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Showing posts with label Technology. Show all posts
Showing posts with label Technology. Show all posts

Saturday, August 15, 2009

Wireless intercoms system



Wireless intercoms are great for communicating with your family and adding security to your home. Installing these systems is as easy as it can get. You don’t have to worry about re-wiring your house or tying into the existing wiring. These intercoms come ready to go right out of the box.

When choosing a wireless intercom system for your home you want to make sure you choose one that will work for your family. Take into consideration how many units you will need for your home. Also, you’ll want to choose a system that works on the right frequency depending on your needs.

Wireless home intercom systems today work in different ways depending on the frequencies that they use. Some systems use a powerline carrier system. This type of wireless intercom system utilizes the electrical system of your house to transmit and receive signals. These systems are prone to interference from appliances using the same electical system of your home.

Some wireless Intercoms use a wirefree 900 MHz wireless system which transmits and recieives messages through airwaves like a conventional radio using the 900MHz frequency range. These systems generally run on batteries but also can be used with a separate power addaptor.

Wireless Intercom Systems using a multi-use radio service or MURS, is said to have a broader frequency range in comparision to the powerline carrier and wirefree systems. These systems are better for cutting down on interference from other systems and also have channels to allow you to convers on a particular channel without fear of being overheard by others using the same frequency.

Install a wireless home intercom system in your home can bring you lots of benefits, adding security and convenience to your life.

Wireless intercom doorbell systems help provid security and convenience to your home by allowing you to know who is at the door before you allow them entry into your home. This can be especially usefull for babysitters or even older children who can stay at home alone.

A wireless video intercom is composed of the following parts: a camera, a doorbell unit, and a small video screen. The camera is placed outside your door and feeds you the image of your visitors. It is usually waterproof so it can withstand rain and harsh weather conditions. Some video intercom models have cameras that are equipped with infrared technology to enable you to see the person outside your door even when it is dark and the lights are turned off.

Real time audio and video are transmitted to the intercom unit inside the house when somebody presses the doorbell outside. Because of this feature, many families opt to install a video intercom in their house because it enables them to see and interact with the people outside their door, thus, making it easier for them to identify their guests. Some models also allow you to control the outdoor camera and monitor what is happening outside.

For added security some wireless door intercom systems allow you to unlock your door or gate through the intercom unit.

Wireless intercom outdoor systems are made to stand up to inclement weather conditions. Intercom systems are becoming more advanced as manufacturers of such electronic devices are keen on making many improvements to their products to keep up with the changing security needs of their customers.

Friday, August 14, 2009

Utilizing Solar Energy in Pakistan

In these days of escalating oil prices, it’s becoming extremely difficult for a common citizen to pay off monthly electricity bills. The bills keep soaring day by day and there seems to be no respite in foreseeable future. These bills can be reduced by resorting to other methods of generating electricity, solar being one of them.

This article dwells on the discussion regarding production of electricity through solar means and discusses a cost-effective strategy to achieve this end.

The photo above shows Solar Panels being used for water extraction in village Rarkou in Nagarparkar, Sindh

The use of solar energy for the generation of electricity is not something new. Most of the countries are doing it successfully for decades and their population benefiting through the use of this free resource. But, to most of the people, it may still look like a mystery. These days, this energy is being utilized to light our homes, run fans, provide power to our fridges and microwave ovens, assist in warming our homes and swimming pools, provide power to our gardens and street lights, run our TVs and computers, and extract water from the sub-soil for irrigation purposes.

A practical example of the use of solar energy could be seen in some villages of Pakistan where each house has been provided with a solar panel that’s sufficient to run an electric fan and two energy saving bulbs. Prior to this arrangement, the whole village used to be plunged in pitch dark during night. One such example is the village with the name of Narian Khorian, some 50 kilometers away from Islamabad, where 100 solar panels have been installed by a local firm, free of cost, to promote the use of solar energy among the masses. Through these panels, the residents of 100 households are enjoying light and fan facilities. Had these panels not been installed, the people living in this area wouldn’t have even dreamt of getting this facility for decades as the provision of electricity from the national grid was a far cry due to the difficult terrain and high expenses involved.

A layman would normally be interested in knowing as to how electricity could be produced using energy from the sun. Simply put, it can be said that the basic item required to generate this electricity is a solar cell, approximately 2 inches x 1/2 inch in dimension. These cells may be available in other dimensions as well. Some 80 to 100 or even more such cells are pasted on a tampered glass sheet whose dimensions are generally 1.5 feet x 4 feet. The glass sheet with cells pasted on it and inter-connected, is called a solar panel. The light from the sun is used to generate electricity through these cells. It may be clarified that it’s the sun’s light and not its heat that produces electricity. The solar cells are called photovoltaics (PV); the word Photo meaning light and voltaics electricity. The life of a solar panel is approximately 20 to 25 years!

To give you an example of the use of solar energy, you must have noticed solar panels installed on poles along with the telephone booths on your left hand side while commuting on the Motorway. Each of these telephones is being powered by this panel. A battery is installed beneath each solar panel to store energy for keeping the telephone in operation during night when there’s no sun light. It’s a stand-alone system, entirely powered by solar energy. During emergency, the commuters make use of these telephones and call for help.

To give you another example, if you happen to drive from Rawalpindi (Faizabad) towards Murree on the newly constructed Murree Road, you would see on your right hand side blinking red hazard lights installed at the top of each WAPDA pole. Each of these lights is being powered by a stand-alone solar system i.e. a solar panel and a battery. Just imagine, how much expensive and full of hassle it would have been if solar panels weren’t used for this purpose and these lights were provided normal electric connections!

In the photo above, solar panels are visible towards left. These Solar panels are being used for providing electricity to extract water and drip irrigation system. Solar panels are provided by Thardeep Rural Development Programme (TRDP) where as Micro Drip has provided the drip irrigation in a Nagarparkar, Sindh village called Wandhan jo Wandio.

The region of Nevarra, Spain, is generating 70 per cent of its electricity through solar and wind energy. And, mind you, this region doesn’t have any coal, gas or oil of its own. It’s really a classic example of making the best use of renewable energy in any country of the world! But, the question that automatically crops up one’s mind is: “If it can be done in Spain, why can’t it be done in our country?” The answer is a big “Yes”.

I will substantiate my statement by presenting you a strategy which, if followed, could be instrumental in generating this electricity in the most cost-effective manner. The cost of the solar systems can be brought down if we go for the manufacture of solar panels in country. Solar panels basically utilize solar cells in their manufacture. . In one panel, approximately, 80 or more solar cells are used, depending upon the power required and the electric gadgets you want to run utilizing these panels. Each solar cell costs approximately Rs. 1000 if imported from abroad. These cells would be required in millions or may be in billions if requirement of the whole country is to be met.

We cannot import such a huge quantity of solar cells from other countries due to financial constraints. So, naturally, there would be no other option but to resort to manufacturing these cells in our own country. Once it has been decided in principle to manufacture solar cells in Pakistan, then we would look for three basic requirements i.e. raw material, trained manpower and necessary infrastructure.

The basic raw material (quartz) is available in abundance in the northern areas of our country. But, this raw material is useless for us as far as its purification and development to a stage where this raw material could be converted into solar cells is concerned. This equipment will have to be imported; but it would be a one-time investment. One would be surprised to know that this raw material is being utilized by the local population of Northern areas for raising the walls of their houses in place of bricks as the poor simpletons don’t know its value. Some of them take it for marble as well!

The other raw material required to manufacture solar cells is silica (sand) which’s in inexhaustible quantity in River Sindh as water these days is otherwise in less quantity in our rivers. At least we should make use of silica in the manufacture of solar cells. So, to venture into manufacturing of solar panels, both the raw materials are available.

The other requirement is that of manpower. I have no qualms in making a statement here that we have the finest and the most hard-working, skilled manpower available in country. From my personal experience, I could say with conviction that the retired personnel of the defence services who have been working on electronics and telecommunication equipment during their service careers would be the best choice for deployment on the manufacture of solar panels and cells. These people are highly skilled and disciplined and get retired at an early age. Shaheen Foundation, Islamabad maintains an up-to-date computerized record of such personnel who are just a telephone call away. The expertise of such workers is not less than any worker deployed in the western countries for such jobs. The only difference is that a European worker of such calibre gets US $ 45 per hour whereas a Pakistani worker, if he is paid $5 per hour (or even less) in his own country would be the happiest man around.

While starting manufacturing of solar cells, it would be advisable if we do it in collaboration with a world-renowned company as India has done. It had a joint venture for the manufacture of wind turbines with a company that has 26000 wind turbines to its credit! This company has a name in wind industry and its wind turbines are being used the world over! This way, we would lay our hands on the best and the latest technology in the field of solar energy and our manpower would also be trained through short orientation courses as they already possess sound knowledge and strong technical base. By adopting this strategy, the cost of the solar cells is bound to reduce drastically with the result that these “prohibitively costly” solar panels would come within the reach of every citizen and the day wouldn’t be far when we’d see these panels mounted on each and every roof in each city of the country including the rural areas. The energy crisis would thus be a history for our citizens.

Presently, there’s one and the only one factory manufacturing solar panels in Pakistan which’s located at Hattar Industrial Area near Taxila, 1-1/2 hours drive from Islamabad. But, due to various compulsions, it’s importing these costly cells from abroad at an exorbitant price.

In a solar system, apart from solar panels (which include solar cells), tampered glass sheets, batteries and inverters (to convert DC electricity into AC) are also used. We have innumerable factories producing good batteries in our country; so there’s no problem in their manufacture! Rather, we can go for maintenance-free batteries! Just augmentation of the manufacturing facilities of the existing factories is required.

Regarding tampered glass, we have many glass manufacturing factories in Pakistan. In this case as well, we’ll have to augment their existing facilities to produce tampered glass of required specifications. Again, I may mention here that it’s a tampered glass sheet on which solar cells are pasted; this glass sheet with solar cells pasted on it is called a solar panel. Tampered glass is after all glass and nothing else. Required machinery could be imported and installed in our existing glass manufacturing factories. There’s no need to set up separate, dedicated factories for each item. Let’s make best use of our existing facilities with a bit of augmentation. This approach would be highly cost-effective!

As far as converter is concerned, we’re already manufacturing thousands of them for our UPS’s which are installed in each and every house now, thanks to load shedding!

It’s generally perceived and is true also that the cost of using solar energy is prohibitively high. But then somebody should answer my question too: If the cost is really that high, then how Nevarra is coping up with this high cost? The authorities in Nevarra must have taken some tangible measures to bring the cost down, out of which, one could be the manufacture of solar panels including solar cells indigenously. If the use of solar energy was that costly, then Nevarra would have abandoned this initiative long ago. I would also like to ask such people: If the cost is that high then why the entire Europe is still making use of this form of energy while the sunshine is very scarce in the European countries. We have to adopt measures to bring this cost down so that an ordinary Pakistani could purchase this system. And to do that, all the points are in our favour.

Investing in a solar electric system has many benefits. It allows you to produce your own electricity with no noise, no air pollution, and no moving parts. Moreover, this system would never run out of fuel (sun light), and it will help reduce the amount of greenhouse gasses emitted by coal and natural gas-fired power plants. Due to these unique characteristics, solar electric technology has been called “the ultimate energy source for the 21st century”.

There are countries where people using solar energy have covered the entire roof tops of their houses with solar panels. They’re generating electricity which is meeting, if not full, at least a part of their electricity requirements. As the cost of electricity provided by utility companies rises, they would be compelled to resort to solar energy in a big way.

In some countries, solar systems have become so popular that senior citizens are investing their pension money in solar parks. The solar panels in these parks are connected to tracking devices that generate up to 40% more energy than fixed systems. One solar park is owned by as many as 700 to 800 individual investors, each of whom owns one or two large solar panels in that park. The income received from these panels adds to their pension amount and is guaranteed to be paid by the utility companies for 25 years. The cost of such panels is substantially reduced with a tax concession from the government. As the annual income is guaranteed, there is a long waiting list of willing investors.

Another use of solar energy could be in the form of solar cookers. A solar cooker is nothing but a concave mirror fixed on a metallic stand. The mirror converges sun’s rays at a focal point through reflection where a utensil is placed that gets heated. I have myself taken tea prepared on a solar cooker! Just imagine! Six thousand refugee families in Sudan are making use of these cookers successfully. Earlier, the women folk used to go out and bring thorny bushes as fuel for cooking purposes. With the arrival of the solar cookers, this practice has ceased and the forests are also saved. The people living in our hilly areas can emulate their example and use these cookers which might not be costing more than Rs. 1000 each! I may mention here that a solar cooker doesn’t utilize solar cells. It utilizes just the reflection of sun’s rays, and the sun’s rays are free!

To conclude, it can be said that solar energy is one of the most viable options for Pakistan. Even countries with less sun light are making the best use of this free resource (sun light). We, in Pakistan, aren’t short of sun light as sun shines on the entire length and breadth of the country throughout the year. We can make use of this inexhaustible resource and contribute towards meeting the shortfall of electricity. If we don’t do it now, then it would be just a matter of time when oil would be touching $ 200 a barrel and the World Bank would be pressing us hard to increase the electricity price by 100 %. Then, we would be left with no option but to grab every opportunity to generate electricity from any available source, what-so-ever! We should opt for the manufacture of solar panels including solar cells in-country. For this purpose, we should establish not one but several factories for the manufacture of solar panels and cells in Pakistan. We have unimaginable quantities of raw material at our disposal and our manpower is second to none. With the availability of abundant raw material at throw-away price and the cheapest yet highly skilled technical manpower, the profits that would be accrued is mind boggling!, It’s said that if enough solar panels using indigenous solar cell are installed and energy efficiencies are ensured, the home owners can receive a zero power bill!

Author’s Contact:

Written by Air Cdre (R) Azfar A Khan

Author can be reached at: azfar44@hotmail.com

Photo Credits:

Photos for this post are courtesy of Saqib from his album Thar and Everywhere.

Small Solar Electric Systems


A small solar electric or photovoltaic (PV) system can be a reliable and pollution-free producer of electricity for your home or office. And they're becoming more affordable all the time. Small PV systems also provide a cost-effective power supply in locations where it is expensive or impossible to send electricity through conventional power lines.

Because PV technologies use both direct and scattered sunlight to create electricity, the solar resource across the United States is ample for small solar electric systems. However, the amount of power generated by a solar system at a particular site depends on how much of the sun's energy reaches it. Thus, PV systems, like all solar technologies, function most efficiently in the southwestern United States, which receives the greatest amount of solar energy.

You can also use PV technology to provide outdoor lighting.

Here you can find the following information:

Solar Water Heaters


Solar water heaters—also called solar domestic hot water systems—can be acost-effective way to generate hot water for your home. They can be used in any climate, and the fuel they use—sunshine—is free.

How They Work


Solar water heating systems include storage tanks and solar collectors. There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don't.

Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In one-tank systems, the back-up heater is combined with the solar storage in one tank.

Three types of solar collectors are used for residential applications:

  • Flat-plate collector

    Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors—typically used for solar pool heating—have a dark absorber plate, made of metal or polymer, without a cover or enclosure.

  • Integral collector-storage systems

    Also known as ICS or batch systems, they feature one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues on to the conventional backup water heater, providing a reliable source of hot water. They should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather.

  • Evacuated-tube solar collectors

    They feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin's coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications.

There are two types of active solar water heating systems:

  • Direct circulation systems

    Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes.

  • Indirect circulation systems

    Pumps circulate a non-freezing, heat-transfer fluid through the collectors and a heat exchanger. This heats the water that then flows into the home. They are popular in climates prone to freezing temperatures.

Illustration of an active, closed loop solar water heater. A large, flat panel called a flat plate collector is connected to a tank called a solar storage/backup water heater by two pipes. One of these pipes is runs through a cylindrical pump into the bottom of the tank, where it becomes a coil called a double-wall heat exchanger. This coil runs up through the tank and out again to the flat plate collector. Antifreeze fluid runs only through this collector loop. Two pipes run out the top of the water heater tank; one is a cold water supply into the tank, and the other sends hot water to the house.

Passive solar water heating systems are typically less expensive than active systems, but they're usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems:

  • Integral collector-storage passive systems

    These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs.

  • Thermosyphon systems

    Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but contractors must pay careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems.

Illustration of a passive, batch solar water heater. Cold water enters a pipe and can either enter a solar storage/backup water heater tank or the batch collector, depending on which bypass valve is opened. If the valve to the batch collector is open, a vertical pipe (which also has a spigot drain valve for cold climates) carries the water up into the batch collector. The batch collector is a large box holding a tank and covered with a glaze that faces the sun. Water is heated in this tank, and another pipe takes the heated water from the batch collector into the solar storage/backup water heater, where it is then carried to the house.

Solar water heating systems almost always require a backup system for cloudy days and times of increased demand. Conventional storage water heatersusually provide backup and may already be part of the solar system package.A backup system may also be part of the solar collector, such as rooftop tanks with thermosyphon systems. Since an integral-collector storage system already stores hot water in addition to collecting solar heat, it may be packaged with a demand (tankless or instantaneous) water heater for backup.

Saturday, August 1, 2009

What is WiMAX Technology

WiMAX system stands for Worldwide Interoperability for Microwave Access. WiMAX system technology is a telecommunications technology that offers transmission of wireless data via a number of transmission methods; such as portable or fully mobile internet access via point to multipoints links. The WiMAX system technologyoffers around 72 Mega Bits per second without any need for the cable infrastructure. WiMAX system technology is based on Standard that is IEEE 802.16, it usually also called as Broadband Wireless Access. WiMAX system Forum created the name for WiMAX technology that was formed in Mid June 2001 to encourage compliance and interoperability of the WiMAX IEEE 802.16 standard.

WiMAX technology often misinterpreted by the people by the names of mobile WiMAX system, 802.16d, fixed WiMAX system and 802.16e. Actually 802.16-2004 or 802.16d is developed by the third party as a standard and it is also referred to called as Fixed WiMAX system because this standard is lacking behind just because of the non-mobility feature that’s why it’s often called as Fixed WiMAX system. During the maturity period of WiMAX system technology system some of the amendments were made to the above mentioned 802.16d and they referred this amending standard as 802.16e. 802.16e introduced mobility and some other features amongst other standards and is also known as Mobile WiMAX system.

Less than one out of five people of the developed world and an even smaller, little percentage of people across the world have broadband internet access today. Existing technologies such as Digital Subscriber Line (DSL), cable, and fixed wireless are overwhelmed by expensive installs, problems with loop lengths, upstream upgrade issues, line-of-sight restrictions, and poor scalability.

WiMAX system is the next stage to a broadband as well as a wireless world, extending broadband wireless access to new locations and over longer distances, as well as considerably reducing the cost of bringing broadband to new areas. WiMAX system technology offers greater range and bandwidth than the other available or forthcoming broadband wireless technologies such as Wireless Fidelity (Wi-Fi) and Ultra-wideband (UWB) family of standards. It provides a wireless alternative to wired backhaul and last mile deployments that use Data Over Cable Service Interface Specification (DOGS1S) cable modems, Digital Subscriber Line technologies (DSL), T-carrier and E-carrier (Tx/Ex) systems, and Optical Carrier Level (OC-x) technologies. (Jiffy Networks, 2006)

The general initiative of metropolitan area wireless networking, as envisioned with 802.16, begins with what is called fixed wireless. A backbone of base stations is connected to a public network, and each base station carries hundreds of fixed subscriber stations, which can be both public hot spots and fire-walled enterprise networks. Later in the development cycle of 802.16e, WiMAX system is expected to encourage mobile wireless technology specifically wireless transmissions directly to mobile end users, This will be similar in function to the General Packet Radio Service (GPRS) and the one times Radio Transmission Technology (RTT) offered by mobile phone companies.

New organizations as well as individuals are increasingly adopting broadband, whereas those already using broadband are becoming dependent on it and are demanding better services with added benefits. To support this exceptional new demand, WiMAX system has emerged as a feasible solution, because of its inherent features that holds great promise for the future of wireless communications.

There has been a lot of excitement about WiMAX system and the impact that this standards based wireless network technology will have on the broadband access market. All this hype has generated great expectations, and the industry has responded with exceptional aggression and commitment toward taking broadband to the next level with WMAX system.

WiMAX Features

WiMax have lots of features to its name. Lots of limitations were found as the use of Wifi technology grew around the world, to overcome these limitations and to invent better and more efficient wireless technology was realized which turned out to be WiMax. WiMax have lots of features which helped in increase usability of WiMAX around the world. It is still not been used to its full potential that’s why there may be more features which may not be known as yet, more and more exploration is required to get WiMax technology to its full use, however we know some of its significant features which are important enough to mention.


Long Rang


Connectivity from long range is much highlighted feature of WiMax. Theoretically it is believed that WiMax technology provides range up 30 mils (50 Km). However in practical experience it is observed that it provides range up to 10 km which is still huge break through in long range connectivity. Users can connect to WiMax base station using SUI from their homes.


Mobility


Another significant feature of WiMax technology is the connectivity on move. This technology amaze the world hence increasing the use of WiMax in some parts of the world dramatically. Especially to the urban places where cables and other network equipments are not feasible to install. Using its long range feature it provides connectivity on such area where other means of high speed Internet are not available.

The other major mobility feature of WiMax technology is that connecting devices (Laptops, PDA etc) can move in certain area and still be connected to the network.


Interfacing


WiMax radio signals are broadcasted to its subscribers from base stations. Base stations are area where all necessary hardware is installed to provide WiMax with in its range. Since one Base station covers limited range so connecting multiple base stations to each other increase that much range for connectivity. Connecting multiple base stations to each other is not big task and can be perform in few hours.


Accessibility


Accessing WiMax base station is not a difficult task, its long range capability provides connectivity at home from base stations within the range. To get high speed internet it’s only required to be because subscriber to WiMax service providers. They will provide you appropriate hardware to become of the subscriber. Installing the hardware is very easy; it is just plug and play. Hardware mostly connects through USB ports or Ethernet and connection can be made by clicking just a button.

There may be several other features which will surely come up as the growth of WiMax technology increases.

WiMAX : Latest for internt

A general perception for WiMAX is that it delivers high speed data that is 70 Mbps 50 kilometers, but in factual situation WiMAX do some thing different. It increase Bit error rate if it operates at 50 kilometers, that’s why it important to use lower bitrates. If the range is low it helps in operating at higher bitrates.


As we know, there are majorly two types of WiMAX, fixed WiMax and Mobile WiMax, in fixed WiMAX network higher gain directional antenna is installed near the subscriber location which helps in increasing signal strengths, better data rate and throughput. However mobile networks are designed for indoors, it uses customer premises equipment (CPE) which is attached with computers and laptops or other WiMax products.


In mobile WiMax Omni directional antennas are used, which have lower-gain when compared to directional antenna; directional antennas are easy to use as they portable. 10 Mbps speed can be achieved within 10 km range if portable mobile WiMAX CPE used in line-of-sight. In contrast to this 10 Mbps speed can be delivered to only 2 km in urban areas as it is not possible to keep antenna on line-of-sight.


In current situation fixed WiMax throughputs 2Mbps at 10 km using high gain antenna. Higher gain directional antenna can be used with Mobile WiMax networks with good range and throughput but in result loose mobility.


As in all wireless or wired networks, the given bandwidth is divided among the users, it is same in WiMax also, available bandwidth is divided among the users in certain radio sector, and performance of the network can drop in case of many users in give sector. To improve the performance in this situation more radio cards are required to be installed in the base station for give sector.


Because of this varying performance of WiMax networks, lots architectures are incorporated into WiMax by independent development and within the 802.16j mobile multi-hop relay (MMR) task group.

Wednesday, July 22, 2009

The smallest USB









Due to the minimum dimension is the ideal solution for all mobile users.

Edimax Technology has introduced the smallest USB adapter on the market - a model EW-7711Utn comes with 40x16x7mm dimensions are achieved by the fact that this device has no external antenna.
Precisely because of the minimum dimensions, is the ideal portable solution for all mobile users and the USB adapter needed only to put in the appropriate slot, after which users can connect to wireless networks. EW-7711Utn supports 802.11b / g standard and is compatible with 802.11n technology, which enables speeds up to 150 Mbps

Edge Tech 128GB USB Flash Drive

Edge Tech announced their 128 GB USB Flash drive. Kingston’s announced their 128GB DT200 USBdrive in advance of Edge Tech’s announcement. But it is Edge Tech that has come out with the cheaper flash drive, Known as the DiskGo 128GB USB flash drive, this drive is more than $150 cheaper than theKingston USB drive.





The DiskGO drive will come encased in a durable aluminum housing with encryption software thrown into the mix for added protection. Edge Tech is also offering protection for your data with the inclusion of CryptArchiver Lite encryption software, a trial version of CryptArchiver which allows users to encrypt up to 25MB of data using 128-bit AES encryption. Edge Tech offers the full version of CryptArchiver for download through its support site which can encrypt up to 32GB, and exceeds the U.S. government standard for encryption strength. Users can choose which cipher method they prefer: 256-bit AES or 448-bit Blowfish encryption.

how the data is stored on a CD.

Data Capacity of CDs

Abstract
You can fit on a S/VCD without overburning:
- approx. 735 MB of MPEG data onto a 74min/650MB disc
- approx. 795 MB of MPEG data onto an 80min/700MB disc

You can fit on a CD-ROM without overburning:
- approx. 650 MB of data onto a 74min/650MB disc
- approx. 703 MB of data onto an 80min/700MB disc


Introduction

Let us ignore for now the terms of megabyte for CD capacity and try to understand how the data is stored on a CD.

As well all know, the data is stored digitally as binary data. This means, however the actual information is actually kept on the disc, this information is in the form of "1"s and "0"s. Physically, the information on a CD is as pits on a thin sheet of metal (aluminium).

An a CD-R disc, the data is physically on an organic dye layer which simulates the metal layer on a real pressed CD.


How is the information structured

Now, on the CD, the information isn't just organised from beginning to end willy-nilly. Otherwise, it would be really hard to find a useful piece of information on the CD.

Rather, the information is organised in sectors. Consider a sector as like a page in a book. Just like you are able to quickly find something in a book if you know the page number, you can quickly find something on a CD if you know the sector number.

Now, remember that the CD was original made to hold audio data. It was decided, that the CD would would 75 sectors per second of audio. Although I cannot guess where this number comes from, it is quite appropriate for the audio CD. It means that you can "seek" an audio CD accurately to 1/75th of a second -- which is more than enough for consumer purposes.

Now, with this in mind, we can work out the total data capacity of user data for 1 sector.


The total data capacity of user data of 1 sector on a CD

CD audio uses uncompressed PCM stereo audio, 16-bit resolution sampled at 44.1 kHz.

Thus 1 second of audio contains:
16 bits/channel * 2 channels * 44100 samples/second * 1 second
= 1411200 bits
= 176400 bytes

Since there are 75 sectors per second
1 sector
= 176400 bytes / 75
= 2352 bytes

One sector on a CD contains 2352 bytes max.



The concept of different MODES and FORMS of burning
Now, audio CD was well and good, but the medium would become much more useful if you could store other data on the disc as well. This became to be know as CD-ROM of course.

Now, the audio-CD uses the ENTIRE sector for audio data.

However, for CD-ROMs this caused a problem. Simply, CDs and the CD reading mechanisms were not 100% faultless. That is, errors (indeed frequent errors) could be made during the reading. For audio CDs, this does not matter as much as you could simply interpolate from the adjacent audio samples. This will obviously NOT DO for data CDs. A single bit error could lead to a program being unexecutable or ruin an achive file.

Thus, for CD-ROMs, part of each sector is devoted to error correction codes and error detection codes. The CD-R FAQ has the details, but in effect, only 2048 bytes out of a total of 2352 bytes in each sector is available for user data on a data CD.

This burning mode is either MODE1 or MODE2 Form1.



MODE2 Form2 sectors of VCDs and SVCDs
Now, for VCDs and SVCDs, the video tracks do not necessarily require the robust error correction as normal data on a CD-ROM. However, there is still some overhead per sector that is used for something other than video data (e.g., sync headers).

S/VCDs video tracks are burnt in what is called MODE2 Form2 sectors. In this mode, only 2324 bytes out of a total of 2352 bytes in each sector is available for user data.

This is MUCH MORE than for CD-ROMs, but still less per sector than audio CD.



The disc capacities of CD-ROMs, audio-CDs and VCDs
Now, obviously what ultimately determines the capacity of a disc is the total number of sectors it contains. This is similar to the total number of pages in a blank exercise book (if you recall the book analogy).

The secondary determinant is the burning mode of the disc.

For audio CDs, it is as if you could fill each page from top to bottom with audio data as the entire sector is used for audio data.

For CD-ROMs, it is as if you need to first rule a margin and then leave the bottom part of each page for footnotes (headers + ECC + EDC). The amount of text you can actually write per page is then less due to these other constraints.

For S/VCDs, we still need to rule a margin on the page, but we don't have to worry about the footnotes (headers). We can fit MORE text than a CD-ROM, but less than an audio-CD.

Now remember, 1 second on a CD = 75 sectors.

Thus:
- 74 min CD = 333,000 sectors
- 80 min CD = 360,000 sectors


Data capacity in Mb for an audio-CD
74 min
= 333,000 sectors * 2352 bytes / sector
= 783216000 bytes
= 746.9 Mb

80 min
= 360,000 sectors * 2352 bytes / sector
= 846720000 bytes
= 807.5 Mb


Data capacity in Mb for a CD-ROM
74 min
= 333,000 sectors * 2048 bytes / sector
= 681984000 bytes
= 650.4 Mb

80 min
= 360,000 sectors * 2048 bytes / sector
= 737280000 bytes
= 703.1 Mb


Data capacity in Mb for a S/VCD
74 min
= 333,000 sectors * 2324 bytes / sector
= 773892000 bytes
= 738.0 Mb

80 min
= 360,000 sectors * 2324 bytes / sector
= 836640000 bytes
= 797.9 Mb


Conclusions

As you can see, the often quoted capacities of 650MB and 700MB refer to CD-ROM capacities.

Due to the fact that S/VCDs use a different burning mode where MORE of each sector is available as user data, the relatively capacities are HIGHER.

Now, since S/VCDs are not composed of PURELY video tracks and have some unavoidable overheads, the actually total capacity left for video tracks is a few Mb less for each disc (about 735 Mb for 74min discs and 795 Mb for 80min discs). This is where the often quoted capacities of 740MB and 800MB come from. They are quite accurate.

All these capacities are available BEFORE overburning. Overburning is where you burn MORE sectors than the disc is rated for. If you overburn, you can typically achieve about 1-2 minutes of additional capacity (depending on your drive and media).

Tuesday, July 21, 2009

Bio Diesel

If you've read or watched the news lately, you've probably come across some article, snippet or sound bite related to oil and oil prices. Even in your daily routines, there's a good chance of someone mentioning it. Whether it's in automotives, economics, history, geography or politics, oil has managed to filter into almost every aspect of our daily lives. It's one of the most discussed (and controversial) commodities that consumers rely on daily. All of this talk about oil sparks continued interest in gasoline alternatives. Things like electric cars and hydrogen fuel cells are being talked about as feasible alternatives to oil. As technology improves, these concepts could become reality. But what about now?



Lost in the mix are the biofuels, fuels made from biological ingredients instead of fossil fuels. These starting ingredients can range from corn to soybeans to animal fat, depending on the type of fuel being made and the production method.

Generally speaking, biodiesel is an alternative or additive to standard diesel fuel that is made from biological ingredients instead ofpetroleum (or crude oil). Biodiesel is usually made from plant oils or animal fat through a series of chemical reactions. It is both non-toxicand renewable. Because biodiesel essentially comes from plants and animals, the sources can be replenished through farming and recycling.

Biofuels, such as ethanol made from corn and biodiesel made from soybeans,

Biodiesel is safe and can be used in diesel engines with little or no modification needed. Although biodiesel can be used in its pure form, it is usually blended with standard diesel fuel. Blends are indicated by the abbreviation Bxx, where xx is the percentage of biodiesel in the mixture. For example, the most common blend isB20, or 20 percent biodiesel to 80 percent standard. So, B100 refers to pure biodiesel.

Monday, July 20, 2009

Make Your Own Solar Charger




























Keep your gadgets powered even when the grid fails you








It's a dark and stormy night—too dark. Your home has lost power. Fortunately, you've got a fully charged power plant, built from an inexpensive solar panel and a rechargeable battery. Eight hours of sun will produce enough juice to watch An Inconvenient Truth—twice—on a portable DVD player. You can even find inverters that will turn the station into an AC outlet. Add additional panels and batteries, and you could power the margarita machine and the flat-panel too.



















Build a Solar Power Station
Cost: $150
Time: 3 Hours
Easy | | | | | Hard

Parts
Step-by-Step
  1. Build the case
    To make a cheap, eco-friendly case, we glued up bamboo flooring scraps (bamboo is fast-growing and renewable). Cut holes in the box for airflow and easy carrying, and build frames to hold the DC charger controller and the battery.
  2. Add the panel
    Attach the solar panel at an angle roughly equal to your latitude for optimum charging (go to census.gov/cgi-bin/gazetteer to find yours). Add a tilt bracket for additional adjustability. Leave space underneath both the panel and the controller for airflow.
  3. Wire it up
    Snip off the cigarette-lighter plug and solder the quarter-inch mono plug onto the "Y" adapter. Insert the mono plug into the 12-volt output outlet on the controller. Connect all four power leads from the battery and the solar panel to the controller's input terminals. Hook up the meter to the controller's input terminal for the solar panel. For more power, attach additional solar panels, and add extra batteries—but don't exceed the 12-volt rating of the controller.
  4. Connect the battery
    Test all connections with a volt- meter before attaching the battery. Connect the red wire with a female- terminal disconnect to the battery's positive (+) terminal, and connect the black wire to the negative (–) terminal. Place the station in the sun, and plug something in.