A ratchet mechanism that allows the motor to turn the knob only in the UNLOCK direction would allow you to unlock from the outside with a key if the RFID fails.
You may be able to read the RFID token THROUGH the door. No holes needed.
Ah, though I want to be able to lock the door with RFID too though. I was thinking of locking the door the same way, by reading the RFID tag and turning the knob in the other direction. I'm not experienced in electronics, but I experimented with stuff, taking them apart when I was a kid so I know a bit about motors and such. If the motor would be "turned off" (like, no power fed to it? I saw some video discussing that idea but I can't recall which one) while no card is being read, would that allow the motor to freely rotate without damaging it?
Also, does RFID really have that range to read through the door? The door is about 6.5cm (2.5in) and made of wood (I don't know if there is metal inside of the door), wouldn't that require quite a large reader, which might need more power and be more expensive? Otherwise, I was thinking of just having an antenna taped to the outside of the door (having the wires go trough the springs of the door), and having a nameplate sticker over it to hide it some (my nameplate was stolen anyway).
How much power do you think the project would take (in standby)?
Do you think an RFID lock mechanism would be safe?
Depends on the programming, and the ability to exit in case of emergency, but, in general, yes.
I'll figure something out about the programming when I got everything I need. I've programmed in a few languages before (java, c++, php, python) but I learn new languages pretty fast
. On the inside I would have two buttons, one for lock and one for unlock. In the case of power outtake I guess I could remove the thing from the door and open it normally.
How much do you think a project like this can cost?
How much do you have?
Well, I could think of spending about $100 - $200 on it, but the cheaper the better, I'm a student afterall :>