Secret Knock Detecting Door Lock

Step 10 Epilog: Changes And Improvements

There are many ways to improve or change this project if you're feeling ambitious.  Here are a few to get you started, feel free to add more in the comments.

• Add an H-Bridge to the circuit so it can lock and unlock the door.
• Make it work in silent mode by removing the knock sensor and attach a capacitance (touch) sensor to the doorknob and record sequences of touches.
• Use a servo to unlock the door rather than this hacked together gear-motor+slip transmission.
• Add a potentiometer to adjust the knock sensitivity and other values.
• Build it into an actual door knocker.
• Use a more economical microcontroller and enable sleep mode for better battery life.
• Make the whole package small enough to fit inside the door.
• Store several knocks so several people can have their own 'private' knocks.
• Add a real-time clock and using different knocks for different days of the week.
• Add a knocker to provide feedback through the door.  It could then offer a challenge-response security where the door starts a knock sequence and the user has to finish it correctly.
• Remove the knock sensor and record pushes of the doorbell or other hidden button.
• Remove the knock sensor and put a photosensor in the peephole, send the open code through the peephole with a keychain flashlight.

And here's a zero-technology solution to the "Yeah, but someone'll overhear your secret knocks!" problem:  Scream while knocking.  No one will overhear the knock over the racket you're making.

Did you build this?

Post a photo (or better yet a video!) photo of it mounted on a door will earn a Master Of Secret Knocks patch*!

*As long as I have patches left to hand out.  Which I do.

Masters of Secret Knocks:

• josiasfilho added a servo and locking ability. 
• Jorad unlatches his door and added feedback in the peephole.
• Crimson-Deity added a pushbutton.
• bserrato added unlocking and a bluetooth camera to photograph people who give an incorrect knock.

Comments

[bserrato]

I saw your project some time back and I thought it was great. I decided to take it and improve on it, the result was a system that locks and unlocks. Also if a person inputs an incorrect knock, the system will send a signal via bluetooth to a computer terminal to snap a picture and save it.

http://www.youtube.com/watch?v=6k6XwyB8Hh0

Check out the vid. Hope you like it.

[Grathio]

That really made my week! It looks fantastic and works great. And the bluetooth camera is a great idea of added security.

[stephin99]

oh my ive got it!!! add a wifi unit and have it text you every time someone enters the code wrong

[bidkar garay]

respect...for you

[bjarni1995]

Great tutorial, i made a prototype of this but i used a servomotor, i found it really easy to edit the code to work with a servo.

-Bjarni

[wout smeets]

 how do you make an h-bridge for this doorlocker




i come from belgian srry for my bad inglish you can anser me on [e-mail]

[wout smeets]

 i have my arduino today



:p

[Grathio]

 There are a number good Instructables on the site for making H-Bridges, just click here.  (Or type "h-bridge" in the search box in the upper right, which is what I did.)

Of those I think this one might be the most helpful since it also mentions how to program the Arduino to use it.

[wout smeets]

thanks