What is the principle of the meal card (radio frequency card) used in universities now? What is the internal structure? (It is better to have a picture)

A: A wireless smart card (also known as a radio frequency card) is a passive (power-free) cipher card with a special key number. It uses two-way radio frequency technology to complete the digital identification of the card, representing the identity and related information of the cardholder. This new technology has many advantages and is gradually replacing photoelectric cards, magnetic cards and contact ic cards. This is the mainstream direction of smart IC cards in the future. Widely used in identity authentication, credit authentication, automatic control, security and other fields, its security, confidentiality and practicality are incomparable to all kinds of general prevention circuits at present.

I. Wireless Smart Card

The wireless smart card introduced in this paper belongs to passive encrypted storage read-only mode. In addition to the 64-bit encrypted serial EPROM, the chip also has the output port of the modulation code generator, which constitutes wireless connection data transmission together with the peripheral RF circuit. Its biggest feature is that it does not need battery power supply, and relies on wireless electromagnetic waves to provide the energy needed by the system.

The internal structure of wireless smart card, its chip has solidified a group of password information in the special key digital group before leaving the factory. Log in under the host identification system, become the user card of the system, and carry out identity identification and various transactions under the rules set by the host system.

The chip size of wireless smart card is only 4mm×8mm× 1mm, so it can be made into business cards stored in wallets, access cards hung on employees' chests, key cards connected with key chains, even decorative gift cards and ultra-miniature hidden cards according to users' needs. It can cooperate with wireless card reader module, host card reader and even computer network system to build a high-performance and intelligent identity management and identification system.

Second, the wireless card reading module

In order to complete the information exchange between the wireless smart card and the host read-write identification system, it is necessary to rely on radio waves as a transmission means. Obviously, the radio transmitting and receiving circuit plays an important role in this system. Modular wireless card reading circuit makes the high-frequency transceiver circuit which is difficult to debug and manufacture solid, and greatly simplifies the manufacture of smart card and its read-write identification system. The wireless transceiver circuit required for bidirectional data transmission is solidified in the module, and finally the serial data signal is output from the out pin of the module. The signal can be sent to a special identification control circuit or a single chip microcomputer manager to control various preset functions. According to the requirements of working voltage, radiation range and output interface, various types of wireless card reading modules are designed. The attached table lists some module parameters produced by Zhongshan Dahua Electronics Factory for readers' reference.

Third, the application examples

How to use a series of numbers output by the wireless card reading circuit depends on the control circuit or computer. For example, smart cards are used for the management of food stamps in canteens. When the computer reads the password of the smart card, it immediately calls out the stored data of the meal card, learns the balance, and enters the amount of the meal ticket, so that the original record of the cardholder's deposit amount will be reduced. Generally, different types of control IC can be used to manufacture control circuits with different functions. Fig. 3 shows the application of RF60 1 integrated block as community access control and anti-theft system. In the figure, K 1 is a switch, and the owner of the system can prepare an "allow" command card and an "expel" command card through the switch. With these two cards, the owner can use the "allow" card for the first time to order the machine to remember hundreds of legal cards, and can use the "expel" card at any time to order to expel the unpopular illegal cards in the future or absorb new legal cards. K2 sets the unlocking time to match electronic locks with different functions.

Smart cards are widely used, such as attendance system, parking charge management, community prevention system, and even as library management, power control, security framework, automatic doors and so on.