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Automatic room temperature control

CONTENTS
• Problem statement
• Introduction
• Methodology
• Circuit Diagram
• Components
• Applications
• Conclusion
• References

Problem statement
• Todays world is affected by a phenomenon of global warming
due to which the temperature is rising which makes the
human lives uneasy.
• Thus, there is a prevalent use of a Air Conditioners in homes
thus there is a huge requirement of power.
• In this project work, we are going to control the temperature
of multiple rooms using Air-Conditioners by sharing the
temperature among them. This will also save electric power.

Introduction
• In this project work the temperature of the two rooms are
controlled using air conditioner .But due to the power
shortage low voltage vary often we are not able to start both
the air conditioner simultaneously .In such cases our project is
aimed at starting one ac among both depending upon the
temperature value at a particular room .
• If the temperature on the particular room is above certain
range then the AC in that room will start up and during this
time the AC in the other room will remain switched off.
• When the temperature goes below 25 degree in the room
where AC is already on will be switched off automatically.

• Then if the temperature on the other room during the time is
above 30 degree then the AC in that room will start up and
vice versa .
• The second feature of our project is aimed at switching of the
AC automatically when there is absence of human beings in a
particular room .
• The entire scheme is designed using number of ATMEGA16 PU
microcontrollers , temperature sensors , digital counter , Relay
etc.

Methodology
• 1. When no people are present in both the rooms then both
room AC will remain switch off.
• 2. When the people enter in the room1 and if its
temperature(T1) > 30 degree then AC1 will be switched on,
while AC2 will remain off.AC1 will continue to run till the
temperature of the room becomes 25 degree.
• 3. When the people enter in the room2 and if its
temperature(T2) > 30 degree then AC2 will be switched on,
while AC1 will remain off.AC2 will continue to run till the
temperature of the room becomes 25 degree.
T1=TEMPERATURE OF ROOM 1
• T2=TEMPERATURE OF ROOM 2

COMPONENTS
• MICROCONTROLLER (ATMEGA 16)
• POWER SUPPLY UNIT
• RELAY DRIVER CIRCUIT
• FAN
• TEMPERATURE SENSOR
• IR Tx and IR Rx
• LCD
• SOFTWARE REQUIREMENTS

Power Supply Unit
1000uF
50Hz
3
IC7812
GND
12-0-12
+12VDC
LED
+5VDC
LED
230VAC
1
2
31
2
- +
IN4007
IC7805
POWER SUPPLY SECTION

POWERSUPPLYSECTION
basically consisting of three sections as follows
• Step down section
• Rectifier Section
• Regulator section

Relay Driver Circuit
• A relay is an electrically
operated switch. Electric
current through the coil
of the relay creates a
magnetic field which
attracts a lever and
changes the switch
contacts.
• The coil current can be
on or off so relays have
two switch positions and
they are double-throw
(changeover) switches.

Temperature Sensor(LM35)
Working Principle-
• It has linear relationship
between output voltage &
Celsius temperature scale.
• It gives an output voltage that
is Proportional to the Celsius
temperature.
• Scale factor is 10mv/ degree C.

IR Transmitter & Receiver
• IR LED is used as a source of
infrared rays. It comes in two
packages 3mm or 5mm. 3mm is
better as it is requires less space.
• IR sensor is nothing but a
photodiode, which is sensitive for
infrared radiation.
• This infrared transmitter and
receiver is called as IR TX-RX pair.

Software Requirements
• AVR STUDIO 4
• LANGUAGES EMBEDDED C

Why Embedded C ?
• It is easier and less time consuming to write in C than
Assembly.
• C is easier to modify and update.
• We can use code available in function libraries.
• C code is portable to other micro controller with little of
no modification.
• Compilers produce hex files that is downloaded to ROM
of microcontroller.
• C programming is less time consuming, but has larger hex
file size.

Applications
• Industrial Automation.
• Home Automation.
• Electric power can be saved using this
project.

Conclusion
• This project will solve the day-to-day problem where AC’s do
not start up due to low voltage , generally in rural areas .
• This will start the AC depending upon the temperature label in
a room by sharing the load .
• Also this project can be extended for controlling the
temperature in more rooms in an apartment in future..

References
1. “Industrial instrumentation” by S.K Singh.
2. “Measurement and instrumentation and its applications” by
E.D doublin .
3. “Measurement and instrumentation” by A.K sahani.
4. http://www.atmel.com
5. http://www.alldatasheet.com
6. C.Sujana,A.P.Ramesh,P.G reddy, “Automatic detection of
human and Energy saving based on Zigbee Communication”,
International Journal on Computer Science and Engineering
(IJCSE) ISSN : 0975-3397, Vol. 3 No. 6 June 2011

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Automatic room temperature control

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