## Wednesday, February 26, 2014

### Colpitts Oscillator

Good evening everyone, today I am going to write about Colpitts Oscialltor, those folks who are studying Electrical & Electronic Engineering or Communication or maybe Applied Physics might find this post helpful.

This oscillator was invented by an American engineer called Edwin H. Colpitts in 1918. This oscillator uses both capacitor and inductor to produce an oscillation at a certain frequency. The distinguishing feature of the Colpitts oscillator is that the feedback for the active device is taken from a voltage divider made of two capacitors in series across the inductor. So Colpitts oscillator is basically a LC oscillator.

We know how LC oscillator works, in a LC oscillator there is a capacitor which becomes charged and discharge through a inductor, as a result capacitor gets depleted, then the inductor charges the capacitor again and again and magnetic field around it depletes, then again capacitor charges the inductor and this process goes on and on. Thus creating an oscillation. But in real life situation capacitor and inductor have resistance which draws power so the oscillation stops at a certain point unless power is given to the circuit properly.

Lets take a look at the circuit diagram first.

From the diagram we can see that the feedback circuit is made of two tapped capacitors with an common inductor. So the whole tank circuit is made up of C1, C2 and L. This circuit uses one single transistor to amplify. The RF choke simply decouples any ac signal in the power lines from affecting the output signal.

How it Works :

When the circuit is powered, the capacitors C1 and C2 are charged. Capacitors discharges through the inductor L, setting up oscillations of frequency determined by its frequency expression. As shown on the figure, it is clear that the output voltage of the amplifier appears across capacitor,C1 and feedback voltage developed across C2. The voltage across C2 is 180degree out of phase with the voltage across C1 or Vout. Voltage feedback to the transistor provides positive feedback. A phase shift of 180degree is produced by the transistor and a further phase shift of 180degree is produced by the C1-C2 voltage divider. This way the feedback is properly phased to produce continuous undamped oscillation.

In this oscillator there is a LC circuit in the feedback loop to provide the necessary phase shift and
to act as a resonant filter that passes only the desired frequency of oscillation.

Frequency of Colpitts oscillator

## Saturday, February 15, 2014

### Mid Range Gaming Build February 2014 \$750

Welcome back everyone! Earlier I have posted budget build within 700\$. Now in that build I used an AMD FX based processor a FX-6300, which many people won't like! So, now I'm gonna post another build using an Intel Core i5 4th generation.

In this build the only thing that I'm going to change is the Processor and essentially the motherboard, the rest will stay the same.

First stop, the processor.

Intel Core i5 4570

This is the latest generation processor from Intel corporation codename Haswell. It is the 4th generation product of their core series. This series is a very successful series, they might be a bit pricey but still make it up with the performance.

Core i5 4570 is a quad-core processor with no hyper-threading that means it will always work as quad-core. It's a 3.2GHz processor, with 6MB high speed level 3 cache, it supports latest instruction sets and it's thermal design power is only 84W.

It supports dual channel DDR3 memory modules up to 1600MHz, it has turbo boost which can boost up the clock speed to 3.6GHz turning off 3 of its cores. The only thing that I don't like is the integrated GPU, it has HD4600 iGPU, I think it's useless, cause for gaming we will be needing an discrete card. Though some people use switchable graphics, I don't really care about the power consumption so whatever.

This processor has decent gaming performance, productivity, and very low idle power consumption.
One negative side is this processor is not overclock-able, it's multiplier is locked, so it can't be overclocked much!

It's price is a noticeably higher than the FX-6300. But if you want a gaming rig you can't go with an i3, dual core is obviously not recommended. So, i5 is it is. It's price is around 200\$ or 16.6K BDT.

Motherboard

For the motherboard, I'm going to use a cheap gigabyte board, which can support the fourth generation core processors.Gigabyte boards are really stable, looks good and

Gigabyte H81M-S2PV

This is the cheapest board that I can find to use with a fourth generation core processor. It has SATA 6Gbps ports, USB 3.0 port, PCI express x16 slot, Realtek Gigabit LAN and Audio, two DIMM slots that supports up-to 1600MHz.

For a budget build it will work fine for now. Just make sure to plan ahead while putting memory modules as this board has only two DIMM slots. It will cost around 65\$ or 5.6K BDT.

The rest will be same as before.

So, take a look at here for the earlier build.

## Wednesday, February 12, 2014

### Budget Build February 2014 \$665

Good evening everyone!

Like the title goes this post will be a budget gaming build. This system is purely targeted for decent gaming at a very low cost and also this system will be enough for daily usage like internet browsing, watching high definition movies, preparing school/college/university presentations, using audio video or picture editing software and all!

Hope this system will give you the best bang for the buck!

Even with a budget system like this you will be able to play most recent games and upcoming games!
You can use steam to get games at appealing price!

This will be an AMD build, will post an Intel build later.

So, first stop the Processor :

AMD FX-6300

Now, I know many of you will argue like AMD processors are not good or they don't perform well! Let me explain the reason for choosing this processor!

First of all this is a Hexa Core processor (it has 6 physical cores) so when it comes to multi-threaded workload it beats the similarly priced Intel Core i3 ( 2 physical cores / 4 hyper-threaded core)  and like I was saying this is purely a gaming build and most games depends mainly on the Graphics card so a 6 core FX-6300 will be enough for a budget rig.

If you play games like Crysis 3 you will see noticeable performance difference in i3 vs fx-6300.

One more thing I'm not going to drop in a R9 290X or GTX 780Ti so we don't have to worry about the CPU bottle-necking the GPU.

This CPU has higher cache memory, although this is not the only thing that makes a processor better still it is a reason.

This CPU in unlocked so this can be overclocked easily. ( I'm not going to overclock this one though)

If you consider other applications, like watching movies, browsing internet or using software for editing most application will run almost the same! You won't feel any difference.

Intel CPU comes with integrated graphics card, as this build is targeted for gaming a discrete card will be used so no point of paying for the integrated GPU!

Though this processor has some negative things too, first of all it might have higher amount of cache memory comparing to similarly priced Intel processors, but it's cache memory is significantly slower than Intel's processors. One other thing it burns way more energy than Intel's Quad core Sandy bridge, Ivy bridge or Haswell parts.

To keep the price lower I am not going to use any aftermarket cooler but if you have a bit more money to spare you can take a look at this one.

Cooler Master Hyper 212 EVO

With this cooler you can overclock to 4.3GHz without any problem. That will give the whole system a bit more processing horsepower.

Cooler will cost around 30\$ or 2.8K BDT.

Processor will cost around 110\$ or 12K BDT.

Now motherboard!

MSI 760GMA P34

MSI is a reputed brand and they manufacture stable products! The reason for choosing this board is it's cheap but supports FX-6300, it has SATA3.0 6Gbps ports, USB 3.0 ports, PCI Express 2.0 X16 slot, decent audio, front panel USB 3.0 connector. A very nice choice for a budget build. Though one negative side of this board is it has only two RAM slots. Still for a budget gaming build I will use this one for now.

It will cost around 55\$ or 5K BDT.

You can also take the 970 board, with that you will get more headroom for overclocking.

Now for the RAM!

AMD DDR3 RAM

For now DDR3 8GB 1600MHz will be enough. Many of the today's games needs 6GB RAM so taking 4GB will reduce performance. Reason for taking a single 8GB Kit is this board does have only 2 RAM slots, so I will just keep one slot free right now. And AMD systems doesn't benefit much from dual channel mode so I guess using single channel won't do much harm. 1600MHz is currently the sweet spot so will stick to that one. You can also use two 4GB sticks.

You can take the AMD / Patriot / Transcend modules. 8GB 1600MHz will cost around 85\$ or 6.7K BDT.

Better if you can find 1.5V CL9 RAM.

(AMD modules are actually Patriot modules)

Now the most important part of this build the Graphics Card!

Sapphire HD 270X Dual-X

As a strictly budget build I can't fit anything better than this one, this card is pretty good for running any games with decent frames per second on a full high definition display.

This card is armed with 1280 stream processors, 2GB memory of 256bit which is pretty much enough for handling any new game.

This card doesn't burn a lot of energy so we wouldn't be needing a beefy power supply unit. Even under full load it only takes 170W.

It runs really cool and quiet, thanks to the dual-x cooling, that means it has headroom for overclocking, even slight overclocking would result in slightly better performance in gaming.

This card has Single Link DVI, Dual Link DVI, HDMI, Displayport everything, 2GB frame buffer is also pretty much the sweet spot for full HD gaming.

This card also has a 4GB edition, with a little extra cash you can take that too!

Let's take a look at a few benchmarks then.

From the benchmarks we can see this card can run all the games at very decent frames per second. Only Crysis 3 is running very slowly, it's because this game is very heavy. Still if Anti Aliasing is turned off it will be playable.

This card will cost around 270\$ or 22K BDT.

Now the power supply unit

Thermaltake Smart 530W

When it comes to power supply I always prefer single Rail, so that I don't have to worry about load balancing. Next I prefer semi modular, less contact point, less contact drop or wastage of power and better cable management.

This particular power supply unit has a single +12V rail with a current rating of 38A, which is pretty ample for this particular build.

This power supply is a 80+ bronze unit, so its efficiency will be well over 80% all the time! Now some people might mislead you saying that the efficiency effects the output, no it doesn't! A 600W power supply unit with 80% efficiency can provide 600W output but it will take 750W as input power from the AC outlet, that means 150W wastage of energy! This efficiency rating will just effect your electric bill and UPS backup time.

Though some people said this power supply unit doesn't have good power regulation and actually have dual rail inside, you can also buy Corsair power supplies too. They are also good.

This power supply will cost around 65\$ or 5.3K BDT.

Take a look at the PSU buying guide for more!

Now time for the storage.

Western Digital Blue 500GB SATA-III

No SSD? Yes no SSD. For a budget build can't manage a SSD. A mechanical HDD will be enough. I would have suggested Hitachi drives but they are no longer available I guess so western digital. It is also a well known manufacturer of hard drives. This drive is a SATA-3 6Gbps drive and 7200rpm so its speed is good and access time is also low. It is good for storing operating system and storing a few games for now.

Tip: Before buying WD drive make sure to match the model number with their site. The drive on the picture's model is WD5000AAKX which is the 16MB cache edition. This drive also has a 32MB cache edition.

It will cost around 60\$ or 4.6K BDT.

Next optional items. First optical disk drive.

Asus 24X ODD

I actually don't remember when the last time I used this one! Though I have one connected to my computer! It can be used for installing operating system or maybe games though operating system can be installed from USB  and games can be downloaded and installed!

This might cost around 20\$ or 1.6K BDT.

Grand total \$665 or  57.2K BDT(without the price of operating system).

Next the case!

Just take any cheap case you like!

Take a look at this one! Can't find any good picture!

For the mouse I can suggest this one!

A4tech Bloody V3

This might cost around 35\$.

Take any good keyboard and UPS!

So that's all for now, hope this will help you to take good decision!

More are coming!

Happy Gaming!

## Sunday, February 9, 2014

### Multimedia Classroom And Digital Contents

[UNDER CONSTRUCTION]
Good Evening everyone, this post is mainly aimed at importance of multimedia classroom, digital contents and its importance. Although I will mostly speak from a point of view of a developing country Bangladesh, where I live in.

Bangladesh, a south Asian developing country, we have a schooling system that is pretty old and existing system is based solely on reading and writing. Mainly students study from books, text books which are old too and then they sit for an examination where all they have to do is to write down what they have read throughout the year. The person who has better memorizing capability and fast enough to write everything down will get more marks. So the whole system depends on just reading and writing. Speaking and watching are neglected to a point where most students don’t even develop these skills which not only limits the ability to learn more but cause issues in the future. Let me give you a small real life example, when I was in school we had to study social science in which we learned about history, politics, solar system, and economics unfortunately all we had to do is to read from just one textbook, memorize it and that’s all. Not to mention that was obviously not that pleasant.
Assume a student has to study on an antiquities, maybe Somapura Mahavihara (yes we had to study this), all the resource he/she has is the textbook and he/she has to memorize it, but if a video and a few high resolution pictures were shown in the classroom it will be a whole lot of easier for him/her to understand and memorize.
I do remember in the school I studied the subject computer studies, and this subject was also very much textbook depended rather than directly using the computer, I understand for a country like us computer can’t be provided to everyone so the books can’t be that advanced but I hoped it would be better, like if we had to do small C or C++ programming it would be really awesome.
Ture that printed books are good for reading but that is for just joy reading. In schools learning is important too and if schools deploy newer technologies that are available will help students to understand stuffs easily and effortlessly. Let’s assume a hypothetical situation where classrooms have large interactive displays, we won’t be needing chalk or marker boards. Teacher can just write on the surface of that display and it will be displayed. Fonts, colors, designs can be modified easily. It will not only decrease the overall need for consumable materials but also make it easier for both instructor and students to learn. In such a display showing a video is also simple. Say the teacher is teaching Pascal’s law in physics if the teacher shows a video of how the force are working and all it will be lot easier for a student to understand. Now like I was saying paper books are good but carrying paper books are a tough work. Students in our country has to carry multiple books which is pretty heavy. If everyone has a small computer or a tab he/she can store each and every book in it and moreover if school provides wi-fi internet or local file access, students can easily directly watch those videos or use those contents. Thus they will be using watching reading listening at the same time and sure it will be more efficient.

Current Condition

Good to know that currently things are changing, Bangladesh is diving more into technology oriented things. Now all the textbooks can be found in the government website and they are free to download.  This allows students to easily download the textbooks and read them. Moreover many schools have started multimedia classrooms which helps students to easily study.

Multimedia Classroom

The word multimedia has self-explanation, multimedia consists of multiple media, which might be audio, video, text and anything else. Unlike the earlier classroom style multimedia classroom will provide students with the access to information through multiple media system. Like in earlier textbook was the only thing, now in a multimedia class an audio-video representation might be presented and of course watching a video will result in better understanding of that topic rather than just reading it from textbook.
For multimedia classroom there should be digital contents and teachers capable of using these contents.

Digital Contents

Now-a-days, you can't go one mouse click without stumbling on digital content. Also known as digital media, digital content comes in many forms, from text and audio and videos files, to graphics, animations, and images. Typically, digital content refers to information available for download or distribution on electronic media such as an ebook reader or in computer, but many in the content industry argue that digital content is anything that can be published. Following this line of thinking, it is safe to say that if you are on the internet, most likely you are looking at, watching, or listening to a piece of digital content.

As a developing country digital content is not that popular yet, but its getting popularity. Even a few years ago this idea was not that popular, students and teachers or even research personnel used paper books and stuffs like that. Now just think about this, how digital content can help you and make your wok easier, if you have to find a certain topic you have to go through the whole paper book, maybe line by line but if its electronic, you can just search for the keyword and it will show up all the matching words! Just imagine how it is lessening your workload, moreover if you think about the size, just imagine how much space you will need to keep 10,000 paper books? Huge area, you will need, kind of like a library or something. But you can store 10,000 electronic books in a cellphone that has 32GB of memory say a HTC one! Isn't it really convenient?

For multimedia classroom digital contents are essential. Digital contents can be like electronic text books which can be displayed on the interactive display or display on a screen via projector or videos on topics which are relevant to the study. Like I mentioned above I’m happy to see PDF copies of all the textbooks which can easily be shown on a display or on a screen using a projector. But amount of digital contents are still low, digital contents should be created according to the topics.

To develop digital contents trained persons should come forward. Those who are developing these contents should have a good knowledge on the curriculum and proper ways to make a student easily understand the topics. Complexion should be avoided.

Like I said earlier, digital contents are not yet popular among us, mainly because technology has not improved that much yet. If we consider the percentage of people who can access computer and internet, that number won't be a very big. But still I'm glad to see that current government has taken steps to create and freely distribute digital content. This can create a huge breakthrough. But to do so government must ensure these contents can be accessed by everyone, everyone of this country.

You can easily download all the school and college text books from here.  So, we are also advancing and in proper direction.

Software and Hardware Requirements:

To establish a proper multimedia classroom hardware and software is needed. If we want to create such a classroom we will both need an interactive board, which is a display actually, and touch sensitive so that if we write with a pen (touch pen) it will be written directly on the display. We have to hook up the display with a computer so that we can play video on it, according to topics, or we can open up the text book or curriculum or plan. It will surely lower the efforts and maximize efficiency. It will be much faster than traditional way. If we can’t manage an interactive display then a projector and screen would work as a substitute. Projector should be connected to a computer so that contents can be displayed on the screen.
For viewing contents we need proper software installed on the computer. For video we need video player and for document file we need document reader.
Moreover interactive software can be used for quiz or multiple choice type questions.

Final Words

Digital content, e-learning, multimedia classroom can pave the way to a more effective, more enjoyable and less effort demanding classrooms. Where learning will be fun, interesting. This whole idea is still flourishing, more and more efforts should be given in this particular area.
First of all, these contents should be free for everyone. As a developing country where a good amount of people live under the poverty line, many of us won’t be able to buy digital contents.
Secondly, steps should be taken so that people all over the country can access these contents. If we think about a rural area or a remote village where computer or internet is not available, steps should be taken to make sure that those areas are brought under coverage.
Thirdly, if we think about schools that are situated in the city, capital city, these schools are well off, so they can easily set up the necessary hardware and software that is needed. But schools located in villages might not be able to spend that much money, government should help them to set stuffs up.
Next a very good initiative was Doel laptop, I have no idea why it was stopped.  It was a very affordable piece of hardware. With only 13K BDT anyone can get this and it is enough for running software that can show PDF documents and videos. So, with this anyone can use the positive side of digital contents.
Moreover teachers can use this Laptop in their classroom to show slides, videos, documents, animations etc.
Trained people should come forward to create digital contents.