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Microcontroller Based Programmable 4-Digit Code Lock System can change the password with alarm useful for Door Lock, Device Lock, Car Lock, and Locker System (Using 89C2051). Today is the world of automation. When we are talking about automation, we must think about microcontroller. Microcontroller finds its application in each and every automation control like Remote controllers, Hand-held communication devices, automatic and semi-automatic washing machines, security system, telephone printing machines, automobiles, indicating and measuring instruments. The project described here being also a microcontroller based project, used for security purpose. The use of microcontroller in this project is to store the data, process data and change data according to the user requirement. This is possible because microcontroller has CPU, memory, I/O ports, timers/counters, ADC/DAC, serial ports, interrupt logic, oscillator circuitry, and many more functional blocks on single chip. Hence it reduces the cost of hardware. Also there is no need to connect external RAM for memory storage. This is the most important feature of microcontroller. There are various types of microcontrollers available in market. The examples are Intel MCS-51, PIC family by microchip, ATMEL 89CXX, 89CXX51. The microcontroller used for this project is ATMEL-89C2051. The important features and pin description are given later. The code lock system described here uses a very simple hardware as shown in the circuit diagram. IC1 and IC2 are bus driver and latch IC’s, which are used for transmitting and receiving data from microcontroller i.e. it is the interface between microcontroller and keypad logic. At pin2 and 3 of microcontroller, relay drivers using transistors are connected. IC5 is a regulator IC, which gives 5V regulated power supply. Software is used to store code, process code according to user requirement and gives output at corresponding port. The device activates an output when correct access code has been entered on a keypad. This code consists of four digits in the range 0 to 9. The code can be changed by the user and is also remembered when the power is off. The circuit is eminently suitable as an electronic door-lock, the switching section of a burglar alarm or as an ignition-blocking device. The output is inactive when the circuit is powered up or has been reset. When the ‘*’ key is pressed, followed by the 4-digit code, the output will go to the 5V level and the relay connected to pin3 of microcontroller will be energized. If the code is incorrect, the wrong alarm LED connected to pin2 of microcontroller will glow. Also relay will be energized which is connected to any noise-generated device. When the code lock is used for the first time, the access code is 1234. This can be changed to, for example 4567 by first pressing ‘0’ followed by ‘#’, then the original code, then the new code. If something has gone wrong, the original code remains valid and error signal will sound. The procedure for operation of the code lock is given below. How to operate Code-Lock: Open the Lock: 1. Put on Power. 2. Press ‘*’ key ‘LOG-IN’ LED D3 will glow. 3. Now enter the old password. 4. If Code is correct ‘SYS-ON’ LED D2 will glow and lock is open. 5. If code is incorrect wrong alarm LED D1 will glow for 1 second. 6. Repeat above steps to try again.
Change the Password :
About 89C2051 Microcontroller :ATMEL 89C2051 is CMOS 8-bit Microcontroller. It has flash programmable and erasable read only memory. It is a 20-pin device. The pin details are given below. It has 15 digital I/O lines. The pin descriptions are given below. 89C2051 provide cost effective, compact and flexible solutions to many industrial applications. It uses only port-1 and port-3. Details of pin-out: X2 (pin-4):- Output of inverting amplifier that forms the part of the oscillator and input to the internal clock generator. In case of external clock, it must be connected to X2. X1 (pin-50):- X1 is the input to the inverting amplifier that forms part of the oscillator circuit. In case of external clock, this pin must be connected to ground. Vcc (pin-20):-This pin is connected to +5V power supply. Vss (pin-10):-Vss is the circuit ground. RXD (pin-2):-serial input. TXD (pin-3):-serial output. INT0 (pin-6):-external interrupt. INT1 (pin-7):-external interrupt. T0 (pin-8):-Timer/Counter0 external input. T1 (pin-9):-Timer/Counter1 external input. Software: Software for this code lock system is already programmed in 89C2051. You have to only insert IC in IC socket and run it.
Dilip Bhoyar (Elektrokit)
Keshav Imperial,Shop Nop B-101,B Wing First Floor,Nagpur, , Shani Mandir, Near Shani Mandir, Sitabuldi, Nagpur-440012, Maharashtra, India, Shankar Nagar
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