1 Introduction
Radio frequency technology has been widely used, especially in the governance of all walks of life, such as: bank electronic wallet, commercial membership card, bus card, medical insurance card, canteen sales card, access control attendance card, ID card, etc. With the computerization of management, the application of radio frequency technology will be more and more extensive, and wireless electronic tags are generated based on radio frequency technology. With display function, it can be managed centrally by computer. Electronic paper (ePaper) is a new generation of display device, which is characterized by ultra-high contrast and ultra-low power consumption. Only use power when refreshing the screen, keep the display when power off, ultra-thin, the thinnest can be 0.1mm, flexible Good, can be bent and folded arbitrarily. Based on the above characteristics of electronic paper. Here we use electronic paper, a new display element, to design a wireless electronic label.
2 Working principle of wireless electronic tags
The wireless electronic tag is also known as a smart tag (Tag or SmartLabe1). Its core is a device with a certain storage capacity that uses radio frequency identification RFID (RadioFrequencyIdenTIficaTIon) technology. Radio frequency identification RFID is a non-contact automatic identification technology. It automatically identifies target objects and obtains relevant data through radio frequency signals without manual intervention. It can work in various harsh environments. The wireless electronic tag is composed of an IC device, an induction antenna, a communication interface, and a display module. The reading and writing process of wireless electronic tags: the reading and writing device (base station) radiates electromagnetic waves to the surrounding environment through the antenna at regular intervals, and then enters the receiving state, waiting for the electronic tag (transponder) to answer. Because RFID itself does not contain a power supply, when RFID enters the electromagnetic field, it first emits electromagnetic waves through its own antenna coupling reader to rectify and filter it. Charging an internal capacitor. When the capacitor voltage rises to a certain value. The wireless electronic tag has enough energy, at this time the electronic tag starts. The control device communicates with the electronic paper display module, sends some data to the electronic display module, and returns a signal to the reader.
The wireless electronic tag IC uses a frequency of 13.56 MHz according to ISO / IEC 156693. In addition to ICs, there are RF circuits and driver circuits for electronic paper, memory, and boost circuits on wireless tags. ISO / IEC15693 is a communication method that obtains voltage through electromagnetic induction. The voltage of the component developed here is + 3V. Since the drive of the electronic display component requires + 15V. Therefore, a booster circuit is used and an independent power supply is used to supply power to the electronic paper drive module. The system hardware block diagram is shown in Figure 1.
3 Electronic paper display module
E-paper is a colored ball with static electricity placed between two layers of transparent flexible film. The particles of two colors have positive and negative charges. The positive and negative electrodes are added to the outside of the film. Because of the principle of same-sex repulsion and opposite-sex attraction, the position of the ball moves, thereby lighting a certain section. Similar to the static display LCD module, the electronic paper truth table is divided into the SEG segment and the TopPlane segment. When there is a potential difference between the SEG segment and the TopPlane segment, the electronic ink in the electronic paper will move, and the corresponding segment will light up or go out.
The electronic paper needs a special driver to drive the display. Here, the electronic paper drive device adopts slc05112.slc05112 built-in interface circuit and drive electronic paper module produced by EPSON company, 3V power supply, easy to communicate with MCU. The electronic paper drive module is connected to the I / O port of the MCU. The timing diagram of the electronic paper drive module is imitated through the I / O port. The main controller can realize the initial startup, refresh display and shutdown of the electronic paper drive module through software. Figure 2 shows the circuit connection of the electronic paper drive interface design.
After RFID obtains the data, the electronic paper is refreshed and displayed. The electronic paper can still be displayed after power-off, so the power consumption of the system is low. The current of slc05ll2 is only 0.1 A in standby mode, and only 28 in the case of 1 = operation. A, one CR2032 battery can guarantee its one-year working life.
4 Data storage and processing system
The application block diagram of the data storage and processing system is shown in Figure 3.
The detailed functions of the system are:
(1) The data communication function is the communication between the computer and the wireless electronic tag, and the communication between the data storage processing module and the computer adopts RS232; the communication between the data communication processing module and the computer can adopt RS232, It can also realize the remote transmission of data by RS485 (theoretical communication distance is 1200m):
(2) Data temporary storage function Because wireless electronic tags are often fixed on the shelves, the price data is finally processed by the computer, so the price and other commodity display information should be written into the system, so it must have a storage function. To obtain a computer independent The working process, that is, do not monopolize the computer when swiping the electronic label, only need the computer when downloading data:
(3) The dynamic link library method uses the dynamic link library method to connect the management program installed in the computer with the data storage and processing module. It can shorten the development cycle of various application systems:
(4) Rechargeable lithium battery powered by power supply, the data in the machine can be saved for more than 1 month after power failure, or even longer:
(5) LCD display LCD display interface, keypad input.
5 Application of RFID electronic tags in supermarkets
In retail markets such as supermarkets, prices vary in different time periods. Whenever there is a price change, the price tag must be replaced. After using the new display element, new price information can be sent and displayed through the writer. This saves manpower and is also environmentally friendly. The prices of supermarket commodities are usually managed centrally through a computer, and then the price tags are printed and affixed to the label bar of the shelves. Due to the wide variety of commodities in supermarkets, some errors are caused by manual operations. After using RFID, logistics and information flow can be symmetrical. Thereby improving the accuracy of the price.
The RFID system can be updated in real time, and it is easy to use. It is easy to find the items that need to be updated. The use of radio wave induction makes it easier to find commodities.
The installation and debugging of the RFID electronic label system is very simple, and the later use and operation and maintenance are also very convenient. It can increase the speed of identifying goods, and can provide reliable performance and high security.
6 Conclusion
The application fields of wireless electronic tags are very wide, but they often lack display functions. The traditional display method can not fundamentally solve the power consumption problem and electronic paper can solve this problem.
This article first describes the wireless electronic tag technology, and then provides a general-purpose device electronic paper interface, the interface is compatible and strong, only a few I / O ports can realize the display of driving electronic paper, and design data storage and processing system . The system can update the electronic label information, so that the information is transmitted in a timely and correct manner. Finally, a typical application of electronic paper wireless tags, namely supermarket price tags. The application completely subverts the existing supermarket price update system, and can automatically complete time-consuming labor-intensive work, so that the supermarket staff can concentrate on deep-level service work for consumers.
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