AUTOMATIC
FAN SPEED CONTROL
This project is a standalone automatic fan speed
controller that controls the speed of an electric fan according to our
requirements. Use of embedded technology makes this closed loop control system
as efficient and reliable. Microcontroller AT89S52 allows dynamic and faster
control .Liquid Crystal display makes the system user friendly. The sensed
temperature and fan speed level values are simultaneously displayed on the LCD
panel. It is very compact using few components and implemented for several
applications including air-conditioners, water heaters, snow melters, heat-exchangers,
ovens, mixers, incubators, furnaces, thermal baths and veterinary operating
tables.
AT89S52 Microcontroller is the heart of the circuit as it controls all
the functions.
The temperature sensor LM35 senses
the temperature and convert it into an electricl signal(analog),which is
applied to the mocrocontroller through ADC. The analog signal is converted
intodigital format by Analog to Digital converter (ADC).The sensed and set
values of the temperature are displayed on the 16x2 LCD.The microcontroller drives control relay by meens of ULN driver circuit to control the fan speed with
the help of high wattage tagged wire wound resistor.
Block diagram
Single Pole Douple Throw(SPDT)
relays are connected to the microcontroller through a ULN driver circuit.The
relays require 12 volts at a current of around
50mA,which can not provide by the microcontroller.So the ULN driver
circuit is added.The relays are used to operate an electrical fan or any other
electrical device.Normally the relays remains off.As soon as pin of the
microcontroller goes high ,the relays operate.
This project uses 5V,500mA &
12V 500mA power supply.7805 and 7812
three terminal voltage regulators are used for voltage regulation
.Bridge type full wave rectifiers are used to rectify the ac output of 230/12 V step down transmitter.This project
is useful in process industries for
maintenance and controlling of boilers temperature.
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