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Introduction to Random Access Mode of APR 9600

2010-05-30T06:03:00.000-07:00

Hi readers, so we are on track looking into my EMAS - Wi Tech project. In our last post we were looking into APR9600 in brief. Now let us look into its usage in our project. The APR9600 has various modes of operation of which we have selected the 'Random Access 8 fixed duration messages' mode, where we could record 8 voice signals and play them back. The below is the table for different modes of operation of APR9600,

Let us look into the Random Access Mode functionality of APR9600 in my next post

Introduction to APR9600

2010-04-29T00:27:00.000-07:00

In our last post we discussed on how to monitor Saline level using an LDR, now let us move to the APR module. Before going to the interface part of APR 9600 with the microcontroller, lets look about APR9600 in brief.

The APR 9600 is a 28 pin device used to record and playback maximum of 8 messages. The APR9600 device offers true single-chip voice recording, non-volatile storage, and playback capability for 40 to 60 seconds. The device supports both random and sequential access of multiple messages. Sample rates are user-selectable, allowing designers to customize their design for unique quality and storage time needs. Integrated output amplifier, microphone amplifier, and AGC circuits greatly simplify system design. The device is ideal for use in portable voice recorders, toys, and many other consumer and industrial applications.

Saline Level monitoring using LDR

2010-04-13T23:58:00.000-07:00

Hi folks, we are looking into one of my project "EMAS - Wi Tech", In our previous post we saw some introduction about it. Now we are going to dig further on the different sensor circuits used. The first one which we would see is how we monitored the saline level using an LDR, Just go through the below para for detials on the circuit what we used.

The LDR sensor circuit consists of a comparator, an LDR and a pair of multi-turn preset resistor (10k ohm). The LDR is connected in series with a preset resistor forms a voltage divider configuration. When no laser beam falls on the LDR its resistance will be very high compared to 10k ohm. So by voltage divider rule small voltage will be available across the preset resistor. But when laser beam falls on the LDR its resistance becomes almost zero. So voltage across the preset will become nearly 5V. This change in voltage across the preset can be detected using a comparator. Comparator is constructed using UA741. The threshold voltage can set using another 10k ohm preset connected to the inverting input of the opamp.
In normal condition output of comparator remains at logic zero because the laser beam is distracted by the saline present in the bottle, but when saline level reduces, the distraction is lost and the laser beam falls on the LDR, because of this comparator output changes to logic one. This change is used by microcontroller to detect the quantity in the saline bottle.

Introduction to EMAS-Wi Tech

2010-04-04T02:50:00.000-07:00

Hi guys last week we were looking on brief into one of my project "Emergency Announcement System In Hospital Using Wireless Technology" which I have abbreviated as "EMAS-Wi Tech". It is now time to look into it in detail. This post will explain the outline of the project and the components used. Just look at the below block diagram which describes the outline of our project.

In the Transmitter side, The Output from the sensors are continuously monitored by the microcontroller, when the microcontroller senses any abnormal values, it transmits corresponding data through wireless medium with the help of the ZigBee module. On the Receiver side, the wireless data obtained by the ZigBee module is sent to the Microcontroller, The microcontroller then analyses the data obtained from the ZigBee module and triggers corresponding messages signals to the APR module. The APR module playbacks corresponding voice recorded signals according to the message signals obtained from the microcontroller.

P89V51RD2, an 8051 Microcontroller is the Main component at the Transmitter side, which is used to sense the output from the Sensors. The Saline Level is sensed using an LDR sensor unit. XBee PRO is used in the ZigBee module at the Transmitter and Receiver sides. PIC16F877A is used at the Receiver side, which senses the output from the ZigBee module. APR9600 is used to playback recorded voice signals based on the input from the Microcontroller.

Emergency Announcement System In Hospital Using Wireless Technology

2010-03-28T02:21:00.000-07:00

The above topic is the name of our project which we did for AU PERS center. Here is a brief detail on our project "Emergency Announcement System In Hospital Using Wireless Technology"

The advancement in technology had favored many fields. The Emergency announcement systems present in the hospitals nowadays, are not implemented real time and any crucial data is transmitted through wired means. There is a probability for the crucial data to get lost, by not reaching the right person at the right time. Our system is designed to overcome these drawbacks by transmitting the data obtained from sensors to the respected persons through wireless means. Sensors are provided to measure the physical values e.g. Saline level, heart beat, etc. The outputs from these sensors are fed to the microcontroller which is monitoring continuously. When abnormal input conditions were sensed by the microcontroller, it transmits respective message to the intended person immediately through wireless medium. The entire system is designed to provide a cost effective solution to save the life of people in need.

More details on my next post.....

NOTE: AU PERS center has been shutted down last year

The usage of ‘gets’ statement in C Programming

2008-11-28T05:24:00.000-08:00

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

2008-11-15T09:31:00.000-08:00

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

2008-11-10T10:09:00.000-08:00

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...

2008-11-01T09:08:00.000-07:00

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

2008-10-22T19:48:00.000-07:00

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

2008-10-14T21:42:00.000-07:00

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

2008-10-12T22:57:00.000-07:00

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

2008-10-08T21:32:00.000-07:00

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

2008-10-08T21:03:00.000-07:00

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!!

2008-10-08T11:22:00.000-07:00

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

2008-10-05T09:51:00.000-07:00

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

2008-10-01T06:31:00.000-07:00

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

2008-10-01T05:44:00.000-07:00

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

2008-10-01T00:30:00.000-07:00

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

2008-09-30T10:35:00.000-07:00

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

2008-09-29T23:05:00.000-07:00

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

2008-09-29T10:17:00.000-07:00

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

2008-09-27T11:00:00.000-07:00

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?

2008-09-27T10:22:00.000-07:00

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

2008-09-27T09:06:00.000-07:00

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

2008-09-27T09:03:00.000-07:00

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

2008-09-26T09:49:00.000-07:00

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!!

2008-09-25T07:48:00.000-07:00

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

2008-09-24T10:07:00.000-07:00

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

2008-09-22T11:51:00.000-07:00

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

2008-09-19T07:05:00.000-07:00

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

2008-09-18T22:11:00.001-07:00

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

2008-09-18T09:34:00.001-07:00

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

2008-09-18T09:24:00.000-07:00

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

2008-09-13T11:08:00.000-07:00

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

2008-09-13T04:40:00.000-07:00

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

2008-09-09T09:52:00.000-07:00

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

2008-09-06T08:14:00.000-07:00

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

2008-09-02T07:10:00.000-07:00

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

2008-09-01T06:49:00.000-07:00

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

2008-08-31T22:00:00.000-07:00

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

2008-08-31T11:16:00.000-07:00

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)

2008-08-31T07:52:00.000-07:00

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

2008-08-27T05:57:00.000-07:00

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

2008-08-27T05:24:00.000-07:00

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

2008-08-27T04:53:00.000-07:00

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

2008-08-26T13:08:00.000-07:00

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

2008-08-26T11:42:00.000-07:00

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

2008-08-24T07:59:00.001-07:00

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.

Electricity Meter

2008-08-21T13:15:00.000-07:00

Electricity meter is a device designed for accounting of electric power in single-phase and three-phase power consumer networks.

Parts of an Electricity Meter

1.Voltage Coil - many turns of fine wire encased in plastic and connected in parallel with load
2.Current coil - three turns of thick wire, connected in series with load
3.Stator
4.Aluminium Rotor Disc
5.Rotor Brake Magnets
6.Spindle with worm gear
7.Display dials

Working of Electricity meter

2008-08-21T02:31:00.000-07:00

The domestic electricity meter basically consists of two important coils for its working.

The voltage coil
The current coil

The voltage coil is connected in parallel to the load and the current coil is connected in series to the load.
The load herein refers to the appliances that consume electricity.
When power passes through these coils, a magnetic field is produced which induces an electro magnetic field in the rotor disc.
As a result of this magnetic field, eddy currents are produced in the rotor disc.
An opposing magnetic field is produced by the permanent stator magnets, which results in rotation of the rotor disc.
The disc rotates according to the power consumed by the consumer unit.

code snippet for serial communication

2008-08-20T05:55:00.000-07:00

Hi here is the code for serial communication using CCS C compiler
// USART TRANSMITION //

//PIN CONFIGURATION: PIN_C6 FOR TRANSMITION & PIN_C7 FOR RECEPTION;
//THIS PROGRAM IS USED TO TRANSMIT DATA FROM CONTROLLER TO HYPERTERMINAL;
//SEE THE FOLLOWING PROGRAM;

#include<16f877a.h> //HEADER FILE;
#use delay(clock=20000000)
#fuses HS,NOWDT,NOPROTECT,NOLVP//CRYSTAL FREGUENCY IS 20MHZ;
#use rs232(baud=9600,xmit=pin_c6,rcv=pin_c7)//TRANSMITION THROUGH RS232 ;
#byte portc=0x07 // SPECIFY PORTC ADDRESS;

main( )
{

set_tris_c(0x80); //SET TX_PIN & CLEAR RC_PIN;

while(1)
{

printf("welcome to"); // IF I=0 DISPLAY "welcome to";
delay_ms(500);

printf("serial communication"); //IF I=1 DISPLAY "serial communication";
delay_ms(500);

}

}

The three main sections of MAX232

2008-08-19T21:19:00.000-07:00

Hi we have seen introduction about serial communication and about MAX232 chip in my previous post. Let us now see at the three main sections of MAX232

Dual charge pump voltage converter – this section uses two external capacitors. One is used to double the +5V input to +10V and the other is used to invert +10V to -10V.

Transmitter section – each of the two transmitters is a CMOS inverter powered by +10V internally generated supply. The input is TTL and CMOS compatible with a logic threshold of about 26% of VCC. The input of an unused transmitter section can be left unconnected. An internal 400k ohm pull up resistor connected between the transistor input and VCC will pull the input high forming the unused transistor output low.

Receiver section – the two receivers fully conform to RS232 specifications. Their input impedance is between 3k ohm either with or without 5V power applied and their switching threshold is within the +3V of RS232 specification. To ensure compatibility with either RS232 input or TTL/CMOS input, the MAX232 receivers have VIL of 0.8V and VIH of 2.4V.

MAX232

2008-08-16T10:37:00.000-07:00

A standard serial interface for PC, RS232C, requires negative logic, i.e., logic 1 is -3V to -12V and logic 0 is +3V to +12V. To convert TTL logic, say, TxD and RxD pins of the microcontroller thus need a converter chip. A MAX232 chip has long been using in many microcontrollers boards. It is a dual RS232 receiver / transmitter that meets all RS232 specifications while using only +5V power supply. It has two onboard charge pump voltage converters which generate +10V to -10V power supplies from a single 5V supply. It has four level translators, two of which are RS232 transmitters that convert TTL/CMOS input levels into +9V RS232 outputs. The other two level translators are RS232 receivers that convert RS232 input to 5V. Typical MAX232 circuit is shown below.

RS232 module

2008-08-16T10:08:00.000-07:00

The RS232 standard is one of the oldest physical communication standards in computer world. The standard defines low-cost serial communication in a robust way where bits are sent sequentially on a copper line. It was originally defined for connecting devices such as computers, terminals and printers to modems. This equipment is connected through their serial port. Nowadays, the computer to computer link with a so-called null modem cable is commonly used.
Communication as defined in the RS232 standard is an asynchronous serial communication method. The word serial means, that the information is sent one bit at a time. Asynchronous tells us that the information is mot sent in predefined time slots. Data transfer can start at any given time and it is the task of the receiver to detect when a message starts and ends.
With synchronous communication, a clock or trigger signal must be present which indicates the beginning of each transfer. The absence of a clock signal makes an asynchronous communication channel cheaper to operate. Fewer lines are necessary in the cable. A disadvantage is that the receiver can start at the wrong moment receiving the information. The RS232 standard specifies that the voltages on the wire for sending logic 0 are from +5V to +15 V. The voltages for sending logic 1 are from -5V to -15V. Most micro controllers are not capable of generating these voltages. So to connect microcontroller to a true RS232 device, you need to convert the TTL voltage of 0V to +5V into voltages between -10V and +10V.

Want to get IC samples

2008-08-16T08:00:00.000-07:00

Hi guys are you having a passion towards electronics, you can give life to your ideas. However you need money to get all the microcontrollers, sensors and other stuffs. Here are some sites which will give you samples.

Microchip.com is the best place to get your PIC microcontrollers.
Cypress.com is the place where you can get some useful sensors but you cannot find out DIP packages.
Allegro Microsystems is the place where you can get Hall Effect sensors and switches.
Maxim offers you analog comparators and other similar stuffs.
National Semiconductors also gives you samples.

Please know about the packages while ordering samples because you can get one which you couldn't use for your circuits.

Serial Port Communication

2008-08-09T12:50:00.000-07:00

Serial port communication with DB9 and RS232 is the most famous interfacing in PIC microcontroller. Hope you would have heard about it. Please be patient to see my post on Serial port communication with PC using PIC microcontroller.

LCD interfacing in my demo board

2008-08-08T17:20:00.000-07:00

We have already seen in my previous post regarding LCD interfacing. I have also provided the code snippet in CCS C compiler for LCD interfacing. However because of some problem with my demo board I was not able to post the picture of the interfacing, but now I have solved the problem with my demo board. The below picture shows the image of LCD interfacing for the code snippet, that I have provided earlier.

My experience at Flowgic India Pvt Ltd

2008-08-08T01:06:00.000-07:00

Hi everyone, I recently attended an interview at Flowgic India Pvt Ltd. It is a vlsi design company and being a core company I was very much eager to get into it. The first round was written test, as the company was vlsi based they asked me to write some programs in verilog for the given conditions. The written test also included some puzzles and two comprehension passage. The duration was 3 hours for written test. Then after clearing the written test I attended the HR interview, mostly they asked me to write C programs. The questions where very much interesting and I liked a lot to answer them. Then the final round was again an HR round they asked me about working of capacitor and inductor, some puzzles, and asked me to draw the timing response curve for two circuits it was a tough one. I am now waiting for my results. Hope for a good outcome.

Written test at BHEL

2008-08-08T01:01:00.000-07:00

BHEL is abbreviation of Bharat Heavy Electrical Limited. I recently attended the written test held for BHEL at SIET College, Teynampet. There were only 50 positions for electronics engineers and I was stunned to see hundreds of people coming to attend the written test. The written test is for totally 2 hours and 30 minutes and included two sections. You have totally 240 questions to answer within this short duration of time. The paper had two parts the first one was from electronics field covering all the basic concepts on electronics. The second part contained aptitude and English Grammar. For every question there are five choices and there were also negative markings (1/5 for each wrong answer). You must able to plan your time well to answer all the questions. Just skip of the questions that have very long sentences like a paragraph and concentrate on the smaller ones it will save you a lot of time. Please be well prepared about the modulation techniques, digital electronics, microprocessor basics and mathematics. Hope this information is useful to you.

Transistors Vs Vaccum Tubes

2008-08-08T00:20:00.000-07:00

Hi we all would have heard about transistors and vaccum tubes. The vaccum tubes are the predecessors and let us see the advantages of transistors over the vaccum tubes.

small size and minimal weight, allowing the development of miniaturised electronic devices.
highly automated manufacturing process, resulting in low per-unit cost.
lower possible operating voltages, making transistors suitable for small, battery powered applications.
no warm-up period required after power application.
lower power dissipation and generally greater energy efficiency.
higher reliability and greater physical ruggedness.
extremely long life. some transistorised devices produces more than 30 years ago are still in service.
complementary devices available, facilitating the design of complementary-symmetry circuits-something not possible with vaccum tubes.
though in most transistors the junctions have different doping levels and geometry, some allow bidirectional current.
ability to control very large currents , as much as several hundred amperes.
insensitivity to mechanical shock and vibration, thus avoiding the problem of microphonics in audio applications.
more sensitive that hot and macroscopic tubes.

Use your keyboard keys to control the cursor

2008-08-01T11:08:00.000-07:00

Sometimes your mouse may not respond properly and you cannot control your cursor movement. During such situation you can use your keyboard keys to control your cursor movement. You have to follow the simple steps below to do it.

First go to control panel and select the accessibility options. From the accessibility options window select the mouse tab as shown below.

Then check the use mouse keys option and click apply button as shown below. That’s it you can now control your cursor using the numeric keypad on your keyboard.

You can change your cursor’s top speed and acceleration from the settings for Mouse keys window as shown below. You can obtain this by clicking the settings button in the accessibility options window.

Some shortcut keys:

Alt+ left shift+ Num lock will open the accessibility window

After enabling the use mouse keys you can use ‘+’ to double click and ‘5’ to right click

Please share your review about this post by leaving a comment.

Best book for Electronics circuits

2008-07-26T07:29:00.000-07:00

Everyone who is joining first year in BE/B.Tech degree program under Anna university affiliated colleges will have a common syllabus. And also the first year has been made non semester by Anna University. Only during the second year the students will be entering into their department. It is from the second year you will start learning your core subjects. For me being a ECE student my core subject was electronics circuit 1 and 2, I had a lot of interest in learning it but unfortunately my staff was not good which slowed me up in my core field. The best book for electronics circuits is 'Electronic Devices and Circuit Theory' by Robert L.Boylestad and Louis Nashelsky. It covers all the information about BJT, FET, CMOS, SCR, rectifiers and lots more. The book may seem to be too big but it's the best book in electronics. You can gain much knowledge from this book instead of getting a Bhakshi and mugging it up which is not going to be useful to you in anyway. If you have read this book please leave a comment about it.

Digital Logic Families

2008-07-21T04:52:00.000-07:00

Information about digital logic families is the commonly asked question in many entrance exams for embedded training course. The most popular digital logic families are transistor-transistor logic (TTL), emitter-coupled logic (ECL), metal-oxide semiconductor (MOS) and complementary metal-oxide semiconductor. Now let us see about the features of each of these families.

The TTL is a logic family that has been in operation for a long time and is considered as standard. They consume more power than an equivalent CMOS device but consume less power when compared to ECL.
The ECL logic family has an advantage in systems requiring high speed operations. The ECL gates use differential amplifier configuration at the input state. They usually operate with negative power supplies.
The MOS is suitable for circuits that need high component density.
The CMOS is preferable in systems requiring low power consumption and they are used for VLSI design.

Know about the various levels of Integration

2008-07-19T11:52:00.000-07:00

There are four levels of integration in Digital ICs. You can find these details asked as viva questions in digital electronics lab. The categorization is based on the circuit complexity as measured by the number of gates in a single package. The various levels of integration are small, medium, large or very large scale integration.

The Small Scale Integration devices contain several independent gates in a single package. The number of gates in SSI is usually lesser than 10.
The Medium Scale Integration devices have about 10 to 1000 gates in a single package. They are used to perform specific elementary digital operations. They include decoders, adders and multiplexers.
The Large Scale Integration devices have thousands of gates in a single package. They include processors, memory chips and programmable logic devices.
The Very Large Scale Integration devices have hundred of thousands of gates within single package. They include large memory arrays and complex microcomputer chips.

Just leave a comment if you know additional details about the levels of integration which will be useful for the readers.

Know the difference between LATCHES and FLIPFLOPS

2008-07-15T07:00:00.000-07:00

Most of you would have learned Digital Electronics in your third semester. You may have heard about these memory elements which are used for storing binary information. The latches are nothing but most basic types of flip-flops. But the latches are level sensitive whereas flip-flops are edge sensitive. This is the basic difference between the two. Thus the change of state in a latch will occur even for an active high input (dc level) i.e., the latch will respond to the change in state when the clock pulse is still in logic1 which will lead to undesirable situation. The change of state in a flip-flop occurs only when their is a change in the clock input. Since the state of a memory element must change only there is a change in control input (ac level) we use flip-flops as storage elements in digital circuits instead of latches. I hope that you can know understand the basic difference between latches and flip-flops. The below image shows the clock response in latches and flip-flops. If you know any other differences then please post a comment so that others may know about latches and flip-flops.

My first blow

2008-07-12T08:01:00.000-07:00

It’s true that “Failure is the stepping stone to success”. I have realized it practically when, I first started to build my electronic circuit ‘LED flasher’. I took the circuit from EFY magazine when I was in my 4^th semester. It's a simple circuit using LM317 along with some resistors, capacitors, diode and LED. The output was to switch the LED ON and OFF for an interval of 15 seconds. The reason I took the ‘LED flasher’ circuit from EFY was because I was able to identify all the circuit components. After getting the required components from Ritchie street I started giving the circuit connection in my breadboard. After completing my circuit connection I checked the circuit through my multimeter and there was no problem with it. I was excited to switch ON my power supply to check my circuit, and it was time to obtain the fruit for my hard work. When I turned ON my power supply I heard the bursting sound from the circuit, it was the capacitor!! And my LED turned BLACK after glowing brightly. I was just shocked with the result of my connection trying to find out what went wrong. Then I found that I was wrong in connecting the pins of LM317. It was my first blow in my path towards electronics. A little caution could have made me attain the fruit of my hard work. But the incident was helpful to me when I started up with my other circuits. The incident made me to be more cautious when I was building other circuits. I believe that this failure has made me to succeed in my project.

Hope you would have you own blow while starting any process(in any field). Leave a comment regarding your first blow so that others can learn much from you.

Introduction to digital circuits

2008-07-10T07:56:00.000-07:00

Digital Circuits fall under two basic categories they are, Combinational and Sequential. The Combinational circuits are those which has no storage elements and the output of the combinational circuits depends only on the present input. The Sequential circuits on the other hand, has storage elements and their output depends on external inputs and the values in the storage elements. The sequential circuits can be further classified into Synchronous and Non synchronous.

A synchronous sequential circuit is a system whose behavior can be defined from the knowledge of its signals at discrete instants of time(clock pulses). The behavior of an asynchronous sequential circuit depends upon the input signals at any instant of time and the order in which the inputs change.

Reed Switch (sensor 1)

2008-07-07T11:26:00.000-07:00

SENSOR 1 - REED SWITCH

The reed switch is an electrical switch operated by an applied magnetic field. It consists of a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope. The contacts may be normally open, closing when a magnetic field is present, or normally closed and opening when a magnetic field is applied.
When a magnetic force is generated parallel to the reed switch, the reeds become flux carriers in the magnetic circuit. The overlapping ends of the reed become opposite magnetic poles, which attract each other. If the magnetic force between the poles is strong enough to overcome the restoring force of the reeds, the reeds will be drawn together. In our project laser based tracking system we used the reed switch for mouse click operation. Note : please be careful while bending the Reed Blade, don' t bend it near the Glass capsule, if you do so it will break. Leave about a 1cm gap and bend the Reed Blade.

Light Dependent Resistor (sensor 2)

2008-07-05T22:47:00.000-07:00

SENSOR 2 – LDR

A LDR or photoresistor is an electronic component whose resistance decreases with the increasing incident light intensity. It can also be referred to as a photoconductor. It is made of a high-resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance. In short as light falls on it the resistance of LDR will decrease from normal conditions. Can be used as Night switch alarm, in counter circuit with laser beam to calculate the person entering into the door etc. LDR's of various sizes and shapes is shown below.

Power supply circuit

2008-07-02T04:20:00.000-07:00

Designing a power supply circuit is one of the basic steps in any projects which you are about to start. Now let us see a +5 volt regulated power supply circuit, which i have used for my project. The circuit diagram is shown below.

The circuit includes a step down transformer and a full wave rectifier followed by a +5 volt regulator. The step down transformer steps down the ac voltage from 230 volts to 12 volt ac. After that it is passed through a full wave rectifier where we obtain an unregulated dc supply of 12 volt. The dc supply is regulated by passing through the regulator 7805. The capacitors are used to avoid ripples in the incoming voltage. The photo below shows my +5volt power supply circuit.

Note that i have included a RED LED to indicate whether the power supply is ON or OFF. I have provided a Heat sink to 7805 inorder to withdraw maximum amount of current from it. Without Heat sink we can draw current only upto 150mA.

About LCD interfacing

2008-06-19T22:49:00.000-07:00

Previously we have seen how to interface stepper motor using TIP122, now let us see interfacing LCD with PIC16F877A

LCD introduction

LCD’s i.e, Liquid Crystal Displays utilize two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each, crystal, therefore, is like a shutter, either allowing light to pass through or blocking the light. The most commonly used alphanumeric displays are 1x16 (single line and 16 characters), 2x16 (double line and 16 characters per line) and 4x20 (four lines and twenty characters per line).

In LCD interfacing we are using HY-1602F6 LCD. It is a two line display with 16 characters on each line. Let us see how to interface an LCD with PIC16F877A.

LCD interfacing

LCD interfacing has two modes 8-bit mode and 4-bit mode.The LCD requires 3 control lines (RS, R/W and EN) and 8(or 4) data lines. The number of data lines depends on the mode of operation. If operated in 8-bit mode then 8 data lines + 3 control lines i.e, total 11 lines are required. And if operated in 4-bit mode then 4 data lines + 3 control lines i.e, total 7 lines are required. The 4-bit mode takes twice as more time as compared to 8-bit mode but it requires less number of data lines. The pin details of 16x2 LCD is shown below.

pin 1 - vss - ground
pin2 - vdd - supply voltage
pin3 - vc - contrast setting
pin4 - rs - register select
pin5 - r/w - read/write select
pin6 - en - chip enable signal
pin7 to pin 14 - DB0 to DB7 - data lines
pin 15 - vcc for backlight
pin16 - gnd for backlight

When RS is low (logic 0), the data is to treated as command. When RS is high (logic 1), the data being sent is considered as text data which should be displayed on the screen.

When R/W is low (logic 0), the information on the data bus is being written to the LCD. When R/W is high (logic 1), the program is effectively reading from the LCD. Most of the times there is no need to read data from the LCD so this line can directly be connected to GND thus saving one controller line.

The EN pin is used to latch the data present on the data pins. A HIGH to LOW signal is required to latch the data. The LCD interprets and executes our command at the instant the EN line is brought low. If you never bring EN low, your instruction will never be executed.

Display Data Ram (DDRAM) stores the display data. So when we have to display a character on LCD we basically write it into DDRAM. For a 2x16 LCD the DDRAM address for first line is from 80h to 8fh and for second line is 0c0h to 0cfh. So if we want to display 'H' on the 7th position pf the first line then we will write it at location 87h.

code snippet for LCD interfacing

2008-06-17T23:55:00.000-07:00

code for interfacing LCD with PIC16F877A in CCS C compiler

//PIN CONFIGURATION: LCD DATA LINE(D4,D5,D6,D7) CONNECTED TO PORTD(3,4,5,6)PINS; CONTROL LINE(RS,RW,ENABLE) CONNECTED TO PORTD(0,1,2)PINS;

//THIS PROGRAM IS USED TO DISPLAY " welcome to LCD INTERFACING ";

//SEE THE FOLLOWING PROGRAM;

#include<16f877a.h> //HEADER FILE;

#use delay(clock=20000000) //CRYSTAL FREQUENCY IS 20MHZ;

#fuses HS,NOWDT,NOPROTECT,NOLVP //SETTING FUSES;

#include //LCD DRIVER FILE;

#byte portb=0x06 //SPECIFY PORTB ADDRESS;

#byte trisb=0x86

#byte portd=0x08 //SPECIFY PORTD ADDRESS;

#byte trisd=0x88

main()

{

lcd_init();

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

portd=0x00;

while(1)

{

lcd_gotoxy(1,1);

printf(lcd_putc,"welcome to"); //IN 1ST ROW "welcome to";

delay_ms(3);

lcd_gotoxy(1,2);

printf(lcd_putc,"LCD INTERFACING"); //IN 2ND ROW "LCD INTERFACING";

delay_ms(3);

}

Nokia secret codes

2008-06-10T05:14:00.000-07:00

Hi friends do you have a phone from NOKIA, then here are some secret codes. Note the information provided below is not verified fully so please be careful while trying these codes.

On the main screen type :

*#06# - for checking the IMEI (International Mobile Equipment Identity).

*#7780# - reset to factory settings (don’t do this if you are not sure).

*#67705646# - this will clear the LCD display (operator logo).

*#0000# - to view the software version.

*#2820# - Bluetooth device address.

*#746025625# - sim clock allowed status.

#pw+1234567890+1# - shows if sim have restrictions.

*#92702689# - takes you to a secret menu where you may fine some of the information below:

1. Displays Serial Number.

2. Displays the month and year of manufacture.

3. Displays (if there) the date where the phone was purchased (MMYY).

4. Displays the date of the last repair – if found (0000)

5.Shows life timer of phone (time passes since last start).

*#3370# - Enhanced Full Rate Codec (EFR) activation. Increases signal strength, better signal reception. It also helps if u want to use GPRS and the service is not responding or too slow. Phone battery will drain faster though.

*#3370* - (EFR) deactivation – Phone will automatically restart. Increase battery life by 30% because phone receives fewer signals from network.

*#4720# - Half Rate Codec activation.

*#4720* - Half Rate Codec deactivation – the phone will automatically restart.

If you forgot wallet code for Nokia S60 phone, use this code to reset: *#7370925538#

Note, your data in the wallet will be erased. Phone will ask you the lock code. Default lock code is: 12345

Press *#3925538# to delete the contents and code of wallet.

Unlock service provider: Insert sim, turn phone on and press vol up (arrow keys) for 3 seconds, should say pin code. Press C, then press * message should flash, press * again and 04*pin*pin*pin#\

*#7328748263373738# resets security code.

Default security code is 12345

Change closed caller group (settings->security settings->user groups) to 00000 and your phone will sound the message tone when your are near a radar speed trap. Setting it to 500 will cause your phone 2 set off security alarms at shop exits, (works with some NOKIA phones) press and hold “0” on the main screen to open wap browser.

Designing a gear box

2008-06-08T20:15:00.000-07:00

as seen in my previous post ,the gear reduction ratio (using spur gear) which we required was 128:1, and we achieved it through software and hardware. We made the 64:1 gear reduction box using three 4:1 gears, 4:1 gear reduction is achieved by using a 20 teeth and an 80 teeth gear. All the gears are cut using 1 module cutter. The basic formula involved in gear design is,

OD = (N+2) x M

OD is the outer diameter
N is the number of teeth
M is the module of the cutter used

So all the 20 teeth gear has outer diameter of 22mm ((20+2)x1) and all the 80 teeth gear has outside diameter of 82mm ((80+2)x1). Before starting with the manufacturing process, you must draw a neat sketch of your gear box in a paper, showing its front view and top view, it will be good if you know a mechanical enginner who knows AUTOCAD or SOLIDWORKS. Knowledge of Engineering graphics is essential because you are going to have your gear box in your mind and draw its front and top view.

Three machines where used for gear box manufacuting, which are

Gear hobbing machine - used for cutting gears automatically, you have to just feed the information to the machine and it will cut the gears perfect. The gears made using the gear hobbing machine will have perfect finish, less time consuming. Best way to make a gear, but the problem is you have to convince the owner to make the gear for you because they will have big orders. Changing the setting for the gear requires more time and manual work. The below figure shows a gear hobbing machine.

Milling machine - used for cutting the gears manually, requires more time and labour cost for making a gear. They will cost Re.1 for each teeth i.e, 100 teeth gear will cost Rs.100. Please go for this machine if you are not finding any Gear hobbing machine in your locality.The below figure shows a milling machine.

Lathe - Before making a gear, you must make a circle having the specified OD, so you go for a lathe. Only after the turning and facing operation the circle must be taken to the gear hobbing machine or milling machine for making gear. Be careful in marking the center hole in the circle. The figure below shows a lathe machine.

The materials which we used for making gears are

acrylic material - half the weight of normal plastic, will look transparent and nice, strength is less when compared to nylon material. much attention must be paid while cutting the gears in this material, failure will result in breakage of gears.
nylon material - completely made synthetic fiber, has high strength and flexibility. less smooth when compared to acrylic material. no problem in cutting gears through nylon material.
brass metal - kind of bronze, an alloy of copper, tin and some zinc. Its a soft metal which can mesh easily with an acrylic or nylon material. Gear which is attached to the shaft of stepper motor is made using this gun metal.

types of gears

2008-06-07T04:34:00.000-07:00

In my previous post i have given details about the introduction to gears, now let us see the different types of gears. Many different forms of gears are used and the types most commonly used are,

Spur gear - Gears whose axes are parallel and whose teeth are parallel to the centerline of the gear are called spur gears. They are used to transmit power from one shaft or element to another in case where those shafts have their axes parallel.

Helical gear - Gears in which the teeth are cut in the form of helix around the gear. Helical gearing is used to connect parallel shafts as well as non-parallel, non-intersecting shafts. The pitch surfaces are cylindrical as in spur gearing, but the teeth, instead of being parallel to the axes, wind around the cylinders helical like screw threads.

Spiral gear - Skew or spiral gearing is used to connect non-parallel, non-intersecting shafts. The pitch surfaces are cylindrical and the teeth have point contact. suitable for transmitting only small power.

Bevel gear - When two shafts, the axes of which intersect, are to be connected by gearing, the wheels are known as bevel gears. The teeth are cut on a conical surface, such as would be represented by a truncated cone. Majority of bevel gear drives the shafts are at right angles, but in some cases the angles between the shafts may be either greater or less than 90 degrees, these are called as angular bevel gears.

Worm and worm wheel - Worm gearing is essentially a special form of helical gearing in which the teeth have line contact and the axes of the driving and driven shafts are usually at right angles and do not intersect. The distinction between helical gearing may be explained as follows : if the number of threads or teeth is such that no one thread makes a complete turn, the gear is called a helical gear. Of on the other hand, a thread makes a complete turn, the result is a worm and the mating material is called worm wheel.

Rack and pinion - The function is to transform circular motion to rectilinear motion : small gears are called pinions and racks are a series of teeth on a straight line. They may be considered as spur gears with infinite radii.

about gears

2008-06-06T04:03:00.000-07:00

New to gears.. let us see the introduction to gears, later on we will discuss about the type of gears and the machines used in manufacturing gears..

Introduction :

There was a need for us to develop a gear box with a speed reduction ratio of 128:1 for my project, but there was no one to guide us in designing a gear box. Later on, i sought the help of some teachers in a polytechnic college and completed my gear box. I will now share my ideas regarding how to design a gear box (using spur gears) which will be useful to you. First let us see about the introduction to gears. The below figure shows our gear reduction box.

A gear is a component within a transmission device that transmits rotational force to another gear of device. Gears are the most common means of transmitting power in mechanical engineering. There are tiny gears for devices like wrist watches and there are large gears that some of you might have noticed in the movie Titanic. Gears form vital elements of mechanisms in many machines such as vehicles, metal tooling machine tools, rolling mills, hoisting and transmitting machinery, marine engines, and the like. Toothed gears are used to change the speed, power and direction between an input and output shaft. A gears most important feature is that gears of unequal sizes can be combined to produce a mechanical advantage, so that the rotational speed and torque of the second gear are different from that of the first.

The desired speed reduction (128:1) was obtained by a combination of software and hardware. By hardware, we designed a gear box with a speed reduction ratio of 64:1 (4x4x4) using three gear trains each having a gear ratio of 4:1. By software, we made the stepper motor to run in half step mode, thus achieving the final gear reduction of 128:1(64x2). That is for every 128 rotations of the gear attached to the shaft of stepper motor, the final gear will rotate only once.

principle of laser tracking system

2008-06-04T23:36:00.000-07:00

We have already seen about laser tracking system in my previous post, now let us see the working principle of laser tracking system. Here we are going to track the tip of the finger as shown in the figure below. The laser beam from the source is made to incident over the steering mirror. The steering mirror is tilted in such a way that the reflected beam falls on the finger tip. The laser beam will form a circular saccade on the tip of the finger.

Fig.Laser Tracking System

The photodetector will detect the backscattered laser signal from the finger(see the diagram below). The saccade is supposed to remain fully inside the tip of the finger while tracking [fig (a)]. The backscattered signal will be high when the saccade remains fully inside the finger tip. As the object moves, a small portion of the saccade may fall outsid the finger tip, and the backscattered signal will momentarily drop. Due to the synchronous operation of the beam-steering mirrors and the photdetection, an accurate recentering vector(blue arrow) is computed [fig (b)]. The center of the saccade is updated accordingly [fig (c)]. By repeating these three steps continously we can track the movement of the finger tip.

Fig. Updating center of saccade

click the link below to know much about laser tracking system

about laser tracking system

2008-06-03T21:07:00.000-07:00

why laser based tracking became famous?

The tracking system at present, scans the entire background along with the object to be tracked and by using intense image processing it separates the object from its background. After separating the object, the motion of the object is detected. This method is complex and expensive. But in laser tracking system instead of scanning the entire background along with the object, we will scan only the object. So no image processing is required at all. We can directly detect the motion of the object. This method requires only few components, hence very simple and inexpensive.

Components used in laser tracking system

The laser tracking system requires three main components. Performance of these components decides the accuracy and efficiency of tracking system. They are

Laser source - a focusable laser diode delivering required optical power. The required optical power depends on the distance between the object and the tracking system. When the object is at greater distance, high optical power is required and vice versa. since the target is likely to represent a small portion of the total field of view, the illuminating energy can be efficiently concentrated, and therefore the system will be extremely power-efficient and work equally well with distant targets. based on safety the laser source is classified into six types. they are class 1, class 2, class 2a, class 3a, class 3b and class 4.
Steering mirrors - can be tilted in both x and y axis, which is used for focusing the laser beam towards the object which is being tracked. please see the post regarding steering mirrors.
Photodetector - a transducer capable of accepting an optical signal and producing an electrical signal containing the same information as in the optical signal. As the requirements for applications vary a lot concerning wavelength, maximum optical power, dynamic range, linearity, quantum efficiency, bandwidth, size, robustness and cost, there are many types of photodetectors. For laser tracking application we require very narrow bandwidth, wide angle photodetectors.

working of steering mirrors

2008-06-02T05:50:00.000-07:00

Steering mirror consist of a mirror(reflecting surface) and actuators. The actuators are used to tilt the mirror to required angle. It is of two types

single axis : mirror can be tilted with single axis freedom
two axis : mirror can be tilted with two axis freedom

since the mirror has to be tilted precisely, piezoelectric actuators are usually used. Piezoelectric actuators uses "inverse piezo effect" i.e, when exposed to an electric potential, piezoelectric materials change shape. The precise motion that results when an electric potential is applied to a piezoelectric material is used for tilting the mirror. fast steering mirrors can be used for laser beam steering mechanism.

code for driving stepper motor in mikro c and ccs c compiler

2008-06-01T02:46:00.000-07:00

code in mikroc for wave drive, half step and high torque stepping

//wave drive mode

main()
{
TRISB=0x00;
PORTB=0x00;

while(1)
{

Delay_ms(3);
PORTB=0b00001000;
Delay_ms(3);
PORTB=0b00000100;
Delay_ms(3);
PORTB=0b00000010;
Delay_ms(3);
PORTB=0b00000001;
}
}

//half step mode

main()
{
TRISB=0x00;
PORTB=0x00;

while(1)
{
Delay_ms(2);
PORTB=0b00001000;
Delay_ms(2);
PORTB=0b00001100;

Delay_ms(2);
PORTB=0b00000100;
Delay_ms(2);
PORTB=0b00000110;

Delay_ms(2);
PORTB=0b00000010;
Delay_ms(2);
PORTB=0b00000011;

Delay_ms(2);
PORTB=0b00000001;
Delay_ms(2);
PORTB=0b00001001;
}
}

//high torque stepping mode

main()
{
TRISB=0x00;
PORTB=0x00;

while(1)
{
Delay_ms(2);
PORTB=0b00001100;
Delay_ms(2);
PORTB=0b00000110;
Delay_ms(2);
PORTB=0b00000011;
Delay_ms(2);
PORTB=0b00001001;
}
}

code in ccs c compiler for driving stepper in wave drive mode

#include<16f877a.h> //including the PIC16F877A header file
#fuses HS,NOWDT,NOPROTECT,NOLVP //setting the fuses(please be careful in setting them)
#use delay(clock=20000000) //setting the clock frequency
#byte PORTB=0x06 //initializing the ports(please refer the memory organization in PIC datasheet)
#byte PORTC=0x07

int run( int r);
int temp;

int run( int r)
{
switch(r)
{
case 1:{
PORTb=0b00000001;
return(2);
}
case 2:{
PORTb=0b00000010;
return(3);
}
case 3:{
PORTb=0b00000100;
return(4);
}
case 4:{
PORTb=0b00001000;
return(1);
}
}
}

VOID main()
{
SET_TRIS_b(0X00);
PORTb=0x00;
temp=1;

while(1)
{
Delay_us(1000);
temp=run(temp);
}
}

i believe the following code snippet will be helpful to you in controlling stepper rotation

Driving stepper motor using TIP122

2008-05-31T22:20:00.000-07:00

If your stepper motor has a high current rating then its better to use TIP120/TIP121/TIP122 for driving your stepper motor. (TIP122 is most commonly available in Ritchie street).

The TIP122 is silicon epitaxial-Base NPN power transistor in monolithic Darlington configuration mounted in TO-220 plastic package. It intended for use in power linear and switching applications.

About Darlington pair:

Darlington transistors or Darlington pair is two transistors connected together so that the current amplified by the first is amplified further by the second transistor. The overall current gain is equal to the two individual gains multiplied together.

A darlington pair behaves like a single transistor with a very hihg current gain. It has three leads (B,C and E) which is equivalent to the leads of a standard individual transistor. To turn on there must be 0.7V across both the base-emitter junctions which are connected in series inside the Darlington pair, therefore it requires 1.4V to turn on.

Circuit Description :

The driver circuit must withstand the voltage and current required by the stepper motor. The stepper motor which i used required 12volts and 1.5A to provide good torque, so i selected using TIP122. Driver for each wire include a TIP122, a 1k ohm resistor and a diode. The resistors are used for limiting the current and the diodes are used to avoid back EMF. The circuit is shown below,

The common terminal of both the winding are shorted and connected to motor supply. When logic 0 input is provided to the base of TIP122, the corresponding motor will remain floating as the impedance between collector and emitter of TIP122 is very high. So no current flows through that motor winding. When logic 1 input is provided to the base of the TIP122, its collector and emitter get shorted as a result the motor wire will be grounded resulting in current flow through the corresponding coil.

I used the PCB displayed above to drive two stepper motors. While driving the stepper motor having high current rating, large amount of heat will be generated hence to dissipate the generated heat you must use an Heat sink. Only by providing heat sink the TIP can drive maximum current.

Driving stepper motor using ULN2003

2008-05-29T23:03:00.000-07:00

The simplest way to drive stepper motor having lower current rating is using ULN2003. The ULN2003 contains seven darlington transistors. The ULN2003 can pass upto 500mA per channel and has an internal voltage drop of about 1V when on. It also contains internal clamp diodes to dissipate voltage spikes when driving inductive loads. The circuit for driving stepper motor using ULN2003 is shown below.

For higher current torque motors, you can use TIP120. The advantage is that the TIP120 can pass more current along with heat sink. The disadvantages are that the more wiring is required and four TIP120 is used to control the motor.

IC's and transistors used for driving stepper motor

2008-05-28T08:14:00.000-07:00

The IC's and transistors which are used for driving stepper motor is as follows, the selection of the IC's or transistors is based on the current requirement of the stepper motor. For the stepper motor which requires low current less than 500mA ULN2003 could be used. For the stepper motor which requires high current greater than 500mA transistors like TIP120, TIP 121 and TIP122 can be used.

ULN2003 - used to drive stepper motor which has current rating less than 500mA. current rating can be improved by piggybacking two ULN2003.

TIP120, TIP121, TIP 122 - used to drive stepper motor which has higher current rating greater than 500mA. Diodes must be used to avoid back emf from affecting the control circuit. Heat sink is required for obtaining the maximum current. More economic and easy to use for driving stepper motors.

SLA7032M, SLA7033M - two phase stepper motor unipolar driver IC's which provides output current of about 1.5A and 3A.
SLA7070M, SLA7071M, SLA7072M and SLA7073M - motor driver IC's for unipolar devices which provides output current of 1A, 1.5A, 2A and 3A.
L297/A/D - stepper motor controller IC generates four phase drive signals for two phase bipolar and four phase unipolar stepper motors in microcomputer-controlled applications. The motor can be driven in Half step, normal and wave drive modes. The direction of rotation can also be switched.
SLA7024M, SLA7026M and SMA7029M - High-current PWM, Unipolar stepper motor controllers/drivers. They provide an output current of about 1.5A, 3.0A and 1.5A.
You can even use mosfet transistors and some other power transistors for driving the stepper motor.
Mostly i prefer using ULN2003 and TIP122 for driving the stepper motors because they are easily available in Ritchie street.

Identifying the leads of Unipolar stepper motor

2008-05-25T07:36:00.000-07:00

Unipolar stepper motors have four coils and either five, six or eight wires. No matter how many wires, unipolar stepper motors are interfaced in the same way. Five wires will go to the controller circuit. Four wires will be excited by pulses from the control circuit and the remaining wire(common) is given to the power supply. To identify the wires, you need a resistance meter.

First, identify the common lead. For the six and eight wire versions, some wires are twisted together to form the common lead and reduce the lead count to five. The common lead is connected to the positive of your battery or power supply.

Eight wire motors: Find the four pair of coils. These will be the wire pairs that have the coil resistance between them. There will be infinite resistance between pairs. One wire from each pair will be all joined together to form the common lead. Without a wiring diagram, you will have to do a lot of experimentation to determine which lead of the pair is for the common.

Six wire motors: Find the two wires whose resistance to two other wires reads the lowest of the measured resistances between wire pairs. Join these two wires together to form the common.

Five wire motors:Measure the resistance between all pairs of wires. One wire will read about one half the resistance to all other wires when compared to the resistance between other pairs. This wire is the common wire. No wires are joined in this case.

Now, proceed to identify individual coils in order of sequence.

Connect the common lead to the positive of your battery or power supply.
Connect any one of the other four leads to ground. This will be coil 4.
With coil4 still grounded, connect another lead to ground. If the shaft does not move, you have coil2. If the shaft rotates clockwise, you have coil3. If the shaft rotates counter-clockwise, you have coil1.
Repeat until you have identified all four coils.

Identifying stepper motors

2008-05-22T06:23:00.000-07:00

While buying a stepper motor you must note the following aspects

First, check for the number of wires coming out. If 5 or 6 or 8, that's good because you have a unipolar stepper. If 4, that's bad beacuse you have a bipolar stepper which requires two phase to drive. Confirm you have a stepper motor by turning the shaft. You should feel the little detents indicating each step. Most probably in ritchie street you will get unipolar motors with 5 or 6 wires.

Second, check the label on the side. The label will have the voltage and step size printed. Look for 12V steppers. If you have a 5V stepper, and it is large, the currents required will be large. Small 5V steppers are no problem to drive. If your stepper motor is new then it will have their voltage rating marked by its side, the problem arises when you are buying stepper motor in second sales. New stepper motor will cost about Rs.1500(for 1.8deg) whereas the second sales stepper motor with the same step angle would be just Rs.250.

Third, get out your digital ohmmeter (probably your multimeter) and start measuring the resistances between the leads. you will get different values depending on which pair of leads you measure. The lowest resistance you find is the coil resistance. Use I=V/R to compute the coil current. If 250mA or less, you are in good shape. Most stepper motors in Ritche street will have very low coil resistance and requires current above 1A.

Fourth, look at the output shaft and determine if it is something you can handle. Check whether the shaft has suitable height so you can use it. Common steppers have plain shafts with 0.125, 0.196 or 0.250 diameter. Gears press fit onto the shaft may be useful to you or can be removed. Don't try to remove the gears by yourself, you will damage the shaft if you try to remove it by yourself. Lathe with chuck must be used to remove the gears to avoid damage to the shaft.

very large or very heavy steppers will mostly require more current than you can control.

Where to find stepper motors

2008-05-20T04:56:00.000-07:00

Stepper motors can be found in almost any piece of electro-mechanical equipment. It can be pulled from old electronic equipment such as floppy drives, dot-matrix printers. Most of the stepper motors in Ritchie street is pulled from printers and the most common step angle you could find is 1.8deg and 7.5deg which is of permanent magnet type. Look for "unipolar" or "4-coil" or "4-phase" motor (they all mean the same thing) with 5 or 6 or 8 wires. Avoid "bipolar" motors because they require an entirely different control scheme. The require two phases to control them and have four wires.

Operating voltage of 12V is convenient for robotics projects. Look for motors with a coil current of 250mA or less (coil resistance of 48ohms or more for a 12V motor <-> V=IR). Higher currents do give higher torque, but will also drain your battery faster. Another key specification is the holding torque which is how much torque the motor can resist when energized.

stepper motor - introduction

2008-05-18T04:25:00.000-07:00

A stepper motor is a electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. Stepper motors enable precise positioning without needing sensors to measure motor position.

Advantages

The rotation angle of the motor is proportional to the input pulse.
The motor has full torque at standstill(if the winding are energized).
Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3-5% of a step and this error is non cumulative from one step to the next.
Excellent response to starting/stopping/reversing.
Very reliable since there are no contact brushes in the motor. Therefore the life of the motor is simply dependent on the life of the bearing.
The motors response to digital input pulses provides open-loop control, making the motor simpler and less costly to control.
It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.
A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.

Disadvantages

Resonances can occur if not properly controlled.
Not easy to operate at extremely high speeds.
More complex to control than DC motors.
Consume precious battery current even when not moving.

Shops in ritchie street

2008-05-13T22:05:00.000-07:00

Hi guys new to Ritchie street ?
don't worry i will guide you to some shops in Ritchie street

--> Modi Electronics - #6, Ritchie street, 1st floor, chennai - 600 002.
Ph - 91-44-2841 4140.
Best shop to buy DC gear motors, stepper motors and LEGO kits, they also sell many projects which you must assemble yourself.

--> Shri Gemini Kits and Spares - #22, Athipattan st, Mount Road,
ch - 600 002. Ph - 2841 8592.

Here you can get projects which is already assembled. It will be like a project center, their is a person named Rajamanikam who will guide you there, he will also give good ideas, classes are also conducted here during weekends for programming AT89C51 using Embedded C (you have to pay for it).

--> Omega Electronics - Best place to buy the components for your project such as resistors, capacitors, PCB's, LED's, IC's, diodes, relays, switches, LDR's, transformers, soldering lead etc. ( there are two shops named omega, one near globe electronics in the main road and other inside the entrance of the building, the main shop will be crowded all the times so you can get your components in the second shop)

--> Texonic - Best place to buy PIC microcontrollers, if you are buying components in a large scale its the best place. PIC Programmer is sold here. Its like an wholesale shop. you can buy the components but the minimum amount for billing is Rs.50 and you should also buy the components in large scale you cannot buy one or two IC's here except PIC.

--> Kailash Electronics - similar to omega electronics where you can get all your electronic components.
-->Their is a shop near Shri gemini kits and spares where you can design your PCB i can't remember the shop name
--> Hertz systems (Allegro systems) - No:109/7, Vanavil apartments, East main road, anna nagar west extn, chennai-600 101. Ph - 43538861, 26150019. (Near SBIOA school)
PIC16F877A and PIC18F452 development board is sold here. Classes are taken for programming PIC with CCS C compiler for Rs.4000(when i attended, not sure about the amount now). The classes will be very much useful to you guys for doing you final year project. A person named Murali is incharge of Hertz systems, he will also give ideas for your project.
--> For those who are residing near tambaram you can get most of the electronic components in Mercy Electronics (near national theatre)

Features of PIC16F877A

2008-05-09T11:05:00.000-07:00

I started with PIC16F877A demo board for my projects. let us now see the features of PIC16F877A, the following image shows my PIC16F877A demo board.

PIC16F877A demo board

Features of PIC16F877A

High-performance RISC CPU

Lead-free:RoHS-compliant
Operating speed:20Mhz, 200ns instruction cycle
Operating voltage:4.0-5.5volts
Industrial temperature range(-40 to +85 degrees)
15 Interrupt sources
35 single word instructions
All single-cycle instructions except for program branches

Special Microcontroller Features

Flash memory:14.3KB(8192 words)
Data SRAM:368 bytes
Data EEPROM:256 bytes
Self-reprogrammable under software control
In-circuit serial programming via two pins
Watchdog timer with on-chip RC oscillator
Programmable code protection
Power-saving code protection
Selectable oscillator options
In-circuit debug via two pins

Peripheral Features

33 I/O pins : 5 I/O ports
Timer0:8-bit timer/counter with 8-bit prescaler
Timer1:16-bit timer/counter with prescaler
Timer2:8-bit timer/counter with 8-bit period register, prescaler and postscaler
Two capture, compare, PWM modules
Synchronous serial port with two modes
USART/SCI with 9-bit address detection
Parrallel slave port
Brown-out detection circuitry for brown-out reset

Analog Features

10-bit, 8-channel A/D converter
Brown-out reset
Analog comparable module

whats the difference between PIC16F877 and PIC16F877A ?

I got two answers for this question from my friends which i want to share with you
- The masking is different in both the microcontrollers

- While burning the code in PIC microcontroller their is an acknowledgement received for each code word written in PIC's memory. In case of PIC16F877 the code word is written one by one and hence their is an acknowledgement required for each code word written and hence the speed of writing is reduced. Whereas in case of PIC16F877A the code word is written in blocks and hence acknowledgement is required only for the block of code word and hence speed of writing is more when compared to that of PIC16F877A.

PIC microcontroller architecture

2008-05-05T10:44:00.000-07:00

Let us see about the architecture categories in PIC microcontroller

Microchips 8 bit PIC microcontrollers fall into three product architecture categories providing a variety of option for any application requirement

Baseline 8 bit architecture - 12 bit program word
Midrange 8 bit architecture - 14 bit program word
High performance 8 bit architecture - 16 bit program word

Baseline Architecture - The baseline architecture includes the PIC10F family and portion of the PIC12 and PIC16 families. These devices utilize 12 bit program word architecture with 6 to 28-pin package options. The concisely defined feature set of baseline architecture enables the most cost-effective product solutions. This architecture is ideal for battery operated applications. The PIC10F200 series provides another industry first, an inexpensive 8 bit flash microcontroller in a six pin package.
Midrange Architecture - The midrange architecture includes members of the PIC12 and PIC16 framilies that feature 14-bit program word architecture. These families are available with 8 to 64 package options. The midrange PIC16 devices offer a wide range of package options, as well as low to high levels of peripheral integration. This PIC16 device features various serial, analog and digital peripherals, such as USB, SPI, I2C, USART, LCD and A/D converters. The mid-range PIC16 microcontrollers have interrupt handling capability with an 8 level hardware stack.
Highperformance Architecture - The high performance architecture encompassed the PIC18 family of devices. These microcontrollers utilize 16 bit program word architecture with 18 to 100 pin package options. The PIC18 devices are high jperformance microcontrollers with integrated A/D converters. All PIC18 microcontrollers incorporate an advanced RISC architecture that supports flash devices. The PIC18 has enhanced core features, 32 level deep stack and multiple internal and external interrupts.

Features of PIC microcontroller

2008-05-01T00:41:00.000-07:00

New to PIC ??

Let us see the dynamic features of PIC which has made it a better choice than other microcontrollers

Features of PIC microcontroller

1.code efficiency - The PIC 8 bit microcontroller is based on Harvard architecture, which means there are separate internal buses for memory and data. The throughput rate is therefore increased due to simultaneous access to both data and program memory. It would be easier if you have known about von neumann architecture which has common bus for memory and data.

2.safety - All the instructions fit into a 12 or 14 bit program memory word. There is no likelihood of software jumping onto the DATA section of a program and trying to execute DATA as instructions.
3.Instruction set - There are 33 instructions you have to learn in order to write software for the 16C5x family. The lesser number of instruction eases our job while writing program in assembly language.
4.Speed - The PIC has an internal divide by 4 connected between the oscillator and the internal clock bus(note : we know their is a divide by 2 in a 8085 microprocessor where we connect a 6Mhz clock inorder to operate the microprocessor at a speed of 3Mhz). The PIC is very fast to work with. The speed of PIC16F877A is 20Mhz but it can even operate at a speed of 30Mhz. some PIC in 18Fx family can be operated at 40Mhz.
5.Static Operation - The PIC is a fully static microcontroller, in other words, if you top the clock, all the register contents are maintained. In practise you would not actually do this, you would place the PIC into a Sleep mode-this stops the lock and sets up various flags within th ePIC to allow you to know what state it was in before the Sleep. In sleep, the PIC takes only its standby current which can be less than 1uA. The need for sleep mode can be easily understood by considering the Fire alarm circuit, since the circuit has to be activated only when their is a fire, the rest of the time the PIC can be made to be in its sleep mode and wake up when their is fire thus saving the power required for the operation of PIC.
6.Drive Capability - The PIC has a high output drive capability and can directly drive LEDs and TRIACs etc. Any I/O pin can sink 25mA or 100mA for the whole device.
7.Options - A range of speed, temperature, package, I/O lines, timer functions, serial communication, A/D and memory sizes is available from the PIC family to suit virtually all your requirements.

PIC microcontroller can be programmed using embedded C. some of the compilers which i have used are mikroC, CCS C compiler and Mplab. It is easier to program in embedded C rather than programming in assembly language. The demo version of these compilers can compile upto 2KB of program memory.

about cheniston serial input software

2008-04-28T02:55:00.000-07:00

The cheniston serial input software is used to control the movement of cursor in PC by giving serial input through the serial port. Serial Input is a windows based application to enable keyboard and mouse input via alternative input devices. It works by taking input from your device(via a serial port), and translating the received data into keyboard and mouse input for windows operating systems.

Serial Input uses the almost universal capability of alternative input devices to send ASCII characters to the machine they are connected to. This basically means that when Serial Input is running it waits for characters to hit the connected serial port, and then translated those into an appropriate input message.

Many ASCII characters are exactly what the user would wish to represent on the computer, for instance 'abc' would be interpreted by Serial Input and 'abc' would be sent to the keyboard buffer for processing by whichever application the user happens to be running - eg: a word processor. In order to cater for mouse input a default set of 'high-end' ASCII characters were initially chosen to represent 8 compass points(N, NE, E, SE, S, SW, W, NW) and 'STOP'.

Mouse movement works with the premise that one character is sent to move the mouse in a particular direction and subsequent characters are sent to redirect or stop the mouse. Left and Right mouse buttons, with single and double click values are also supported. The increment in X direction and Y direction can also be changed. The movement delay of the cursor can also be changed by clicking the advanced button in mouse tab.

The ASCII character mapping is given below

click here to download serial input software

about microbrn

2008-04-26T21:48:00.000-07:00

microbrn is a software from ozitronics which is used for burning the hex code in PIC microcontrollers. It is also named as micropro, i used this software for dumping my hex code into PIC. It provides options of setting the fuses while burning the code into PIC, please be careful while setting the fuses, because even if your program works good but improper setting of the fuses will stop it from working properly.

If you are using mikroC then you have the burden of setting fuses sometimes by yourself while dumping the code into PIC, but in case of CCS C compiler their will be no problem because you will be defining the fuses while coding. I have provided the common fuse settings for PIC16F877A below,

A correct COM port value must be given in FILE-->PORT to program the PIC. The COM port value can be found from the DEVICE MANAGER after connecting the USB PIC programmer to your systems USB port. To go to the device manager follow the steps below

right click on the my computer icon which appears in the desktop.
select properties from the menu that appears.
select the hardware tab from the system properties window.
click the device manager button which appears in the window.
after connecting the USB PIC programmer, check the PORT VALUE by clicking the '+' sign in the ports(COM & LPT) in the device manager window. When proper PORT VALUE is not given, an error message 'There appears to be a problem in accessing the COM port' will be displayed in a window.

you can also verify whether the code has been dumped into PIC or not by selecting the VERIFY button.

click here to download microbrn*

*click on the file named DIYpack25EP.zip

about PIC simulator IDE

2008-04-22T21:20:00.000-07:00

Its a best simulator software for PIC microcontroller developed by oshonsoft to test your program, just browse and select the hex file which you have obtained after compiling the code, it also provides environment for testing your interfaces like LCD, stepper motor, LED board, and it also provides microcontroller view where you can provide inputs to the INPUT PORT pins and to check the output from the OUTPUT PORT pins.

PIC simulator IDE is powerful application that supplies PIC developers with user-friendly graphical development for windows with integrated simulator(emulator), basic compiler, assembler, disassembler and debugger. PIC simulator IDE currently supports the following microcontrollers from the microchip PICmicro 12F and 16F product lines.

Main features of this simulator includes

main simulation interface showing internal microcontroller architecture.
FLASH program memory editor, EEPROM data memory editor, hardware stack viewer.
microcontroller pinout interface for simulation of digital I/O and analog inputs.
variable simulation rate, simulation statistics.
breakpoint manager for code debugging with breakpoints support LCD module simulation interface for character LCD modules.
graphical LCD module simulation interface for 128x64 graphical LCD modules.
stepper motor phase simulation interface for stepper motor driving visualization.
7-segment LED displays simulation interface

The demo software can be used 30 times so dont close the window after opening it until you shutdown your system, however you can obtain the cracked version of PIC simulator IDE from rapidshare. I will provide you the link for downloading the demo version.

click here to download the demo version of PIC simulator IDE

about ccs c compiler

2008-04-20T20:05:00.000-07:00

The CCS C compiler was developed exclusively for the PIC MCU - making it the most optimized compiler for Microchip parts. The compiler has a generous library of built-in functions, preprocessor commands, and ready-to-run example programs to quickly jump-start any project. Drivers for real-time clocks, LCD's, A/D converters and many more are innate features to the CCS C compiler.

The compiler contains standard C operators and built-in libraries that are specific to the PIC registers. Access to hardware features from C.

Features includes:

1, 8, 16 and 32 bit integer types and 32 bit floating point.
standard one bit type(short int) permits the compiler to generate very efficeint bit oriented code.
#BIT and #byte will allow C variables to be placed at absolute address to map registers to C variables.
bit arrays.
fixed point decimal.
constants(including strings and arrays) are saved in program memory.
flexible handling of constant data.
variable length constant strings
address mode capability to create user defined address spaces in memory device.

The CCS C compiler for PIC10, PIC12, PIC14, PIC16 and PIC18 microcontrollers has over 180 built-in functions to access PIC MCU hardware is easy and produces efficient and highly optimized code. Functions such as timers, A/D, EEPROM, SSP, PSP, USB, I2C and more

Built-in libraries that work with all chips for RS-232 serial I/O, I2C, discrete I/O and precision delays.

serial I/O functions allow standard functions such as GETC() and PRINTF() to be used to forRS-232 like I/O.
formatted printf allows easy formatting and display in HEX or decimal.
multiple I2C and RS232 ports may be easily defined.
#use rs232() offers options to specify a maximum wait time for getc.
Functions such as INPUT() and OUTPUT_HIGH() properly maintain the tri-state registers.
Simple functions like READ_ADC() to read a value from A/D converter.

click here to download the demo version of CCS C compiler*

*you must fill an information form for downloading the demo version

about mikroC

2008-04-17T19:57:00.000-07:00

mikroC is one of the powerful and easy to use software for programming PIC microcontrollers in embedded C. mikroC is a powerful, feature rich development tool for PICmicros. It is designed to provide the customer what the easiest possible solution for developing applications for embedded systems, without compromising performance or control. Applications can be developed quickly and easily using mikroC for PIC microcontrollers. It provides a simple windows based point-and-click environment for developing applications.

PIC and C fit together well: PIC is the most popular 8-bit chip in the world, used in a wide variety of applications, and C, prized for its efficiency, is the natural choice for developing embedded systems. mikroC provides a successful match featuring highly advanced IDE, ANSI complaint compiler, broad set of hardware libraries, comprehensive documentation, and plenty of ready-to-run examples. demo version is available for download i have provided the link below, you can even search for cracked version in internet.

click here to download demo version of mikroC

VEHICLE NAVIGATION USING PIC MICROCONTROLLER

2008-04-12T23:07:00.000-07:00

The problem of handling materials in an industry must be done in an efficient way. Present system for handling materials in industry uses conveyor belts to displace the object from one place to another. The conveyor belt system occupies large amount of space even when there is no load to be transported and can accept load from a particular source and deliver it to a particular destination point. In this project we present a simple ‘Vehicle Navigation Using PIC Microcontroller’ were we replace the conveyor belt system with a line follower robot which can handle the materials in an industry. Thus the large amount of space occupied by the conveyor belt system can be avoided.

The navigation system can load the materials from different sources and can deliver it to respective destination points, which is restricted in the case of conveyor belt system. The line follower robot is a self operating robot which follows a line that is drawn on the floor. The path between the source and destination points can be changed easily by just modifying the line. Thus the system is simple and cost effective than conveyor belt system when there is a change in path. The navigation system can even sense any obstacles in its path and can take an alternate path to reach the destination.

POWER OF LOGIC GATES

2007-08-02T07:22:00.000-07:00

FOOTBALL ROBOT - SOCCERBOT

INTRODUCTION :

Most of them would have developed the football robot using a microcontroller or using any complex circuit. Here is a simple circuit to design a football robot using simple logic gates. The circuit involes the usage of one OR gate IC and a motor driver IC L293D. The diagram is shown below for your reference.

CIRCUIT DESCRIPTION :

The F,B,R,L inputs to the OR gates comes from the switches which specifies the desired direction of control. For example, consider the case when L is pressed then the outputs B and C goes high and the direction of motor control to the motor driver IC becomes 0110. This means that the motor1 turns in backward direction and motor2 turns in forward direction where motor1 is on left side and motor2 is on right side. Thus the robot can be controlled using a single or gate instead of complex circuits. This results in less soldering and more economical.

Thus we can understand the power of logic gates from the above design..

FOLLOW THE PRICIPLE OF TDI
THINK.. DESIGN.. INNOVATE..