By: Craig Ross (cjr37) and Ricardo Goto (rhg22)
For our final project, we designed and built (and exhaustively tested) an RFID-based proximity security system for use with Cornell Identification cards, which have been RFID-embedded since fall of 2003. The idea for this project was sort of spawned from our general interest in RFID technologies and the near-simultaneous occurance of Lab 2 (Keypad Security System) and the antiquated lock system at our fraternity house breaking.
“Old and Busted…New Hotness” -Will Smith
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.
Educational topics explored in this lab include (but are not limited to) passive filter design, active filter design, amplification circuits, RF antenna design, digital logic, serial communications, RFID theory, pin interrupts, timer interrupts, and soldering. In short, for this project we used elements of basically every introductory level ECE course we have taken. Since we are dealing with such a complicated topic, on the hardware side of things we tried to rely as much as we could on proven circuit designs. This would enable us to focus more on getting our system working well as a whole rather than spending countless hours debugging small parts of our project. For this, the Microchip® microID 125 KHz Reference Guide (see citations section) proved to be an invaluable resource for both theory and results.
Source: Cornell University