The university I study at has a special elevators for masters, and masters have somthing like a coin that they can use the elevator. As I know it's an rfid tag and it is a 125khz one. and have a 100 turn coil.
My masters know that I want to do that, and there is no problem with doing this. Its something like a university project. I know that the tags have a special serial, and I can find one of that tags serial by using a RFID reader. However the current tags are not writable. Can I do this project by using a microcontroller? If so how? Also one of my friends is a specialist can he help me?