Speaking Technology - Electrical and Electronics Engg

9 Level Cascaded Multilevel Inverter Simulation (Simulink)

2013-04-15T08:47:00.001+05:30

Hello friends, After such a long break, I want to share a Matlab/Simulink model which I made for simulating 9 level cascaded multilevel inverter as mentioned in the title of this post. To be precise, this post deals with Single Phase Multilevel Inverter.

Usually the objective of multilevel inverter designers is to get a purely sinusoidal wave out of a Constant or variable DC Voltage source or current source. The inverters using DC Voltage Source are called VSI i.e. Voltage Source Inverters while the inverters made using Current source are called CSI i.e. Current Source Inverter. The circuit for both the types of inverters are basically same. Only difference is the presence of an extra inductor present in CSI.

In this post, I want to discuss only about Voltage Source Inverter (VSI). Using VSI, we can obtain a square wave output of 1 level or we can obtain an output of upto 2 level by making the changes in switch firing delay.

But if we want to get a purely sinusoidal wave, then it’s difficult (or probably impossible) with simple H-bridge based single phase inverter. For this reason, we use the concepts of multilevel inverters wherein the whole inverter system combined together will give an output in the form of steps which looks similar to sine wave inverters. Using large number of levels, by adjusting the delays and at the end by using a proper capacitor, we can get a purely sinusoidal wave.

As per my knowledge ‘APC’ Inverters by “Schneider Electric”, is one of the best inverter which produces a purely sinusoidal waveform.

Basically there are 3 topology of Multilevel Inverters

1.    Diode Clamped Multilevel Inverters
2.    Flying Capacitors Multilevel Inverters
3.    Cascade Multilevel Inverters

In my model, I have used the Cascaded multilevel Inverter topology which is far better than others when cost of implementation is concerned. Using this topology, we can obtain n level using (n-1) H-bridges, with each bridge consisting of 4 switches like MOSFET, IGBT, etc.

Here, I have used 8 H-bridges Single phase Inverters and connected them in series. By varying the switching timing in the ‘pulse generator’ block, I obtained 9 levels or steps in the output.

The Simulink block diagram is shown below:

[You can download the Simulink model from this link].

Complete Simulink model of the Inverter

I have created subsystem for each H-bridge and used the subsystems to avoid clutter in the workspace. The models present inside each H-bridge is shown in the figure given below:

Subsystem of H-Bridge Inverter Blocks

The 9 level voltage output obtained is shown in the figure given below:

Output Waveforms

The comparison between the sinusoidal wave and the obtained output can be observed by looking at the image. It can be inferred that the output is nearly close to the sinusoidal wave, but a lot can be done to improve. If the pulse width is adjusted properly, a nearly perfect sine wave can be obtained.

If you have any query/doubt/suggestions/constructive criticism, then do comment below and let me know.

Alphabetic Character display on 7 Segment LED using Arduino

2013-02-05T00:04:00.000+05:30

Hello Friends, In one of my previous post related to 7 segment LED, I shared arduino codes for displaying numbers on the 7 segment LED with a time delay of 1 second. You can refer that post from here:

Simple Counter using 7 segment LED with 8051 microcontroller

While writing my previous post on 7 segment LED, I wondered, if could write code for displaying alphabetical character on 7 segment LED. So in this post, I want to share with you my arduino codes using which you can see how alphabetic characters can be displayed on a 7 segment LED. This program is quite different from the program shared in the previous post because unlike the previous program on 7 segment LED wherein all the numbers were automatically displayed one by one, in this post you can see your desired character only after you press that key in the Serial Monitor. Alternatively, you can also use 'Hyperterminal' or 'Docklight' for sending data through serial port.

The demo video of this experiment and the complete code is given below. You can also download the full code in a single file from this link.

Please note that the 7 segment LED is connected in common anode mode, that means all 7 anodes of leds are connected together and should be connected to +5V and a particular LED will turn on when ‘Ground’ is applied to its terminal, which in this case is done using microcontroller. (For more details on the theoretical part refer previous post on 7 segment LED).

Demo Video:

Arduino Code:

int a=2;
int b=3;
int c=4;
int d=5;
int e=6;
int f=7;
int g=8;
int p=9;
void setup()
{
  pinMode(a,OUTPUT);
  pinMode(b,OUTPUT);
  pinMode(c,OUTPUT);
  pinMode(d,OUTPUT);
  pinMode(e,OUTPUT);
  pinMode(f,OUTPUT);
  pinMode(g,OUTPUT);
  pinMode(p,OUTPUT);
  Serial.begin(9600);
}
void loop()
{
  digitalWrite(p,HIGH);
  while(Serial.available()==0);
  
  char letter=Serial.read();
  Serial.println(letter);

  switch(letter)
  {
    case 'A':
      showa();
      break;
    case 'B':
      showb();
      break;
    case 'C':
      showc();
      break;
     case 'D':
       showd();
       break;
     case 'E':
       showe();
       break;
      case 'F':
        showf();
        break;
      case 'G':
        showg();
        break;
      case 'H':
        showh();
        break;
      case 'I':
        showi();
        break;
      case 'J':
        showj();
        break;
      case 'K':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'L':
        showl();
        break;
      case 'M':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'N':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'O':
        showo();
        break;
      case 'P':
        showp();
        break;
      case 'Q':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'R':
        showr();
        break;
      case 'S':
        shows();
        break;
      case 'T':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'U':
        showu();
        break;
      case 'V':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'W':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'X':
        point_blink(); //indicating it is not possible to display the specified character
        break;
      case 'Y':
        showy();
        break;
      case 'Z':
        showz();
        break;
      default:
        Serial.println("unknown character\nTry typing alphabets in CAPITAL");
  }
  
}
void showa()
{
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,HIGH);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showb()
{
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showc()
{
  digitalWrite(a,LOW);
  digitalWrite(b,HIGH);
  digitalWrite(c,HIGH);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,HIGH);
}
void showd()
{
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,HIGH);
}
void showe()
{
  digitalWrite(a,LOW);
  digitalWrite(b,HIGH);
  digitalWrite(c,HIGH);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showf()
{
  digitalWrite(a,LOW);
  digitalWrite(b,HIGH);//high
  digitalWrite(c,HIGH);//high
  digitalWrite(d,HIGH);//high
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showg()
{
  digitalWrite(a,LOW);
  digitalWrite(b,HIGH);//high
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,HIGH);//high
}
void showh()
{
  digitalWrite(a,HIGH);//high
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,HIGH);//high
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showi()
{
  digitalWrite(a,HIGH);
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,HIGH);
  digitalWrite(e,HIGH);
  digitalWrite(f,HIGH);
  digitalWrite(g,HIGH);
}
void showj()
{
  digitalWrite(a,HIGH);//HIGH
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,HIGH);//high
  digitalWrite(g,HIGH);//high
}
void showl()
{
  digitalWrite(a,HIGH);
  digitalWrite(b,HIGH);
  digitalWrite(c,HIGH);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,HIGH);
}
void showo()
{
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,HIGH);
}
void showp()
{
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(c,HIGH);//HIGH
  digitalWrite(d,HIGH);//HIGH
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showr()
{
  //looks same as A
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,HIGH);//high
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void shows()
{
  digitalWrite(a,LOW);
  digitalWrite(b,HIGH);//high
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  digitalWrite(e,HIGH);//high
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showu()
{
  digitalWrite(a,HIGH);//high
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,LOW);
  digitalWrite(g,HIGH);
}
void showy()
{
  digitalWrite(a,HIGH);//high
  digitalWrite(b,LOW);
  digitalWrite(c,LOW);
  digitalWrite(d,HIGH);//high
  digitalWrite(e,HIGH);//high
  digitalWrite(f,LOW);
  digitalWrite(g,LOW);
}
void showz()
{
  digitalWrite(a,LOW);
  digitalWrite(b,LOW);
  digitalWrite(c,HIGH);//high
  digitalWrite(d,LOW);
  digitalWrite(e,LOW);
  digitalWrite(f,HIGH);//high
  digitalWrite(g,LOW);
}
void point_blink()
{
  Serial.println("Not Possible to display this character");
  digitalWrite(a,HIGH);
  digitalWrite(b,HIGH);
  digitalWrite(c,HIGH);//high
  digitalWrite(d,HIGH);
  digitalWrite(e,HIGH);
  digitalWrite(f,HIGH);//high
  digitalWrite(g,HIGH);
  for(int i=0;i<20;i++)
  {
    digitalWrite(p,LOW);
    delay(100);
    digitalWrite(p,HIGH);
    delay(100);
  }
}

You can download the full code from here. Kindly do leave a feedback in the comment box, if you have any. If you have any queries then do comment below and let me know. Currently I am working on the applications of microcontrollers in power electronics domain. I will keep you posted on the same in the upcoming days.

4x4 Keypad Interfacing with Arduino [Program]

2012-12-23T23:37:00.000+05:30

Hello Friends! Last week while trying out some odd experiments, I came across a task wherein I was required to do 4x4 keypad matrix interfacing with Arduino UNO microcontroller board.

4x4 numeric keypads are most widely used in numerous mini project which requires the user or the operator to give command to the system or to feed in some data into the embedded system.

In this post, I want to share with you the Arduino code which I made for 4x4 keypad interfacing. The program shared hereby is simple and easy to understand.

If you search more over the internet, then you may find some program involving keypad matrix interfacing using libraries, but problem with those codes are that, if you want to make some modifications in the code, then you are required to 'break in your head' to understand the complete code of the library file. Contrary to those codes, this program does not involve any library and is completely coded by me based on the conventional algorithm which is most commonly found in numerous books and internet sources.

In this program, the row pins are connected to A5, A4, A3, A2 and the column pins are connected to A1, A0, 10, 11. If you are changing the connections, then make sure that you update the changes in the first 8 lines of the the program

The code for 4x4 keypad interfacing with Arduino board is given below:

/*Program demonstrating 4x4 Numeric Keypad interfacing with Arduino UNO
Program Written by: Amit Biswal (Speaking Technology)
URL               : http://amitbiswal.blogspot.com       
*/
int r1=A5;
int r2=A4;
int r3=A3;
int r4=A2;

int c1=A1;
int c2=A0;
int c3=10;
int c4=11;

void setup()
{
  Serial.begin(9600);
  
  pinMode(r1,OUTPUT);
  pinMode(r2,OUTPUT);
  pinMode(r3,OUTPUT);
  pinMode(r4,OUTPUT);

  pinMode(c1,INPUT);
  pinMode(c2,INPUT);
  pinMode(c3,INPUT);
  pinMode(c4,INPUT);
  
}
void loop()
{
  int val;
  //setting the columns as high initially
  digitalWrite(c1,HIGH);
  digitalWrite(c2,HIGH);
  digitalWrite(c3,HIGH);
  digitalWrite(c4,HIGH);
  
  //checking everything one by one
  //case 1: col1 =0 while other col as 1
  digitalWrite(r1,LOW);
  digitalWrite(r2,HIGH);
  digitalWrite(r3,HIGH);
  digitalWrite(r4,HIGH);
  //checking each column for row1 one by one
  if(digitalRead(c1)==0)
  {
    Serial.println("key 1 pressed");
  }
  else if(digitalRead(c2)==0)
  {
    Serial.println("Key 2 pressed");
  }
  else if(digitalRead(c3)==0)
  {
    Serial.println("Key 3 pressed");
  }
  else if(digitalRead(c4)==0)
  {
    Serial.println("Key A pressed");
  }
  
  //case 2: col2 =0 while other col as 1
  digitalWrite(r1,HIGH);
  digitalWrite(r2,LOW);
  digitalWrite(r3,HIGH);
  digitalWrite(r4,HIGH);
  //checking each column for row1 one by one
  if(digitalRead(c1)==0)
  {
    Serial.println("key 4 pressed");
  }
  else if(digitalRead(c2)==0)
  {
    Serial.println("Key 5 pressed");
  }
  else if(digitalRead(c3)==0)
  {
    Serial.println("Key 6 pressed");
  }
  else if(digitalRead(c4)==0)
  {
    Serial.println("Key B pressed");
  }
  
  //case 3: col3 =0 while other col as 1
  digitalWrite(r1,HIGH);
  digitalWrite(r2,HIGH);
  digitalWrite(r3,LOW);
  digitalWrite(r4,HIGH);
  //checking each column for row1 one by one
  if(digitalRead(c1)==0)
  {
    Serial.println("key 7 pressed");
  }
  else if(digitalRead(c2)==0)
  {
    Serial.println("Key 8 pressed");
  }
  else if(digitalRead(c3)==0)
  {
    Serial.println("Key 9 pressed");
  }
  else if(digitalRead(c4)==0)
  {
    Serial.println("Key C pressed");
  }
  
  //case 1: col1 =0 while other col as 1
  digitalWrite(r1,HIGH);
  digitalWrite(r2,HIGH);
  digitalWrite(r3,HIGH);
  digitalWrite(r4,LOW);
  //checking each column for row1 one by one
  if(digitalRead(c1)==0)
  {
    Serial.println("key F pressed");
  }
  else if(digitalRead(c2)==0)
  {
    Serial.println("Key 0 pressed");
  }
  else if(digitalRead(c3)==0)
  {
    Serial.println("Key E pressed");
  }
  else if(digitalRead(c4)==0)
  {
    Serial.println("Key D pressed");
  }
  //giving delay between keypress
  delay(200);
  
}

If you have any suggestions for the improvement of the given code, then do comment below and share the knowledge.

Simple Counter using 7 segment LED with 8051 microcontroller

2012-11-22T18:46:00.000+05:30

Hello friends, Welcome back! In this post, I want to share with you a simple experiment that I did today. Basically this experiment uses the concept of interfacing of 7 segment LED with 8051 microcontroller. A simple counter has been made using 8051, which will display numbers from ‘0’ to ‘9’, one by one with a delay of few seconds.

The connections made in this circuit are shown in the block diagram:

Simple counter using 7 segmenet LED and 8051: Block Diagram

Please note that the 7 segment LED is connected in common anode mode, that means all 7 anodes of leds are connected together and should be connected to +5V and a particular LED will turn on when ‘Ground’ is applied to its terminal, which in this case is done using microcontroller.

The assembly language program for this experiment is given below:

;seven segment led
;Programmed by: Amit Biswal
;URL: http://amitbiswal.blogspot.com
org 0000h
;pin connections:
;pin 0.6=a
;pin 0.5=b
;pin 0.4=c
;pin 0.3=d
;pin 0.2=e
;pin 0.1=f
;pin 0.0=g
repeat:
mov p0,#10000001b ; displaying 0
acall delay
mov p0,#11001111b ; displaying 1
acall delay
mov p0,#10010010b ; displaying 2
acall delay
mov p0,#10000110b ; displaying 3
acall delay
mov p0,#11001100b ; displaying 4
acall delay
mov p0,#10100100b ; displaying 5
acall delay
mov p0,#10100000b ; displaying 6
acall delay
mov p0,#10001111b ; displaying 7
acall delay
mov p0,#10000000b ; displaying 8
acall delay
mov p0,#10000100b ; displaying 9
acall delay
sjmp repeat
delay:
mov r3,#010h
l3:mov r2,#0ffh
l2:mov r1,#0ffh
l1:djnz r1,l1
djnz r2,l2
djnz r3,l3
ret

The program is self explanatory and is well commented. If you find any difficulty with this, then do comment below.

You can also watch the demo of this experiment in the youtube video embedded below:

Controlling LED brightness using Arduino board

2012-11-15T20:16:00.004+05:30

Hello readers! In my previous post, I posted my miniproject on 8051 microcontroller based traffic light controller. But now a day, 8051 seems to be very outdated microcontroller. So this time I thought of doing some small experiments using Arduino.

If you don’t know about Arduino, then do checkout this outgoing link (arduino.cc). Basically Arduino is an open source prototyping platform using which you can easily build some extraordinary projects.

In this post, I have used Arduino Atmega328 board to control the brightness of LED using a PWM pin of Arduino.

So to get started, let us assemble the hardware in the breadboard. Follow these steps:

Connect pin 11 (we have used pin 11 in our program) of the arduino to a 220 ohm resistor.
Connect the LED in series with the resistor. Remember; connect the anode of LED to resistor and the cathode to the GND pin of the Arduino.

Now when you are done with your hardware assembling work, upload the program (or the so called sketch in arduino terms) to the Arduino board.

Program:


/*
Program to increase and decrease the brightness of LED
By: Amit Biswal
http://amitbiswal.blogspot.com
*/
int greenLED = 11;
int i;
void setup()
{
  pinMode(greenLED,OUTPUT);
}
void loop()
{
  for(i=0;i<=255;i=i+50)
  {
    analogWrite(greenLED,i);
    delay(500);
  }
  for(i=255;i>=0;i=i-50)
  {
    analogWrite(greenLED,i);
    delay(500);
  }
}

Now after you upload your sketch, you can see that the LED is slowly increasing its brightness and when it reaches its maximum value, it decreasing its brightness until it is switched off.

The program is self explanatory. I have used pin 11, which is one the 6 PWM pins available on Arduino. Then I have incremented/decremented the PWM value by a step of 50 units every time. After every increment/decrement, I am giving a delay of half second, so that human eye can observe the changes happening.

You can watch the demo video of this experiment, to get a clear idea of what is happening.

If you have any doubt or suggestions then do comment below and let me know.

Traffic Lights controller using 8051 microcontroller (Easy Assembly Program)

2012-11-10T13:44:00.001+05:30

Hello friends! In one of my previous post, I wrote on the differences between microcontroller and microprocessors. In this post I want to enter into the application part of microcontrollers. Now a day microcontrollers find their application in almost every electronics applications ranging from remote based toy cars to mobile phones, aircraft, etc.

In this post, I want to share with you, a microcontroller based mini project which I submitted as my assignment in my B.Tech course of “Microcontroller and Its Applications”. As the name of the title says, the topic is “Traffic Lights controller using 8051 microcontroller”.

Though you can find this project in almost every website on microcontrollers, I wanted to share my own program which is much smaller compared to other programs.

The general layout of the traffic lights is shown in the diagram:

Road Junction and Traffic Lights with Pin Name on them (Click to enlarge)

The green colour depicts green LED while red colour depicts red LED. The corresponding pins to which the LEDs are connected are also given beside the colour boxes.

The logic table for this project is shown below: (considering the LED will glow when pin output = 0)

Delay	P0.0	P0.1	P0.2	P0.3	P0.4	P0.5	P0.6	P0.7
1^st	0	0	1	0	1	0	1	1
2^nd	1	1	0	0	1	0	1	0
3^rd	1	0	1	1	0	0	1	0
4^th	1	0	1	0	1	1	0	0

Program:


org 0000h
here:
mov p0,#0d4h
acall delay1
mov p0,#53h
acall delay1
mov p0,#4dh
acall delay1
mov p0,#35h
acall delay1

sjmp here

delay1:
MOV R2,#42d
MOV R1,#00d
MOV R0,#00d
loop: DJNZ R0,loop
DJNZ R1,loop
DJNZ R2,loop
RET

You can watch the demo video of this project in the embedded youtube video:

Caution: Please note that, the program which I created for this program is very trivial one. Even my Professor said that this is not the efficient way of controlling traffic. So I will be working for a more efficient way of controlling traffic in future. So if you plan to submit this as any assignment then, Be careful.

Your suggestions and criticism for this program are always welcome.

Difference between ‘Time Ratio Control’ and ‘Current Limit Control’

2012-10-17T00:38:00.002+05:30

In DC-DC converters, the average output voltage is controlled by varying the alpha (α) value. This is achieved by varying the Duty Cycle of the switching pulses. Duty cycle can be varied usually in 2 ways:

Time Ratio Control
Current Limit Control

In this post we shall look upon both the ways of varying the duty cycle.

Before moving on, I would like to tell you that, Duty Cycle is the ratio of ‘On Time’ to ‘Time Period of a pulse’.

Time Ratio Control:
As the name suggest, here the time ratio (i.e. the duty cycle ratio Ton/T) is varied.

This kind of control can be achieved using 2 ways:

Pulse Width Modulation (PWM)
Frequency Modulation Control (FMC)

A. Pulse Width Modulation (PWM):
In this technique, the time period is kept constant, but the ‘On Time’ or the ‘OFF Time’ is varied. Using this, the duty cycle ratio can be varied. Since the ON time or the ‘pulse width’ is getting changed in this method, so it is popularly known as Pulse width modulation.

Pulse Width Modulation

B. Frequency Modulation Control (FMC)
In this control method, the ‘Time Period’ is varied while keeping either of ‘On Time’ or ‘OFF time’ as constant. In this method, since the time period gets changed, so the frequency also changes accordingly, so this method is known as frequency modulation control.

Frequency Modulation Control

Current Limit Control:
As is obvious from its name, in this control strategy, a specific limit is applied on the current variation.

In this method, current is allowed to fluctuate or change only between 2 values i.e. maximum current (I max) and minimum current (I min). When the current is at minimum value, the chopper is switched ON. After this instance, the current starts increasing, and when it reaches up to maximum value, the chopper is switched off allowing the current to fall back to minimum value. This cycle continues again and again.

Current Limit Control

Difference between Microcontrollers and Microprocessors

2012-10-13T22:11:00.001+05:30

This is one of the most common doubts which arise in the minds of every person who is a beginner to microcontrollers and microprocessors. This question is so common, that it is taught to the students in the very first class of microcontrollers & microprocessors and answer to this can be easily found in the initial introductory chapters of any book on microcontrollers.

The primary objective behind this post is to familiarize with the very basic differences which separate a microcontroller from a microprocessor.

The difference between both can be summarised in the points mentioned below:

8051 IC

Microprocessor contains only a CPU. In contrast Microcontroller contains few other components apart from CPU, which includes RAM, ROM and other peripherals like ports, clock, timer, UART (Universal Asynchronous Receiver Transmitter), ADC (Analog to digital converter), DAC (Digital to analog converter), Drivers for LCD, etc
Microprocessor can be considered as just the processor, while microcontroller can be seen as a small computer which is embedded on a single IC (Eg. 8051).
Since microcontroller can be embedded on a single IC, it is used mostly for embedded applications or for a more specific job. On the other hand, microcontroller are used for wider range of applications. For example, In Automotive applications, microcontrollers are used only for some specific tasks; while in computers, microprocessors are used for many applications ranging from ‘basic mathematical computation’ to ‘design and implementation of complex engineering problems’.
Since microcontroller has inbuilt memory and peripherals, it is cheaper when compared to microprocessors which becomes costlier on addition of external memory and circuit components.
Due to the absence of memory in the microprocessors, it is difficult to perform Boolean operations in them as compared to controllers.
For the same reason, number of instructions required to access data from external memory is more in the case of processors compared to the controllers.

So to summarise, we can state the difference between both in layman’s term as:

“Microprocessor is present inside a Microcontroller”.

This is valid to some extent because:

Microcontroller = Microprocessor + Few Extra components

One most important thing, I want to mention is that, though microcontroller is cheaper than microprocessor, we can’t use controller instead of processor or vice versa in their applications. In every application, the requirements are different and we can’t substitute one with the other.

MATLAB GUI for solving simultaneous equations

2012-10-08T21:26:00.003+05:30

Hello readers! After a long break, I am again using this space to share with a MATLAB based code, which I implemented as a small personal mini project (or a so called minute project).

You may know that solving equations in MATLAB is not a big task, we can easily do so using matrices. But evertime entering the values using command prompt sometimes seems to be very frustating. So this prompted me to prepare a GUI based application using MATLAB.

In this post I want to share with you a Graphical User Interface (GUI) made using MATLAB programming which can solve simultaneous equations in 2 variables.

You can see in the screenshot of the interface, that you need to enter the values of the coefficients of x & y and on the click of the button “Calculate”, the values of x and y will be displayed in the ‘answer’ section of the dialog box.

This program also takes care of the failure cases of solving simultaneous equations. Eg. The case when there are more than 1 unique solution i.e. Infinite solutions, the answer will be shown as ‘Inf’ that is Infinity in MATLAB’s language.

So the code for this GUI development is given below:

Code:


function varargout = mygui(varargin)
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @mygui_OpeningFcn, ...
                   'gui_OutputFcn',  @mygui_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end
if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
function mygui_OpeningFcn(hObject, eventdata, handles, varargin)
handles.output = hObject;
guidata(hObject, handles);
function varargout = mygui_OutputFcn(hObject, eventdata, handles) 
varargout{1} = handles.output;
function pushbutton1_Callback(hObject, eventdata, handles)
a1=str2num(get(handles.a1,'String'));
b1=str2num(get(handles.b1,'String'));
c1=str2num(get(handles.c1,'String'));
a2=str2num(get(handles.a2,'String'));
b2=str2num(get(handles.b2,'String'));
c2=str2num(get(handles.c2,'String'));
R=[a1 b1;a2 b2];
V=[c1;c2];
I=inv(R)*V;
set(handles.ans1,'String',I(1,1))
set(handles.ans2,'String',I(2,1))

Important Note: Just copying and pasting this set of program may not work. You need another file named as ‘mygui.fig’ which I had created for this program. So download the given set of code from the link given below:

[Download Link]

Download the zipped folder and extract both the files in it then run the m-file using MATLAB software.

I welcome your feedback on this application.

Matlab: Convert state space model to transfer function without ‘ss2tf()’ function

2012-09-22T10:54:00.003+05:30

Hello everyone! In this post I want to share with you a simple Matlab program to convert state space model to transfer function.

In modern control systems, state space models are in common use because of its advantage over classical control system involving transfer function. One of the most common advantage is transfer function can be used only for zero initial condition, whereas state space models can be used for systems involving both zero and non-zero initial conditions.

Now let us come to the main topic, i.e. converting state space model to transfer function in Matlab. In Matlab, we can perform this task in 2 ways:

Using the direct command ‘SS2TF()’
Without using ‘SS2TF()’ command

Let me brief about each of the 2 ways:

I. Using Direct command
In this way, Just enter the matrix A,B,C and D from the state space model of

X'=Ax+Bu
Y=Cx+Du

And then use the syntax:

[num,den]= ss2tf(A,B,C,D)

This will return the numerator and denominator of the transfer function. The Matlab codes are shown below:


%program to convert state space model to transfer function
%using SS2TF() function
%Author:    Amit Biswal @ Speaking Technology
%URL:       http://amitbiswal.blogspot.com
clc
clear all
A=[0 1 0;0 0 1; -1,-2,-4]
B=[0;0;10]
C=[1 0 0]
D=[0]
[num,den]=ss2tf(A,B,C,D)
T=tf(num,den)

II. Without using direct command

In this method, we will use our theoretical knowledge and apply the formula for transforming state space model to transfer function, i.e

T(s)=C(sI-A)^-1B+D

The Matlab codes for the same are shown below:


%program to convert state space model to transfer function
%without using SS2TF() function
%Author:    Amit Biswal @ Speaking Technology
%URL:       http://amitbiswal.blogspot.com
clc
clear all
A=[0 1 0;0 0 1; -1,-2,-4]
B=[0;0;10]
C=[1 0 0]
D=[0]
s=tf([1 0],1);
I=eye(3);
T=(C*((inv((s*I)-A))*B))+D

The m-file for the second program can be downloaded from here [Download Link]

Matlab program to count the number of perfect squares between 2 numbers

2012-09-15T22:36:00.002+05:30

Hello readers! In this post, I want to share with you a simple program to count the number of perfect square between 2 numbers. For example, If I enter 2 numbers say 1 and 9, then it should give me the result as 3 since there are 3 perfect square numbers between 1 and 9, which are 1,4 and 9.

This post was requested by one of our visitors 'Snehlata Tripathi' in a comment under one of our older post on how to "find the highest and lowest perfect square number of desired digits using MATLAB program".

In this post, I have prepared a simple matlab program which will initially ask for the the 2 numbers and then go on to check whether the number lying between them are perfect square or not. If any number is found to be perfect square, then the counter is incremented by one. At the end the value of counter is presented as the answer.


% program to count the number of perfect squares between 2 numbers
% Author: Amit Biswal @ Speaking Technology
% URL: http://amitbiswal.blogspot.com
clc
clear all
num=0;
n1=input('Input the smaller number:');
n2=input('Input the larger number:');
if n1>n2
    fprintf('First number should be smaller than second!!\n Please Try Again')
elseif n1==n2
    fprintf('The numbers are equal!!\n Please Try Again')
else
   n0=n1;
   while(n1<=n2)
      root=sqrt(n1);
      if root==fix(root)
          num=num+1;
      end
      n1=n1+1;
     
   end
    fprintf('Number of perfect squares between %d and %d is %d',n0,n2,num)
end

Well, this program may not be the efficient one and there is always a room for improvement. So I welcome your feedback and efficient algorithms. If you have any query, doubt or suggestions, then you can comment below and let me know. Thankyou for reading!

Single Phase half wave thyristor circuit [simulation]

2012-09-02T10:37:00.005+05:30

Single Phase half wave thyristor circuit [simulation].

In some of my previous posts, we have seen the simulations of half wave and full wave rectifiers using simple diodes. Now in this post, I would like to move on to power electronics domain with the first post being “Single Phase half wave rectifier using thyristor”.

In a thyristor or a so called SCR (Silicon controlled rectifier) circuit, the thyristor is turned on after a delay angle alpha (α) using a firing circuit. α is also called firing angle.

So, in the circuit shown below, the SCR starts conducting only after a delay angle of α, which is controlled by the potentiometer across the Anode and Gate terminals of the SCR. When the SCR starts conduction, the voltage appears across the load resistor of 1kΩ as shown in graph-2, otherwise during off condition of SCR, the voltage appears only across the SCR as shown in graph-3.


Circuit diagram/schematic of single phase half wave thyristor circuit (R-Load)

Note that these simulations were performed in the NI MultiSim software.

Graph-1: Source Voltage

Graph-1 here depicts the source voltage. It can be easily inferred from the graph that the source voltage is sinusoidal.

Graph-2: Voltage across the load

You can see the in the above graph that the voltage appears across the load only after a certain delay angle (firing angle). Conduction occurs only in positive half cycles, since during negative half cycles, the SCR is switched off.

Part of the sinusoidal waveform which do not appear across the load resistor appears across the thyristor as shown in the graph-3. These waveforms appear when the thyristor is on OFF mode


Graph-3: Voltage across the thyristor

How does Night Vision Goggles work?

2012-08-12T23:20:00.000+05:30

How does Night Vision Goggles work?

Last week, I was watching an English movie, in which few soldiers switched off the lights of a room and started firing in the dark after wearing some special kind of goggles enabling them to view even in the dark.

Now after a week, I got to read about those special goggles called as ‘NIGHT VISION GOGGLES’. Well these so called night vision goggles are one of the applications of Semiconductor Physics.

So in this post, I would like to share with you what i have read about these Goggles.

Well, the components present in a night vision goggles can be divided into 3 parts namely,

Night Vision Goggle

Photocathode
Photomultipliers
Phosphor Screen

First of all when the light is switched off, the dim light enters the lens of the Goggles. As everyone may know that light is essentially composed of photons, so we may say that the photons enters the lens and then strikes the first component of this device called photocathode. These photo cathodes are basically light sensitive semiconductor surface, which converts the photons into electrons. In simple words, it converts the light energy to electrical energy.

Now the electrons generated in the first stage enters the second component of the device and are passed through photomultipliers. As the name suggests, the job of the photomultiplier is to multiply the number of electrons entering its surface. So the number of electrons increases after coming out of the photomultiplier and is passed on to the next component.

Now in the third stage, the electrons strike the phosphor screen which give rise to tiny flashes of light. These light flashes appear in the screen giving an idea of the location of a particular object in dark rooms.

If you have any more information on this topic, then do comment below and let all of us know. Also do not forget to share if you find it informative.

Reference: Economic Times Magazine, Dated: Aug-12-2012

[Image Credits]

Full wave bridge rectifier circuit [Multisim Simulation]

2012-07-22T09:08:00.004+05:30

Full wave bridge rectifier circuit [Multisim Simulation].

In one of my previous posts we studied about the half wave rectifier and simulated it using the National Instrument’s Multisim Simulation software. In this post, I would like to continue with the rectifier circuit, by explaining the full wave rectifier.

Basically a rectifier is usually used to rectify the pulses or waveforms of AC to DC. Another name of Full wave rectifier is Bridge rectifier as is mentioned in the title of this post.

This circuit consists of a set of 4 diodes connected in a bridge like structure. At any instant of time, only 2 diodes will be functional and other 2 will remain idle. In the positive half of the cycle, 2 diodes which are in forward bias mode will form the circuit and will conduct. In the negative half cycle, other 2 diodes which were earlier in reverse bias mode will be in forward bias mode and other 2 will be in reverse bias mode.

Coming to the simulation of this circuit, the circuit diagram drawn using the NI Multisim is shown below:

full wave rectifier circuit diagram

You can see that 4 diodes are connected in a bridge kind of structure and the oscilloscope is connected across the resistor to observe the voltage waveforms across the resistor.

Here the components used are:

Sinusoidal voltage source: 10V, 50Hz
4 diodes: 1N4007
Resistor: 100k ohms
Oscilloscope

When we run the simulation, only 2 diodes will conduct in each half cycle and will give rise to a voltage waveform which doesn’t contains any negative half of the original sinusoidal waveform. You can see the waveforms in the image given below:

full wave rectifier output waveforms

After measuring using a probe, the rms voltage across the resistor is found to be 6.88V. So 10V signal is converted to 6.88V signal without having any negative cycle. Rest of the voltage i.e. (10-6.88) = 3.12V is the voltage drop across the diodes. Voltage drop across each diode is 1.56V.

But in practical dc application, we can’t use a DC with such a heavy ripples. So to reduce the ripples, we can make use of capacitors.

These ripple reducing capacitors are often termed as smoothening capacitor. In the circuit below, you can see that the electrolytic capacitor of 100uF has been connected in parallel to the resistor. This capacitor performs charging and discharging operation and converts the full wave rippled output to a smooth DC output across the resistor. The circuit with a smoothening capacitor is shown below:

full wave rectifier using smoothening capacitor

The value of the capacitor shouldn’t be very small, otherwise it will not be effective in reducing the ripple to the required extent. Choosing an appropriate value can result in a very smooth DC output. In the image given below, you can see that 100uF capacitor works perfect with this circuit giving a perfectly smooth DC output. You can try simulating using a 100nF or other lesser valued capacitor, you will find the ripples which can be used to study the charging and discharging operations of the capacitor. The output waveforms are shown below:

output waveform of full wave rectifier using smoothening capacitor

After measurement using a probe, it is found that the rms voltage across the resistor in this case is 8.26V.

Why semiconductors are used in solar cells not conductors

2012-07-14T13:04:00.001+05:30

“Why conductors are not used in solar cells?”

2 days back, one of my readers asked me this question on the facebook fan page of Speaking Technology.

why semiconductor only used in solar cell why not conductors?

Frankly speaking this question triggered my mind that though I have studied a lot about semiconductors and solar cells in our engineering course, but never thought of using conductors in the solar cells. Why is that so?

Then I thought there must be some reason behind this and I started hunting for few books on semiconductors in my library and did a few internet search and alas I found the answer!:)

Why semiconductors used in solar cells instead of conductors

Here is the description of what I understood:

Solar cells or the so called photo-voltaic (PV) cells work on the principle of photo electric effect. In photo electric effect the photons strike the element surface and the energy of the photons is transferred to the electrons present in the valence band of the element. This energy is sufficient to excite the electrons from valence band to conduction band, thus giving rise to free electrons. These free electrons form the base for the electric current in the circuit. The element on which the photons strike can be a conductor, semiconductor or insulator.

Taking the case of insulator, the energy band gap between the valence band and conduction band is very large which means a large amount of energy is needed to eject out the electrons. Generally the photons from the sunlight do not possess this amount of energy. Photons of high frequency like X-rays may be able to perform this task.

Now coming to the case of semiconductors, the energy band gap is quite less. The photons can easily eject the electrons out of it provided the energy of the electrons is more than the threshold energy required.

In case of conductors, the band gap is very little or negligible. So the electrons can be ejected very easily.

Now the question is when photo electric effect can be applied on the conductor, then why it can’t be used in solar cells?

The question to this lies in the ELECTRIC FIELD present within the semiconductors.

The free electrons alone cannot give rise to current, they will just move randomly. To make the electrons move in the circuit, there must be some driving force. This driving force is “Electric Field”.

Due to the presence of PN junction, there is a small electric field present within the semiconductors without which the solar cells won’t work. In the PN junctions, the electrons and holes try to mix with each other but they are not able to completely mix, Otherwise the junction will become neutral and will be of no use. When few electrons and holes combines with each other and rush towards the opposite charge, repulsive force comes into play due to the heavy rush of similar charges.

A potential barrier is formed and when equilibrium is attained, we find the presence of small amount of electric field within it. This acts as a driving force for the free electrons.

But in the case of conductors, since there is no equivalent PN junction, so the free electrons move randomly.

So the conductors cannot be used in the solar cells or the photovoltaic cells.

Currently research is going on to use “conducting polymers” and “transparent conducting films” in solar cells.

If you find any more info related to this interesting topic, then do share with us by commenting below. Do share this post with your friends if you found it interesting.

PN junction diode as half wave rectifier [Multisim Simulation]

2012-05-29T21:16:00.001+05:30

In our day to day electronics applications, we need many circuits which enable us to rectify the AC waves to DC. In current electronics scenario, we need circuits as small as possible to minimize costs. Since rectifier circuit is one small part of any big electronics application, so we need to minimize the size of every circuit involved in any project.
One such simple and small rectifier is a half wave rectifier which uses a PN junction diode. Though this is not any advanced circuit which can be used for high accuracy rectification with minimum ripple, but still this circuit forms the basis of rectifiers.

In this post I am going to tell about the half wave rectifier circuit using PN junction diode.

The basic circuit of the half wave rectifier is shown below:

circuit simulation using NI Multisim - Click to enlarge

The simulation of this circuit has been done using the NI multisim software.

Here we are using a 10V, 60Hz AC voltage source, 100K ohm resistor and pn junction diode 1N4001 all connected in series with each other. To check the waveforms of the load resistor R1, I have connected an oscilloscope across the resistor.

When the simulation starts, during the positive half cycle of the AC source, the diode is forward biased and hence act as a conductor, allowing the positive part of the since wave to pass through. During negative half cycle, the diode is reverse biased and hence act as an insulator, so the negative part of the wave appears as zero at the output.

Hence the sinusoidal wave is rectified partially. Since it is partially rectified, so it is called Half wave rectifier.

The output wave across the resistor R1 is shown in the snapshot shown below.

Rectified waveform across resistor R1 - Click to enlarge

If you have any queries or any problem simulating this simple circuit then you can comment below.

Also read: Full Wave bridge rectifiers using diodes

Complement Image using MATLAB Image Processing

2012-05-23T00:14:00.001+05:30

Complement Image using MATLAB Image Processing.

Hi, In my previous post about we discussed how to create discrete wave sequences from the continuous signals in Matlab. Well those things are particularly used in Digital Signal Processing, but in this post i want to discuss something related to Digital Image Processing.

As you can see from the title, in this post we are going to learn how to complement a given image using MATLAB. Basically we will be doing a simple image processing.

You might know what is complementing that is in simple binary form, we get 0’s for 1’s and 1’s for 0’s. So similar to this concept, while complementing an image we convert dark regions to light and light regions to dark.

So before doing this work, follow few steps:

Get the image you want to process
Rename it as pic1 (JPG format) (This is because we are using ‘pic1’ as the name in the MATLAB program. Or else you can also change the file name in the Matlab program itself with the actual name of your picture along with its format like ‘.JPG’, ‘.PNG’, etc)
Now copy and the paste the following code in a ‘m file’ and run the program.

The code is as follows:

clc

clear all
pic1 = imread('pic1.jpg');

pic2 = imcomplement(pic1);
subplot(2,1,1)
imshow(pic1)
subplot(2,1,2)
imshow(pic2)

Complementing image using MATLAB

If you have any difficulty understanding the code or implementing it, then you can comment below or you can contact me via my contact page or facebook or twitter.

Plot continuous and discrete time wave sequences in MATLAB

2012-05-10T20:18:00.000+05:30

How to Plot continuous and discrete time wave sequences in MATLAB.

In digital signal processing, basically we deal with non continuous that is discrete signal. So to perform all digital signal operations like convolution, correlation, filtering, fourier transform, etc we need to know how to compute or observe a continuous signal in discrete form in MATLAB.
In this post I want to share with you a MATLAB program which displays a sinusoidal signal in both domains.

Basically in this program, we have used 2 important commands:

plot(x,y) to obtain the graph in Continuous time(CT)
stem(x,y) to obtain the graph in Discrete time (DT)

The Matlab program is given below:
%Computing the graph of wave sequences both in CT and DT clc clear all x=0:1:40; y=10*sin(2*pi*x/15); subplot(2,1,1) plot(x,y) %CT title('CT sine wave') grid subplot(2,1,2) stem(x,y) %DT title('DT sine wave') grid

Continous and Discrete sequences output in Matlab

If you have any queries or feedback related to this post, then do comment below and notify me.

Controllability & Observability test on a control system using Matlab

2012-05-09T15:41:00.000+05:30

Controllability & Observability test on a control system using Matlab.

In state space analysis in Control system, sometimes we come across controllability and observability test on a control system. In this post I want to share with you an elementary Matlab program demonstrating the results of whether the system is observable and controllable or not using the well known Kalman’s Test algorithm.

In this program, I have used the state space analysis approach using a 3x3 matrix for A, 3x1 matrix for B and 1x3 matrix for C as per the equation:

X= Ax + Bu
Y= Cx + Du

In this program, you can change the value of A, B and C as per your system parameters. You can also modify this program if you want to use 2x2 or 4x4 matrix as per your problem requirement.

The program is given below:

%{
Kalmans test for controllability and observability
 x* = Ax + Bu
 y  = Cx + Du
controllability condition Q = [B AB A2B]
Observability condition T=[CT ATCT (AT)2CT]
%}
clc
clear all
A=[0 0 1; -2 -3 0; 0 2 -3]
B=[0; 2; 0]
C=[1 0 0]
D=0
Q=horzcat(B,A*B,(A^2)*B)
t1=transpose(C);
t2=transpose(A);
T=horzcat(t1,t2*t1,((t2)^2)*t1)
if rank(Q)==3
    fprintf('Controllable\n')
else
    fprintf('Not controllable\n')
end
if rank(T)==3
    fprintf('Observable\n')
else
    fprintf('Not Observable\n')
end

If you have any doubt, query or suggestions then you can post your comments below.

Find perfect square numbers, highest, lowest of desired digits using MATLAB program

2012-05-04T11:27:00.000+05:30

Find perfect square numbers, highest, lowest of desired digits using MATLAB program.

Using this program prepared using MATLAB M-File program, you can find the highest and lowest perfect square number of your desired digits.

When you run this M file code, you will be asked the number of digits that you want, At this step, just enter the number of digits and wait for the result to be displayed.

While preparing this program, i have not considered the optimum time complexity algorithms, so this program can give results in less time for 6 digits. Though you can get accurate answers for higher digits also, but it will take a long time.

Currently I have tested this set of code in MATLAB Version 7.0 in 2.13 GHz processor and found that till 5 digits, it gives answers instantly. While for 6 digits it takes 2 seconds and for 7 digits it takes 50 seconds.

The M-File code is as follows:

clc
clear all
%program to find the highest and lowest perfect square number of desired digits
n=input('enter the number of digits')
lowlt=10^(n-1);
uplt=(10^n)-1;
j=1;
num=lowlt; 
while(num<=uplt)
    whole=sqrt(num);
    natural=fix(whole);
    diff=whole-natural;
    if (diff==0)
        psqr(j)=num;
        psqrt(j)=whole;
        j=j+1;
    end
    num=num+1;
end
fprintf('\n------------------------\n%d digit perfect square\n HIGHEST:%d root:%d\n LOWEST :%d root:%d',n,psqr(j-1),psqrt(j-1),psqr(1),psqrt(1))

If you want to see the perfect squares in the increasing order, then you can add the code given below:

fprintf('\n------------------------\nNumber Square Root\n')
i=1;
while(i<j)
  fprintf('%d   --> %d \n',psqr(i),psqrt(i))
  i=i+1;
end

Note: This program is best recommended for upto 7 digits computations.

If you want to do computations for more than 7 digits, I recommend using C/C++ compilers, since they can perform fast looping related computations. The algorithm will remain same unless and until you are considering time complexity.

Tip: If you enter higher digits example 8 or more, then it would take large amount of time to process, during which MATLAB appears to be stuck, so you can restart MATLAB after closing it from the task manager by pressing ‘Ctrl+Alt+Del’ keys.

You may be interested in: Matlab program to count the number of perfect squares between 2 numbers

Matlab Program to plot Bode and Root Locus plot for the given transfer function

2012-05-03T00:35:00.002+05:30

Matlab Program to plot Bode and Root Locus plot for the given transfer function.

In the initial basic course of Control systems in Engineering, you might be taught how to draw bode plot and root locus plot on the semi-log and general purpose graph sheets respectively. Well this can also done in MATLAB using a 1 line command.

In this post I want to tell how to draw bode and root locus graph in MATLAB which consumes fractions of seconds compared to the huge amount of time we spend on drawing those manually during written exams.

So suppose we have the transfer function as

s + 12
-------------
2 s^2 + s + 4

Then the Matlab program for the bode plot will be as follows:

clc
clear all
num=[1, 12];
den=[2, 1, 4];
system=tf(num,den)
bode(system)

MATLAB screenshot of the bode plot for variation of both magnitude and phase with respect to Frequency

In this program the ‘bode(system)’ command automatically displays the bode graph for the system whose numerators and denominators have been defined in the 3rd and 4th lines.

For more details about creating transfer function read this post.

MATLAB program to create transfer functions [Control Systems]

Secondly if you want to create root locus, then you may use the following command instead of bode() command

rlocus(system)

This will create the root locus of the given transfer functions.

Introduction to Stepper Motor and Its type (Seminar PPT)

2012-04-28T08:21:00.001+05:30

Introduction to Stepper Motor and Its type (Seminar PPT).

In this post I want to share with you a PowerPoint presentation on the topic of stepper motor. This presentation was presented by me during one of my seminar on stepper motors(SM).

Basically this presentation contains pictorial representation of the types of stepper motor depicting their constructional details and some of its applications. I have tried not to include any theoretical details in the presentation so as to make presentation least boring and just explained the theory of operation during the seminar using oral presentation.

Basically the SM is an incremental motion motor. Unlike the other motors, its rotation is not continuous but in steps for each input current pulse received.

These kinds of motors are generally used for open loop position control which requires very low speed but high precision rotation. Most interesting thing about this motor which makes it different from other kinds of motor is its rotor which does not contain any windings and commutator.

The important types of stepper motor are:

Variable reluctance type
Permanent magnet type
Hybrid type

Variable reluctance type SM can be operated using 4 modes which are:

1 Phase ON (Full step operation)
2 Phase ON
Half step operation
Microstepping

Some of the applications of SM in commercial, medical and military purpose include blending, metering, cutting, purging, mixing etc.

Stepper motor

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What is Corona in transmission lines and its occurrence

2012-04-23T00:14:00.000+05:30

What is Corona in transmission lines and its occurrence?

In power system engineering, we see various transmission and distribution losses occurring in the transmission lines. In India, the Transmission and Distribution losses amount to 35% which is one of the highest in the world. Corona loss is one of the T&D losses which occur in a transmission line.

In this post I want to tell you what exactly is corona and what is responsible behind the occurrence of corona.

In transmission lines, you might have seen 2 conductor cables at certain predefined distance to each other: one phase and other neutral. When the potential difference between the 2 cables, increases beyond a certain value called Critical Disruptive Voltage (usually beyond 30kV), then the cables start glowing with a violet glow. This phenomenon is said to be the occurrence of corona.

This violet glow usually occurs along with a hissing sound, power loss and radio interference. It is also responsible for producing ozone gas.

Animation of Electric Discharge (Corona Discharge is quite similar to this process)

Image Courtesy: Mike's Electric Stuff

This violet glow is more uniform when the transmission conductor cables are polished smoothly otherwise, the violet glow is more at the rough surface of the conductor.

Let me tell you the physics behind this process...

In between the overhead conductors, air is present which is itself composed on ions. So when the potential difference between the conductors exceeds say 30kV, then the ions get charged and start moving from higher potential to lower potential region across a potential gradient. These charged ions or say electrons collide with the particles of the conductors to eject electrons from its surface. This ejected electrons when seen as a huge mass appears to be violet glow over the surface of the conductor.

Possible impact of Indian Budget 2012 on Power and Energy Sector

2012-04-21T16:24:00.001+05:30

Possible impact of Indian Budget 2012 on Power and Energy Sector.

After the release of Union Budget 2012 in India, industry experts in each sector have started analysing the probable impact of budget on their business and industrial sector. The featured story was the increase in the number of services for which service taxes will be charged. This decision has already triggered a price rise in FMCG and food products.

In this post, I want to point out the possible impact of the union budget on the power and energy sector.

First of all I would like to point out the key point in the Budget that is going to influence the whole electrical or power industry. That is the decision of reducing the import duty on coal.

At first look, this decision of reducing the coal import duty will surely help out curbing the energy deficit of our country. Thermal power stations like NTPC and other industries having their own captive power plants will surely benefit from this by increasing their production capacity. Since the price of coal will decrease, so their operational cost will automatically come down along with increased power production.

But this decision is going to badly affect the renewable energy sector which is still in its incubation state in India.

MNRE Logo

Increased import of coal is not good for us in the long run. This will increase our dependency on non-renewable exhaustible sources of energy. In addition to this, it will add to environmental pollution.

In spite of the fact that India has a huge potential for wind energy which is currently the most efficient renewable energy source, Indian Budget 2012 has not laid any special focus on this sector.

Due this decision, solar energy sector is going to be the most affected industry due to the heavy prices of photovoltaic cells.

Concluding this post, as per my opinions, the budget must have laid out some incentives or policies which could have helped the renewable energy sector of our country, so that we can reduce our dependency on the conventional sources of energy.

Basics of Optical Fibre communication – Semiconductor Physics [PPT]

2012-04-08T16:15:00.001+05:30

Basics of Optical Fibre communication – Semiconductor Physics [PPT].

Optical fibre communication forms the base of telecommunication networks today. Some of the processes involved in optical fibre communication include:

Generation
Modulation
Transmission
Amplification
Reception by photo detectors

In this post i want to share with you a presentation that i had prepared during my course of semiconductor physics. This presentation contains the very basics of the optical fibre communication.

Some of the slides have been explained using animations, so for better understandings, you can download this ppt directly from the slideshare website and view it in your computer.

[Related Reading: How to download embedded slideshare documents (with Video Tutorial)]

Do not forget to share this ppt with your friends and your feedback is most welcomed.

Optical fibre communication basics

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