Circuit Design
The first wire on the left is used as a slave select for the RFID reader which causes the the module to listen to the SPI wires when set to low. This is set to digital pin 7 on the Arduino but is easily changeable. The next 3 wires are for the other SPI wires, SCK, MOSI, and MISO respectively, which need to connect to their matching pin on the Arduino UNO, digital pins 13, 11, and 12 respectively. The 5th pin from the left is an interupt pin but is not used for this project. The 6th wire and 8th wire are used for ground and 3.3V respectively. The 7th is used as a reset which causes the chip to run when set to high. This is set to digital pin 3 on the Arduino but is easily changeable.
The 3 SPI PINS, digital pins 13, 11, and 12 for SCK, MOSI, and MISO respectively, are also used by the Data Logging Shield to communicate with the SD Card slot. The SD Card slot also uses digital pin 10 as the slave select pin for SPI communications with the SD Card. The Real Time Clock uses I2C through analog pins 4 and 5, SDA and SCL respectively.