Mac OS X Mountain Lion review

In the tale of two operating systems, Apple's Mountain Lion is a less ambitious endeavor. Rather than completely rewriting the book as Microsoft is attempting with Windows 8, Apple's latest operating system simply cleans house, clearing clutter, while bringing more cloud and sharing features into the fold -- specifically to make the desktop play nice with iOS devices. Some of the new features come directly from iOS, and many are welcome, but some seem unnecessary. Ultimately, what you get is the familiar layout of Apple's operating system and much less of a learning curve than with what we've seen so far of Windows 8's completely new touch-screen-focused interface.

The Mountain Lion release marks the second time Apple has offered an incremental upgrade, rather than releasing a new cat entirely (previously Leopard upgraded to Snow Leopard, for example). But don't let the modest feature or name upgrades deter you from seriously considering Mountain Lion: Apple doesn't change the game with the update, but improves everything from Safari to Messaging and adds new iCloud and sharing capabilities that make moving between devices easier.

Where Windows 8 dives head first into the touch-screen tablet market with a completely revamped user interface, Apple has improved upon what was already available, and -- in my opinion, based on using both Mountain Lion and early versions of Windows 8 -- Apple has made the wiser decision. By keeping the mobile and desktop operating systems separate, Apple can still deliver the best experience on each of its devices.

Installation

Installation for Mac OS X Mountain Lion requires a couple of steps. Start by running Software Update and check for Mac App Store updates -- this is always a good practice before a major upgrade, to make sure you have the latest versions of Apple's core apps.

From there, simply navigate to the Mac App Store, purchase the upgrade, and begin downloading. You'll need to have an account with Apple via the Mac or iTunes Store in order to purchase Mountain Lion. The OS is about 4GB (approximately the size of a full-length film download), so depending on your connection, you may want to start the download before going to bed or leaving for work. When the download is finished, the Mountain Lion installer appears in the Dock and launches automatically.

Mac OS X Mountain Lion installs in place, so you won't need to create a separate disk or run the installation off an external drive. All of your photos, documents, applications, and other saved files will be there when you're finished with the upgrade. Once the installation is complete, your Mac will automatically restart and you'll be ready to start exploring.

iCloud integration makes getting started easy

As the first major operating system release since iCloud, Mountain Lion was built with several new cloud features integrated into many of the apps.

One great new feature for those with a brand-new Mac is the ability to sign in through the Setup Assistant with your Apple ID and sync all your settings along with your apps. Your e-mail, contacts, calendars, Facebook and Twitter accounts, and more will automatically be synced up with other devices and made ready for use on your Mac by entering your Apple ID. This will be a welcome feature for iOS users setting up a new Mac for the first time because right off the bat you'll immediately be able to take advantage of all the new sharing features in Mountain Lion. One important thing to note, however, is that Apple says that Facebook integration will come in a later free update this fall.

With Apple's latest version of Mac OS X, upon launch of any app that lets you create documents, you'll now have all of your cloud-synced projects available whether you created them on your Mac or on an iOS device.

OS X Mountain Lion Technical Specifications

General Requirements

• OS X v10.6.8 or later
• 2GB of memory
• 8GB of available space
• Some features require an Apple ID; terms apply.
• Some features require a compatible Internet service provider; fees may apply.

Supported Models

• iMac (Mid 2007 or newer)
• MacBook (Late 2008 Aluminum, or Early 2009 or newer)
• MacBook Pro (Mid/Late 2007 or newer)
• Xserve (Early 2009)
• MacBook Air (Late 2008 or newer)
• Mac mini (Early 2009 or newer)
• Mac Pro (Early 2008 or newer)

Feature-Specific Requirements
   
Time Machine
Requires an additional hard drive or Time Capsule (sold separately).

Photo Booth
Requires a FaceTime or iSight camera (built in or external), USB video class (UVC) camera, or FireWire DV camcorder. Backdrop effects when using a DV camcorder require fixed focus, exposure, and white balance.

FaceTime
Video calls require a built-in FaceTime camera, an iSight camera (built in or external), a USB video class (UVC) camera, or a FireWire DV camcorder, and a 128-Kbps upstream and downstream Internet connection. Making HD video calls requires a built-in FaceTime HD camera and a 1-Mbps upstream and downstream Internet connection. Receiving HD video calls requires a supported Intel-based Mac.

AirDrop
Supports the following Mac models:

• MacBook Pro (Late 2008 or newer)
• MacBook Air (Late 2010 or newer)
• MacBook (Late 2008 or newer)
• iMac (Early 2009 or newer)
• Mac mini (Mid 2010 or newer)
• Mac Pro (Early 2009 with AirPort Extreme card, or Mid 2010)

Boot Camp
Supports existing Boot Camp installations with Windows XP Service Pack 2, Windows Vista, or Windows 7. New Boot Camp installations require Windows 7 (sold separately).

Exchange Support
Requires Microsoft Exchange Server 2007 Service Pack 1 Update Rollup 4 or Exchange Server 2010. Auto-setup requires enabling the Autodiscovery feature of Microsoft Exchange Server.

AirPlay Mirroring
Requires a second-generation Apple TV or later. Supports the following Mac models:

• iMac (Mid 2011 or newer)
• Mac mini (Mid 2011 or newer)
• MacBook Air (Mid 2011 or newer)
• MacBook Pro (Early 2011 or newer)

Power Nap
Supports MacBook Air (Mid 2011 or newer), MacBook Pro with Retina display.

Gestures
Requires a Multi-Touch trackpad, Magic Trackpad, or Magic Mouse.

VoiceOver Gestures
Requires a Multi-Touch trackpad or Magic Trackpad.

Mac App Store
Available only to persons age 13 or older in the U.S. and many other countries. Requires compatible hardware and software and Internet access; broadband recommended (fees may apply). Terms apply.

Dictation
Requires a microphone (built in or external) and a broadband Internet connection.

What’s Included

Applications
Automator, Calculator, Calendar, Chess, Contacts, Dashboard, Dictionary, DVD Player, FaceTime, Font Book, Image Capture, iTunes, Launchpad, Mac App Store, Mail, Messages, Mission Control, Notes, Photo Booth, Preview, QuickTime Player, Reminders, Safari, Stickies, System Preferences, TextEdit, Time Machine

Utilities
Activity Monitor, AirPort Utility, AppleScript Editor, Audio MIDI Setup, Bluetooth File Exchange, Boot Camp Assistant, ColorSync Utility, Console, DigitalColor Meter, Disk Utility, Grab, Grapher, Keychain Access, Migration Assistant, Network Utility, RAID Utility, System Information, Terminal, VoiceOver Utility

Languages
English, Japanese, French, German, Spanish, Italian, Dutch, Swedish, Danish, Norwegian, Finnish, Traditional Chinese, Simplified Chinese, Korean, Brazilian Portuguese, Portuguese (Portugal), Russian, Polish, Czech, Turkish, Hungarian, Arabic, Catalan, Croatian, Greek, Hebrew, Romanian, Slovak, Thai, Ukrainian

Text Source : Apple.com and Cnet.com

Read more »

Samsung Galaxy S3

Samsung Galaxy S3 is a revolutionary handset from the Korean manufacturer, Samsung and in several countries to be a prima donna among gadget lovers. Every users certainly amazed with the capabilities and performance in the Galaxy S3. Samsung Galaxy S3  is a best android smartphone in its class. With the Super AMOLED screen, the Galaxy S3 is capable of displaying images look very real, very sharp color display that we may not be able to distinguish the sharpness of the Super AMOLED screen with Retina Display screen which is owned by iPad and iPhone 4S.

Samsung Galaxy S3 was powered by multiple processor types Exynos 4212  with a process speed of 1.4 GHz, Quad-core Cortex-A9 CPU and a 16GB internal RAM. With 16GB of internal memory, you can install some applications or games without worrying about making the smartphone speed decreases. It is used to support the performance of the phone itself, Samsung Galaxy S3 used the Android OS Ice Cream 4.0. So interesting, Samsung galaxy S3 already support 4G network as well as the Samsung Exhibit 4G. For camera lovers, so perfect to choose Samsung galaxy S3 because it has been equipped with 8 MP resolution camera on the back as well as professional cameras and 1.9MP on the front.

Samsung Galaxy S3 also provides new features that are easy to use, S VOICE. S Voice is a feature that can make the Samsung Galaxy S3 respond to you. Say to wake! Even more than that, you can tell the Samsung GALAXY S3 to turn off the alarm for a few minutes and let you sleep a while longer. Answering or reject the call, raise or turn down the volume of your music, and even gave the cue when the cameras start shooting.

For more detail, a full specification of Samsung Galaxy S3 below:

Dimension

• 136.6 x 70.6 x 8.6 mm
• 133g

Display

•  4.8 inch HD Super AMOLED
• (1280x720) display

Network/Bearer and Wireless Connectivity

•  2.5G (GSM/ GPRS/ EDGE): 850 / 900 /1800 / 1900 MHz
• 3G (HSPA＋ 21Mbps): 850 / 900 / 1900 / 2100 MHz
• 4G (Dependent on market)

Memory

•  16/ 32GB User memory (64GB available soon) ＋ microSD slot (up to 64GB)

Colour

•  Pebble Blue and Marble White

Services and Applications

• S Beam, Buddy photo share, Share shot 
• AllShare Play, AllShare Cast (available soon)
• Smart stay, Social tag, Group tag, Face zoom, Face slide show
• Direct call, Smart alert, Tap to top, Camera quick access
• Pop up play
• S Voice
• Burst shot & Best photo, Recording snapshot, HDR

OS

•  Android 4.0 (Ice Cream Sandwich)

Battery

• 2,100 mAh

Connectivity

•  WiFi a/b/g/n, WiFi HT40
• GPS/GLONASS
• NFC
• Bluetooth® 4.0(LE)

Audio and Video

•  Audio Codec: MP3, AMR-NB/WB, AAC/AAC＋/eAAC＋, WMA, OGG, FLAC, AC-3, apt-X
• Video Codec: MPEG4, H.264, H.263, DivX, DivX3.11, VC-1, VP8, WMV7/8, Sorenson Spark Recording & Playback: Full HD (1080p)

Camera

•  Main(Rear): 8 Mega pixel Auto Focus camera with Flash & Zero Shutter Lag, BSI

•  Sub (Front): 1.9 Mega pixel camera, HD recording @30fps with Zero Shutter Lag, BSI

Sensors

• Accelerometer, RGB light, Digital compass, Proximity, Gyro, Barometer

Google™ Mobile Services

• Google Search, Google Maps, Gmail, Google Latitude
• Google Play Store, Google Play Books, Google Play Movies
• Google Plus, YouTube, Google Talk, Google Places, Google Navigation, Google Downloads

Here's Samsung Galaxy S3 Selections:

Samsung Galaxy S3 (Marble White)	Customer Review: Click Here for More Info
Samsung Galaxy S3 (Pebble Blue)	Customer Review: Click Here for More Info
Samsung Galaxy S3 (Ceramic White)	Customer Review: Click Here for More Info

Read more »

Google Nexus 7

Cheap tablet with high intelligence, the sentence was very perfect for the Nexus 7. Nexus 7 is a tablet PC with a 7-inch (180 mm) diagonal screen, developed and marketed by Google in conjunction with Asus. The tablet was the first device  with Android version 4.1, nicknamed "Jelly Bean". Google Nexus 7 comes with  a Nvidia Tegra 3 quad-core chip, 1 GB of RAM and available with Wi-Fi and built-in near field communication (NFC) connectivity, it is emphasized as an entertainment device with integration with Google Play, serving as a platform for multimedia consumption including e-books, television programs, films, games, and music. The tablet is priced at $ 199 for 8GB of internal memory. But this tablet was not available with a microSD slot.

For tablet users would not be able to survive using only the memory capacity of 8GB with no microSD slot. Would require tablets with greater storage capacity. Dont worry, Google itself has produced two variants of Google Nexus tablet 7, the first variant has an internal memory of 8GB and the other has 16GB variants, differing only in the capacity of the internal memory. Surely people would prefer Android tablet that has a greater storage capacity. The tablet is officially priced at $ 249. For the camera, this tablet provides a 1.2MP camera on the front of the tablet. This tablet was so perfect when we look in detail. Its body is made of plastic material makes this tablet PC has a lighter weight.

For more information, let us refer to the specifications of Google Nexus 7 below:

Developer	Google, Asus
Manufacturer	Asus
Product family	Google Nexus
Type	Tablet computer
Release date	July 13, 2012 Australia United States July 17, 2012 Canada United Kingdom August 27, 2012 France Germany Spain
Introductory price	8 GB: US$199, £159, €199 16 GB: US$249, £199, €249
Operating system	Android 4.1.1 (Jelly Bean); released July 13, 2012; 47 days ago (2012-07-13)
Power	Internal rechargeable non-removable lithium-ion polymer 4,325 mAh 16 Wh battery
System-on-chip used	Nvidia Tegra 3 T30L
CPU	1.2 GHz quad-core Cortex-A9
Storage capacity	8 or 16 GB flash memory
Memory	1 GB DDR3 SDRAM
Display	7 in (180 mm) diagonal IPS-backlit LCD capacitive touchscreen with 16:10 widescreen aspect ratio 1280×800 pixels (216 ppi) with 16M colors Scratch-resistant Corning Fit Glass
Graphics	416 MHz twelve-core Nvidia GeForce ULP
Sound	MP3, WAV, eAAC+, WMA
Input	Accelerometer, gyroscope, proximity sensor, digital compass, GPS, magnetometer, microphone
Camera	1.2 MP front-facing High-definition (720p) resolution
Connectivity	3.5 mm (0.14 in) headphone jack, Bluetooth 3.0, Wi-Fi (802.11 b/g/n @ 2.4 GHz), NFC, Micro USB 2.0, docking pins
Online services	Google Play
Dimensions	198.5×120×10.56 mm (7.81×4.7×0.416 in)
Weight	340 g (12 oz)
Website	http://www.google.com/nexus/#/7

                                  Google Nexus 7 with  8 GB memory internal                                                           
                             Google Nexus 7 with 16 GB memory internal

Read more »

Microsoft Surface Tablet

Microsoft Surface is a phenomenal tablet that has just been released and marketed by most major operating system vendors in the world, Microsoft. The tablet is covered by a chassis made ​​from magnesium, curve of the body is beautiful, smooth edge pieces, using ClearType screen HD besides using Windows  RT OS makes this tablet is a true iPad competitor. The tablet is very thin, light, and certainly comfortable use, especially Windows PC application can be run properly. New gadget named Microsoft Surface is really - really a scourge for tablet competitors. Microsoft Surface will be available in two versions, Surface with Windows RT operating system and use an ARM CPU (The display is a 10.6-inch, 16:9 widescreen HD Display) and Surface Pro with Windows 8 Pro and use  an Intel CPU(Full HD Display). This product was announced by Microsoft CEO Steve Ballmer at a meeting in Los Angeles on June 18, 2012, held at Milk Studios.

Hardware

VaporMg is used as a casing Microsoft Surface form of magnesium that includes  Surface's components, paired with a Physical Vapor Deposition (PVD) cover, which is a manufacturing process that produces a durable cover. VaporMg allows magnesium to be melted and shaped so that the Microsoft Surface has a light weight only 0.68 kilograms. Also included in both Surface models is a USB port, a micro-SD slot, and a magnetic strip to attach accessories such as the 'Touch Cover' and 'Type Cover'. There are also two cameras, front-facing and rear-facing. The rear-facing camera will be angled at 22 degrees to allow proper framing of another person while the "kickstand" is in use. The "kickstand" is a .77 mm thick built-in stand that spans the width of the device and allows Surface to be propped up at an angle in landscape orientation for a hands-free viewing experience. Surface Pro has perimeter venting which allows air to flow out the sides, and helps avoid airflow being impeded by hands holding the device.

For CPU, Surface with Windows RT will use an Nvidia Tegra CPU. Surface Pro with Windows 8 will use a chip "Ivy Bridge" Core i5 like chip in  the current Windows laptop. The Surface device demoed in the Microsoft Surface Events had a new connection port with five pins. This was known as a magnetic charging connector during Microsoft’s presentation event by Steven Sinofsky.

Touch Cover and Type Cover

Microsoft will offer two keyboard covers for Surface: Touch Cover and Type Cover. Both, when folded up, serve as protective covers that connect to the Surface via a magnetic strip. When opened, the covers are keyboards. So we like holding a magazine or book. The Touch Cover is 3 mm in thickness and has a touch-sensitive keyboard. The Type Cover is thicker and includes a tactile keyboard. The keyboards have a gyroscope and accelerometer sensors to determine, based on position, whether or not to accept input. Both also include a multitouch touchpad. Touch cover and type of cover has a nice color pink and light blue, but there is also an option with dark colors.

Price

An unexpected surprise from Microsoft as it has made ​​a tablet themselves. But the tablet is completely different from the previous tablet. Unfortunately Microsoft still does not give news about the price of Microsoft Surface.

The Surface will be available with general availability of Windows 8, which will launch on October 26, 2012. The Surface Pro will be available three months after that. The Surface will initially be available in Microsoft Stores and online.

Read more »

Blackberry Curve 9320 Amstrong

Research in Motion launched the BlackBerry Curve 9320 Armstrong last May after it have launched Blackberry Curve 9220 Davis. Blackberry 9320 is designed to stay connected with social media and is equipped with a special button that can connect directly to the user's BlackBerry Messenger application. So for you who are very happy with the social media, Blackberry 9320 is very suitable to use this phone so you will be easier for social networking. For users of the old curve can upgrade to the new device so that they can have faster access speeds and better.

Blackberry 9320 has a dimension of 109 x 60 x 12.7 mm with a weight of 103 grams(lighter than the previous series) and for the design of blackberry 9320 is not much different from the blackberry curve 9220. The operating system used is Blackberry OS 7.1 in addition this phone is equipped with 512 MB ​​RAM and 512 ROM so it will have a very good performance. Do not worry for you who want a phone that has a camera on the blackberry because on the blackberry 9320 also has provided 3.2 MP camera of 2048 × 1536 pixels, and to improve the quality also equipped with LED Flas, Geotagging and imange stabilization. For more details about the overall specs of the Blackberry Curve 9320 Armstrong can be seen below.

General	2G Network	GSM 850 / 900 / 1800 / 1900
	3G Network	HSDPA
	Announced	2012, May
	Status	Available. Released 2012, May

Body	Dimensions	109 x 60 x 12.7 mm
	Weight	103 g
	Keyboard	QWERTY

Display	Type	TFT, 65K colors
	Size	320 x 240 pixels, 2.44 inches (~164 ppi pixel density)
		- Touch-sensitive optical trackpad

Sound	Alert types	Vibration; Polyphonic(64), MP3 ringtones
	Loudspeaker	Yes
	3.5mm jack	Yes

Memory	Card slot	microSD, up to 32 GB
	Internal	512 MB ROM, 512 MB RAM

Data	GPRS	Yes
	EDGE	Yes
	Speed	HSDPA, 7.2 Mbps; HSUPA, 5.76 Mbps
	WLAN	Wi-Fi 802.11 b/g/n
	Bluetooth	Yes, v2.1 with A2DP
	USB	Yes, microUSB v2.0

Camera	Primary	3.15 MP, 2048x1536 pixels, LED flash
	Features	Geo-tagging, image stabilization
	Video	Yes
	Secondary	No

Features	OS	BlackBerry OS 7.1
	Sensors	Accelerometer, proximity, compass
	Messaging	SMS(threaded view), MMS, Email, Push Email, IM
	Browser	HTML
	Radio	Stereo FM radio with RDS
	GPS	Yes, with A-GPS support
	Java	No
	Colors	Black
		- BBM key - MP3/eAAC+/WMA/WAV/Flac player - MP4/H.263/H.264/WMV player - Organizer - Document viewer - Voice memo/dial - Predictive text input

Battery		Standard battery, Li-Ion 1450 mAh
	Stand-by	Up to 432 h
	Talk time	Up to 7 h
	Music play	Up to 30 h

Misc	SAR US	1.56 W/kg (head)     0.75 W/kg (body)
	SAR EU	1.24 W/kg (head)     0.72 W/kg (body)
	Price	$223.00

                                                         $223.00

Read more »

Sunforce 11240 1000 Watt Pure Sine Wave Inverter with Remote Control

Inverter is a very useful electronic device for converts dc to ac. Inverter function is equal with a generator. Just, inverter use a accumulator as a power source, but generator use a fossil fuels. Inverter is a portable device for carried everywhere such as picnic, camping, anyplace that far from a fossil fuels.
Sunforce 11240 1000 Watt is the most used inverter. Sunforce 11240 1000 Watt produces Pure Sine wave and be equipped with Remote Control.

This is the Product feature:

•     Connects to a 12 volt battery and converts DC to AC pure sine wave for power on the go
• Ideal for power failure emergencies and guarantees optimum compatibility with sensitive equipment, computers, motors, televisions and more
• 2000 Watts surge power, 1000 continuous power
• Safety features include: an overload alarm and LED light, a soft start system, low battery shut down, DC input overload voltage, output overload, overload temperature, short circuit shut down, and a high speed cooling fan
• System includes: two 110V household electrical outlets, a DC/AC power inverter remote control modular connector cable and key chain remote

                                                         $193.30

Read more »

Medium power FM transmitter circuit

Description.

This is the circuit diagram of a moderate power FM transmitter circuit employing two transistors.The voice signals picked by the microphone will be amplified by the transistor Q1.The second transistor is wired as an oscillator operating in the FM band.The output of T1 is given to the base of T2.T2 performs the modulation also.The tank circuit comprising of components L1 and C6 determines the frequency of the signal, and can be varied by adjusting C6.The capacitor C7 couples the FM signal to the antenna.

Circuit diagram with Parts list.

Notes.

• You can assemble the circuit on a general purpose PCB. 
• The circuit can be powered from a9V PP3 battery.
• The Antenna A1 can be a 1M long wire.
• The inductor L1 can be made by making 6 turns of 0.8mm enameled copper wire on a 5.5mm diameter/4.5mm length plastic former.
• With a matching antenna and proper tuning this transmitter can have range upto 100meters.

source: circuitstoday.com

If you haven't much time to make your FM transmitter. I provides some FM Transmitter Selections:

SD/MMC/USB/MP3 Wireless In Car FM Transmitter. . .	Customer Review: Click Here for More Info	$3.95
FM Transmitter Car Charger and Mount Compatible with Apple iPod / iPhone	Customer Review: Click Here for More Info	$9.78
Coby CA-745 Wireless FM Car Transmitter with Digital Display	Customer Review: Click Here for More Info	$17.99
GOgroove FlexSMART X2 ADVANCED Wireless In-Car Bluetooth	Customer Review: Click Here for More Info	$44.99
SANOXY Wireless LCD FM transmitter for ipod nano. . .	Customer Review: Click Here for More Info	$5.50

Read more »

1000W Inverter circuit and kit

This power inverter circuit will provide a very stable Output Voltage.Frequency of operation is determined by a pot and is normally set to 60 Hz. Various “off the shelf” transformers can be used. Or Custom wind your own for best results.

Additional MosFets can be paralleled for higher power. It is recommended to Have a “Fuse” in the Power Line and to always have a “Load connected”, while power is being applied. The Fuse should be rated at 32 volts and should be aproximately 10 Amps per 100 watts of output. The Power leads must be heavy enough wire to handle this High Current Draw! appropriate Heat Sinks Should be used on the RFP50N06 Fets. These Fets are rated at 50 Amps and 60 Volts. Other types of Mosfets can be substituted if you wish.

At 1000 Watts and operating from a 12 Volt Source, the Input Current will be close to 100 AMPS. That would Require a HUGH Size of a Primary Wire.

If you haven't much time to make your own 1000w inverter. I provides some 1000W Inverters Selections:

Cobra CPI1000 1000W 12V DC to 120V AC Power Inverter with USB Port	Customer Review: Click Here for More Info	$79.10
Sunforce 11240 1000 Watt Pure Sine Wave Inverter with Remote Control	Customer Review: Click Here for More Info	$193.55
Power Bright PW1100-12 Power Inverter 1100 Watt 12 Volt DC To 110 Volt AC	Customer Review: Click Here for More Info	$69.88
Whistler Pro-1200W 1,200 Watt Power Inverter	Customer Review: Click Here for More Info	$73.99
Energizer 84025 1000-Watt Power Inverter	Customer Review: Click Here for More Info	$70.67

Read more »

250W PWM Inverter Circuit SG3524

A 250W PWM inverter circuit built around IC SG3524 is shown here. SG3524 is an integrated switching regulator circuit that has all essential circuitry required for making a switching regulator in single ended or push-pull mode. The built in circuitries inside the SG3524 include pulse width modulator, oscillator, voltage reference, error amplifier, overload protection circuit, output drivers etc. SG3524 forms the heart of this PWM inverter circuit which can correct its output voltage against the variations in the output load. In a non PWM inverter the change in output load directly affects the output voltage (when output load increases output voltage decreases and vice versa), but in a PWM inverter the output voltage remains constant over a range of output load.

Circuit diagram of 250W PWM inverter.

About the circuit.

Resistor R2 and capacitor C1 sets the frequency of the ICs internal oscillator. Preset R1 can be used for fine tuning of the oscillator frequency. Pin 14 and pin 11 are the emitter terminals of the internal driver transistor of the IC. The collector terminals of the driver transistors (pin 13 and 12) are tied together and connected to the +8V rail (output of the 7808). Two 50Hz pulse trains which are 180 degree out of phase are available at pin 14 and 15 of the IC. These are the signals which drive the subsequent transistor stages. When signal at pin 14 is high, transistor Q2 is switched on which in turn makes transistor Q4, Q5, Q6 ON are current flows from the +12V source (battery) connected at point a (marked with label a) through the upper half of the transformer (T1) primary and sinks to ground through the transistors Q4, Q5 and Q6. As a result a voltage is induced in the transformer secondary (due to electromagnetic induction) and this voltage contributes to the upper half cycle of the 220V output waveform. During this period pin 11 will be low and its succeeding stages will be inactive. When 11 of the IC pin goes high Q3 gets switched ON and as result Q7, Q8 and Q9 will be also switched ON. Current flows from the +12V source (marked with label a) through the lower half of the transformer primary and sinks to the ground through transistors Q7, Q8, Q9 and the resultant voltage induced at the T2 secondary contributes to the lower half cycle of the 220V output wave form.

The output voltage regulation section of the inverter circuit works as follows. The inverter output (output of T2) is tapped from point’s labelled b, c and supplied to the primary of the transformer T2. The transformer T2 steps down this high voltage , bridge D5 rectifies it and this voltage ( will be proportional to the inverter’s output voltage) is supplied to the pin1 (inverting input of the internal error amplifier of the IC) through R8, R9, R16 and this voltage is compared with the internal reference voltage. This error voltage will be proportional to the variation of the output voltage from the desired value and the IC adjusts the duty cycle of the drive signals ( at pin 14 and 12) in order to bring back the output voltage to the desired value. Preset R9 can be used for adjusting the inverters output voltage as it directly controls the amount of voltage fed back from the inverter output to the error amplifier section.

IC2 and its associated components produce an 8V supply from the 12V source for powering the IC and its related circuitries. Diodes D3 and D4 are freewheeling diodes which protect the driver stage transistors from voltage spikes which are produced when the transformer (T2) primaries are switched. R14 and R15 limit the base current of Q4 and Q7 respectively. R12 and R13 are pulldown resistors for Q4 and Q7 which prevents their accidental switch ON. C10 and C11 are meant for bypassing noise from the inverter output. C8 is a filter capacitor for the voltage regulator IC 7808. R11 limits limits the current through the indicator LED D2.

Notes.

• Mount the SG3524 on a holder.
• All capacitors other than C10 and C11 must be rated at least 15V.
• Preset R9 can be used for adjusting the inverter’s output voltage.
• Preset R1 can be used for adjusting the inverter’s operating frequency.
• Transistors in the driver stage require heatsink.
• T2 is a 220V primary, 12V secondary, 1A transformer.
• T1 is a 12-0-12 V primary, 220V secondary, 300VA transformer.
• Driver transistors must be isolated from the heatsink using mica sheets. Mounting kits for these transistors are easily available in the market.
• An optional finned aluminium heatsink can be attached to the 7808.
• If 1A bridge is not available, make one using four 1N4007 diodes.

Here's 250W Inverters Selections: 

250w Grid Tie Power Inverter Converter Solar 10.8v-30v DC 110v AC	Customer Review: Click Here for More Info	$87.90
250W Portable Power Station - 250W Pure Sine Power Inverter. . .	Customer Review: Click Here for More Info	$349.95
Samlex SAM-250-12 12-Volt 250-watt DC to AC Inverter	Customer Review: Click Here for More Info	$31.78
Playstation 2 Gaming Inverter-250 Watt	Customer Review: Click Here for More Info	$29.95
250-Watt Peak Power Inverter with USB Port	Customer Review: Click Here for More Info	$23.91

Read more »