Shaunak's Universe

A regulated 5 volt DC supply is essential for powering micro-controller and TTL based circuits. The output of most wall-warts and adapters is to rippled and impure for use in digital circuits. Lets build an inexpensive power supply using some discrete components and a fixed voltage regulator IC.

You will need:

• a step down transformer [12V]
• four silicon diodes [1N4007]
• a resistor [47Ω]
• capacitors [2 x 220µF, 0.3µF and 0.1µF]
• three terminal voltage regulator IC [LM7805]
• a small general propose PCB, some wires, and a suitable output port (I use a
• audio connector).

The circuit of the supply is as given below:

Fig: Circuit Diagram, click to expand.

A Picture of all components you will need, a resistor, capacitors, a regulator and diodes:

Fig: Components, click to enlarge.

The circuit consists of three main blocks, the rectifier, filter and regulator. The rectifier is used to transform the mains AC voltage to a suitable DC voltage. The output of the rectifier is however an impure DC signal so we use a filter to clean the signal and finally a regulator to deliver precisely 5 volts, irrespective of the load connected to the output.

Rectifier

It consists of a transformer and a diode bridge. The diodes are standard silicon 1N4007 diodes. We have chosen a 12V transformer because the regulator IC needs at-least 7.5V of input voltage to function properly.

Filter

We use a pi-filter here. The two 220µF capacitors and resistor form the filter. Pi-filters are great for light load applications like digital circuits. Be sure to check the polarity of the capacitors before connecting them. The resistor shown above is one rated to dissipate up-to 5W of power across it. You may use smaller 3W resistors, but availability may be an issue. Don't use the tiny 0.25 W or 0.5W ones though.

Regulator

The voltage is regulated by three terminal voltage regulator IC – LM7805. This regulator provides stable 5V DC output against large fluctuations in input voltage and load. It also has internal protection circuits which 'brownout' the device when overloaded. To decide the pin-outs, hold the regulator with its face towards you and legs pointing upward, the pin to the right is the input, middle pin is ground and left most pin is output.

Construction Tips

• The transformer can be made to snugly fit onto the PCB by bending the screw mounts under and around the board as shown in the picture below.
  
  
• A 6.3mm or 3.5mm female mono TRS connector (tip, ring, sleeve), also known as an 'audio jack' serves as a great output port. The power can then be delivered via standard audio cables.
• Since the power resistors is quite large, solder it vertically to save space on the board.
• Mount the entire board on thermocol when finished to prevent accidental short circuits.

The finished circuit fits neatly into a 2” by 1.5” PCB, excluding the output jack and plug. You can also include a small switch at the out-put for easy operation. The IC can be heatsink-ed on multiple layers of aluminum foil to dissipate the heat, or if you are enclosing this in a metal box, pin the IC to the sides of the box. This is not entirely necessary though.



Fig: The finished circuit, click to enlarge



Fig: 5.03 V, click to enlarge

Links:

TRS connector: http://bit.ly/1ropoc
LM7805 data-sheet: http://bit.ly/15iCku

Questions and suggestions are welcome, please use the comment form below.

Update: You can grab the Eagle CAD project files, including PCB layout here: http://www.mediafire.com/?mqjiwcneyy4

If you are unhappy with the quality of service of your current mobile service provider and want to shift service providers without having to change your phone number, you will now be able to do so seamlessly. All a matter of submitting an application and waiting for a couple of days.

The TRAI on Wednesday announced a framework for 'mobile number portability' which will allow subscribers, who fulfill TRAI's basic requirements to switch service providers without changing numbers.

You will be eligible to shift providers only if you have been a subscriber of your mobile operator for more than 90 days, and have no outstanding payments due towards the operator. The basic steps for changing service providers are:

• You need to submit an application to both, the provider you are moving from and the provider you are moving to.
• Once the application is submitted, your provider will validate your application within 24 hours.
• If you meet all the basic requirements, your application will be approved and your provider will be shifted within 36 hours. For subscribers in Kashmir, Assam and North East service areas, this deadline is set to 10 days.
• Providers may charge a fee for this service.
• If you change your mind, you may revoke your application within 24 hours. The fee however will not be refunded.

A complete list of requirements and guidelines can be found in section 10 through section 12 of the TRAI press regulation. A word of warning though, it is not an easy read. Download it from here: http://bit.ly/14wVpz

What do you get when you connect a country, with one billion people, with lots of free time, to the internet? Human generated spam.

If you have ever visited any major Indian web publisher, chances are you have run into it already. Sify, MSN India, Rediff, IndiaTimes, you name it. Any exposed comment form, potentially becomes a candidate for parasitic unsolicited advertisement.

It's a sure bet in Vegas that any visitor to one of these Indian web portals will be greeted to at-least one such comment:

“Dear Friends, Are you interested to make Rs.20,000 to Rs.1,20,000 A Day ? This is not a get rich quick scheme. This is a legal opportunity to make good money."

Fig: Human Generated Spam.

I do not wish to imply that this enthusiasm towards making easy money is limited to the Indian subcontinent alone. But the ratio of parasitic advertisement to genuine user feedback is alarmingly high in web sites targeted at audiences in India and her neighbors.

Humans, with lots of free-time, access to the internet and a desire to make easy money, become highly efficient spambots. Bots, capable of defeating most anti-spam measures with biological precision and flooding sites with 'piggy-back' advertisements and referral links, in hope of improving their bank balance.

What's The Harm?

The internet by nature depends and thrives on users and their generated content. If the very content that is to drive these sites turns out to be unsolicited advertorials, the very foundation is shaken. That coupled with the fact that these spam comments considerably subtract from user experience. They serve as a major annoyance to genuine traffic, driving it away faster than you can say Web 2.0. No genuine users, no good content, no advertisement, no dough. It a simple equation really.

Advertisers pay for advertisement on sites because they want to get a message to the site's traffic, who they view as potential customers. Now, if a large percentage of traffic comprises of 'micro-advertisers' themselves, who do not really form 'customer candidates', advertisers would definitely not like to pay for it. Gradually, but surely, advertisers are going to start recognize this 'undesired' traffic factor in Indian sites, if they already haven't, They would reluctant towards advertising on India-centric sites at the same rates they pay internationally.

Thus, while the regular Indian 'comment-to-comment salesman' may seem harmless, comic, and a integral part of the Indian way of life, they damage the prospect of Indian internet and new age businesses.

And lastly it leaves us to wonder, does anyone ever make any money this way?

Mimicry is said to be the best form of flattery. But you cant be too pleased with it if it causes you a loss of revenue. Riding on twitter's phenomenal success and their own recent lack of it, Yahoo has launched its 'adaptation' of it and christened it, Meme.

Meme does manage to strike a chord. Its fresh, well designed and smooth. It has its own set of innovations and is based on a tried and tested idea. Right from the name to the interface, everything is dynamic, fun and slick. Those familiar with twitter (who isn't?) will be right at home with Meme. The underlying concept is the same. You post short messages which show up in your followers time-line and vice-versa.

Fig: Screenshot of the interface.

The primary variation from twitter is that Meme allows you to post four types of content. Text, Photo, Video and Audio. Photos can be uploaded from your hard drive but video and audio need to be hosted else where. This is for obvious storage space constraint reasons. Yes, computer storage has become cheap over the years, but it is still not cheap enough for Yahoo to allow users to upload a gazillion terabytes of audio and video content.

I found the concept of audio posting to be unique and thought provoking. All around us, internet media nonchalantly ignores the most basic form of human communication, speech. While videos and images are streamed around, the simple human voice is not paid too much attention. It will be really nice if Yahoo allows users to upload audio directly from their hard drives, or perhaps, capture from their microphones.

Fig: Audio posting interface.

Meme faces unrelenting competition it faces from the Goliath of micro-blogging, Twitter. That, added to Yahoo's recent spate of failure with social media, Meme's future is questionable. Full marks to yahoo for trying though.

Meme is currently in closed Alpha. I was sent an invite by Pallab [Thanks!] and now I do have a few invites to send out in turn. If you would like one please leave a comment here or message me on twitter.

My Meme is: http://meme.yahoo.com/shaunak

A video recording of your screen or desktop can be greatly useful when trying to explain some steps to someone, or showing off your Minesweeper skills. All you need is a screen capture tool like Istanbul. It can be downloaded from: The Istanbul homepage or its Linuxappfinder listing. Istanbul should be also be available on the repositories of all major distros. To install Istanbul on Fedora, open the terminal and type:

su -c 'yum install istanbul -y'

Or you can use the package manager [System » Administration » Add/Remove Software]. Ubuntu users might want to refer to the community documentation.


Fig: The Package Manager

Once installed, run it. It shows up as a red dot in the task-bar. Right clicking it brings up the options and configuration menu, and left clicking it starts the recording. You can select an area or window to record, or record your whole screen. Some basic scaling options are also available.


Fig: Taskbar Icon


Fig: Options Menu

To stop recording, click the icon again. The application will then prompt you to save the screencast. Istanbul currently saves to Ogg Theora format only. The saved video can be played back on VLC media player.


Fig: Save Options

Sharing the Screencast

Dailymotion is the only major video sharing site that supports direct Ogg Theora upload and sharing. Youtube and the others transcode it to propitiatory formats. But that should hardly matter, since the end result achieved either way. There is also a HTML < video > tag. Ogg Therora video is supported via the Video tag in Firefox and Opera. Here is a short sample screen cast in which I use Linear's SPICE simulator to demonstrate a series positive clipper circuit.

Adrian Sutil put Force India on the front row of the starting grid at Monza by qualifying in his VJM02. Hamilton just managed to grab the pole from Sutil in the closing seconds of the third qualifying session. Teammate Vitantonio Liuzzi, who was in the car replacing Giancarlo Fisichella, qualified a respectable seventh. A small note of vindication for Force India fans; Giancarlo Fisichella, who moved to Ferrari from Force India, qualified fourteenth.

This remarkable performance goes another step towards erasing the 'backmarker' tag off Force India. It shows that the strong performance at Spa was not simply luck and that Force India has developed a highly effective car that can perform well in a wide variety of circuits and conditions. The car is well balanced, reliable and highly competitive. The team have done a tremendous job of putting together a top class car on a limited budget.

The Italian circuit, Autodromo Nazionale Monza is a wide and clear track, with long straights and minimal curves. Rich in history, heritage and atmosphere. It is home to the Ferrari Racing team. The long straights will heavily favor the KERS enabled cars, but the curves are broad and offer plenty of overtaking opportunity.
It was at Monza, that Michael Schumacher announced his retirement from Formula 1 racing at the end of the 2006 season, after winning the 2006 Italian GP.

Although a pole finish may be a long shot, a third place for Force India looks feasible. But then again, optimism never hurt anyone. Did it?

Links:

• Qualifying Results: http://bit.ly/3Y7s9s
• Autodromo Nazionale Monza: http://bit.ly/zqU0e
• How the VJM02 is built: http://bit.ly/2rv49