Avr Microcontroller Based On The Rfid Reader 125khz Design

in Frequency

RFID (Radio FrequencyIdentification, RFID) is the use of sensors, electromagnetic field or electromagnetic waves as the transmission means, complete way of non-contact Communicate , Access to relevant data, an automatic identification technology. Identification of the technical work completed without human intervention, easy to implement automated and easily damaged, can identify fast moving objects can also recognize multiple Radio frequency card Operation fast and convenient, has been widely used.

Existing number of readers, reader chips needed as base stations, high cost. This paper introduces a discrete component formed 125kHzRFID reader, simple circuit structure, the cost is very low, for reading EM4100-based ID card.

1, RFID system of classification RFID system of classification has many applications are based on the usual frequency points, depending on the operating frequency, can be divided into the following four:

(1) low frequency (120 ~ 135kHz). The band has a strong market penetration, use of unrestricted, the performance is not Environment Impact, low cost, generally less than the maximum recognition distance of 60cm, mainly used in access control, " Card "Consumer management, vehicle management systems;

(2) high frequency (10 ~ 15MHz). Compared with the low frequency of the band with anti-collision, multiple tags can also identify the advantages, but the environmental impact of its performance, identify distance is less than 100cm, mainly used in library management and logistics systems;

(3) UHF (850 ~ 960MHz). The higher frequency band than can be achieved with the advantages of long-distance recognition, the maximum recognition distance of up to 10m, but their performance affected by environmental factors, the price is also expensive, mainly used in railway vehicle identification, container identification and other systems ;

(4) Microwave (2.45 ~ 5.8GHz). The band can achieve long-range identification, recognition distances up to 100m, but its price is also the most expensive, mainly used Intelligent Transportation System.

2, RFID system components Radio frequency identification system generally by the reader, Electronic Tag antenna composed of three parts.

(1) readers: read or read / write electronic tag information in the device, the main task is to control the RF module to read the label launch signal, and receives tag response, the identity of the tag to decode the information, will identify information on the label other relevant information related to the transfer Host For processing. A typical reader contains a high-frequency module (transmitter and receiver), the control unit and connect the coupling with the transponder device. In addition, many readers have additional interfaces (RS232, RS485, etc.) in order to receive the data transmitted to another system (such as personal computers).

(2) electronic tag (transponder): from the chips and built-in antenna, the chip has some form of electronic stored data on the object to be identified as the identification of goods to be identified information, it is the RF real data carrier identification system, built-in antennas and RF antenna used to communicate. Typically, the transponder is not their own power supply, and only in response to reader within the scope of the transponder is active. The energy required transponder, by coupling unit (non-contact) transmission to the transponder.

(3) Antenna: tag and reader data transfer between the carriers.

4.2EM4100 data encoding

EM4100 using Manchester coding, as shown in Figure 4: bit data "1" corresponds to the next level jump, bit data "0" level corresponds to the jump.

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Avr Microcontroller Based On The Rfid Reader 125khz Design

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This article was published on 2010/09/25