In this keypad lock project I have used the AT89S52 microcontroller, one of the series of 8051 microcontroller by ATMEL corp. Here I’m using 4X4 keypad to take input from the user (to enter password) and display the corresponding results on a 16X2 LCD. Since AT89S52 doesn’t have its own internal oscillator, thus we need to provide an external crystal of 11.0592 Mhz to make it function able. I am using a 7805 voltage regulator IC to convert 9V to desired 5V output.