Knock Detecting Lock


[Steve] shows us his version of the knock detecting lock system. The idea is pretty simple, knock in a certain pattern and the door unlocks. We’ve seen it before several times. This solution is somewhat cleaner than the others, not only in physical design, but also in how you reprogram it. Simply push the reprogram button and enter your new knock. We’re a bit surprised that the suction cups actually hold it on the door. Maybe it’s just us, but we can never seem to get those things to hold very well. There are lots of great pictures as well as the source code available on his site.

[via HacknMod]

18 thoughts on “Knock Detecting Lock

  1. robomonkey: It would be fun if you just pressed the program button quickly to open/lock the door, and held it down to program.

    It may be one of those doors whose deadbolt unlocks when you turn the door handle from the inside.

  2. “We’re a bit surprised that the suction cups actually hold it on the door. Maybe it’s just us, but we can never seem to get those things to hold very well.”

    Get some dishwashing soap. Clean the surface you wanna put it on and clean the cups. let it dry and don’t touch on the surface. Take your tongue (or much better: a damp sponge) and wipe over the cup. Press it down – et voila.
    Most people don’t care about really cleaning the surfaces, so it doesn’t hold well. Same people that say Second adhesive never works for them… clean (and i really mean: get rid of all fat sitting on your surfaces) and glue and you will never get it apart again…

  3. Nice, and nice presentation in that video.
    I know the suction-cups are not going to last, but you can affix it how you want of course, this is more for portable presentation I guess so I for one look past that.

  4. If I or another normal person used this the knock would be pretty simple but there are some guys I used to know for whom this could actually be secure. They loved to freestyle (rap) and would pound out beats on the desk for each other. Some of them were pretty complex. Even so, I wouldn’t use it for anything I really wanted to keep secure.

    1. Very good idea. If you imagined a 3×3 keypad on the door, you could use rhythm and position to have pretty good security, even with the neighbors listening. We have a similar system where I work for detecting the spread of bullets from machine guns. We have a target with metal bars along the bottom and left sides. Both bars have a piezoelectric sensor at each end, and the shockwave from the bullets sends vibrations through the bars.

      You could also have a automatic formula for changing the position pattern depending on the day of the month and the hour of the day.

  5. I like…the bit about the suction cups is not important as someone already mentioned, because I finally version would be fixed.

    I think that I would rather have something digital broadcasting using a key fox, but something secure and encrypted, but I’ve only started playing with the arduino so I don’t know how it would cope with encryption.

  6. so anyone who hears the knock can then enter without breaking anything ? That includes neighbors, people you let in and people with a directional microphone…

    It is a bit like a digicode where you would be shouting the code each time you want to enter

  7. RFID in pocket or bluetooth pair from phone in pocket connected prior to accepting knock would add physical item for security. Door edge clasp could hang around top or side of door for stability on temporary mount would also allow for a mag strip reader to be added on outside of door for another possible physical item. Each physical item used could allow for multiple parties with personal separate patterns to open. Bluetooth or other radio comm could also allow pattern creation and programming on one’s phone where the door could receive the pattern you tapped onto phone touch screen just before knocking on door.

    Air or light gaps under door or even eye hole viewer could allow for light or shadow additions to the knock combination by using light detection sensors so only covering eye hole during part of the knock pattern but not during other parts of the knock. Flashlight/laser pointer could add light instead of using shadow detection for use in unsteady lighting conditions where light is part of the combination.

    For the guest access allowances or maybe kids’ bedroom doors, my thoughts drift to a dance pad controller for some reason flopped under the door to make the user move a little un-naturally on the pad buttons for entry with the knock patterns.

  8. Tritium is a low-energy beta emitter, not an alpha emitter. (Getting a helium-4 nucleus emitted from a hydrogen-3 nucleus is a little arithmetically challenging.)

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