Digital logic design project. creation of a security system using the IC's XOR & NOR.

1. 4 BIT PASSWORD
SECURITY SYSTEM
USING XOR AND
NOR
Digital Logic Design

2. 1
4-bit Password Security System (using NOR & XOR):
The idea is of this system is that the 4 switches “Key Code Switches” acts as holding the correct
password for unlocking the lock. On the other hand, the other 4 switches “Data Entry Switches”
acts as data entry points where the code is to be entered to open the lock. The “Key Code
Switches” have static value and is hidden from the person who is trying to open the lock. If the
person who is trying to open the lock enters the code at “Data Entry Switches” which is similar
to the code kept static at the “Key Code Switches” then the green LED will light up and the lock
will open while, if he enters the wrong code then the red LED will lit up which is an alarming
situation that some wrong person is unlocking the lock.
MaterialRequired:
 4001 quad NOR gate
 4070 quad XOR gate
 Two, four-position DIP switches
 Two light-emitting diodes
 Four 1N914 “switching” diodes
 Ten 10 kΩ resistors
 Two 470 Ω resistors
 Pushbutton switch, normally open
 Two 6 volt batteries
Equipments:
1) NOR Gate: 2) XOR Gate:

3. 2
3) 1N914 Switching Diode: 4) DIP Switches:
5) Push Button: 6) Resistors:

4. 3
Truth Table:
XOR Truth Table: NOR Truth Table:
Pin Configurationof ICs:
XOR Gate: NOR Gate:

5. 4
Circuit Diagram:
Procedure:
i. Install the IC’s and resistors neatly on the bread board.
ii. Wire the pins 7 & 14 of both IC’s to Vcc& GND respectively.
iii. Wire one end of the switches with Vcc.
iv. Wire one end of resistors to GND.
v. Now connect the other end of the switches to the resistors and wire it to the gates of XOR
IC.
vi. Now the output of the XOR is sent as inputs in NORIC and is grounded with help of a
resistor simultaneously.
vii. Connect the led lights (green & red) and ground them with help of resistors.
Precautions:
i. Always check to see that the power switch is OFF before plugging into the outlet. Also,
turn instrument or equipment OFF before unplugging from the outlet.
ii. Check the IC’s before using them in the circuit.
iii. The wiring must be neat and clean.
iv. Don’t use battery more than 12 Volts or it might result in causing damage to the LED’s.

6. 5
Schematic diagram from Proteus Software:

7. 6
Image of Implementation Work:
 When the user entered password is different from the password which is kept static.
 When both the passwords are same.