arduino based door locking system

Here is an electronic locking system in which the Arduino Nano plays the role of the processing unit.
The circuit allows the activation of the electronic door lock only when the correct password is entered.
It uses the Arduino Nano to provide a keyboard interface door lock for the front door.
This is a keyless system where you can enter your home using your own personal code with just a few buttons.
The keyboard lock realizes the function by entering the password. The password is user-programmable.
Circuit and work using a micro controller (MCU)
Reduce external components.
The circuit includes the Arduino Nano board and the transistor PN2222A (T1)and BD139 (T2)
, 4x4 matrix keyboard (S1-S16)
, Solenoid locks and some other components.
The 4x4 matrix keyboard is connected to the Arduino digital pin d4 via d12.
The keyboard simply arranges 16 button switches in the form of a 4x4 matrix.
Usually, the hexadecimal keyboard will have keys for numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9, letters a, B, C, and D, and symbols * and.
The hexadecimal keyboard will have eight connecting lines, respectively, through resistors R1, R2, R3, R4 and capacitors C1, C2, C3, C4 representing rows and columns. The matrix-
The encoding scheme requires fewer output pins, so there are fewer connections required for the keyboard to work.
Electronic door lock system schematic diagram as shown in figure shown in. 2.
Arduino receives parallel data from the keyboard.
The Arduino Software keeps scanning the keyboard to see if the button is pressed.
When a valid code input is received, the digital pin D4 is higher and the solenoid lock is triggered for five seconds.
The transistor T2 is capable of providing up to 1.
The current of the solenoid is 5 amps.
LED1 indicates that the lock has been opened.
Entering an invalid code causes it to flash several times.
The diode d4 protects the circuit from any back potential that may occur when the lock is turned off.