Project idea
A password-based access system built on an 8051-family MCU uses a matrix keypad for entry, stores the password in an external EEPROM, and drives a lock via a motor driver for secure, configurable access control.
The authorized user can change the password at runtime, while correct entries actuate the solenoid lock and wrong attempts trigger visual/audible alerts as per typical lock module operation and driver capabilities.
 
Project description
An AT89S52 (8051) reads a 4×4 matrix keypad, compares input against a password stored in 24C04 EEPROM, and controls an H-bridge driver to actuate a 12 V solenoid door lock, with alerts on error using indicators and the driver’s ability to handle inductive loads.
Password change mode writes the new code to EEPROM through I2C, while a 12 V/2 A adapter powers the lock and a 5 V rail powers logic, consistent with common adapter specs and module-level driver/lock requirements.
The design targets homes, offices, and labs, and can be built on a general-purpose PCB or breadboard-style phenolic board sized for these modules and wiring.
 
Total list of components
8051 Microcontroller
EEPROM
Matrix Keypad
Resistors
Capacitors
Transistors
Cables and Connectors
Diodes
PCB and Breadboards
LED
Transformer/Adapter
Push Buttons
Switch
IC
IC Sockets
Mini Door
Software Specifications
Keil µVision IDE
MC Programming Language: Embedded C
 
Features
Password-protected entry with on-device password change stored in non-volatile 24C04 EEPROM for durability and retention.
16‑key keypad interface for numeric/functional inputs with adhesive, low-profile installation options.
Lock actuation via L293D H‑bridge driving a 12 V solenoid lock suitable for doors, cabinets, and similar enclosures.
Operates from a 12 V/2 A adapter with a regulated 5 V logic rail, matching common accessories and module power needs.
 
Applications
Home and apartment main/inner doors, lockers, and cabinets using compact 12 V solenoid locks.
Office doors, equipment racks, and storage rooms requiring configurable access.
Institutional labs and workshops where quick password reconfiguration is beneficial.
 
Project Includes:
Fully assembled and tested circuit
Circuit diagram
Source code 
(For DIY KITs - only the components will be provided)
 
Project Types:
DIY KIT(Do IT YourSelf KIT) - We are providing only components in this kit for this project
DIY KIT with Code & Circuit Connections - Along with the components, you will get the Code and the Circuit Connections file to help you build the project easily.
Readymade Breadboard - We are providing fully assembled, tested and ready-made project using plug-n-play jumper wires and breadboard with all the other components, code & circuit diagram.
Readymade Soldered - We are providing fully assembled, tested and ready-made project soldered on a PCB with all the other components, code & circuit diagram.
 
Dimensions (cm)
Assembled unit (controller + driver + wiring on 5×7 cm proto and lock mount): approximately 15 × 12 × 6 cm, sized from module footprints like L293D board 4.4 × 3.7 × 1.4 cm and compact lock 2.8 × 2.7 × 1.9 cm.
 
Shipping dimensions (cm)
With protective padding and adapter: approximately 22 × 16 × 10 cm to accommodate lock, adapter, and mounted controller safely.
 
Weight
Estimated net weight: ~0.6 kg, dominated by the solenoid lock (~0.15 kg) plus adapter and controller assembly mass.
 
Estimate project weight: 1kg
 
Notes: All the products are made by LearnElectronics India and not for re-sale.