I'm trying to rig up my door to be unlockable using RFID and an Arduino. The problem is the actual mechanics of unlocking the door. There's a few limitations:
- I can't actually unlock the door. It's permanently locked and can only be opened from the outside with the key.
- It's a handle, not a knob
- It's an incredibly stiff handle, so any mechanism that would actually turn the handle would need a significant amount of force
- I'm renting the place, so I can't make any major or permanent modifications to the door or the door jamb or anything.
I tried using a motor and threaded rod to make a linear actuator, but that's slow and loud. I'm trying to consider whether it would be practical to put a tiny solenoid in the hole where the door's bolt goes when it's closed. (The hole in the strike plate in the door jamb) The hole is much larger than it needs to be (1" deep for a 1/2" bolt), so theoretically, if I had a solenoid that's 1/2" long when unpowered, it would fit in there, and could directly push the bolt so the door could be opened without turning the knob.
Unfortunately, I don't have any experience with this sort of thing, so I have no idea if this is even remotely practical. What would you recommend? Is a tiny solenoid a reasonable solution, or am I better off finding a way to physically turn the door knob?