[[wysiwyg_imageupload::]]RFID based system.
RFID work at 125 KHz frequency with radio waves. There is a coil inside the RFID tag and when it is influenced by a magnetic field, it sends a 12 byte identity code to RFID reader for further processing. The RFID tag is used as a unique identity for account of a particular user. When a vehicle drives through the toll plaza, its driver is prompted to scan his RFID tag. If the identity (serial number of the tag, i.e., 12 byte data) is matched with the one already stored in the system, the toll amount is deducted from his account. After this, the vehicle gets immediate access to drive through.
RFID system interfaced with AT89C51 requires the controller to continuously scan the input from the RFID reader. In this topic, the program has been made more efficient by incorporating a serial interrupt.
LCD is initialized to display the code. When a card/tag comes in the proximity of RFID reader, the microcontroller reads the code and sends it to the LCD module.
RFID (Radio-frequency identification and detection) reader is a device which is used to communicate with RFID tags by receiving and transmitting signals. These signals use radio waves for wireless communication. RFID tag is applied to products, individuals or animals to identify and track them. The identification is done through a unique serial number. This topic covers the interfacing of a passive RFID system with AT89C51. The code of RFID tag is also displayed on an LCD interface. The free source code for the program is available in C. RFID module basically consists of two parts, namely, a tag and a reader. A typical RFID system consists of an antenna, a transceiver and a transponder (RF tag). The radio frequency is read by the transceiver and the information is transferred to a device for further processing. The information (the unique serial number) to be transmitted is stored in the RF tag or transponder. The transponder contains a chip and an antenna mounted on a substrate. The chip transmits the relevant information through antenna.