18-06-2014, 04:39 PM
UNIVERSAL MOTOR SPEED CONTROL USING IGBT
UNIVERSAL MOTOR SPEED CONTROL USING IGBT.doc (Size: 1.78 MB / Downloads: 19)
ABSTRACT
There are several applications with ac motors in our daily life. We require different speeds at different instants depending on the applications. There are several techniques to control the speed of dc motor. The purpose of a motor speed controller is to take a signal representing the demanded speed, and to drive a motor at that speed. The controller may or may not actually measure the speed of the motor.
IGBTs (Insulated or Isolated Gate Bipolar Transistor) combine the simple gate drive characteristics of the MOSFET with the high current and low saturation voltage capability of bipolar transistors by combining an isolated gate FET for the control input, and a bipolar power transistor as a switch, in a single device. The IGBT is mainly used to change the frequency of the motor
INTRODUCTION TO EMBEDDED SYSTEM
An embedded system is a special-purpose computer system designed to perform one or a few dedicated functions, sometimes with real-time computing constraints. It is usually embedded as part of a complete device including hardware and mechanical parts. In contrast, a general-purpose computer, such as a personal computer, can do many different tasks depending on programming. Embedded systems have become very important today as they control many of the common devices we use.
Since the embedded system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product, or increasing the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.
Physically, embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure.
1 APPLICATIONS OF EMBEDDED SYSTEM
We are living in the Embedded World. You are surrounded with many embedded products and your daily life largely depends on the proper functioning of these gadgets. Television, Radio, CD player of your living room, Washing Machine or Microwave Oven in your kitchen, Card readers, Access Controllers, Palm devices of your work space enable you to do many of your tasks very effectively. Apart from all these, many controllers embedded in your car take care of car operations between the bumpers and most of the times you tend to ignore all these controllers.
In recent days, you are showered with variety of information about these embedded controllers in many places. All kinds of magazines and journals regularly dish out details about latest technologies, new devices; fast applications which make you believe that your basic survival is controlled by these embedded products. Now you can agree to the fact that these embedded products have successfully invaded into our world. You must be wondering about these embedded controllers or systems. What is this Embedded System?
MICRO CONTROLLER 89C51
Introduction
A Micro controller consists of a powerful CPU tightly coupled with memory, various I/O interfaces such as serial port, parallel port timer or counter, interrupt controller, data acquisition interfaces-Analog to Digital converter, Digital to Analog converter, integrated on to a single silicon chip.
If a system is developed with a microprocessor, the designer has to go for external memory such as RAM, ROM, EPROM and peripherals. But controller is provided all these facilities on a single chip. Development of a Micro controller reduces PCB size and cost of design.
One of the major differences between a Microprocessor and a Micro controller is that a controller often deals with bits not bytes as in the real world application.
Intel has introduced a family of Micro controllers called the MCS-51.
Internal RAM
The 89C51 have a bank of 128 of internal RAM. The internal RAM is found on-chip. So it is the fastest Ram available. And also it is most flexible in terms of reading and writing. Internal Ram is volatile, so when 89C51 is reset, this memory is cleared. 128 bytes of internal memory are subdivided. The first 32 bytes are divided into 4 register banks. Each bank contains 8 registers. Internal RAM also contains 128 bits, which are addressed from 20h to 2Fh. These bits are bit addressed i.e. each individual bit of a byte can be addressed by the user. They are numbered 00h to 7Fh. The user may make use of these variables with commands such as SETB and CLR.
FLASH MEMORY
Flash memory (sometimes called “flash RAM”) is a type of constantly-powered non volatile that can be erased and reprogrammed in units of memory called blocks. It is a variation of electrically erasable programmable read-only memory (EEPROM) which, unlike flash memory, is erased and rewritten at the byte level, which is slower than flash memory updating. Flash memory is often used to hold control code such as the basic input/output system (BIOS) in a personal computer. When BIOS needs to be changed (rewritten), the flash memory can be written to in block (rather than byte) sizes, making it easy to update. On the other hand, flash memory is not useful as random access memory (RAM) because RAM needs to be addressable at the byte (not the block) level.
Pushing onto the stack
In the 8051 the stack pointer (SP) points to the last used location of the stack. As we push data onto the stack, the stack pointer is incremented by one. Notice that this different from many microprocessors, notably x86 processors in which the SP is decremented when data is pushed onto the stack. As each PUSH is executed, the contents of the register are saved on the stack and SP is incremented by 1. Notice that for every byte of data saved on the stack and then SP is incremented only once. Notice also that to push the registers onto the stack we must use their RAM addresses. For example, the instruction “PUSH” pushes register R1 onto the stack.
Program counter
The important register in the 8051 is the PC (Program counter). The program counter points to the address of the next instruction to be executed. As the CPU fetches the OPCODE from the program ROM, the program counter is incremented to point to the next instruction. The program counter in the 8051 is 16bits wide. This means that the 8051 can access program addresses 0000 to FFH, a total of 64k bytes of code. However, not all members of the 8051 have the entire 64K bytes of on-chip ROM installed, as we will see soon
Serial Communication
Computers can transfer data in two ways: parallel and serial. In parallel data transfers, often 8 or more lines (wire conductors) are used to transfer data to a device that is only a few feet away. Examples of parallel data transfer are printers and hard disks; each uses cables with many wire strips. Although in such cases a lot of data can be transferred in a short amount of time by using many wires in parallel, the distance cannot be great. To transfer to a device located many meters away, the serial method is used. In serial communication, the data is sent one bit at a time, in contrast to parallel communication, in which the data is sent a byte or more at a time. Serial communication of the 8051 is the topic of this chapter. The 8051 has serial communication capability built into it, there by making possible fast data transfer using only a few wires
CONCLUSION
The project “SPEED CONTROL OF UNIVERSAL MOTOR USING IGBT ” has been successfully designed and tested. Integrating features of all the hardware components used have developed it. Presence of every module has been reasoned out and placed carefully thus contributing to the best working of the unit.
Secondly, using highly advanced IC’s and with the help of growing technology the project has been successfully implemented