3. Introduction
Security is a prime concern in our day-to-day life. Everyone wants to
be as much secure as possible. An access control for appliances
forms a vital link in a security chain. The Microcontroller Based
Password Protected Home Appliances is an access control system
that allows only authorized persons to access an appliance. The
system is fully controlled by the 8 bit microcontroller ATmega8.
There is a Keypad by which the password can be entered through it.
When they entered password matches with the password stored in
the memory then we get access to the appliances.
4. Why ATmega8…
• Added EEPROM to store data over a power off time.
• An internal oscillator to make the AVR working without any other
secondary oscillatory source.
• The AVR is optimized for C-programming.
• It allows programming and serial communication over USB.
• It uses only one clock pulse for one instruction set, hence it’s operating
speed is quite high compared to PIC and 8051 Microcontrollers
5. The
objectives of
our project
are listed as
above
To protect home
appliances from
unauthorized
persons.
Operating both
AC and DC
components one
at a time. To design a
keyless lock
system by using
electronic digital
lock code.
Objectives
10. 4-Pin Push Switch
When we don't push the button, the
circuit is open and no current flows in it
so the LED remains off. When we push
the button the circuit closes and current
flows, the LED will be on.
How does it works ?
Power Rating: 50mA, 24V DC
11. LCD
Features:
• 5 x 8 pixel matrix with cursor
• Built-in controller (Hitachi HD44780)
• 5V power supply
• 16 Characters * 2 Line Displays
• Display Mode and Backlight Variations
• RoHS Compliant
12. IC 7805
Pin No. Function Name
1 Input voltage (5V-18V) Input
2 Ground (0V) Ground
3 Regulated output; 5V (4.8V-5.2V) Output
Pin Description:
7805 is a voltage regulator integrated circuit.
The voltage source in a circuit may have
fluctuations and would not give the fixed
voltage output. The voltage regulator IC
maintains the output voltage at a constant
value.
18. Fortunately, there were a few options
available to us. We can either use batteries,
a wall adapter, or a SMPS. In our case we
will be using a wall adapter, to power our
whole circuitry, although SMPS or a battery
can be used in order to increase the
portability
Where to get the power for our circuit?
20. Circuit Diagram
Here, IC 7805 plays a pivotal role, it downgrades the 12V DC
supply from the mains to a constant 5V DC thereby protects
the microcontroller from damage against overflow of current
22. Pin Description
Pin 15 and Pin 16 functions as a power supply for the backlight of the LCD
screen, DB0-DB7 are used for data transfer between the LCM and the MPU
24. It acts as a pull up transistor
which allows the current to
flow in order, to turn the
LED backlight “ON”
Preset knob is being
adjusted to get a proper
LCD display
26. PD0-PD7 of the MCU is
being interfaced to the
eight interconnects of the
keypad
The rows are
connected to
PD0-PD3
The columns are
connected to
PD4-PD7
28. Matrix Keypad Connection
• The rows R0 to R3 and C0 to C3 are
connected to i/o pins of Microcontroller, by
setting the proper DDR Register they are
connected and made Input/output.
• At first Columns are kept at High Impedance
State. And in their PORT value we set them
all as LOW, as soon as we change their DDR
bit to 1 they become LOW.
• One by One we make each Column LOW
(from high Z state) and read state of R0 to
R3.
29. Matrix Keypad Connection(Contd.)
• C0 is made LOW while all other Columns
are in HIGH Z State. We can read the Value
of R0 to R3 to get their pressed status.
• If ROWS are high the button is NOT
pressed.
• But when a key is pressed it is connected
to LOW line from the column thus making
it LOW.
30. Matrix Keypad Connection(Contd.)
• C0 High Z again and make C1 LOW.
And read R0 to R3 again. This gives
us status of the second column of
keys.
• Similarly we scan all columns.
34. What is a Relay?
It is an electrical device, typically incorporating
an electromagnet, which is activated by a current
or signal in one circuit to open or close another
circuit.
35. Pins of a 5-pin Relay
Normally Open(NO)
Normally Closed(NC)
Common(COM)
Coil
36. How does it works?
The input section has a coil which generates
magnetic field when a small voltage from an
electronic circuit is applied to it. The output
section consists of contactors which connect
or disconnect mechanically.
38. Buzzer
A buzzer connected to PORT C1 (PIN 24) of the
micro controller through a driver transistor.
The buzzer requires minimum 5 volts at a
current of around 50 mA, which cannot be
provided by the micro controller. So the driver
transistor is added. As soon as pin of the micro
controller goes high, the buzzer operates.
Voltage : 5-27V DC
44. Steps to download the HEX code
Green LED blinks, indicating
proper connections
Prog ISP Tool for burning
the HEX File into the MCU
Red LED blinks, indicating
burning successful
45. AVR Studio 5
Atmel AVR Studio 5 is the Integrated
Development Environment (IDE) for
developing and debugging embedded
Atmel AVR applications. The AVR Studio 5
IDE gives us a seamless and easy-to-use
environment to write, build, and debug
your C/C++ and assembler code.
47. When we completed this
project, we had learned and
understood the process of
constructing a Digital Code
lock Lock which contained
hardware and software
development. We also
know and understood the
microcontroller ATMega 8
and how to implement it
on our project.
We succeeded in
determining the faults in
our circuit and rectified it
accordingly.
Our digital code lock
performed as expected. We
were able to implement all
the functions specified in our
proposal.
The biggest hurdle we had to
overcome with this project
was interfacing the
microcontroller with the
hardware components.
We feel that this digital
code lock is marketable
because it is easy to use,
comparatively inexpensive
due to low power
consumption and highly
reliable.
This digital code lock is
therefore particularly
useful in application in any
household appliance.
49. Modifications
Circuit
modifications
can be made
to drive heavy
appliances
Portability of
the circuit can
increased.
Simultaneously
more than one
appliance can
be used.
4 Unused
Switches can be
used to control
different
appliances
