This document discusses speed control of a DC motor using pulse width modulation (PWM) technique. PWM controls the speed of a DC fan motor based on temperature readings from a DHT22 temperature sensor. The Arduino microcontroller measures the temperature and humidity using the DHT22 sensor and adjusts the duty cycle of the PWM signal to the motor to control its speed according to the measured temperature levels. By varying the on-off time of the PWM signal, the average power delivered to the motor can be adjusted to control its speed for different temperature ranges.

1. Speed control of DC motor by PWM
technique
Prepared By:
KATHAN SHAH
4/8/2017 1

2. Introduction to the project
• This project is based on speed control of dc motor using
PWM technique.
• Here we will use temperature controlled dc fan whose
speed is changed according to the level of temperature .
• For measuring the surrounding temperature of system ,
temperature sensor called DHT 22 is used ,which can
also measure humidity .
• speed of the motor is specified for certain range of temp.
through arduino or any equivalent microcontroller.
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3.  Definition: Pulse Width Modulation is a technique that conforms a
signal width, generally pulses based on modulator signal information.
 The general purpose of Pulse Width Modulation is to control power
delivery, especially to inertial electrical devices.
 The on-off behavior changes the average power of signal.
 Output signal alternates between on and off within a specified period.
 If signal toggles between on and off quicker than the load, then the
load is not affected by the toggling.
 A secondary use of PWM is to encode information for transmission
About PWM
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4. Duty Cycle
 Definition: The Duty Cycle is a measure of the time the modulated
signal is in its “high” state.
 It is generally recorded as the percentage of the signal period where
the signal is considered on.
Period (T)
Duty Cycle
(D)
VL
VH
On Off
%100
Period
TimeOn
CycleDuty
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5. Advantages Of PWM Technique
• The main advantage of PWM is that power loss in the switching
devices is very low.
• When a switch is off there is practically no current , and When it is on
and power is being transferred to the load, there is almost no voltage
drop across the switch.
• Power loss , being the product of both , is thus in both cases close to
zero.
• PWM also works well with digital controls , which because of their
on/off nature , can easily set the needed duty cycle.
• Also the temperature sensor DHT22 has low percentage error (0.5%)
and its temperature range is high ( -40 to 80C ) which is considerable
compared to other temperature sensor like LM35 , DHT11 etc.
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6. Hardware Requirements
• Arduino Uno R3: Arduino is a ATMEL based microcontroller which is
used to take a controlling action i.e to change the speed of dc fan
according to the input obtained from the DHT22. It simply adjust the
duty cycle for various temperature range . It is 14 digital I/O pin
device.
• DHT 22: DHT 22 is a family of DHT sensors which is used to measure
the temperature and humidity accurately . It is 4 pin device . It has
internal circuit which can convert analog signal to the digital one
,which can be easily read by microcontroller.
• DC Fan: Here dc fan is just simply a dc motor whose speed is being
changed by varying the duty cycle.
• Power Adapter: power adapter is used to step down the supply ac
voltage in the range of arduino so it can operate safily . We can also use
transformer , rectifier and 7805 regulator set instead of power adapter.
• LCD Display: Here LCD display is used to display the temperature
and duty cycle value . It is 16 X 2 LCD, which is used only for writing
purpose.4/8/2017 6

7. Software Requirements
• Arduino IDE: Arduino IDE is a software used for the program
development for integrated circuit like Arduino . It is compatible with
any Arduino board like Arduino Uno , LilyPad Arduino ,Red board ,
Arduino Mega , Arduino Leonardo.It can compile the ATMEL based
program generally written in C/C++.It can also compile program .
After compilation we can install program on the Arduino board.
• Proteus: Proteus is used for real time simulation , PCB layout and
schematic arrangement.
• Eagle : Eagle is also used for simulation , schematic circuit and PCB
layout . Here the schematic is made in eagle.
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8. Block Diagram
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9. Application
• Air Conditioning
• Refrigeration System
• Ventilation System
• Transformer OFAF cooling
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10. Future Work
• In future we will prepare flow chart which will give brief information
about the steps of program.
• We will make real time simulation.
• Program implementation in the hardware
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11. THANK YOU
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