PIC Microcontroller Doorknob Combo Lock
Overview
Basically this makes a doorknob act as combination lock. Turn the doorknob and it changes values on display, once the proper combo is input it will trigger a solenoid to release the lock.
Detailed Writeup
- Electronics -- This consists mainly of the display, relay, power, solenoid, and a PIC to drive the whole thing.
- Hardware -- This is a modification to the door handle to have it turn a trim-pot and use an eye bolt used to catch the solenoid's piston.
Conclusion
- The Good
- It works without any problems. Doorknob is responsive, locks solidly, and will allow you to unlock it twice in succession with a single correct password(So it can be shut again)
- Minimal damage to the door, only required 2 small screws into the frame to hold up the solenoid.
- The Bad
- Three power supplies! It could easily be done with 2, I just didn't find one lying around that matched what I needed. I'm sure there is a way to do just 1, but I didn't spend enough time get it
- No easy way to get in to fix it if it ends up breaking, which is kind of the point ;-)
- The Ugly
- The wiring is horrendous, since it has wires sticking out from the door, to the wall, and too the door handle from the inside. I used a phone jack even to plug the PIC into the trim-pot, adding to the mess further. It's all tucked away fairly neatly now(Except the phone wire), but is still horrible.
- Future Improvements
- Put everything inside the door itself so it looks much neater. This would mean swapping the positions of the solenoid and the eye screw. I didn't want to harm the door itself is why I didn't do this, since it is the 'correct' solution.
- Use 2 solenoids so it could be defeated by simple removing the hinges
- Use one power supply. Really just needs about 2 amps, and a current limiting resistor on the solenoid
There is a video of it running below, the password being used is 1B50. It is hard to tell what's going on unfortunately since the control box is on the ground
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2008-04-10 03:44:54
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