ 3.3 V, no external circuit and support SPI interface, to meet the circuit work requirements.
2.3 Current transformer module
In this paper, the SX-AC-A05 AC current transformer module is used in Sishen Electronics Studio. The rated current is in the range of 0~5 A. When measuring, it only needs to pass the signal wire of the measured signal through the hole of the transformer, and has a small volume. High precision features for power measurement and protection.
2.4 Power Management Module
The system uses a 24 V power adapter to power the current transformer module. The low-dropout linear regulator LM7812 and LM7805 are stepped down to 5 V to power the microcontroller STC12C5A60S2, and then the AMS1117 is stepped down to 3.3 V to power the RFID reader. .
3 plug structure design
The electronic tag uses a non-contact IC card and stores the rated current value of each appliance, and the electronic tag is embedded in various electrical plugs. FIG. 2 is a schematic diagram of the electrical plug.
4 software design
Initialize the microcontroller port, RFID reader, LCD1602 display module, A/D conversion and timer. When the electronic tag plug is attached to the RFID reader read/write area, the RFID reader feeds the signal back to the microcontroller, micro-control The device reads the rated current value stored in the electronic tag, and displays the rated current value of the electrical device through the LCD1602 display module and turns on the relay. When the appliance is turned on, the microcontroller detects the operating current value of the appliance in real time through the current transformer. When the working current value of the appliance exceeds the rated current value, the microcontroller immediately turns off the relay to stop the power supply. Figure 3 is the main program flow chart.
5 Experimental results and analysis
The experimental voltage is 220 V AC, and the intelligent safety socket and Fluke model 17B digital multimeter measure the working current of each electrical appliance. A total of 5 experiments are performed to record the measured current values, and the error between the intelligent safety socket and the measured current value is calculated. As a result, the experimental results are shown in Table 1.
Through the above test, the average relative error of the measured current of the RFID-based intelligent safety socket is 3.412%. From the above experiments, the current measurement effect of the RFID-based intelligent safety socket is good, thereby realizing the protection of the home line.
6 Conclusion
In this paper, the traditional socket can not achieve the function of exceeding the rated current power-off. From the RFID radio frequency technology and the electrical plug structure, the electronic tag is embedded in the plug structure of each electric appliance, which can realize the intelligent power-off function for different electric appliances. Thereby protecting the electrical appliances and household electrical lines. In this paper, the design scheme and implementation process of RFID-based intelligent safety socket are expounded from the aspects of micro-control hardware circuit design, plug structure design and software design. The design solves the problem that the traditional socket can not be intelligently powered off, and solves the short circuit problem of the electric appliance, thereby avoiding the fire caused by the short circuit of the household appliance.
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