A simple lock system with an RFID module.
All you need is an Arduino with an RFID module, an ultrasonic sensor, and some leds, and a servo motor to work with this code, and of course some RFID card as well. Before you using the code you need to get the ID from each RFID card that you want to use, to unlock the lock, when you done that part, just write those ID's in the right array in the code file and you are up to go.