Embedded access:

INTRODUCTION:

• Here the RFID system is designed.
• The need for automatic access have become very prominent in the modern century today.

BLOCK DIAGRAM FOR RFID:

Major components of ATTENDANCE system (RFID):

TAG(RFID):

• It comprises a silicon microchip made of silicon that is mounted on a substrate base.
• The chip is attached to an antennae.
• The whole chip is encapsulated in either glass or plastic veil.
• It also has an adhesive back coating in order for it to stick to some tag or object.

PRACTICAL APPROACH OF RFID:

• In order to take the attendance of all the members within a organisation we can employ this system.
• The basic idea is to use a swiping access card as a means of biometric register(not really.)

2.READER:

• It comprises of  a scanner equipped with antennas in order to transmit and receive data from tag.

3.MICROCONTROLLER:

• Its primary function is to receive the readers data input and then processes it.

DIFFERENT TYPES OF RFID SYSTEM:

The Active system:

• Within this system the tag comprises is own power source similar to any battery or external power source .
• Constraint involved here is only the lifetime of the existing  power devices.
• These devices can be employed  for long distance communication and to also to keep a track of expensive goods vehicle.

The Passive system:

• Within this  system the tag gets sufficient  power via transfer of power from the  reader antenna towards the tag antenna.
• These devices  are employed for short distance communication.

TWO MAIN METHODS OF POWERING UP TAG(RFID TAG):

1. The Passive system employing  Induction coupling method:

• Within this system  the RFID tag obtains power from the data reader via inductive coupling method.
• Data reader comprises of a single coil connected to an AC supply so that  a magnetic field encircles it.
• Now the tag coil is placed next to the reader coil(very close).Subsequently  an electromotive force induces inside it according to the nature of Faraday’s law of induction.
• The resulting  Electromotive force  causes a current surge  into the coil within the reader, thereby creating a magnetic field surrounding it.
• According to Lenz law, the magnetic field so produced from the tag coil negates  the reader’s magnetic field and there will be an eventual increase in the current within the reader coil.
• The Data reader understands this as the input data  information.
• This sort of RFID system is much appropriate for negligible short distance transmission .
• The subsequent Alternating Current  voltage created about the tag coil is thereby converted to DC with the aid of  rectifier and filter setup.

An example of a Passive RFID system with EM wave propagation method:

• Here the antenna that is embedded within the reader sends out  electromagnetic waves.
• These waves are subsequently  received by the antenna embedded within the tag as  a potential difference is created across the dipole.
• Subsequently the voltage so produces  is rectified and finally filtered to get the  desired Direct current(DC) power.
• Note that the receiver antenna is placed at a different impedance thereby  making it to reflect a part of the received signal.
• Finally the reflected signal is obtained by the data reader and compared to existing databases programmed into the system  accordingly and timingly.

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