Introduction: Secret Knock Door Lock

Hey guys, Its time to get into another project that can blow up your mind.
This project is about door lock safety, you have to set a special knock by which you can unlock your door.


To make this project you require:
1. Arduino (any board will be suitable) ×1
2. Piezo Speaker ×1
3. Red LED ×1
4. Green LED ×1
5. Relay module ×1
6. Solenoid lock ×1
7. 1M resistor ×1
8. 220 ohms resistor ×2
9. Jumper wires


In this Instructable, the main principle is that, the arduino can detect and record the frequency of every knock and the time between every knock. This project also has the function to record new knock if required. You can place it behind the door and the speaker just in front outside the door. And thus your installation is completed.

Step 2: Circuit Connection

I have made the circuit connection in the fritzing software. So, I am giving both the fritzing and Image file.

Step 3: Coding.

To make this project we require the code.

The code is here :

Step 4: Testing