CN201017327Y - A radio frequency identification device - Google Patents

Abstract

The utility model discloses a radio frequency identification card reading device, which comprises a radio frequency module, and the radio frequency module comprises a frequency generator circuit, an LC oscillation loop circuit, a filter circuit, an amplifying circuit and a two-stage shaping circuit, and the frequency generator circuit Outputting signals to the LC oscillating loop circuit, the LC oscillating loop circuit outputting signals to the filter circuit, the filtering circuit outputting signals to the amplifying circuit, and the amplifying circuit outputting signals to the two-stage shaping circuit. Adopting the technical solution of the utility model, low power consumption can be achieved. Usually, the power consumption of no-card detection is 20-50uA, and the power consumption of card reading is 20mA; the cost is low, and the cost is greatly reduced compared with the existing technical solution; there is no button, no need Press the button to read the card, perform automatic intelligent detection, and then read the card after detecting the card.

Description

A radio frequency identification device

technical field

The utility model relates to the technical field of radio frequency identification (RFID), in particular to a radio frequency identification card reading device.

Background technique

Radio frequency identification is a non-contact automatic identification technology, which automatically identifies target objects and obtains relevant data through radio frequency signals. The simplest RFID system consists of four parts: Tag, Reader, Antenna, and computer. In practical applications, other hardware and software support are required. RFID is essentially a means of item identification, the purpose of which is to meet the needs of specific applications by reading or retrieving the data carried in the tag. The data in the tag can provide identification of a part being manufactured, a commodity being shipped, a location, the identity of a vehicle, an animal or an individual.

At present, radio frequency identification technology is developing rapidly and is widely used in many fields such as industrial automation, commercial automation and traffic control management. Specifically, the label refers to a non-contact IC card, which has a 64-bit globally unique code inside and can be read by 125K radio frequency. In the field of 125K low-frequency information identification technology, its technical characteristics are low frequency and short distance, but it can be applied to security, access control, patrol inspection systems, and card reading devices have been widely used in China. Fig. 1 is a schematic diagram of the circuit structure of the card reading device. As shown in Figure 1, the circuit structure of the card reading device consists of a main control single-chip microcomputer chip, a radio frequency chip, a clock chip, and a storage chip.

Fig. 2 is a card reading circuit diagram in the prior art. As shown in Figure 2, a card reader circuit that is widely used in the patrol inspection market is a card reader circuit based on the radio frequency chip U2270B. The main control single-chip microcomputer chip can be 51 series or PIC series single-chip microcomputer, etc., and the storage chip is EEPROM. 24LC256 chip, etc., the clock chip is PCF8563T. The main working process is that the user holds the card reader within the effective distance, presses the button to read the card, and the system starts to work. If the card is read successfully, the buzzer will sound once, the LED light-emitting tube will flash several times, and the single-chip microcomputer will read the card from the RF chip. After U2270B senses that the data from the card is received, it simultaneously fetches the current time data from the PCF8563T clock chip, and then saves them together in the 24LC256 chip. When the 24LC256 chip data is full, the user can connect the card reader to the host computer through the serial port to upload data.

One of the shortcomings of the existing solution is high power consumption, which reaches 60mA when reading a card. Most of the current is consumed when the U2270B chip reads a card. On the other hand, in order to avoid the current consumption of the U2270B chip when it is not reading a card , the existing U2270B solution generally needs to use a button to control the card reading, that is, when the user uses the reader to read the card, he needs to press the button within the effective card reading distance, the U2270B works to read the card, and the system shuts down when the card is not read U2270B, and in sleep state to reduce power consumption. The second disadvantage of the existing solution is that the cost is relatively high, mainly because the cost of the U2270B chip and the PCF8563T clock chip is relatively high.

Utility model content

The purpose of the utility model is to provide a radio frequency identification card reading device, which can reduce the power consumption of the card reading device and save costs.

For this purpose, the utility model adopts the following technical solutions:

A radio frequency identification card reading device, including a radio frequency module, the radio frequency module includes a frequency generator circuit, an LC oscillating circuit, a filter circuit, an amplifier circuit and a two-stage shaping circuit, and the frequency generator circuit outputs signals to the An LC oscillating circuit circuit, the LC oscillating circuit circuit outputs signals to the filter circuit, the filter circuit outputs signals to the amplifying circuit, and the amplifying circuit outputs signals to the two-stage shaping circuit.

The frequency generator circuit includes a first field effect transistor, a second field effect transistor and a resistor, the first field effect transistor is grounded, the second field effect transistor is connected to a positive power supply, and the resistor is used for current limiting protection.

The LC oscillating loop circuit includes an induction inductance coil and an LC oscillating capacitor, and a connection point between the induction inductance coil and the LC oscillating capacitor at a node vibration point.

The filter circuit includes a diode, an operational amplifier, three capacitors and three resistors, the diode is used to filter the input signal into a positive half cycle signal, and the operational amplifier, three capacitors and three resistors are used to convert the positive The 125K frequency of the half-cycle signal is filtered out to form the amplitude change of the low-frequency signal, which is output to the first pin of the operational amplifier.

The amplifying circuit includes an operational amplifier, three resistors and two capacitors, which are used to amplify and output the amplitude variation of the input low frequency signal.

The two-stage shaping circuit includes two operational amplifiers, five capacitors and three resistors, which are used to shape the input signal into a Manchester encoded square wave signal, and output the signal to the read-in pin of the single-chip microcomputer.

The technical scheme of the utility model is adopted, and the key is canceled to detect and read the card, that is, the card reader detects whether there is a card within the effective distance several times per second, and then reads the card if there is a card, which greatly reduces power consumption and facilitates card reading. The hourly current is 10mA, and the static detection current is 20-50uA; the amplifier chip LMV324 is used instead of the U2270B RF chip, the FLASH memory chip SST25LF080A is used instead of the 24LC256, the storage space is 32 times that of the latter, and the DS1302 replaces the PCF8563 clock chip, thereby greatly reducing the cost.

Description of drawings

Fig. 1 is a schematic diagram of the circuit structure of the card reading device;

Fig. 2 is a card reading circuit diagram in the prior art;

FIG. 3 is a schematic structural view of a radio frequency module in a radio frequency identification card reading device in this specific embodiment;

Fig. 4 is a circuit diagram of the card reading device in this specific embodiment.

Detailed ways

The technical scheme of the utility model will be further described below in conjunction with the accompanying drawings and through specific embodiments.

Usually, the card reading circuit is in a low-power sleep state, and is woken up by the main control microcontroller twice per second (the number of wake-ups can be customized), and then starts frequency drive, reference voltage, and working voltage for the RF module, and detects at the same time, such as valid card reading If there is no IC card within the distance, the main control MCU will turn off the frequency drive, reference voltage, and working voltage, and the card reading circuit will enter a low-power sleep state, waiting for the next wake-up operation; if there is an IC card within the effective reading distance, the main control MCU will start The card reading operation of the radio frequency module reads the card. If valid data is read, the main control microcontroller reads the current time from the clock chip, and then stores the current time and IC card data into the memory chip. After completion, the card reading circuit enters low Power consumption sleep state, waiting for the next wake-up operation. If it is necessary to upload data, connect the card reading circuit to the host computer correctly, and the host computer can perform related operations.

Fig. 3 is a schematic structural diagram of a radio frequency module in a radio frequency identification card reading device in this specific embodiment. As shown in FIG. 3 , the radio frequency module includes a frequency generator circuit 101 , an LC tank circuit 102 , a filter circuit 103 , an amplifier circuit 104 and a two-stage shaping circuit 105 . The frequency generator is composed of field effect transistors M1, M2 and R6. The input stage is the RDEN pin of the single-chip microcomputer, which is connected to M1, M2, and M1 is grounded, and M2 is connected to the positive power supply. Afterwards, M1 and M2 are jointly output to the next stage. The LC oscillating circuit module consists of a card reading inductance coil H1 and a capacitor C6. The node vibration point is the connection point of H1 and C6, and the next stage takes the signal from the node vibration point. The filter module is composed of diodes D1, U4A and C7, C8, C9, R7, R8, R9. D1 filter node vibration point signal is a positive half-cycle signal, and U4A and related resistors and capacitors filter out the 125K frequency of the positive half-cycle signal to form a low frequency The amplitude of the signal changes and is output to the first pin of U4A. The amplification module is composed of U4B and R10, R11, R12, C10, and C11. It is used to amplify the amplitude change of the upper-level low-frequency signal and output it to the lower two levels for shaping. The two-stage shaping module is composed of U4C, U4D and R13, R14, R15, R16, R17, C12, C13, and C14. It shapes the upper-level signal into a standard Manchester-encoded square wave signal, and outputs it to the INPUT pin of the microcontroller. Read the code directly.

Fig. 4 is a circuit diagram of the card reading device in this specific embodiment. As shown in Figure 4, U1 is the main control microcontroller PIC16F628A; U2 is the FLASH memory chip SST25LF080A with a capacity of 8Mbit; U3 is the clock chip DS1302; U4 is the integrated op-amp chip LMV324, which integrates 4 op-amps, U4A and U4B. , U4C, U4D; Y1 is the working crystal oscillator of the single-chip microcomputer, Y2 is the working crystal oscillator of the clock chip; L1 is the LED light-emitting diode; B1 is the buzzer; D1 is the filter diode; It is a field effect three-stage tube; the rest of the resistors and capacitors act on the relevant working circuits.

The third pin of U1 is connected to the buzzer B1, the second pin is connected to the L1 light-emitting tube through the current limiting resistor R2, the fourth pin is the working reset pin of U1; the fifth pin is grounded; the 14th pin is connected to the positive power supply Vcc; 15, 16 The pins are connected to the working crystal oscillator; pins 8, 10, 11, 12, and 13 are the connecting pins of DS1302 and SST25LF080A.

Pin 1 REF of U1 provides reference voltage signal for LMV324 card reader circuit, pin 9 RDEN provides 125K frequency drive signal for card reader LC oscillation, pin 18 provides work for LMV324 card reader circuit through current limiting resistor R5 and decoupling capacitor C3 Voltage VDD; the 17th pin INPUT is the reading pin, that is, the IC card data sensed in the LMV324 card reading sensing circuit is read from this pin by the microcontroller.

Specific working process: U1 is usually in a sleep state, woken up by the internal watchdog, and then performs operations such as detection and card reading. The frequency is about 2 times per second (customizable). Power supplies the working voltage to LMV324 and 125K frequency to RDEN for detection. If the IC card is not detected within the effective card reading distance, U1 will go to sleep and wait for the next automatic wake-up to read the card. If the IC card is detected, then Carry out the card reading operation. After the card reading is successful, read the current time of the system from U3, and store the time and IC card data into U2. After the successful storage, U1 turns off the related functions of REF, VDD, and RDEN pins, and then enters sleep again. Wake up the card reading operation next time, and so on.

When reading the card, the 125K frequency is added to the LC oscillation circuit composed of H1 and C6 from the RDEN pin, after passing through M1, M2, and R6, where C6 is the LC oscillation capacitor, and H1 is the induction coil. When there is a card within the effective distance, the non-contact IC card will modulate the LC oscillating circuit in reverse phase to make the amplitude change, and then the diode D1 will take the signal through the LC oscillating point and filter it into a positive half-cycle signal, and then add it to the LMV324 chip and related resistors and capacitors. The amplifying filter shaping circuit, finally outputs the Manchester coded waveform from the INPUT, and U1 performs the effective identification operation.

If you need to upload data to the host computer, you can connect to the relevant serial communication chip through the 6th pin of U1, and the relevant commands of the host computer will control operations such as uploading data.

Among them, the LMV324 chip integrating four amplifying circuits can be replaced by two LMV358 chips integrating two amplifying circuits, etc.; the single-chip microcomputer PIC16F628A can be replaced by MSP430 series single-chip microcomputers, etc.

The utility model has the advantage of low power consumption, usually the power consumption of no card detection is 20-50uA, and the power consumption of card reading is 20mA; low cost, which is greatly reduced compared with the existing technical solutions; no buttons, no buttons are needed for card reading, Carry out automatic intelligent detection, detect the card and then read the card.

The above is only a preferred embodiment of the utility model, but the scope of protection of the utility model is not limited thereto, any person familiar with the technology can easily think of it within the technical scope disclosed in the utility model Changes or replacements should fall within the protection scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims (7)

1. A radio frequency identification card reading device, comprising a radio frequency module, characterized in that, the radio frequency module comprises a frequency generator circuit, an LC oscillating loop circuit, a filter circuit, an amplifying circuit and a two-stage shaping circuit, and the frequency generator The circuit outputs signals to the LC oscillating circuit circuit, the LC oscillating circuit circuit outputs signals to the filter circuit, the filter circuit outputs signals to the amplifying circuit, and the amplifying circuit outputs signals to the two-stage shaping circuit . 2. A kind of radio frequency identification device according to claim 1, is characterized in that, described frequency generator circuit comprises first field effect triode, second field effect triode and resistance, and described first field effect triode Grounding, the second field effect transistor is connected to the positive power supply, and the resistor is used for current limiting protection. 3. A kind of radio frequency identification card reading device according to claim 1, it is characterized in that, described LC oscillating loop circuit comprises inductive inductor coil and LC oscillating capacitor, the connection point of node vibration point induction inductive coil and LC oscillating capacitor . 4. A kind of radio frequency identification card reading device according to claim 1, is characterized in that, described filtering circuit comprises diode, an operational amplifier, three electric capacity and three resistances, and described diode is used for filtering input signal as For the positive half-cycle signal, the operational amplifier, three capacitors and three resistors are used to filter out the 125K frequency of the positive half-cycle signal to form a low-frequency signal amplitude change, which is output to the first pin of the operational amplifier. 5. A kind of radio frequency identification card reading device according to claim 1, is characterized in that, described amplifying circuit comprises an operational amplifier, three resistors and two capacitors, is used for amplifying the amplitude change of the input low-frequency signal and output. 6. A kind of radio frequency identification card reading device according to claim 1, is characterized in that, described two-stage shaping circuit comprises two operational amplifiers, five capacitors and three resistances, is used for shaping the input signal into The Manchester coded square wave signal is output to the signal read-in pin of the microcontroller. 7. A kind of radio frequency identification card reading device according to claim 1, is characterized in that, also comprises main control single-chip microcomputer, FLASH memory chip and clock chip, and described main control single-chip microcomputer model is PIC16F628A, and described FLASH memory chip model It is SST25LF080A, and the model of the clock chip is DS1302.

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