The circuit presented here can be-used as a lock for important elec¬tronic/electrical appliances. When card is inserted inside its mechanism, depending upon the position of punched hole on the card, a particular appliance would be switched on. The card is inserted just like a floppy disk inside the disk drive. This card should be rectangular in shape with only one punched hole on it. T7 o The circuit uses eight photo-transistors (T1 through T8). When there is no card in the lock, light from incan¬descent lamp L1 (40-watt, 230V) falls on all the photo- transistor de¬tectors. Transistor T8 is used as enable detector for IC1 (74LS244). When light is incident on it, it conducts and its collector voltage goes low. This makes transis¬tor T16 to cut-off, and its collector voltage goes high. This logic high on its collector terminal will inhibit IC1 as long as light is present on photo-transistor, IC1 will get enabled only when the card is completely inserted inside the lock mechanism. This arrangement en-sures that only the selected appliance is switched on and prevents false op¬eration of the system. You can make these cards using a black, opaque plastic sheet. A small rect¬angular notch is made on this card to indicate proper direction for insertion of the card. If an attempt is made to insert the card wrongly, it will not go completely inside the mechanism and the system will not be enabled. When card for any appliance (say appliance 1) is completely inserted in the mechanism, the light will fall only on photo-transistor T1. So only T1 will be on and other photo-transistors will be in off state. When transistor T1 is on, its collector voltage falls, making transistor T9 to cut-off. As a result, collector voltage of transistor T9 as also pin 2 of IC1 go logic high. This causes pin 18 (output Q1) also to go high, switching LED1 on. Simulta¬neously, output Q1 is connected to pin 1 of IC2 (ULN2003) for driving the relay corresponding to appliance 1. Similarly, if card for appliance 2 is inserted, only output pin 16 (Q2) of IC1 will go high”making LED2 on while at the same time energising
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http://electronicsforuefylinux/circuit/feb2003/apr99_cardlock.pdf
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http://electronicsforuefylinux/circuit/feb2003/apr99_cardlock.pdf

[attachment=12341]
DIGITAL LOCK CODE USING 8051
ABSTRACT
Security is a prime concern in our day-today life. Everyone wants to be as much secure as possible. An access control for doors forms a vital page link in a security chain. The microcontroller based Door locker is an access control system that allows only authorized persons to access a restricted area. The system is fully controlled by the 8 bit microcontroller AT89C2051 which has a 2Kbytes of ROM for the program memory. The password is stored in the EPROM so that we can change it at any time.
The system has a Keypad by which the password can be entered through it. When the entered password equals with the password stored in the memory then the relay gets on and so that the door is opened. If we entered a wrong password for more than three times then the Alarm is switched on.
When we go inside and come back then the microcontroller will sense the person using the Laser light, the microcontroller will automatically open the door for you.
1. INTRODUCTION
“Password Based Door Security System using Microcontroller” is used in the places where we need more security. It can also used to secure lockers and other protective doors. The system comprises a number keypad and the keypads are connected to the 8 bit microcontroller AT89C2051. This is one of the popular Microcontroller. It has only 20 pins and there are 15 input/output lines. The microcontroller has a program memory of 2 Kilobytes. The microcontroller continuously monitor the keypad and if somebody enters the password it will check the entered password with the password which was stored in the memory and if it they are same then the microcontroller will switch on the corresponding device. The system will allow the person who knows the password and it will not allow who don’t know the password and the system will also show the persons who try to break the protection barrier.
CHAPTER-2
PROJECT DESCRIPTION
2. PROJECT DESCRIPTION
2.1 BLOCK DIAGRAM
2.2 BLOCK DIAGRAM EXPLANATION

INTEL’S 8051 Architencture
The generic 8051 architecture sports a Harvard architecture, which contains two separate buses for both program and data. So, it has two distinctive memory spaces of 64K X 8 size for both program and data. It is based on an 8 bit central processing unit with an 8 bit Accumulator and another 8 bit B register as main processing blocks. Other portions of the architecture include few 8 bit and 16 bit registers and 8 bit memory locations. Each 8051 device has some amount of data RAM built in the device for internal processing. This area is used for stack operations and temporary storage of data. This base architecture is supported with onchip peripheral functions like I/O ports, timers/counters, versatile serial communication port. So it is clear that this 8051 architecture was designed to cater many real time embedded needs.
The following list gives the features of the 8051 architecture:
 Optimized 8 bit CPU for control applications.
 Extensive Boolean processing capabilities.
 64K Program Memory address space.
 64K Data Memory address space.
 128 bytes of onchip Data Memory.
 32 Bi directional and individually addressable I/O lines.
 Two 16 bit timer/counters.
 Full Duplex UART.
 6 source / 5 vector interrupt structure with priority levels.
 Onchip clock oscillator.
Now you may be wondering about the non mentioning of memory space meant for the program storage, the most important part of any embedded controller. Originally this 8051 architecture was introduced with onchip, `one time programmable' version of Program Memory of size 4K X 8. Intel delivered all these microcontrollers (8051) with user's program fused inside the device. The memory portion was mapped at the lower end of the Program Memory area. But, after getting devices, customers couldn't change any thing in their program code, which was already made available inside during device fabrication.
So, very soon Intel introduced the 8051 devices with re programmable type of Program Memory using built in EPROM of size 4K X 8. Like a regular EPROM, this memory can be re programmed many times. Later on Intel started manufacturing these 8051 devices without any on chip Program Memory.

PRESENTED BY
Biswajit Das
Mukesh Kr. Guleriya
Nikhil Sood
Ankur Chauhan

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[attachment=12431]
LIST OF COMPONENTS
1. LDR
2. LM 324
3. ULN 2003
4. RELAY
5. VOLATGE REGULATOR (IC-7805, 7812)
6. LED (White & red)
7. RESISTOR (10KΩ, 220Ω)
8. CAPACITOR (2200µF,110µF)
9. DIODE
10. Transformer (12-0-12)
PROJECT WORKING
The circuit presented here can be used as a lock for important electronic/electrical appliances. When card is inserted inside its mechanism, depending upon the position of punched hole on the card, a particular appliance would be switched on. The card is inserted just like a floppy disk inside the disk drive. This card should be rectangular in shape with only one punched hole on it
The circuit uses four LDR and four white LED’s. When there is no card in lock then light is fall on LDR, the strength of LDR is adjusted by variable resistor (1kΩ). When light is fall on LDR, the resistance of LDR varies according to the incident light, so the resistance of LDR becomes low and current starts flowing through it. The LDR is connected to comparator IC (LM-324) and other input is given directly. At pin 4 and 11 the supply input is given, 5 Volt and 0 Volt respectively. The output is taken from pin no. 1, 7, 8 and 14. These output is connected to the ULN2003 and corresponding red LED’s. The ULN2003 IC works at 12 volt which is given at terminal 9 and terminal 8 makes ground. When output of LM324 is given at terminal 1, 2, 3, 4 then output is obtained at terminal 16, 15,14, 13 respectively means corresponding output is obtained and Relay’s is connected to these outputs for driving the corresponding appliances.
When card for appliance 1 is inserted then LDR of corresponding card is working and then comparator IC compare both the inputs, if output is high the signal is given to the ULN2003 and corresponding LED is glow and corresponding output of ULN is obtained at other side. Relay is connected between the ULN and appliance. When signal is applied at the Relay, it connects to the corresponding appliance for working and the appliance start working.

WILL U BE ABLE TO PROVIDE ME THE PCB LAYOUT OF THIS CIRCUIT?

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