For my first intermediate project, I plan to make a keypad controlled lock, using buttons, a homemade switch, and a piezo buzzer, among other things.
The way this will work is as follows:
You will type in a code using the buttons. If the code is correct, it will allow the “door” to be opened. When the door is open, the connection made by the switch is broken. If the code is incorrect, or if someone just tries to open the door without entering a code, the piezo buzzer will sound. I am also considering including an LCD screen to say things like “(in)correct code,” “alarm on/off,” etc.