RFID description

RFID-based parking system introduction 

Radio-frequency identification(RFID) is an automatic identification method wherein the data stored on RFID tags or transponders is remotely retrieved.The RFID tag is a device that can be attached to or incorporated into a product, animal. or person for identification and tracking using radio waves. Some tags can be read from several meters away, beyond the line of sight of the reader. RFID  technology is used in vehicle parking systems of malls and buildings .


The system normally consists of a vehicle counter, sensors, display board, gate controller, RFID tags and RFID reader. Presented here is an automatic vehicle parking system using PIC 16F877A microcontroller.

Basically, an RFID system consists of an antenna or coil, a transceiver (with decoder) and a transponder (RF tag) electronically programmed with unique information.There are many different types of RFID systems in the market. These are categorized on the basis of their frequency ranges. Some of the most commonly used RFID kits are low-frequency (30-500kHz), mid-frequency (900kHz-1500MHz) and high-frequency (2.4-2.5GHz).

RFID antenna. Figure 1 shows the internal diagram of a typical RFID antenna. The  antenna emits radio signals to activate the tag and read/write data from/to it. It is the conduit between the tag and the transceiver, which controls the system’sdata acquisition

figure 1: internal structure of RFID tag

how (passive RFID)RFID tag can transfer data by no having a battery?

RFID tag (passive) will get a supply from a RFID reader. when RFID reader on, so RFID reader will transfer a magnetic field by copper coil(RFID antenna) to the RFID tag when it touch it or near by in some range. when RFID receive a EMF from RFID reader , then it will go to the chip and from chip RFID tag will transfer back RFID reader that case we call it as back scatter. both RFID tag and reader have antenna (copper coil) it same as wireless power transfer.

RFID wiegand input format description:

Wiegand protocol provides 2 lines for data transfer. A pulsed transition on the DATA1 line indicates a logic 1 bit, while a pulsed transition on the DATA0 line indicates a logic 0 bit.  In their idle state both lines are held high. During data transfer the appropriate logic line will pulse low for 50us followed by period of 2ms where both lines are held high.

In this fashion each bit it transmitted in sequence until all bits are sent.  The end of the transmission is signaled by both lines being held high for more than 50ms.

 Figure below show an example of the timing sequence for wiegand protocol