Back in about 2003, I first heard about RFID modules being implemented by Wal-mart to control their inventory and warehousing. Well, I know it’s been well implemented throughout the world for many, many things these days, here’s how to build your own RFID reader so you can learn more about RFID plus free schematics are provided.
At the highest level, our device uses an antenna coil to power the RFID tag embedded in our Cornell ID’s and read the induced response from the card. This response is then filtered and manipulated into useful data and interpreted by the Atmel Mega32 microcontroller which runs the actual security program. In addition to interactions with the ID cards, the system is in contact with an administrator computer via a serial communications link and hyperterm. The security system can store up to 20 45-bit codes which are derived from communications with each unique RFID tag. If a card is read and it is not in the code database, a red LED flashes for 3 seconds. Likewise, if the code can be found in the database, a green LED lights for 3 seconds. From hyperterm, the administrator has the power to add codes, delete codes, list all codes, “unlock” the door (the equivalent of the green LED flashing), and initialize routines which allow codes to be added to the database by gathering data from the reader itself.