RFID Based Security Systems

Published on May 2016 | Categories: Types, School Work | Downloads: 25 | Comments: 0 | Views: 239
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RFID based Security Systems

Radio Frequency means radio waves are used as carrier for transmission of data over wireless medium. Radio Frequency Identification (RFID) is a system that facilitates the tracking of objects, primarily for inventory tracking, via a three part technology comprised of a reader, a transceiver with decoder and a transponder (RF tag).

 RFID stands for Radio Frequency identification.

The reader emits a radio signal that activates the tag and reads and writes data to it.

 As products are shipped, received or stored, the information (encoded on a bar code like tag) can be read and received by the reader, which is attached to a computer.

RFID has been integrated into the EPC global network and uses the EPC (Electronic Product Code). The EPC is a unique number that identifies a specific item in the supply chain. The EPC is stored on a RFID tag , which combines a silicon chip and a reader. Once the EPC is retrieved from the tag, it can be associated with dynamic data such as the origin of an item or the date of its production.

 The development of RFID was spurred by the need to enhance tracking and access applications in the 1980’s in manufacturing and other hostile environments. This non contact means of gathering and tracking information proved to be resilient. RFID is now an established part of specific business processes in a variety of markets.  Passive tags can be low frequency (LF) or high frequency (HF).  LF tags operate at 125 KHz, are relatively expensive, and have a low read range (less than 0.5 meters).  RFID readers or receivers are composed of a radio frequency module, a control unit and an antenna to interrogate electronic tags via radio frequency (RF) communication.

 Many also include an interface that communicates with an application (such as the library’s circulation system).  Readers can be hand-held or mounted in strategic locations so as to ensure they are able to read the tags as the tags pass through an “interrogation zone.”  The interrogation zone is the area within which a reader can read the tag.  The size of the interrogation zone varies depending on the type of tag and the power of the reader.

Passive tags, with shorter read ranges, tend to operate within a smaller interrogation zone.

RFID Reader

 It consists of a RFID reader IC which is used to read tag.  A coil is used to generate magnetic field which powers up RFID tag.  It uses one of its pin to transmit data serially to microcontroller.  The microcontroller then cross examines it with ID’s present in its database .  If it is a valid ID then microcontroller allows access to a person.

If it is not a valid ID then microcontroller sounds alarm.

Power Supply

 Power Supply is derived from 230V ac supply.  It is stepped down to 12V using step down transformer.  By the use of 4 IN4007 diodes the ac voltage is rectified to DC voltage.  Using a 7805 regulator IC 5V is regenerated which is used as a power source for 8051µc and rfid reader.

Block diagram of RFID system

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RFID Antenna
The antenna in an RFID tag is a conductive element that permits the tag to exchange data with the reader.

 Passive RFID tags make use of a coiled antenna that can create a magnetic field using the energy provided by the reader's carrier signal.

Passive RFID Tag (or Passive Tag)

A passive tag is an RFID tag that does not contain a battery; the power is supplied by the reader. When radio waves from the reader are encountered by a passive rfid tag, the coiled antenna within the tag forms a magnetic field. The tag draws power from it, energizing the circuits in the tag. The tag then sends the information encoded in the tag's memory.

Advantages of a passive tag

 The tag functions without a battery; these tags have a useful life of twenty years or more.  The tag is typically much less expensive to manufacture  The tag is much smaller (some tags are the size of a grain of rice). These tags have almost unlimited applications in consumer goods and other areas.

Disadvantages of a passive RFID tag

 The tag can be read only at very short distances, typically a few feet at most. This greatly limits the device for certain applications.  It may not be possible to include sensors that can use electricity for power.  The tag remains readable for a very long time, even after the product to which the tag is attached has been sold and is no longer being tracked.

Summary on RFID tag
RFID Reader IC

 IM283 is a fully-integrated 125 kHz RFID reader circuit. It is specially designed for being a space and cost efficient kernel IC of an RFID reading and writing base station.  IM283 is accessible by a standard micro - controller as an intelligent front - end peripheral device.
Features of IM283

 Low-voltage circuit.  Read and Write capabilities  Supports most 125kHz tags on the market.  Supported frequency range: 100 to 150 kHz

 Operating temperature range: -40 to +125°C

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RFID reader collision
Reader collision occurs in RFID systems when the coverage area of one RFID reader overlaps with that of another reader.

This causes two different problems: Signal interference: The RF fields of two or more readers may overlap and interfere. This can be solved by having the readers programmed to read at fractionally different times. Multiple reads of the same tag: The problem here is that the same tag is read one time by each of the overlapping readers. The only solution is to program the RFID system to make sure that a given tag (with its unique ID number) is read only once in a session.

RFID system with EPC network

Transponder for RFID

An RFID transponder is a special kind of radio transmitter and receiver. It is activated when it receives a signal of a specific kind. RFID transponders are present in smart cards and Radio Frequency Identification tags.

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Tag collision
Tag collision in RFID systems happens when multiple tags are energized by the RFID tag reader simultaneously, and reflect their respective signals back to the reader at the same time. This problem is often seen whenever a large volume of tags must be read together in the same RF field. The reader is unable to differentiate these signals; tag collision confuses the reader.

Solution to tag collision

 Different systems have been invented to isolate individual tags; the system used may vary by vendor. For example, when the reader recognizes that tag collision has taken place, it sends a special signal (a "gap pulse").  Upon receiving this signal, each tag consults a random number counter to determine the interval to wait before sending its data. Since each tag gets a unique number interval, the tags send their data at different times.

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Disadvantages of RFID
Dead areas and orientation problems - RFID works similar to the way a cell phone or wireless network does. Just like these technologies, there may be certain areas that have weaker signals or interference. In addition, poor read rates are sometimes a problem when the tag is rotated into an orientation that does not align well with the reader. These issues can usually be minimized by properly implementing multiple readers and using tags with multiple axis antennas. Security concerns - Because RFID is not a line of sight technology like bar coding, new security problems could develop. For example, a competitor could set up a high gain directional antenna to scan tags in trucks going to a warehouse. From the data received, this competitor could determine flow rates of various products. Additionally, when RFID is used for high security operations such as payment methods, fraud is always a possibility. Ghost tags - In rare cases, if multiple tags are read at the same time the reader will sometimes read a tag that does not exist. Therefore, some type of read verification, such as a CRC, should be implemented in either the tag, the reader or the data read from the tag. Proximity issues - Tags cannot be read well when placed on metal or liquid objects or when these objects are between the reader and the tag. Nearly any object that is between the reader and the tag reduces the distance the tag can be read from.

High cost - Because this technology is new, the components and tags are expensive compared to barcodes. In addition, software and support personnel that are needed to install and operate the RFID reading systems (in a warehouse for example) may be more costly to employ. Vulnerable to damage - Water, static discharge or high power magnetic surges (such as from a close lightning strike) may damage the tags.


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