"Knock, Knock!" Arduino Escape Room Puzzle

This is a video tutorial explaining how to create a "knock, knock" puzzle as seen in some escape rooms, in which players need to tap out a particular rhythm (such as a secret doorknock), to activate a relay and unlock a maglock. Two versions are demonstrated - one using a Piezo sensor which is activated by vibration, and one using a microphone input which can detect any percussive sound. The secret knock pattern required to solve the puzzle can be set to any rhythm you want, and the player's input is normalised before comparison to make it tempo-independent. There are also configurable settings for input sensitivity and error tolerance. To download the Arduino code, wiring diagram, and list of components used in this video or any of my other tutorials, please see my Patreon at   / posts   - thanks!