Secret Knock Detecting Lock


I was going through my old youtube playlists recently and I stumbled upon a video that I hadn’t seen for over a year ago. I thought it was really cool and some of you may not have seen this before. It’s a knock detecting lock made by inventor Steve Hoefer. It detects a knocking sequence and unlocks a door when the knocking is produced correctly.

This is a really cool idea for a micro-controller. This is definitely thinking outside the box as far as security goes. I think using it would seem so natural. Also I think the benefit is that your knock could be complex, but somewhat easy to remember. Could you imagine somebody trying to crack it by standing there knocking a long time? I don’t, plus they would be likely to get unwanted attention.

What do you think about this innovation? Do you guys think it’s practical for use?

link for info on how to build:


4 thoughts on “Secret Knock Detecting Lock

  1. That’s a pretty cool video there, but I think that would only be effective as an addition means of security. Because the knock is audible, almost anyone in the area that hears the knock could potentially remember it, and use it later. But it is definitely not a bad idea as an additional means of security, assume the knock would be changed very often.

    • Good point about it being changed very often. I came to that conclusion too after thinking about it for a while. Maybe if you knew Morse code you could work a system out.

  2. Pretty cool idea, is what I think. To have to knock to unlock a door, awesome. I kind of find it similar to using biometrics to unlock a door. Other than a voice or fingerprint, a knocking sound is used. However, a fingerprint or voice can’t be forgotten. But a knock? It’s possible. But, I would think there would be a key to unlock the door just in case. Also, adding to the fact that someone around could potentially remember it, someone could also place a microphone somewhere near and record all your knocks. But, overall cool idea. With a few security improvements, it could be useful.

    • I totally agree that with a few security improvements it could be useful. Thankfully some people have already been making improvements. This one guy used his peephole for a visual feedback mechanism.

      There is even a few students that have built it with a RFID instead of a knock.

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