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Temperature Dependent AC Motor Speed Control MOHAMMAD KHALEEL1, KANAPARTHI SWETHA2, YANAMANDALA KESAVA3, SHAIK
MOHAMMAD GOUSE4
1,2,3,4Students, EIE, JNTU, Kanuru, Penamaluru, Vijayawada-520007, INDIA [email protected], [email protected], [email protected],[email protected]
ABSTRACT
This project is a standalone Temperature based AC Motor speed controller that controls the speed of the Motor
based on the read temperature. Use of embedded technology makes this closed loop feedback control system
efficient and reliable. Microcontroller (AT89S52) allows dynamic and faster control. Liquid crystal display
(LCD) makes the system user-friendly. It is very compact using few components and can be implemented for
several applications including propulsion system, wood cutting machines etc.
Keywords: AC Motor, Triac, microcontroller (AT89S52), snubber circuit, ADC, LM35 sensor etc
[1] INTRODUCTION
The objective of this project is to design and construct a AC motor speed control system using temperature
sensor which will be controlled by microcontroller. The AC motor speed can be changed according to a certain
level of temperature.
In this project which is that the AC motor speed can be changed automatically which will be controlled by
microcontroller. There are four speed levels of AC motor which involved n this project which is speed 1, speed
2, speed 3, speed 4. The microcontroller which is used in this project in AT89S52. The temperature will be
detected by the temperature sensor. Thermistor is used as the temperature sensor.
Temperature Sensor senses the temperature and converts it into an electrical (analog) signal, which is applied to
the microcontroller through ADC. The analog signal is converted into digital format by the analog-to-digital
converter (ADC). The sensed temperature value and the AC motor speed will be displayed on the LCD. The AC
motor speed will be varied based on the temperature read from the ADC.
The speed of AC motor can be varied rapidly on and off by TRIAC. The main advantage of using a TRIAC to
vary the speed of an AC motor is the TRIAC reduces the energy flow to the motor and TRIAC works very well
for alternating currents. The speed of the motor can be seen on LCD display.
This project uses regulated 5V, 500mA power supply. 7805 three terminal voltage regulator is used for voltage
regulation. Bridge type full wave rectifier is used to rectify the ac out put of secondary of 230/12V step down
transformer.
2. HARDWARE COMPONENTS
The below figure shows the block diagram for temperature dependent AC motor speed control
Fig.1. Block Diagram
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Power unit
Microcontroller AT89S52
LCD Display
Temperature Sensor LM35
ADC0808
Triac
Induction motor
2.1 Power Unit
The input to the circuit is applied from the regulated power supply. The a.c. input i.e., 230V from the mains
supply is step down by the transformer to 12V and is fed to a rectifier. The output obtained from the rectifier is a
pulsating d.c voltage. So in order to get a pure d.c voltage, the output voltage from the rectifier is fed to a filter
to remove any a.c components present even after rectification. Now, this voltage is given to a voltage regulator
to obtain a pure constant dc voltage.
Fig.2. Power Supply Unit.
2.1.1 Transformer
Usually, DC voltages are required to operate various electronic equipment and these voltages are 5V, 9V or
12V. But these voltages cannot be obtained directly. Thus the a.c input available at the mains supply i.e., 230V
is to be brought down to the required voltage level. This is done by a transformer. Thus, a step down transformer
is employed to decrease the voltage to a required level.
2.1.2 Rectifier
The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The rectifier may be a
half wave or a full wave rectifier. In this project, a bridge rectifier is used because of its merits like good
stability and full wave rectification.
2.1.3 Filter
Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the
D.C. Output received from this filter is constant until the mains voltage and load is maintained constant.
However, if either of the two is varied, D.C. voltage received at this point changes. Therefore a regulator is
applied at the output stage.
2.1.4 Voltage regulator
As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical regulator
designed to automatically maintain a constant voltage level. In this project, power supply of 5V and 12V are
required. In order to obtain these voltage levels, 7805 and 7812 voltage regulators are to be used. The first
number 78 represents positive supply and the numbers 05, 12 represent the required output voltage levels.
2.2 Microcontroller AT89S52
Microprocessors and microcontrollers are widely used in embedded systems products. Microcontroller is a
programmable device. A microcontroller has a CPU in addition to a fixed amount of RAM, ROM, I/O ports and
a timer embedded all on a single chip. The fixed amount of on-chip ROM, RAM and number of I/O ports in
microcontrollers makes them ideal for many applications in which cost and space are critical.
The Intel 8051 is Harvard architecture, single chip microcontroller (µC) which was developed by Intel in 1980
for use in embedded systems. It was popular in the 1980s and early 1990s, but today it has largely been
superseded by a vast range of enhanced devices with 8051-compatible processor cores that are manufactured by
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more than 20 independent manufacturers including Atmel, Infineon Technologies and Maxim Integrated
Products.
8051 is an 8-bit processor, meaning that the CPU can work on only 8 bits of data at a time. Data larger than 8
bits has to be broken into 8-bit pieces to be processed by the CPU. 8051 is available in different memory types
such as UV-EPROM, Flash and NV-RAM.
2.3 LCD Display
LCD stands for Liquid Crystal Display. LCD is finding wide spread use replacing LEDs (seven segment LEDs
or other multi segment LEDs) because of the following reasons:
The declining prices of LCDs.
The ability to display numbers, characters and graphics. This is in contrast to LEDs, which are limited
to numbers and a few characters.
Incorporation of a refreshing controller into the LCD, thereby relieving the CPU of the task of
refreshing the LCD. In contrast, the LED must be refreshed by the CPU to keep displaying the data.
Ease of programming for characters and graphics.
These components are “specialized” for being used with the microcontrollers, which means that they cannot be
activated by standard IC circuits. They are used for writing different messages on a miniature LCD.
A model described here is for its low price and great possibilities most frequently used in practice. It is based on
the HD44780 microcontroller (Hitachi) and can display messages in two lines with 16 characters each. It
displays all the alphabets, Greek letters, punctuation marks, mathematical symbols etc. In addition, it is possible
to display symbols that user makes up on its own.
Automatic shifting message on display (shift left and right), appearance of the pointer, backlight etc. are
considered as useful characteristics.
Fig.3. LCD Display
2.4 Temperature Sensor LM35
In this project, in order to obtain the fan speed based on temperature, initially this temperature value has to be
read and fed to the microcontroller. This temperature value has to be sensed. Thus a sensor has to be used and
the sensor used in this project is LM35. It converts temperature value into electrical signals.
LM35 series sensors are precision integrated-circuit temperature sensors whose output voltage is linearly
proportional to the Celsius temperature. The LM35 requires no external calibration since it is internally
calibrated. . The LM35 does not require any external calibration or trimming to provide typical accuracies of
±1⁄4°C at room temperature and ±3⁄4°C over a full −55 to +150°C temperature range.
The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout
or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies.
As it draws only 60 μA from its supply, it has very low self-heating, less than 0.1°C in still air.
2.5 ADC0808
The ADC0808, ADC0809 data acquisition component is a monolithic CMOS device with an 8-bit analog-to-
digital converter, 8-channel multiplexer and microprocessor compatible control logic. The 8-bit A/D converter
uses successive approximation as the conversion technique. The converter features a high impedance chopper
stabilized comparator, a 256R voltage divider with analog switch tree and a successive approximation register.
The 8-channel multiplexer can directly access any of 8 single ended analog signals.
2.6 Triac
TRIACS are three terminal devices that are used to switch large AC currents with a small trigger signal.
TRIACS are commonly used in dimmer switches, motor speed control circuits and equipment that automatically
control mains powered equipment including remote control. The TRIAC has many advantages over a relay,
which could also be used to control mains equipment; the TRIAC is cheap, it has no moving parts making it
reliable and it operates very quickly.
The three terminals on a TRIAC are called ‘Main Terminal 1’ (MT1), ‘Main Terminal 2’ (MT2) and ‘Gate’ (G).
To turn on the TRIAC there needs to be a small current IGT flowing through the gate, this current will only flow
when the voltage between G and MT1 is at least VGT. The signal that turns on the TRIAC is called the trigger
Vol 05, Article 03256; March 2014 International Journal of VLSI and Embedded Systems-IJVES
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signal. Once the TRIAC is turned on it will stay on even if there is no gate current until the current flowing
between MT2 and MT1 fall below the hold current IH.
2.7 Induction Motor
An induction or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to
produce torque is induced by electromagnetic induction from the magnetic field of the stator winding. An
induction motor therefore does not require mechanical commutation, separate-excitation or self-excitation for all
or part of the energy transferred from stator to rotor, as in universal, DC and large synchronous motors. An
induction motor's rotor can be either wound type or squirrel-cage type.
3. SOFTWARE COMPONENTS
Keil compiler
Proload
3.1 Keil Compiler
Keil compiler is software used where the machine language code is written and compiled. After compilation, the
machine source code is converted into hex code which is to be dumped into the microcontroller for further
processing. Keil compiler also supports C language code.
Keil is a cross compiler. So first we have to understand the concept of compilers and cross compilers. After then
we shall learn how to work with keil. Keil is a German based Software development company. It provides
several development tools like
IDE (Integrated Development environment)
Project Manager
Simulator
Debugger
C Cross Compiler , Cross Assembler, Locator/Linker
Keil Software provides you with software development tools for the 8051 family of microcontrollers. With these
tools, you can generate embedded applications for the multitude of 8051 derivatives. Keil provides following
tools for 8051 development
C51 Optimizing C Cross Compiler,
A51 Macro Assembler,
8051 Utilities (linker, object file converter, library manager),
Source-Level Debugger/Simulator,
µVision for Windows Integrated Development Environment.
The keil 8051 tool kit includes three main tools, assembler, compiler and linker. An assembler is used to
assemble your 8051 assembly program. A compiler is used to compile your C source code into an object file. A
linker is used to create an absolute object module suitable for your in-circuit emulator.
3.2 Proload
Proload is software which accepts only hex files. Once the machine code is converted into hex code, that hex
code has to be dumped into the microcontroller and this is done by the Proload. Proload is a programmer which
itself contains a microcontroller in it other than the one which is to be programmed. This microcontroller has a
program in it written in such a way that it accepts the hex file from the Keil compiler and dumps this hex file
into the microcontroller which is to be programmed. As the Proload programmer kit requires power supply to be
operated, this power supply is given from the power supply circuit designed above. It should be noted that this
programmer kit contains a power supply section in the board itself but in order to switch on that power supply, a
source is required. Thus this is accomplished from the power supply board with an output of 12volts.
4. RESULTS
Table.1. Temperature and speed levels
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Fig.4. temperature range 10-20
Fig.5. temperature range 20-30
Fig.6. temperature range 30-40
Fig.7. temperature range 40<
Fig.8. Overall preview of our project
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CONCLUSION Here, we did the project with a AC motor speed with fixed PWM duty cycle for each 10 degree centigrade
interval from 10 to 40< degree Celsius. Care should be taken such that delays will not affect the open loop
control system performance. Temperature should not vary abruptly, otherwise it will cause degradation of the
system performance. By using Keil software we implemented our project.
ACKNOWLEDGEMENTS We would like to express our heartfelt gratitude to our guide Mr.G.Jalalu, Assistant Professor, Department of
Electronics and Instrumentation Engineering, VR Siddhartha Engineering College, Kanuru, Vijayawada. He has
given us tremendous support in both technical and moral front. Without his support and encouragement, we
would never have been able to complete the project successfully.
We profoundly grateful to Dr.G.N.Swamy, professor, Head of the Department, Electronics and Instrumentation
Engineering, VR Siddhartha Engineering College, Kanuru, Vijayawada for giving us the opportunity and for
extending constant support and valuable guidance throughout the project.
We are thankful to Dr. G.Sambasiva Rao, principal, VR Siddhartha Engineering College, Kanuru, Vijayawada
for his support during the completion of project.
Finally, we extend our thanks to our parents and our friends for their help and encouragement for the success of
our project.
REFERENCES
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