The Secret Knock Detecting Door Lock

Grathio, the Instructables user who creates this DIY, gives you two notes first up: this is a joke project. A great learning experience but do not use this system for your door lock security as it has limitations and actually it may reduce the safety of your room. Secondly, this is not a project for beginners. The coding is interesting and the setup takes some proficiency (and you will need to use a saw to cut PVC pipes). So if you are up for some challenge and want to have some fun then, go for it – and only then.

To create an electric circuit for secret knock detection, startup by wiring the crucial parts: the Piezo sensors through a pair of leads; LEDS with ohm resistors; 1 5v Gear reduction motor with the diodes; and the programming button with +5v. The actual schematic is provided by the instructor and is it pretty straight forward. As for the physical structure, cut the arms and legs of the door lock from a PVC pipe as per the requirement. Here, a 5 inch long arm and two 2 5/16″ long legs are put to use.

This DIY relies on two main mechanisms for its operations. The first is the lock turning mechanism. This one is executed with a clamp that attaches to the D-shaft of the motor and attaches nicely over the lock latch in order to turn the lock. The second mechanism is of knock detection, made by gluing Piezo sensors on a PVC pipe.

Like most DIYs, this one too offers a lot of scope for improvement. A servo motor, for instance, can be programmed to open the door. A potentiometer can be used to improve the knock listening capability. A battery saver mode can be used to give a longer life to the gadget. And so much more… – the question is: how imaginative and resourceful are you?