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Because I have not tested all electronic circuits mentioned on this pages, I cannot attest to their accuracy; therefore, I do not provide a warranty of any kind and cannot be held responsible in any manner.
Homemade RFID reader
27. August 2008 - 12:15 — admin
Easy homemade RFID tags reader based on the PIC microcontroller.
The RFID cards is powered by the magnetic field emitted by the RFID reader. The RFID tags transfers information back to the reader by loading the magnetic field, which cause the RFID reader to sense the change in load.
The most common design for RFID reader is to use a series resonate circuit. This consists of a single inductor and a capacitor excited by a low impedance voltage source. If the Q of the circuit is high enough, the voltage at the sampling point will exceed that of the supplied voltage. When the RFID sends a one by loading the magnetic field, this causes the Q of the circuit to drop.
Link: RFID reader