The usage of ‘gets’ statement in C Programming

Well we have already discussed about the usage of ‘fflush’ statement, let us now discuss about the usage of ‘gets’ statement. String is an array of characters and we use the format specifier ‘%s’ to directly get these array of characters, which is not possible in the case of array of integers. In the case of array of integers we use the ‘for’ loop to get the values since we don't have any format specifier for array of integers.

To get array of characters we use the format specifier ‘%s’ as shown below

puts(“Enter the string”);
scanf(“%s”,ex_str);
puts(ex_str);

Output:

Enter a string
sample text
sample

What is wrong in the output?? We know that ‘Space’ and ‘Enter’ key act as a delimiter. So if you execute this program and give input as ‘sample text’ the value stored in ‘ex_str’ is ‘sample’ and not ‘sample text’ this is because the space in between the words ‘sample’ and ‘text’ acts as a delimiter thus storing only ‘sample’ in the character array (string). To overcome this problem we use the ‘gets’ statement. The ‘gets’ statement takes only the ‘Enter’ key as delimiter. The below part of the code shows how to use ‘gets’ statement.

puts(“Enter a string”);
gets(ex_str);
puts(ex_str);

Output:

Enter a string
sample text
sample text

Just think of getting a name of a person which contains first name, last name and middle name so this ‘gets’ statement is much useful in those situations. Happy Programming!!

The usage of ‘fflush’ statement in C programming

The keyboard has an input buffer in it and every time you read data from the keyboard the value stored in the input buffer is read. For every key press there will be a value loaded into the input buffer which means that the ‘Enter’ key, ‘Tab’ key also has a value being stored in the buffer when pressed.

We know that the ‘Enter’ key and the ‘Tab’ key acts as a delimiter while accepting data. Consider the below C Program

void main()
{
int num;
char ch;
clrscr();
printf(“Enter a number\n”);
scanf(“%d”,&num);
printf(“Enter a character\n”);
scanf(“%c”,&ch);
printf(“The value of num is %d and ch is %c”,num,ch);
getch();
}

The output of the program is shown below

Enter a number
12
Enter a character
The value of num is 12 and ch is

Wonder why this happens? Well let us look at the problem. When you type the number 12 and press ‘Enter’ key, the value corresponding to key press ‘1’ and ‘2’ is read from the input buffer and gets assigned to the variable ‘num’ once you press the ‘Enter’ key(delimiter). Now the value of the ‘Enter’ key is stored in the input buffer. So when you want to read a character, the value of the ‘Enter’ key which is stored in the input buffer is assigned to the character variable ‘ch’. This results in giving a wrong output. This is where the ‘fflush’ command comes into picture. The ‘fflush’ clears the specified buffer, so after getting the integer value we need to clear the input buffer (which stores the ‘Enter’ key value) before getting the character value. So the C program is changed as shown below.

printf(“Enter a number\n”);
scanf(“%d”,&num);
fflush(stdin);
printf(“Enter a character\n”);
scanf(“%c”,&ch);

Hope you know understood the importance of ‘ffush’ statement

Types of ROM's

We have been hearing the terms volatile memory and non-volatile memory from our 1st year of college. Here is a brush up of what we have heard so far.
The OTP (one time programmable) are used for firmware applications.
The ROM is also known as the program memory or code memory and RAM is also known as the data memory.
The EEPROM are electrically erasable PROM and needs electrical supply to clear the data.
The UVPROM requires UV light to pass through the window to clear the data.
The FLASH ROM are the advanced ones where data is loaded and retrieved in blocks, where each block is greater than 2 bytes, so the operation is faster in the case of FLASH ROM, whereas in the case of EEPROM data is loaded and retrieved byte by byte so it would take much time to access data when compared to FLASH ROM.

Hectic week approaching...

The rain was troubling me much last month, because of it I had to delay every jobs of mine. I even failed to attend two of my classes at AU PERS center. Those two classes covered array of pointers and structures, It was bad that I missed the classes on array of pointers which was an interesting and tough topic. However I hope I could get my doubts cleared on it. The upcoming week I have one week practicals and I have to complete twenty programs within this week and get it signed from the lab incharge. The twenty programs seems to be pretty tough and time consuming I tried to complete only three and it took me two hours and I spent most of my brain work there, now trying to get some relaxation. Hope that I could complete the programs on time and I also have to prepare for the test after this week on C module. I hope that this week is a hectic one and I have to plan well to face it.

Code snippet for working with an ADC

We have already seen the need for an analog to digital converter and also how the conversion takes place, the below code is used to work with an ADC in my PIC development board where the PIC16F877A senses the input from an ADC through RA0 pin and displays the digital value in the LCD which is connected to PORTD and also send the converted data to PORTB.

#include<16f877a.h>
#use delay(clock=4000000)
#include
#byte portb=0x06
#byte porta=0x05
#byte portd=0x08

int16 temp;

main( )

{

lcd_init( ); //INITIALISE THE LCD ;

set_tris_b(0x00); //PORTB IS CONFIGURED AS A O/P;

set_tris_a(0x01); //PORTA IS CONFIGURED AS A I/P;

set_tris_d(0x00); //PORTD IS CONFIGURED AS A O/P;

setup_adc_ports(ra0_analog);

setup_adc(adc_clock_internal);

set_adc_channel(0);

while(1)

{

temp=read_adc(); //OUTPUT IS STORED IN TEMP;

portb=temp;

lcd_gotoxy(1,1);

printf(lcd_putc,"ADC:%4lx",temp); //DISPLAY ON LCD;

delay_ms(500);

}

}

Here you can see in the code that while configuring the pins of PORTA since we are going to sense the analog input from RA0 we hace configured it as an input (set_tris_a(0x01)).

Analog to digital converter module

We have already seen about the need for analog to digital converters in my previous post. Now let us look into how the analog to digital converter module actually works. The below figure represents the analog to digital converter module.


You can see the input pins where the analog data comes from, which are connected to the inputs of an analog multiplexer. The function of the analog multiplexer is to connect the selected input channel to the holding capacitor. The holding capacitor is connected to the output of the analog multiplexer and when a conversion is initiated, the analog multiplexer disconnects all inputs from the holding capacitor, and the successive approximation converter performs the conversion on the voltage stored on the holding capacitor thus providing a digital value at the output.

The need for Analog to Digital Converters

We have seen the advantages of digital signals over the analog signals in transmission of signals. Microcontrollers are very efficient at processing digital numbers, but they cannot handle analog signals directly. An analog-to-digital converter, converts an analog voltage level to a digital number. The microcontroller can then efficiently process the digital representation of the original analog voltage. By definition, digital numbers are non-fractional whole numbers.
In this example, an input voltage of 2.343 volts is converted to 87. The user’s software can use the value 87 as the representation of the original input voltage. The analog input voltage must be within the valid input range of the A/D for accurate conversion. Hope you would have heard about the quantization process of rounding off and the quantization error. The A/D converter which is having higher resolution gives less quantization errors. Hence a 12-bit converter which has 4096 states is much efficient than a 10-bit converter that has 1024 states.

About 8085 simulator's

If you are a college student in your third year then you can realize how important 'Microprocessor and its Applications' subject is. If you attend any technical HR interview then there is sure questions from this subject. For this subject practical knowledge is much more important than theory knowledge. Learning 8085 microprocessor well forms a good base for learning other microprocessors and microcontrollers. So you should try to learn the instruction set and work with Assembly Language Programming of 8085. Even though you may not have a 8085 kit with you but you can download free 8085 simulators that are available in Internet and go on with writing ALP and executing them. These simulators will surely help you to gain good knowledge in 8085 microprocessor. If you get microprocessor book of Goankar then you will be getting free CD with simulator and you can even get the simulator if you get Bhakshi. Well you can have a good knowledge only if you have interest towards learning it. So create your interest towards microprocessor 8085 and it will surely help you in future while attending interviews.

Day 3 at AU PERS center

The government holidays are affecting my embedded system course at Anna University. I think that this October month is having a lot of government holidays that any other month. Even though I had joined the course at September, but because of these holidays I have completed only 3 classes at Anna University. Well the classes are going on well and my staff is concentrating much on practical knowledge apart from teaching theory well. He has completed till arrays and still there are pointers, functions, structures and unions, files and lots more to go. On day 3 he completed with single dimensional array but when he started with pre increment and post increment operators the classes deviated from arrays and he started to fully explain about those operators with practical examples. Then we came back and the class and it took additionally 20 minutes to get over but it was an interesting session. All the programs were like puzzles and I was wrong with most of my answers but at last understood to an extent. Hope when you take up any C programming classes you can be sure of getting into situations like these so don’t miss any classes.

Hurray got into Visteon!!

Hi guys I have already posted about my experience in Visteon interview process. Well I told you that I am waiting for my results and I got my results last week. I was happy to hear that I have been selected for Visteon. Now I am happy since I have got into my core field-electronics which I like the most and all my hard work has been credited. I can now quit my IT job and get into my core field and work with full satisfaction. However I am going to miss my friends. I have to miss my NIIT classes, loose my SCJP voucher. Anyway if we want to get something better we have to loose another one that's become true in my case. Hope that I will enjoy my work at Visteon.

Get Together

It was a long time after my college days, So we planned for a get together at marina beach while chatting online. One among my friends took the responsibility of deciding the timing and told us that he would message me. Later after two days I got a call from my friend and he asked me to come to marina beach on saturday at 5PM. I was ready on that day and was at marina beach at 4.45PM itself but I couldn't find out the exact meeting place, So It took me some time to reach the correct place. I was hoping to see all of my friends when I was near to the spot, but unfortunately one nine persons were there. I thought that our friendship circle was too strong but only some think like me and they came for the get together. Others just told that they had some work with their jobs and so they can't come but all these seems to be blank reasons. I never thought even my close friends in my college would tell me the same reasons. Anyway I realized that everything would change as days passes by.

SimBot at NIT Trichy

SimBot is a competition for Line Follower robot. The rule is that we must build a line follower robot that must have the obstacle detection mechanism. The obstacle will be a white box of specified height and width. There will be three parallel tracks, the line follower must begin from one end that we can choose. If the Line Follower faces any white obstacles on its way then it should take the parallel path. The below picture shows three parallel tracks with obstacles.


The robot which reaches the finish line first wins the game. We used DC motors with 150 RPM but those who came for the competition used 300 RPM twice the speed of us, so we lost in timing but anyway we had a good experience out there. I couldn't take a video at the time of the race but here is the sample video where our line follower tracks the line.

The best book for C Programming

C Programming is a strong high level language invented by Dennis Ritche. It forms the base for many programming languages. Where ever you go for an interview they will test your C Programming skills and if you are strong in C then you get a job for sure. Because C being the base to learn other programming languages. Learning C is basic like learning ABC in your primary classes. Well C is that much powerful and the best book for learning C language is Let Us C by Yashvant Kanethkar. There are also other books on C written by the same author and you can get it to have a through knowledge in C Programming. The book is simple and easy to learn and there is lot of practical examples. If you are mastering the book Let Us C then you can be sure in clearing the written test for any interview which has C language. In Embedded systems also C Language forms a basic part, because most of us use Embedded C language to program the microcontrollers and ALP and BASIC are out of use. Even if you join in any Embedded Training Centers then the first module will be C Programming, so if you are a beginner please concentrate in C Programming well. Practical knowledge matters more than theoretical one.

My WaterBot drowned in Water

It was during my third year I participated in the 'Water Loo' event at Saveetha Engineering College. I and my team mate had controversy over the design of our robot because he designed a large one using Wood as shown below.


This was the first robot which we completed before time which was quite unusual to us. Then we went to the college, the day before the event for practice. But our robot started to get drown as the wood absorbed water. So the design was an entire flop and all our hard work went in vain. But we never wanted to give up, and then we designed a robot with thermocole basement so that it can float well in water. We worked the whole day without sleeping and finally completed our design. The day came for the event and we didn't even have a practice match. Who ever pushes maximum number of balls into the goal post wins the game, but unfortunately because of latch up problem our robot got drowned and all the circuits got collapsed. Our team got totally frustrated and didn't no what to do. Then finally with the help of a long stick we got our robot back, but the entire circuit got short circuited. It was the worst day and we came back sad. Here is the photo of our drowned robot.You can also see the video of the robot which took the first prize, the robot had a good simple design and turned perfectly in every directions.

C Programming class at AU PERS center

Today was the second class for me at AU PERS center. We reached the place by 6PM, but our staff who has to take the class was late by 20 minutes, so the classes started only at 6.30PM. Today we were taught on conditional statements and loop statements in C Programming. The class went well and our staff asked us all to write programs after teaching every concept. It was a good approach as we can understand well every syntax and there usage. He concentrated much to build up our practical knowledge apart from mugging up. Well I had a fine day today. On the way back to my home I had a nice chat with my old friend who is working in scope e in temple tower. We had a nice chat today and then I reached my home by 10PM.

Interview at Visteon

It was a nice day to be there in Olympia Technology Park. I was there to attend the first round for Visteon Technical services on Saturday. Being a core job I was eagerly waiting for the written test. The written test was for an hour and I did well and got short listed for the next round. The next round is Group Discussion, I was in the first batch and I did well in GD. The topic was 'Whom will your support? Tata Nano or Land return to farmers'. I spoke on both sides and the Group Discussion went for 20 minutes and during the last five minutes the HR asked anyone to summarize. I tried to summarize but not able to do it, another person took the chance and I don't want to interrupt him. At last they asked me to wait at the reception for the GD results. Then after 20 minutes one person came out the announced the result, out of 10 persons 4 got selected and I was happy to be one among them. Then they asked me to attend the Technical HR round on Monday at 3PM. I did well in the Technical HR round, told them about my projects and we had a good chat session, both the persons who interviewed me were great, they asked me to be free not to be tensed and it boosted my confidence. The interview was over and I was waiting at the reception for the results. They told me that they will announce the results within a day or two, hope I get selected in Visteon to continue my passion towards electronics.

Oscillator modes in PIC microcontroller

Handling oscillators while using PIC microcontroller may be simple but improper usage may lead to improper execution of the program. There are 4 oscillator modes in PIC microcontroller they are

• HS (High Speed) - greater than 4Mhz
• XT (Standard Crystal) - 1Mhz to 4Mhz
• LP (Low Power) - upto 200Khz, commonly used for 32.768Khz for real time clock
• RC (External RC) - an external resistor or capacitor is used

There are also other modes like IntRC (Internal RC) and ER (External Resistor)
If you are using IntRC mode than you can use an additional port as I/O, this is very much useful in 8 pin PIC microcontrollers.

Rounds in Visteon

If you are a ECE, EEE or EIE then you can have a good career at Visteon. There are three rounds in Visteon. The first round is written test. There will be 40 questions and you have to answer them within 1 hour. The questions will be from microprocessor, basics in electronics and digital electronics. You have to mark the answers in an OMR like sheet, shading the correct options. You can strike out and mark the correct answer so don't get tensed if you have marked wrongly. The time will be enough for the first round. No negative marks so answer every questions. The second round is Group Discussion, I hope you know much details about it. The final round is HR and you will be asked only in technical side by the HR. So be well prepared about your projects, microcontroller, etc.

Why I applied for VISTEON?

One of my friend who is a mechanical engineer named vinoth mohan was eager to go to Visteon. He used to tell me about the company always when he visits my home. He asked his cousin to send details when there is a opening at Visteon. Yesterday he got a mail from his cousin that Visteon is going to conduct interview and asked him to forward his resume to the specified mail id. He was happy and came to my home to check his yahoo mail. He logged into his yahoo mail account and looked at the inbox. Seeing his cousin's name in the inbox he was happy to check the mail and started thinking of forwarding his resume to Visteon. But unfortunately the openings were only for ECE, EEE and EIE. He got disappointed looking at the requirements, but he told me to forward my resume to that mail id. That showed his good nature, I thank GOD to have a good friend like him. Then I forwarded my resume to the specified mail id and I received a mail form Visteon asking me to attend the interview.

Easy way to grab a job

Getting a job is not an easy task nowadays. You can hear today that, the IT growth is sliding down and many are loosing their jobs in IT industry, however if you have the talent then you can be sure to have a place in any company. However to make yourself employable you must be specialized in a particular field. Only then you can be sure of getting a job and secure your career. There are many places offering good educational programs that will surely help you to find a job. However you need to find the right one. Career Education.net is the best site that helps you to find out various online and offline educational programs. One of the useful information provided at Career Education.net is about the ultrasound schools. The ultrasound testing is the more accurate method to measure to care for fetus and pregnancy. There is a good career opportunity for the persons, who complete a course in an ultrasound school. A lot of such useful information is provided at Career Education.net and you can make the best use of it.

My first day in AU PERS center

I hope that you know about AU PERS center in Anna University. If you are hearing this for the first time just look at my previous post on AU PERS center. They asked me to be their at 6PM for the classes. I with my friend shiva kumar arrived at the center by 5.45PM hoping that the classes would begin at 6PM. We paid Rs.12,500 and got our receipt and hurried to the class, thinking that we would be late. But we were wrong, we waited for other students to come there and settle down.Then by 6.30PM the classes started. The first class was on C programming. The staff took the basics well. He taught us basics and my friend got frustrated hearing the same basics in C programming from his 8th standard. He was always looking at his watch to see when the clock ticked 8PM. Then at last the class was over, I had a nice day and returned home by 10.30PM.

Frustration at HP

Yesterday I got a call from Pelatis Consultancy, they asked to tell me about myself. I thought that it was a BPO and just answered them. But after sometime they asked me about my academic marks, I started to doubt because no BPO is going to ask for marks. Then I asked them, for 'which BPO I am going to attend the Interview?' They told me that there is openings in HP, but didn't told me anything about the post for which the interview is conducted. They sent me a mail and asked me to be in Olympia Technology Park by 10AM with the print out of the mail. In the mail the name of the contact person was also mentioned. I thought that the opening is for technical post so started 8AM from my home and after overcoming the traffic I went there to Olympia Technology Park at 10.10AM. There was a long queue extending from the reception counter. I stood in the queue waiting for my chance to submit my resume and attend the interview. It took about an hour to reach the reception counter, but I was happy since I have reached near to the reception counter and was eager to give my resume. But then came the problem, the security guard asked the freshers to hand over the resume and leave the place and told that they would look at the resume and call us afterwards. I just got totally frustrated, because after waiting for a long time I couldn't tolerate his announcement. I just cant fight with him alone, so gave my resume to the security guard like others and moved out from HP office. The day was a total disappointment for me. Hope they will not do such activities in future, if they think from my point of view. A company will learn a good reputation only by respecting others not by commanding others.

Hurray got 'Z' Scholarship at NIIT for BJS exam!!

Hi guys I have already posted details about Bhavishya Jyothi Scholarship exam conducted by NIIT on september 19th. I booked for the exam and got my hall ticket on 19th september. My venue for exam is Ethiraj college, hope all of you would have known this place much better than me. The duration of the test is 1 hour 30 minutes. They asked questions based on aptitude skills, logical reasoning, that's what I could remember. I did my exam well and I got a call from NIIT parrys on september 23rd that I have got 'Z' scholarship in BJS exam. The 'Z' scholarship is for top 500 students in BJS exam. When you get a 'Z' scholarship you can get 100% percent fee waiver for doing courses at NIIT. I have chosen ANIIT program. Hope you could get your fee waiver next time, so enroll yourself for next BJS exam.

TIps for BPO interview - Tech Support

It's quite boring sitting in home for a long time, so I just want to go to a Tech Support Interview in BPO. Got reference through my friend and went there on monday. I don't want to mention the name of the BPO. Just went there to get some experience on BPO interviews. I just want to attend for Tech Support because my friend's told me that I could get some good questions to answer. Most of the people who came for the interview with me were doing their CCNA course. The questions were based on these topics,
Routers and switches, IP address, MAC address, PING command, OSI layers and functions of each layers, SCSI, DNS server, MODEM and Firewall. That's what i remember, so if you are attending for Tech support interview in any BPO prepare in hardware and networking concepts that will surely help you. Please put your aggregate below 75 or even below 70, because i got rejected for my aggregate only. So please be careful in putting marks in your resume, because every BPO HR will see your longevity of service for the company then your talent. They know that a person with good aggregate will not be in work for more than three months and BE graduates are their last choice while selection.

Deferring DOJ

It's been a long time, i am still waiting for my company to call me for training. I got placed in my 3rd year and passed out from my college with lots of hope to have a better career. Well all my dreams are still being as a dream because of the IT companies deferring the Date of Joining of the candidates. Because of the offer i couldn't even make any decision further for my further studies. Where ever i attend interviews they were just looking for the experienced candidates not the freshers. It's like that there is always hanging an invisible 'no vacancy' board for the freshers in every offices. The only thing that makes me confident still is my hope that my company would call me in future within months. It's not the hope of a single person but a hopes of students who have got placed in IT firms awaiting for their call letters. Hope we all would get answers for our questions.

Bhavishya Jyothi Scholarship exam on september 21st

A lot of colorful banners and posters on the roadside, pasted over the EB post, compound walls and, banners that were hanging in the trees and telephone pillars. The contrasting colors of the banners and posters caught my attention and I started reading at it. All these displayed the common message about the Bhavishya Jyothi Scholarship exam conducted by NIIT center. I had already been in NIIT during my second year of my graduation doing my Core Java course, and I completed it successfully and got the certificate from NIIT. Some of my juniors attended this examination and got scholarship for joining J2EE course and benefited a lot. If you want to do a course in NIIT then enroll yourself for this exam and get discount for your courses. The last date to register for the test is September 20th and the cost for registering for the test is Rs.100.

It's time to decide your final year project

Are you a final year engineering students in your 7th semester. I hope that your department would have asked you to submit your project ideas, well only a few students might have been submitted while the remaining others might have not considered this one seriously. Most of the students have the intention of getting the project from project centers like pantech, adithya and blue chip etc, i can't change your attitude if you don't have a passion to do your project of your own. However even if you are getting projects done through a project center you must hurry because as you pass on days, the amount for every project will increase. Also while selecting the projects please select a project in which you have a little bit of idea. I have seen some of my juniors selecting projects in VLSI not knowing anything about it, they were just coaxed by the project centers. So it's my kind of advice to be careful before selecting any project, please see to that you know something about the project you are going to do so that you can manage well in the reviews. It's time for you guys to decide on your projects.

Training centers plays with us

If you have uploaded your resume in any job portals then beware of training centers which calls you. They will make a phone call to you and ask you to tell about yourself just like a BPO interview. They will tell you that we require trainees for hardware or software you have cleared the phone interview and attend the next round. Please don't believe these people their only intention is to make you enroll in the course for money. They will keep all the interview process just to boost up that entering the training is so much tough. But they are just deceiving you so beware. Even if you are not clearing the first round they will tell you were selected and there is only limited amount of seats so enroll today. If you see any of these companies just kick their ass and come back!! I have went for a lot of these companies but i don't want to mention there names here. So if any person calls you for an interview ask them their company name and search for the details in the Internet and then go. Don't waste your money and energy believing their seducing words.

Have you heard of AU PERS center

Hi recently we have seen many embedded training centers in chennai. Their is a short term embedded training course conducted in anna university for every three months. The name of the center in anna university that conducts the course is AU PERS center. They told me that the certification is valued a lot when you search for jobs in core companies and assured me of 100 percent teaching satisfaction then any other training center in chennai. The professors from anna university and IIT will be taking the classes in the evening from 6 t0 8. You can do the practical work anytime in weekdays, it is holiday on weekends. But the course fee is too much in a government institute, wonder how much it is?? Rs.30,000. And their is no assurance in placement but they told me that they will assist. This month a new batch is starting from september 26th and you have to register for the course by paying Rs.2500 and maximum number of students in the batch is only 10. So if you have any idea then just go to anna university, ask for the place AU PERS center, you may find it out. Otherwise ask for center of ocean technology or center of water resources because the AUPERS center is near to that and you will find it easily. There is also another course on content writing, sorry i don't have much information about that course.

About UTL technologies

Hi friends I have already informed you about the embedded centers in Chennai. I visited some of the centers and talked with the passed out students who have completed the course, I want to discuss with you my experience with them.

First I went to UTL Technologies. There are actually two courses on embedded systems a certification course and a diploma course. The certification course is for about two months and there is only normal track and no fast track for certification course and the fee for this course is Rs.17, 000. For the diploma course in embedded system the duration of the course is four months in normal track but there is fast track so that you can complete the course within two months. The fee for fast track is Rs.30, 000 if you pay full single down payment. There are actually four modules and the certification course will cover only the first tow modules whereas the diploma course will cover full four modules. The infrastructure looks poor in Chennai. I talked with two students there, one person is from SKR engineering college and he has joined the course only a week before and C language classes are going for him. He told me that the coaching was good regarding C language but no idea about other modules. Then I called one passed out batch students, he told me that he got placed through UTL technologies in Midas communication technologies and he worked very hard to get a placement. The teaching is average but you have to work hard to get placement, he told me like this.

PGDEVD course at CDAC Noida

Hi last month i attended the entrance examination for joining the course PGDEVD - Post Graduate Diploma In Embedded system and VLSI design. The course is only offered by CDAC Noida and not in any other CDAC centers. The duration of the course is 6 months and we have to complete a project at the completion of the course. The syllabus for entrance examination includes c programming, digital electronics, some aptitude questions and some questions on microcroprocessor, the books which i referred are given below

• 'Let us C' by Yashwant Kanetkar
• 'Digital Design' by Morris Mano
• 'Quantitative Aptitude' by R.S.Agarwal

I got selected for CDAC Noida but i dropped my plan to go there because i was not able to get positive opinions from students who did their course from there. However it is good to do a course in CDAC centers and i am now feeling sad that i didn't joined the course in CDAC Noida. Just decide yourself about your future don't make any decisions from others opinions. It will surely lead you in the wrong way. I have experienced it myself.

How to get into CDAC

Hi CDAC - Centre for Development and Advanced Computing is a government organization that offers short term courses on Embedded system. Their are also other courses offered in CDAC centres in India. Please see the website for more details about the course syllabus. The famous courses offered by CDAC centres are

DESD - Diploma in Embedded System Design
DSSD - Diploma in System Software Development
DABC - Diploma in Advanced Business Computing

For joining these courses they conduct a common entrance test (CET) throughout India and you have to take the test. At the time of filling up the application form you must select three centres where you wish to study. Based on your marks they will allocate you to the centres that you specified based on the priority. CDAC Hyderabad and CDAC Pune are the best centres to study. Prepare well and do well.

About Embedded Training Centers in India

Hi guys i am going to discuss with you about the embedded training centers located in India. Some of the best training centers in India are CDAC, Vector Hyderabad, UTL technologies, MIT, emblitz, Cranes Banglore, Oasis, DOEACC.

The best among this that i would refer you to join is CDAC because the infrastructure facility in CDAC is the best and it is a government institute coming under the control of Ministry of Communication and IT. To join an embedded course named 'DESD' you have a written test conducted throughout India and based on your marks you can get a place in CDAC center anywhere in India.

About UTL technologies they are telling that they have a written test but in chennai they are admitting people without any written test.

About Cranes i heard that the coaching is good and they will be concentrating much in C Programming skills. The cost of the course here is more. But they are bringing MNC's for placement so you can get a good pay if you get selected in any one one of them.

Sorry i don't have much information about other centers if you have any doubts you can contact to my mail ssecganesh@gmail.com

Introduction to Photodiodes

What is a Photodiode?
A photodiode is a type of photo detector capable of converting light into either current or voltage, depending upon the mode of operation.
Detailed view about photodiode
Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifically as a photodiode will also use a PIN junction rather than the typical junction. Photo diodes are semi conductor devices responsive to high energy particles and photons. Photodiodes operate by absorption of charged particles and generate a flow of current in an external circuit, proportional to the incident power. Photodiodes can be used to detect the presence or absence of minute quantities of light and can be calibrated for extremely accurate measurements from intensities below 1pW/cm2.

Applications of Photodiodes
Photodiodes are utilized in such diverse application such as spectroscopy, photography, analytical instrumentation, optical position sensors, beam alignment, surface characterization, laser range finders, optical communications and medical imaging instruments.

Optocouplers in detail

What is present inside an optocoupler?
Optocoupler typically come in a small 6-pin or 8-pin IC package, but are essentially a combination of two distinct devices: an optical transmitter, typically a gallium arsenide LED (light-emitting diode) and an optical receiver such as a phototransistor or light-triggered diac. The two are separated by a transparent barrier which blocks any electrical current flow between the two, but does allow the passage of light. The basic idea is shown in the figure below, along with the usual circuit symbol for an opto coupler.

Physical seperation
Usually the electrical connections to the LED section are brought out to the pins on one side of the package and those for the phototransistor or diac to the other side , to physically separate them as much as possible. This usually allows optocoupler to withstand voltages of anywhere between 500V and 7500V between input and output.

Signals that are given as input
Optocoupler are essentially digital or switching devices, so they’re best for transferring either on-off control signals or digital data. Analog signals can be transferred by means of frequency or pulse-width modulation.

How it works?
A common implementation involves a LED and a phototransistor, separated so that light may travel across a barrier but electrical current may not. When an electrical signal is applied to the input of the opto-isolator, its LED lights, its light sensor then activates, and a corresponding electrical signal is generated at the output. Unlike a transformer, the opto-isolator allows for DC coupling and generally provides significant protection from serious over voltage conditions in one circuit affecting the other.

With a photodiode as the detector, the output current is proportional to the amount of incident light supplied by the emitter. The diode can be used in a photovoltaic mode or a photoconductive mode.

Introduction to OptoCoupler

What is an OptoCoupler?

A device that uses a short optical transmission path to transfer a signal between elements of a circuit, typically a transmitter and a receiver, while keeping them electrically isolated is said to be an optically coupled device or an opto coupler.



Why to use an OptoCoupler?
There are many situations where signals and data need to be transferred from one subsystem to another within a piece of electronics equipment, or from one piece of equipment to another, without making a direct ‘ohmic’ electrical connection. Often this is because the source and destination are (or may be at times) at very different voltage levels, like a microprocessor which is operating from 5V DC but being used to control a triac which is switching 240V AC. In such situations the link between the two must be an isolated one, to protect the microprocessor from over voltage damage.

Problem with Relays
Relays can of course provide this kind of isolation, but even small relays tend to be compared with ICs and many of today’s other miniature circuit components. Because they’re electro-mechanical, relays are also fairly bulkynot as reliable and only capable of relatively low speed operation. Where small size, higher speed and greater reliability are important, a much better alternative is to use an optocoupler. These use a beam of light to transmit the signals or data across an electrical barrier, and achieve excellent isolation.

Light Emitting Diode

Hi let us see the operation of Light Emitting Diode (LED). The internal structure of an LED is shown above for clear understanding.

A light-emitting diode, usually called an LED, is a semiconductor diode that emits incoherenet beam of spectrum when biased in the forward direction of the p-n junction. This effect is a form of electroluminescence. A LED is usually a small area light source, often with extra optics added to the chip that shapes its radiation pattern. LEDs are often used as small indicator lights on electronic devices and increasingly in higher power applications such as flashlights and area lighting. The color of the emitted light depends on the composition and condition of the semiconducting material used, and can be infrared, visible, or ultraviolet.

When sufficient voltage is applied to the chip across the leads of the LED, electrons can move easily in only one direction across the junction between the p and n regions. In the p region there are many more positive than negative charges. In the n region the electrons are more numerous than the positive electric charges. When a voltage is applied and the current starts to flow, electrons in the n region have sufficient energy to move across the junction into the p region. Once in the p region the electrons are immediately attracted to the positive charges due to the mutual Coulomb forces of attraction between opposite electric charges. When an electron moves sufficiently close to a positive charge in the p region, the two charges "re-combine".

Each time an electron recombines with a positive charge, electric potential energy is converted into electromagnetic energy. For each recombination of a negative and a positive charge, a quantum of electromagnetic energy is emitted in the form of a photon of light with a frequency characteristic of the semi-conductor material (usually a combination of the chemical elements gallium, arsenic and phosphorus). Only photons in a very narrow frequency range can be emitted by any material. LED's that emit different colors are made of different semi-conductor materials, and require different energies to light them.

Automatic Meter Reading(AMR)

The automatic meter reading is one of the part of the project 'Embedded based power tampering detection and automatic meter reading using GSM'. Please refer to the previous post about tampering techniques and circuits used for detecting them.

What is the Drawbacks of manual reading?
The automatic metering system is designed to make the prevailing electricity billing system simpler and efficient. The conventional metering system is done manually. An employee of the Electricity Board will be coming to take the reading and enter in the card. There are more chances of manual error, delay in processing, tampering of the meter and misusage of the Electricity by other sources. It requires so many workers, one set of workers to note down the reading and other set to cut the power if the payment is not paid at the right time and we have very poor servicing.

How we can rectify it?
Instead of utilizing man power in billing system, we can automate the system and the man power can be utilized to provide quality service.

In the Automatic System designed, the units consumed are measured at the consumer side and is transmitted to the Electricity Board side where the amount equivalent is calculated and transmitted back to the consumer module. The monetary values are displayed both at the consumer module and electricity board side.

How does it work?
The project uses the ATMEL AT89C51 microcontroller for communication with the GSM modem.The AMR system uses the electro optical interface for converting meter dials into digital form. The AMR system starts at the meter. Some means of translating readings from rotating meter dials, or cyclometer style meter dials, into digital form is necessary in order to send digital metering data from the customer site to a central point with the use of electro optical interface. The data from the meter is stored in the microcontroller and the each rotation of the disc is calculated with this optical interface method.

The data from the microcontroller is fed to the GSM modem in a periodical basis say once in every week. The units transferred to the Electricity board are manipulated and the bill is sent to the customer site via the same GSM. Along with the bill, the due date for the payment of bill can also be transmitted.

Magnetic Tampering

Magnetic tampering technique is done by bringing a high powered magnet in close proximity of the domestic electricity meter. When this is done, the disc stops rotating. The circuit for the magnetic tampering detection circuit is as shown above.

The vital component used in the occurrence of the magnetic tampering technique in the domestic electricity meter is the Reed switch. The reed switch contains two magnetizable and electrically conductive reeds which have end portions separated by a small gap when the switch is open. The reeds are hermetically sealed in opposite ends of a tubular glass envelope.

In the magnetic tampering technique, a high power magnet is brought in contact with the electricity meter. When this happens, the rotor disc is exposed to a high magnetic field. Then the resultant opposing magnetic field to the rotor is highly increased leading to slowing down of rotor or perfect stopping of the disc rotation. The electricity meter is thus manipulated and ultimately power is consumed without being paid for.

Now when a reed switch is placed on the electricity meter and is connected to the micro controller, the magnetic tampering can be effectively identified. When a high power magnet is bought in proximity of the electricity meter in the presence of the Reed switch two leads come in contact with each other and result in the closed circuit thereby helping in detection of the signal by the micro controller. Thus the tampering is detected and the micro controller receives the information, which it passes on to the LCD unit and the GSM modem.

Current Reversal Tampering

The aluminium rotor disc present in the electricity meter runs in the clockwise direction as long as the neutral and phase connections are connected properly to it. But if these two wires are reversed, the meter starts to malfunction thereby rotating in the reverse direction ther by leading to reduction in meter reading. Hence to monitor the proper rotation of aluminium rotor disc and to avoid the current reversal tampering, a pair of LED and Photodiode duo ( LED 1 and LED 2 ) are placed above and below the aluminium rotor disc as shown in the figure above.

To let the light from LED fall on the photodiode, a slot is cut on the aluminium rotor disc. When the disc rotates in clockwise direction, light from LED1 falls first on the Photodiode 1 followed by the other, LED2 light falling on Photodiode 2. The output of the photodiodes are given to individual microcontroller ports with the help of a pull up circuit. As long as the sequence of LED1 and LED2 output enters the microcontroller, there is no tampering. If the order of photodiode output to the microcontroller is reversed, LED2 output reaching the microcontroller first followed by LED1 output, then there is the possibility of Current reversal tampering being attempted.

When the ports A and B respectively for Photodiode 1 and Photodiode 2 outputs are detected in order, two LEDs placed outside the electricity meter glow in order to indicate the perfect working of the electricity meter. When the ports are detected in reverse order, the LEDs glow in the reverse order as well, so as to indicate malfunctioning.

As the rotor disc rotates in the opposite direction, the tampering information is sent to the micro controller. When micro controller receives the signals, it transfers it to the LCD and the GSM modem. So an information about the tampering that has occurred is displayed in the LCD, as well as sent to the electricity board through the GSM modem.

Thus the tampering of the electricity meter using the current reversal technique is detected and intimated to the electricity board for further action.

Please see my previous post on the project 'Embedded Based Power Tampering Detection and Automatic Meter Reading System Using GSM' for more details.

Neutral Tampering

This tampering is done by disconnecting the neutral wire in the domestic electricity meter. The circuit designed for the detection of neutral tampering is shown above.

The component used for the neutral tampering detection circuit is an Optocoupler connected in parallel to the Voltage coil.

The circuit works as follows. As long as the neutral and the phase are connected to the voltage coil, the parallely connected Optocoupler LED produces a high output therby biasing the base of the photo transistor which produces an output at the emitter. This output is continuously monitored by the microcontroller.

When the neutral wire from the electricity meter is disconnected, the power supply to the LED is also disconnected and hence it does not glow. As soon as the LED fails to glow, the photodiode is unbiased and its output drops to low level or logic “0” signal and it sent to the micro controller. The microcontroller senses this change in optocoupler output and thus intimates the GSM modem to send a message to the Electricity board regarding the Neutral tampering.

The micro controller is programmed using embedded C so as to intimate and transfer signals according to the signals received ( either “1” or “0”). When micro controller receives the signals, it transfers it to the LCD and the GSM modem. So an information about the tampering that has occurred is displayed in the LCD, as well as sent to the electricity board through the GSM modem.

Power Tampering Module

The block diagram of the complete power tampering module is shown above. please refer to the previous post to know about the project 'Embedded Based Power Tampering Detection and Automatic Meter Reading System Using GSM'. We will discuss the details of each and every module seperately.

When tampering is detected, the information of the detection is sent to the micro controller. A program to this effect is written using embedded C and it is stored inside the ATMEL AT895C1 micro controller. For example, when a magnet is bought in the proximity of the electricity meter, the reed switch is affected and thus magnetic tampering is identified. Once this is done, the micro controller makes sure that a message “ MAGNETIC TAMPERING “ is displayed on the LCD.

This message is then passed on to the electricity board by use of the GSM technology. The buffer is used for temporary storage of the data.

Tampering Techniques

The three significant and common techniques of tampering the electricity meter are discussed below.

NEUTRAL TAMPERING

As quoted, an electricity meter contains a voltage coil and a current coil. Both these coils should be properly energized for ensuring the rotation of disk. In this type of tampering, the neutral wire from the voltage coil is removed. When this is done, the rotation of the disk is hampered and it stops rotating, which in turn stops the rotation of the electricity meter. Hence irrespective of the amounts of power consumed, there is no account of the units consumed.

CURRENT REVERSAL TAMPERING

In this type of tampering, the polarities,neutral and phase are reversed. When this tampering is done, the rotor disk, instead of flowing in the forward direction tends to rotate in the reverse direction and hence, the units of power measured moves in the reverse direction. In other words, the readings decrease, rather than increasing. Hence the units are manipulated and they display erroneous meter reading or low meter reading, than the actual amount of power consumed.

MAGNETIC TAMPERING

When a magnet of sufficient strength is brought near the electricity meter, the field opposing the rotation of the aluminium rotor disc increases thus making the rotor disc run in slow pace or stop either. This type of approach to make the electricity meter malfunction by means of placing a magnet near the meter is Magnetic Tampering.

Embedded Based Power Tampering Detection And Automatic Meter Reading Sytem Using GSM

Our country has been ranked high in the list of ‘countries with high power theft’. Power theft occurs in various areas such as Industrial, Commercial and Residential areas. The theft by residential customers are responsible for most of the power loss in the country. A significant amount of this power theft is done at domestic levels by the tampering of the electricity meter.

The scope of this project is to identify three of the most commonly adapted techniques of power tampering and in furtherance, intimate to the electricity board or the authority concerned about the occurrence of the theft. This module of the project makes sure that valuable amounts of power can be saved by taking immediate action against those involved in the practice of meter tampering.

The three common methods of power tampering are NEUTRAL TAMPERING, CURRENT REVERSAL TAMPERING AND MAGNETIC TAMPERING. In our project, we detect these tampering methods by means of respective sensors and intimate it to the Electricity Board via GSM.

Further, the project also aims to eliminate manual manipulation of readings by linemen. The project provides an enhanced power tariff and billing system by transmitting the units of power used and the appropriate bill amount to the user and the electricity board. The entire transmission and reception process is done in a wireless medium.