Overall this project is easy. The longest surely was the coding, since I'm intermediate at best. There are 3 sections for this project : the Bluetooth setup, the slave keypad , the master receiver box.
The master box is connected to the intercom of my apartment. When it receives the proper password from the slave keypad it closes a relay that presses the door unlock switch of the intercom. Power is provided from a 15v dc regulator inside the telephone of the intercom. The master box can have 4 different passwords, the fourth one being valid for 24 hours only. This is convenient if you wanna give someone a time limited access to your apartment. The passwords are protected by a master password, so that you cannot read the passwords by simply pressing the buttons on the master box.
The slave box has 2 LEDs , and a 4x3 keypad that was modified to single out the * key out of the matrix so that it is used as a power button. Pressing the star button will drive a transistor that will connect the 9v battery to the 5v regulator of the box, and once the MCU starts it will output 5v and drive the transistor that is powering it. It will then wait to connect to the master Bluetooth module and once connected, it will turn off the LED. You can now enter your PIN , it will send it and turn off the transistor to shut down the keypad box, disconnecting the battery from the regulator.
The master box receives the password and validates it. If correct it closes the switch for 4 seconds, then waits for the next connection.