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Here’s a digital frequency comparator for oscillators that indicates the result through a 7-segment display and a light-emitting diode (LED). When the frequency count of an oscillator is below ‘8,’ the corresponding LED remains turned off. As soon as the count reaches ‘8,’ the LED turns on and the 7-segment display shows ‘8.’

This demo circuit uses two NE555 timers configured as astable free-running oscillators, whose frequencies are to be compared.

The circuit of the digital frequency comparator portion comprises two 74LS90 decade counter ICs (IC2 and IC6), two 74LS47 7-segment display driver ICs (IC3 and IC7), 74LS74 set/reset flip-flop (IC4), 74LS00 NAND gate (IC8) and two 7-segment displays (DIS1 and DIS2). The astable free-running oscillators built around the timers are the frequency sources for the corresponding counters.

When power supply to the circuit is switched on, timing capacitor C1 starts charging through resistor R1 and potmeter VR1. When the capacitor voltage reaches 2/3Vcc, the internal comparator of IC1 triggers the flip-flop and the capacitor starts discharging towards ground though VR1. When the capacitor voltage reaches 1/3Vcc, the lower comparator of IC1 is triggered and the capacitor starts charging again. The charge-discharge cycle repeats. That means, the capacitor charges and discharges periodically between two-third and one-third of the power supply (Vcc). The output of NE555 is high during charging and low during discharging of capacitor C1.

The other oscillator (IC5) works similarly. The oscillator frequency can be varied by the potentiometer (VR1 or VR2). Output pins (pin 3) of the oscillators (IC1 and IC5) are connected to the respective decade counters (IC2 and IC6) through the DPDT switch.

IC2 and IC6 count the initial eight cycles. IC 74LS90 is a 4-bit ripple decade counter. It consists of a divide-by-two section and a divide-by-five section counter. Each section has a separate clock input. The input of the divide-by-five section (CP1) is externally connected to the P output (pin 12) of the divide-by-two section (CP0). When the divide-by-two section receives clock pulse, it becomes a divide-by-ten counter.

Decade counter 74LS90 is reset by a high pulse at its pins 2 and 3. Initially, pins 2 and 3 are pulled down by resistor R2. The P through S outputs of IC2 are connected to the A through D inputs of IC3. Pin 11 (S) of IC2 is also connected to pin 3 of IC4(A) for providing the clock pulse. The count is displayed on the 7-segment display.

The 7-segment decoder/driver (74LS47) accepts four binary-coded decimals (8421), generates their complements internally and decodes the data with seven AND/OR gates having the open-collector output to drive the display segments directly. Each segment-driver output is capable of sinking 40mA current in the ‘on’ state. Pins 3, 4 and 5 of the display driver are connected to Vcc to disable the ripple-blanking input (RBI), blanking input (BI)/ripple-blanking output (RBO) and lamp test (LT).

IC3 provides segment data to the 7-segment display through current-limiting resistors R3 through R9 (each 220 ohms).

IC 74LS74 (IC4) controls the reset pin (RST) of NE555. It is a dual D-type flip-flop with direct clear and set inputs and complementary outputs. The input data is transferred to the outputs on the positive edge of the clock pulse. Since the Q output is connected to the data input D, the flip-flops work in toggle mode.

Initially, reset pins 1 and 13 of the flip-flops are pulled high via resistor R10. When the reset pin of any flip-flop receives a low pulse from NAND gate N2 of IC8, the flip-flop is reset and its Q output goes high. On receiving a clock pulse, the Q and Q outputs of the flip-flop go high and low, respectively, and the LED turns on. The low output of IC4 resets the oscillators. The reset signal is derived with the help of NAND gates N3 and N4.

When switch S2 is pressed, both the oscillators and the respective counters start working. As soon as any of the counters counts ‘8,’ the corresponding display shows ‘8’ and LED glows. This means that oscillator has a higher frequency. Now both the counters stop counting because the flip-flop output goes low to reset both the astable oscillators.

In case the frequencies of both the stable oscillators are same, both the displays show ‘8’ and LED1 and LED2 glow at the same time.

Sourced By EFY Author V. Gopalakrishnan

Here is a low-cost and simple wireless stepper motor controller using infrared signals. Using this circuit you can control the stepper motor from a distance of up to four metres.

The circuit comprises transmitter and receiver sections. The communication between the transmitter and receiver sections is achieved through infrared signals.

In the transmitter section, timer NE555 ICs (IC1 and IC2) are configured as astable multivibrators with frequencies of around 1 Hz and 38 kHz, respectively. The output of IC1 is given to reset pin 4 of IC2, so the 38kHz carrier signal is modulated by 1Hz modulating signal. The modulated signal from pin 3 of IC2 is transmitted by the infrared LED.  Resistor R5 limits the current through the IR LED.

The transmitted signal is sensed by IR receiver module TSOP1738 (IC6) of the receiver section and its output at pin 3 is used as clocks for dual flip-flop 74LS74 Ics (IC3 and IC4), which are configured as a ring counter.

When the power is switched on, the first flip-flop is set and its Q1 output goes high, while the other three flip-flops are reset and their outputs go low. On receiving the first clock pulse, the high output of the first flip-flop gets shifted to the second flip-flop. Thus on reception of every clock pulse, the high output keeps shifting in a ring fashion.

The outputs of flip-flops are amplified by the Darlington transistor array inside ULN2003 (IC5) and connected to the stepper motor windings marked ‘A’ through ‘D.’ The common point of the windings is connected to +12V DC supply.

To stop the motor, the flip-flops can be reset manually by pressing reset switch S1. On releasing the reset switch, the stepper motor again starts moving. If any interruption occurs between the transmitter and the receiver, the motor stops.

Sourced By EFY Author :  Jaydip Appasaheb Dhole

Come a long way from the days of dial-up net access with its lose service and broadband connections are now the example for lots of people around the globe. While lots of of the issues that dial-up users suffered through when utilizing their modems have been solved by the presence of an always-on connection, broadband modems and wireless routers can still cause headaches from time to time.

If you are facing a controversy together with your broadband connection & its source is not immediately obvious, take a glance at these broadband issues & fixes to help you to narrow down the issue:

Instead of being speedy to jump to the conclusion that you have got a local issue when you are unable to access a website, first decide with certainty that the trouble is not with the remote servers that you are trying to connect to. Even if the issue shows itself when visiting over site, it pays to be thorough before moving on to the next step.

Using your Windows command line, type ping google.com and hit the enter button. This will have your computer try to exchange tiny packets of knowledge with a popular web-site that you can trust is online and obtainable. If the ping shows as successful then you know that your computer is communicating with remote servers successfully; if not, you can assume the trouble is a bit closer to home.

Peripheral firmware trouble.
 more complicated machines that they serve, peripherals are computers , jogging their own operating method & so subject to the same glitches & issues that they regularly see on our PC. If the application operating your modem or router is acting up, there is sure fix: the power cycle.

Not  as fun to do as it is to say, power running basically means cutting power to the offending devices for a minute or, then plugging them back in. This will permit your modem & router to reboot, restarting all on-board application & resolving any related issues.

It is a common scenario: a controversy with a web connection leads us to check every facet of our network over and over again, only to find that the ethernet cable in the router had wiggled lose. While they regularly try to persuade ourselves that the issue could not be that simple, it often is. Whether you have children, pets or even a window open wide to permit a powerful breeze, wires and cables tend to get shifted around under any circumstances.

While it may appear redundant, always take the time to make sure that each necessary hard connection is solid & that all wires & cables are where they ought to be; even in case you solve only a single case of net trouble in every attempts this way, you are bound to save yourself both time & frustration!

Firewall

Sometimes the issue can be found right in front of you! Routers and modems are often painted as the bad guys in problematic net scenarios, but often the trouble can be a application issue on the computer itself. Given its nature, common piece of application that can add to connection issues is your firewall. While firewall application does a great job of monitoring and defending against undesirable connections between your computer and the outside world, the wrong settings can have your firewall blocking even you.

If you have only recently installed or updated your firewall and have subsequently faced a defective connection, the issue is  definitely there. Double-check your settings to be positive that they are correct and think about switching to an simpler firewall solution in case you don not need all of the complicated bells and whistles.

Your net service provider depends on a staggering amount of infrastructure to keep you connected and is subject to technical issues of its own from time to time. If you have thoroughly checked each potential issue area but continue to come up empty-handed, contacting your ISP for technical support and service information is the next obvious step.

Dear freinds you know about i pods ?I pods had been since their beginning in 2001, Apple iPods have been the product of choice for individuals who listen to digital music. Recently, Apple has branched out & allowed their iPods to display pics & play videos, but the music aspect of this digital media player is what lures hoards of people in to the Apple stores to buy an iPod.

Its simple design and large memory capacity have been defining features since the first generation. Apple iPods have come a long way since their creation, but despite all of the technological advancement, the basic form and structure has remained very similar. The iPod motif has now been emblazoned on separate pieces of hardware, including the video iPod, the incredibly little iPod Nano and the entry level iPod Shuffle. Each version is a separate entity, but each fills a niche wanted by consumers.

Starting with the iPod Shuffle, you have the lowest priced of all Apple iPods. It lacks an LCD screen and the famous touch wheel that gives you control over all of the other iPod products. In lieu you upload your play lists to the Shuffle and are given the choice to either listen to them in regular play mode or shuffle mode. The iPod Shuffle is available in sizes, gigabyte and half a gigabyte, meaning you can have up to hundred and fifty songs.

The next step up is the iPod Nano. This is the smallest of the actual Apple iPods. It contains a full color LCD screen which can be used to navigate through songs or display photographs. It is available in black or white and comes in a variety of memory sizes all above gigabyte. As an added bonus, it contains the new version of the iPod operating technique, giving you powers historicall the past bestowed only to Mac computers. At around a quarter of an inch thick and an ounce and a half in weight it is ideal for taking to the gym.

Finally, they have the granddaddy of all of the Apple iPods  the fifth generation video iPod. This iPod has a giant full color screen to show songs, pics, tv shows, movies and video podcasts. Clocking in between thirty and sixty gigabytes, you can store songs and videos on this iPod to last you through a flight around the globe.

When the new generation iPhone launches . some time this year there is a lovely chance that it will have a bigger display. The Wall Street Journal reports that Apple has began to order parts for the tool, including a display that is larger then the 3.5-inch that the iPhone has used since it was released. The screen on the 2012 iPhone will be at least four inches, according to the document.

About a bigger iPhone screen have been around  as long as the iPhone itself, which mounted to an amazing amount of noise before the announcement of the iPhone 4S last year.The iPhone five, as it was known at the time, had a lot of rumors about it that did not pan out, of the most prominent being the move to a bigger display. Rumors had it that the size of the next-gen Retina display could be three.7-, 4-, or 4.2 inches, though the latter was quickly dispelled.

Apple had no comment on the matter, but the article noted that Apple could be making the move in order to compete with rivals, like Samsung. While it is true that Samsung is a force to be reckoned with, there has been much conjecture about why the iPhone is the size it is, and why Apple has not felt pressure to chance the display size since 2007. If it does happen I would expect to see something right around 4-inches, not anything in the HTC X range (four.7-inch).

Normally, when we talk about an Android-powered system, we would venture into the realm of smartphones and tablets, and very rarely (if ever) into the world of digital cameras. The line is about to be blurred this day, as the Nikon Coolpix S800c was just announced to come with a copy of the Android operating system – Android 2.3 Gingerbread, to be exact. Yes sir, how does this digital camera shape up in the face of a mobile operating system running in the background? Well, we shall have to take a closer look at its machinations and inner workings right after the jump, shall we not ?

For starters, with Android running on the Nikon Coolpix S800c, you might actually feel that you are using a smartphone at times – until you realize that you are unable to make any phone calls or receive text messages. Good thing it has Wi-Fi connectivity built in though, as it would not be much of an Android device if there were not Internet connectivity to make it interactive.

Setting up the camera for Internet connection using operations which are similar to those used by Android smartphones is possible, not to mention easy. You are also able to post whatever you have snapped and recorded onto social networking sites like Google+, Facebook, and Twitter in a jiffy, but make sure you are within the vicinity of a Wi-Fi network, otherwise it would all amount to nought.

Not only that, the Nikon Coolpix S800c has a new feature known as “Upload to Smart Device”, where this app can be used to transfer high-resolution photos and movies to smart devices which are powered by the Android or iOS operating system, again, over a wireless connection. As for the performance of the Nikon Coolpix S800c, what kind of camera specifications does it pack?

We do know it will come equipped with a 10x optical zoom NIKKOR lens, in addition to a built-in lens-shift vibration reduction (VR) function. There is also a backside illumination CMOS sensor that boasts of an effective pixel count of 16-megapixels so that you can shoot images with little noise at the high sensitivities – perfect for low light conditions or night landscapes.

You are also able to record 1920 x 1080p/30-fps full-HD movies with stereo sound, and the included high-performance GPS module is able to record your current position (latitude and longitude) information, applying them to photos and movies as they are recorded. 

Our broadband speed and our broadband experience is something we really need to think about when deciding on a new package .The speed of a broadband package is sometime which an increasing number of people are finding is becoming a priority of theirs.
Here are the reasons why we are care about their broadband speed, and what we should take into consideration:

There is more to think about though when choosing broadband speeds. In the event you can afford it, looking in to fibre optic broadband is a great idea, it is new know-how & claims to beat the speed of ordinary broadband hands down. In the event you can nott afford to alter to fibre optic then contact your provider & ask about what packages they can offer you.
Keep in mind other things to, like the amount of downloadable date you will need per month & whether you need parental control . Overall, the important thing is to keep in mind not to rush in to purchasing your broadband package.
Contact different companies & ask about what different offers & deals, describe to them that you need to prioritise speed & hopefully they can discover a package that suits you perfectly.