mohammad khaleel , kanaparthi swetha ,...

Vol 05, Article 03256; March 2014 International Journal of VLSI and Embedded Systems-IJVES

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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

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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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http://en.wikipedia.org/wiki/AC_motor

http://en.wikipedia.org/wiki/Electric_current

http://en.wikipedia.org/wiki/Rotor_(electric)

http://en.wikipedia.org/wiki/Electromagnetic_induction

http://en.wikipedia.org/wiki/Stator

http://en.wikipedia.org/wiki/Commutator_(electric)

http://en.wikipedia.org/wiki/Universal_motor

http://en.wikipedia.org/wiki/DC_motor

http://en.wikipedia.org/wiki/Synchronous_motor

http://en.wikipedia.org/wiki/Wound_rotor_motor

http://en.wikipedia.org/wiki/Squirrel-cage_rotor





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Fig.4. temperature range 10-20



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

[1]. F.M.H. Khater and D.W. Novotny, “An equivalent circuit model for phase back voltage control of AC

machines”, IEEE Transactions on Industry Applications, vol. 22, no. 5, Sept./Oct., pp. 835-841

[2]. T.A. Lipo, “The analysis of induction motors with voltage control by symmetrically triggered thyristors”,

IEEE Trans. on Power Apparatus and Systems, vol. PAS-90, no. 2, March/April 1971, pp.515-525. [3]. J. Davoine, R. Perret and H. Le-Huy, “Operation of a self-controlled synchronous motor without a shaft

position sensor”,in Conf. Rec. IEEE IAS Annual Meeting, 1981, pp. 696-701. [4]. IEEE Trans. on Industry Applications., H.W. Van der Broeck, H. Skudelny and G. Stanke, “Analysis and

realization of a pulse width modulator based on voltage spacevectors”,vol. 24, no. 1, Jan./Feb., 1988, pp.

142-150. [5]. J. Stephan, M. Bodson and J. Chaisson, “Real-time estimation of the parameters and fluxes of induction

motors”, IEEE Trans. on Industry Applications, vol. 30, no. 3, 1994, pp. 746-758.

[6]. Y. Kishimoto, S. Asaba, K. Nakata and S. Kawatsu, “Control device for induction motor”,U.S. Patent

5,231,339, July 27, 1993. [7]. D. Leggate and R. Kerkman, “Pulse based time compensator for PWMvoltage inverters”,in Conf. Record of

IEEE IECON, 1995, pp. 474-481.

[8]. T.M. Jahns, G.B. Kliman and T.W. Neumann, “Interior PM synchronous motors for adjustable-speed

drives”, IEEE Trans. on Industrial Applic.,vol. 22, no. 4, July/August 1986, pp. 738-747. [9]. M.A. Bilewski, A. Fratta, L. Giordano, A. Vagati and F. Villata, “Control of high performance interior PM

synchronous drives”, in Conf. Rec.IEEE-IAS Annual Meeting, 1990, pp. 531-538.

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