Knock Lock – Unlock a Door with a Secret Knock

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Piezoelectric elements can be used to make sound or detect sound. Steve Hoefer has made a Knock Lock, which is a device that can listen to knocks on the door. If the sequence of knocks is the same as the recorded knock sequence it unlocks the deadbolt on the door. Steve was the guy who also made the Dice Reading Machine.

Via: Zedomax

"While working on another project I ran across the Arduino knock sensor tutorial. Sensing a single knock is a great little project for learning about microcontrollers, but what about sensing specific knocks? Seeeeecret knocks? And if we could detect a secret knock, shouldn’t it unlock a door? If you can’t tell by looking this was cobbled together from spare stuff around the lab, it’s not much more than a piezo speaker, a tiny gear reduction motor, and an Arduino. And PVC pipe."

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20 Comments


  1. Well a lock is there for security. Needs a key, and this key can easily be copied. Someone can record it easily, or if you are like me, you can just memorize the rhythm. Imagine neighbor being able to copy your keys without reaching you pocket…


  2. @anon:
    If you read his site, he says that it is sensitive enough to tell the difference between two different people’s knocks, so security could be tightened by taking advantage of that. An ordinary lock can’t tell the difference between 2 keys or a lock pick or lock bumping. I think this might turn out to be just as secure.

    “The detection is surprisingly accurate and can even be dialed up so it’s precise enough to detect an individual person’s variation on a knock, similar to a Morse coder’s ‘fist’. (Though when the verifying is this tight it also triggers false negatives which are annoying.)”

    Either way it’s a pretty cool device!


  3. I think this is really meant for a room in the house. It’d be nice have for your own game room/office setup.

















  19. well see if it had an auto shut off that you could set to a timer
    so if someone tryed to get in it would shut off after like 3-5 trys of
    not getting it right for a certain amount of time that would be helpful.
    cuz then if someone did try get in, it would shut off cuz you know they wouldnt get
    it right the first couple trys. and then if ya came home and it was off then youd
    know someone tryed to break in and then you can just use your key to get inside.
    it just saves time if anything.which is better then using a key. but yeah i dont know
    if it was tested n stuff i would consider getting it, if not then no

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