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RFID Access Control SystemLucius KnightETEC 474Senior ProjectHardware Description4.28.09

RFID Access Control SystemIntroductionThis document describes the RFID access control system and its hardwareimplementation. The system includes a microcontroller, RFID module, antenna, RFIDtags, a lock, and H-Bridge, an LCD, a keypad, a serial connection, a power supply, and avarious other components.MicrocontrollerThe RFID access control system will be built around a Cypress CY8C29466 PSoC. Ithas 24 GPIO, 32kB of flash, 2kB or RAM, and is capable of communication using I 2 Cand UART. The PSoC is powered by +5 volts. All unused GPIO are set as outputs insoftware so they can be left floating and unused inputs are pulled low to ground.RFID ModuleThe SM125-M1 is an OEM module from SONMicro. It is designed for 125 kHz RFIDapplications. It performs all of the RFID processes such as amplifying, filtering,demodulating, decoding, and digitizing. Data is sent from the RFID module to the PSoCover I 2 C with 4.7kΩ pull-up resistors. The I2C_SCL and I2C_SDA on the RFID Moduleare connected to P1_5 and P1_7 of the PSoC (U1). An LED is connected to TAGF of theRFID module and is used to signal a tag within read range. A buzzer is connected toP0[5] of the RFID module and is used to signal a successful tag read. The RFID moduleis powered by +5 volts. All unused GPIO are set as outputs in software so they can beleft floating and unused inputs are pulled low to ground.AntennaThe antenna for this project is an OEM part from SONMicro. It is a loop antennadesigned for 125 kHz and is approximately 850μH. It is connected to pins ADVR andIND2 of the RFID module (U2).RFID TagsThe passive RFID tags used in this system will be powered and read by the RFID module(U2) using the antenna (L1). The maximum read range between the tags and antenna isabout 12cm.LockThe locking mechanism for the project is a Schlage FE595VCAM619ACC. Inside it, aDC motor (M1) is controlled by the H-Bridge (U3). When an “unlock” signal is sent tothe motor, it turns a spring which forces a pin downward, engaging the lockingmechanism. When a “lock” signal is sent to the motor, it turns in the opposite direction,moving the pin upward, to disengage the locking mechanism.H‐BridgeThe L293D is an H-Bridge used to control the motor (M1) in the locking mechanism. Itreceives signals on IN1 and IN2 from P1_2 and P1_3 on the PSoC (U1). EN1 is tied to+5 volts to enable the H-Bridge. The motor (M1) is connected to OUT1 and OUT2 of theH-Bridge. A logic 1 – 0, from the PSoC, turns the motor in one direction, a 0 – 1 turns it[1]

RFID Access Control Systemin the opposite direction and a 1 – 1 stops it. The H-Bridge is powered by +5 volts. Allunused outputs can be left floating and unused inputs are pulled low to ground.LCDThe LCD module used in this project is a 16x2 character display by Lumex. Its modelnumber is LCM-S01602DTR/A and it’s compatible with the Hitachi HD44780U chipset.In order to conserve GPIO on the PSoC, the LCD will run in 4 bit mode. The data linesD4 – D7 will be connected to P2_0 – P2_3 of the PSoC (U1). The control lines E, RS,and R/W’ are connected to P2_4 – P2_6 respectively. The power for the LCD modulewill come from the +5 volts supply and a potentiometer will be used to control thecontrast of the LCD. All unused inputs are pulled low to ground.KeypadThe keypad in this project is the 96AB2-102-R by Grayhill. It is used to control the userinterface and enter data. It is a 3x4 matrix of switches including the numbers 0 through 9along with the characters * and #. ROW1 – ROW4 are connected to P0_0 – P0_3 of thePSoC (U1). COL1 – COL3 are connected to P0_3 – P0_6 of the PSoC (U1) with internalpull-up resistors.Serial ConnectionThe serial connection of this project uses UART to transfer data stored in the PSoC (U1)to a terminal emulator on a personal computer. This is accomplished by a female DB9jack driven by a MAX2321 RS232 driver chip. P1_4 and P1_6 on the PSoC areconnected to T1in and R1out on the MAX2321 (U5). T1in and R1in on the MAX2321are connected to pins 2 and 3 of the DB9 connector. The various capacitors connected tothe MAX2321 are in the manufacturer’s recommended configuration for voltage levelconversion that is used by the driver chip. The MAX2321 is powered by +5 volts. Allunused outputs can be left floating and unused inputs are pulled low to ground.Power SupplyThe power supply for this project consists of an AC/DC wall adapter and a DC voltageregulator, the uA78M00 by Texas Instruments. The wall adapter outputs between 9 and12 volts into the voltage regulator which outputs +5 volts to the system. Bypasscapacitors are connected to ground to remove unwanted AC voltages.Miscellaneous ComponentsIn order to reprogram the PSoC (U1), an In System Serial Programmer jack is connectedto Sdata, Sclk, and XRES of the PSoC. It is also connected to +5 volts and ground. TheSdata and Sclk pins on the PSoC also double as the input and output of an external crystalthat oscillates at 32,768Hz which is used for better accuracy of the real time clock. Thesetwo different components can be connected to the same set of pins on the PSoC becausethey will never be used at the same time.[2]