To set up it, you connect the 8 pins of the keypad to the Arduino’s digital input pins. Using the Keypad library for Arduino makes it easy to manage the keypad and detect which button is pressed. Allowing you to create features like password input, menu selection, or triggering specific actions based on the keys pressed.

Navigate to the Libraries icon on the left bar of the Arduino IDE. Click Install button to install keypad library. A popular application of keypad is the password input. In this application, we specify two special keys: A key to start/re-start the password input. For example, key "*" A key to terminate the password input. For example, key "#"

In order to determine the Key pressed on the Keypad, we have use a special library called, well “Keypad”. You should first download this library and place it in Arduino/libraries directory (C:\Program Files (x86)\Arduino\libraries or C:\Program Files\Arduino\libraries). NOTE: The library “Keypad” was developed by Mark Stanley and Alexander Brevig.

The code for a password lock system using a keypad and Arduino involves reading the keypad input, comparing it with a predefined password, and controlling the relay based on the input. The code typically includes functions for initializing the keypad, reading input, comparing passwords, and controlling the relay.