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	Gaggia 90951 Platinum Vision Automatic Espresso Machine with Milk Island, Platinum List Price: $2,299.00 Sale Price: $1,718.98 You save: $580.02 (25%)
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	Description Vision Quest is a coming of age movie in which high school wrestler Louden Swain (Matthew Modine) decides he wants to be something more than an average high school athlete and sets his sights on a prize that many don't think he can win -- he then sets out to reach his goal alone, without much support from his father or coach...

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	Leontyne Price Sings Barber List Price: $7.99 Sale Price: $7.98 You save: $0.01 (%)
	Description Early in her career, Leontyne Price formed an artistic liaison with Samuel Barber that resulted in his composing the female lead in Antony and Cleopatra for her. The disastrous premiere of that opera prevented Price from making a complete recording--a tragic loss in my opinion...

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	Col. Culpeper's Flying Circus
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	Danger Sign - High Voltage (Bilingual) - 14" x 10" OSHA Safety Sign List Price: $12.99 Sale Price: $8.99
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The Growth Of The Lasik Vision Institute

Since the baby boomers are such a large part of the middle aged population, naturally health and well-being issues are taking center stage these days. Along with aging comes vision problems that affect almost everyone. This is one of the reasons why the Lasik Vision Institute is a growing and flourishing business.

Often people will overlook the aches and the pains, and even the graying hair and wrinkles that accompany the aging process. However, when vision is affected, people tend to quickly seek out solutions to the problem.

Corrective eye surgery is becoming an increasingly popular solution that can correct problems with astigmatisms, as well as near-sighted and far-sighted conditions. The Lasik Vision Institute specializes in this very thing with a team of highly trained laser eye surgeons who are considered to be some of the top Lasik eye doctors in their field.

The Lasik Vision Institute has opened a number of vision clinics across the US in an effort to satisfy the demand for corrective eye surgery. There is such a high demand because The Institute uses the latest and most advanced laser eye surgery techniques available. While not yet in all major metropolitan areas, the company is constantly working to expand their reach to bring these vision solutions to more people.

The Lasik Vision Institute has developed a very strong and positive reputation over the years in which they have provided laser eye surgery in the US. They have performed more than 650,000 corrective eye surgery procedures and have developed a high level of trust from their patients because they only employ highly skilled laser eye surgeons. In addition, they only use laser technology that has been fully approved by the FDA in order to help assure the highest quality results.

Another aspect of the Lasik Vision Institute that is noteworthy is their attention and dedication to providing personalized patient care. In addition to the professionalism of the laser eye doctors, there is also a complete team, also highly-trained and skilled who work with the patients step by step, from the stage of gathering information, planning and preparing for the procedure, to making sure that they receive proper after-care.

As a company, the Lasik Vision Institute claims to be dedicated to providing low-cost Lasik surgical procedures, by managing their costs and reducing overhead wherever possible. In this way, they hope to make corrective eye surgery available to as many people as possible. Another way they try to achieve this availability for more people is by offering payment plans for those who cannot afford to pay for the entire procedure up front.

About the Author

A free report awaits you at our laser eye surgeryportal site, where you can enrich your knowldege further about the lasik vision institute. Your comment is much appreciated at our laser vision correction blog.

Any one heard a condition that music causes a sort of high or colors to creep run your vision or even bleeding

I was in the car with some of my friends, and this is the most powerful experience I've had with music. For some odd reason a song put me into a trance like state where i started to convulse, see odd colors in my vision and my nose started to bleed, but it wasn't painful but more like an amazing high that took me to another world in such bliss I didn't want the music to stop! Some one please tell me what this is, although I do love the experience, it is kind of scary, and I definitely would not want this to happen if i were driving or working! please help!

You may be experiencing an epileptic seizure. I would see a doctor about this immediately. To see if symptoms of seizure match up with your experience, read "signs & symptoms" here:

http://www.reference.com/search?r=13&q=Epileptic%20seizures

Also, here is neurophysiology blog I found where they are talking about exactly what you describe, it seems that many of them are confirmed epilepsy sufferers:

http://neurotalk.psychcentral.com/showthread.php?t=15608

OH YA, and about the bloody nose, in a seizure, you may be pressurizing your head by inadvertantly exhaling against a closed throat, or you may have just bumped it while you were out.

A Vision for High Speed Rail

	SanDisk 16GB MicroSDHC Memory Card with Adapter + SanDisk MicroSDHC to MiniSDHC Adapter + USB2.0 High Speed Card Reader Sale Price: $32.75
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	SanDisk 16GB MicroSDHC Memory Card with Adapter (Bulk Package) + USB2.0 Extreme High Speed Card Reader Sale Price: $32.99
	Description Product Specifications: SanDisk microSDHCTM 16GB SDSDQ SanDisk is proud to announce our newest format and capacity to the SD card family: microSD High Capacity (microSDHC) 16GB flash card. This will help and ensure your transition from the microSD format to the microSDHC format for our cards and for compatible host devices...

	SanDisk 8GB MicroSDHC Memory Card with Adapter (Bulk Package) + SanDisk MicroSDHC to MiniSDHC Adapter + USB2.0 High Speed Card Reader Sale Price: $15.45
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	USB Cable For Panasonic Lumix DMC-FS3/DMC-FS5/DMC-FS7 & More! Sale Price: $0.01
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	Opteka X-GRIP Professional Camera / Camcorder Action Stabilizing Handle with Hot-shoe for Flash or Video Light List Price: $59.99 Sale Price: $34.95
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(2 in 1 Memory Deluxe) Mini Glove Camera Case for Sony Cyber-shot Panasonic DMC FX Panasonic DMC LX Casio Exilim Fujifilm FinePix Canon Powershot Olympus Stylus Nikon Coolpix Camera Case + 2GB microSD Memory Card w/ SD Adapter List Price: $29.99 Sale Price: $19.99

Description Compatible with camera not larger than 4x3x1 inches (LxWxH). Partial Compatible List: Casio Camera Case Casio Digital Camera Case for Casio Exilim Ex-v7 Casio Exilim Ex-z1050 Casio Exilim Ex-z75 Casio Exilim Ex-s3 Casio Exilim Ex-s500 Casio Exilim Ex-z30 Casio Exilim Ex-z40 Casio Exilim Ex-z50 Casio Exilim Ex-z500 Casio Exilim Ex-z55 Casio Exilim Ex-z57 Casio Exilim Ex-z60 Casio Exilim Ex-z600 Casio Exilim Ex-z70 Casio Exilim Ex-z700 Casio Exilim Ex-z750 Casio Exilim Ex-z850 Digital Camera and other similar case...

(2 in 1 Memory Premium) Eva Nylon Camera Case for Sony Cyber-shot Panasonic DMC FX Panasonic DMC LX Casio Exilim Fujifilm FinePix Canon Powershot Olympus Stylus Nikon Coolpix Camera Case(multiple colors available) + 2 GB microSD Memory Card w/ SD Adapter Sale Price: $21.99 - $29.99

Description Compatible with camera not larger than 4x3x1 inches (LxWxH). Partial Compatible List: Casio Camera Case Casio Digital Camera Case for Casio Exilim Ex-v7 Casio Exilim Ex-z1050 Casio Exilim Ex-z75 Casio Exilim Ex-s3 Casio Exilim Ex-s500 Casio Exilim Ex-z30 Casio Exilim Ex-z40 Casio Exilim Ex-z50 Casio Exilim Ex-z500 Casio Exilim Ex-z55 Casio Exilim Ex-z57 Casio Exilim Ex-z60 Casio Exilim Ex-z600 Casio Exilim Ex-z70 Casio Exilim Ex-z700 Casio Exilim Ex-z750 Casio Exilim Ex-z850 Digital Camera and other similar case...

(2 in 1 Memory Deluxe) Slim Eva Nylon Camera Case for Sony Cyber-shot Panasonic DMC FX Panasonic DMC LX Casio Exilim Fujifilm FinePix Canon Powershot Olympus Stylus Nikon Coolpix Camera Case + 2GB microSD Memory Card w/ SD Adapter Sale Price: $19.99 - $29.99

Description Compatible with camera not larger than 4x3x1 inches (LxWxH). Partial Compatible List: Casio Camera Case Casio Digital Camera Case for Casio Exilim Ex-v7 Casio Exilim Ex-z1050 Casio Exilim Ex-z75 Casio Exilim Ex-s3 Casio Exilim Ex-s500 Casio Exilim Ex-z30 Casio Exilim Ex-z40 Casio Exilim Ex-z50 Casio Exilim Ex-z500 Casio Exilim Ex-z55 Casio Exilim Ex-z57 Casio Exilim Ex-z60 Casio Exilim Ex-z600 Casio Exilim Ex-z70 Casio Exilim Ex-z700 Casio Exilim Ex-z750 Casio Exilim Ex-z850 Digital Camera and other similar case...

	Mobile PowerFlex Car Travel Power Adapter for your Canon Vixia HF200 and other Camcorders! w/ Bonus Micro USB cable for charging mobile phones and USB compatible devices **Includes Lens Cleaning Kit List Price: $69.99 Sale Price: $29.99
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	Camcorder and Digital Camera In-Car Portable AC to DC Power Converter for Charging and Powering - Also Powers and Charges USB Enabled Devices w/ Bonus Micro USB cable for charging mobile phones and USB compatible devices *Includes Cleaning Blower Brush (camcorder not included) List Price: $69.99 Sale Price: $29.99
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Traveling to Europe With Your Digital Camera?

The Vacation Season is fast approaching and naturally you will be taking your digital camera along for the journey. After all your vacations are far and few between and it is nice to look back on those memories as you slave away at your job. However, when you travel with a digital camera, it is a completely different experience from that of traveling with a film camera. This is a lesson that far too many travelers seem to be learning the hard way, especially if you’re traveling to Europe. After a couples years of relying solely on digital for taking photos when I travel, there are things you should consider before you head off on your next trip.

Charging Batteries is one of the biggest stumbling blocks you'll face when you travel. Outlets can be scarce in hotels. On a recent trip to Europe, only one of the five modern hotels I stayed in had more than one outlet available for use when charging up electronics. Charging your battery can be more of a hassle if you're traveling by train: If you take an overnight train in Europe, they don't have power adapters at the seats (certain trains do, but it's not something you can count on). I suggest bringing at least two rechargeable batteries, three if you plan to travel with overnight trains, or don't think you'll be able to charge every night. If your camera uses regular AA batteries, consider yourself lucky-you'll find those everywhere. Scope out the situation in your room when you check in: You should get at least one usable outlet, but don't count on more than that.

Bring your plugs. Some digital cameras typically come with a power brick that can handle international voltages, so you won't need a voltage adapter. However, you will need a power plug adapter to convert a US outlet plug to the local plug. Most of Europe is on the same outlet now-but not all countries accept the general "Europe" plug. Be sure to research what you'll need to jack in, and try to buy it before you leave (try CompUSA, Radio Shack, Rand McNally, or your local luggage store). If you don't have a chance to get what you need Stateside, don't fret: You should have no trouble finding an outlet converter overseas.

How do I offload my images? For fellow travelers using digicams, this was the number one problem I have heard repeatedly. Many comments from folks traveling for a week or more are: "I'm taking more pictures than I expected to." "I'm not shooting at the best resolution, because I need the room on my memory card." "I'm only halfway through my trip, and I have only 50 shots left." When you travel, odds are you'll take more pictures than you expect to also. A 1 GB card is very useful, and should suffice for low-usage shooters. But for those of us, who can go through a gigabyte or more in a day, not a week? Whether it's because you’re a high-volume shooter, shooting in RAW format, or a combination of the two. What I discovered is many who had digital SLRs, that had 5 megapixels or more reported they were traveling with a laptop to off load their images. None of these folks were traveling on business, so they didn't need to bring a laptop along. The sad fact is, for now, a laptop remains the most efficient and usable means of off loading images. Epson and Nikon have dedicated handheld units with a hard drive, card reader, and LCD display for copying over and viewing your images. But neither has a full-blown keyboard. If you're first buying a laptop, and intend to travel with it, I suggest going for the smallest one you can. Fujitsu, Panasonic, Sharp, and Sony all have models under four pounds. A laptop provides several additional advantages. For one thing, you can see your pictures on a big screen-to view how you're doing, and if you see any problems you want to correct with your exposure, for example, or if your pictures are being affected by dirt. For another thing, you can properly label your folders, so you know which pictures were taken where. Most newer laptops have integrated memory card readers, but otherwise, you can buy a small external card reader. For the wire-free approach, use a PC Card slot adapter for your memory card; and invest in a 32-bit Cardbus adapter (Delkin and Lexar Media offer these), for speedier transfers. Nothing's worse than coming back to the hotel after a long day of sightseeing, and needing to stay awake another 40 minutes just to off -load two 1 GB cards, at about 20 minutes a pop. If you bring a laptop, I also suggest investing in a portable hard drive. A portable hard drive can serve multiple purposes: It can be a means of backing up your photos on the go; a means of giving you a way to take your photos with you if you have to leave your laptop unattended; and a means of expansion, if you somehow manage to fill up your laptop's built-in hard disk. If you don't want to bring a laptop, and already have an Apple iPod, Belkin sells an attachment for using your iPod with memory cards; or, consider the pricey units from Nikon and Epson. And if you're in a bind, remember you can always buy memory overseas. I was surprised that when I went to Europe, the prices were high, but not so outrageously so that I wouldn't buy another card if I were in a bind. Cards were more readily available, too, than they were when I last traveled through Europe three years ago. Look at it this way: Even if you overpay on the card, you can still reuse it-which beats overpaying for a single use 35mm film cartridge when you were in a bind in years' past.

Be prepared for problems. Things happen when you travel and I've had more things go awry carrying my digital SLR than I have had with my 35mm over the years. Lens paper is always useful to have on hand, but if you have a digital SLR, another supply is absolutely critical: An air blower bulb, to blast out the dust and dirt that will inevitably get trapped inside your camera. I never had problems with my 35mm SLR, but with my digital SLR, I constantly find dirt gets trapped inside, when I change lenses. And there's nothing worse than having a splotch marring your otherwise awesome shots. Finally, remember the philosophy of redundancy. Whether your battery dies and you have no way to charge it, or you run out of space on your memory card(s), and don't want to buy another at a higher-than-usual price, I suggest packing a second camera if you can. A digital point and shoot is a good option but I usually carry a point and shoot 35mm to use if I run into any problems just so I won’t lose any precious pictures.

About the Author

For More Free Resources visit

www.tours-guide.com

What should I sell this camera (kit) for?

I will soon be selling my Panasonic Lumix FZ18 to help me pay for a Nikon D40.

You can read about the camera here---

http://www.dpreview.com/reviews/compare_post.asp?method=sidebyside&cameras=panasonic_dmcfz18&show=all

The camera is two years old. You can see what they are selling for on Amazon.

Panasonic HVX200 Letus Extreme 35 DOF adaptor Nikon test

	Brunton Solar Controller Battery Charge Monitor Sale Price: $18.40 - $30.46
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	La Crosse Technology WS-9029U Wireless Weather Station with Digital Time List Price: $29.95 Sale Price: $20.37 You save: $9.58 (32%)
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	Brinno PHV132512 Electronic PeepHole Viewer List Price: $129.99 Sale Price: Too low to display
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	3 in 1 Video Intercom with Three Color 7" Monitors and Night Vision Outdoor Camera Sale Price: $349.90
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	ABC News Primetime No Place to Hide Sale Price: $19.95
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10 Ideal Tips for Buying Surveillance Cameras at Discounts Prices

Security is a prime concern the world over. Homes and shops are equipped with state-of-art surveillance systems that include: cameras, monitors, recorders, and cabling to name just a few needs.

Before buying a surveillance camera and its peripherals you need to evaluate your needs and study the local laws about installing security cameras. There are surveillance systems available online and offline at a wide range of costs but buyers need to be aware that low-quality components will not provide adequate security. In general surveys indicate that a complete system should cost USD 500-USD 1000 per camera. One can consider a whole range of surveillance products: fake security cameras; covert surveillance cameras; wireless security cameras; wired surveillance cameras; night vision security cameras; and home surveillance cameras.

Before buying a surveillance system you must:

1. Read all about security surveillance and evaluate your needs. Think whether you should spend large sums of money to solve minor problems.

2. Make a list of what components would best suit your purpose. Know what to look for in a workable surveillance system.

3. Log onto the internet and browse through surveillance products and note down their price as well as features.

4. Visit others who have surveillance systems installed and find out what their experience has been.

5. Read reviews of surveillance products to get familiar with cameras and peripherals.

6. Get quotes both online and offline and make comparisons of costs as well as installation and maintenance.

7. Ask about warranties and possibilities of upgrading the surveillance system in future.

8. Check about live feeds over the internet and recoding needs too. Picture quality is another aspect that needs careful thought. Cheaper cameras will give unclear or fuzzy pictures and the surveillance will be useless.

9. Follow the law always and do not record audio as its illegal.

10. Buy from reliable stores and not from here today gone tomorrow outfits. Since a security system is a long-term investment it is best to buy from a reliable vendor.

It is important to buy surveillance camera and peripherals of superior quality and function. There are many online stores that offer surveillance cameras at great discounts. Often as promos accessories are offered at lower prices if a person chooses to buy a surveillance camera and accessory package. So survey the costs carefully online and offline and think about the advantages of buying a system from an auction site. Another possibility is buying a second hand surveillance system that has been refurbished and comes with guarantees.

With constant innovations surveillance cameras now come with in built intelligence and can detect suspicious behavior before a crime is committed. Surveillance equipment is widely used in public places, homes, offices, government buildings, and banks. Most surveillance cameras feed live video to control rooms that are monitored by security personnel. There are cameras that can detect gun shots and facial expressions too! So when buying a system consider advancements in technology, price, adaptability with local security systems, and the law.

About the Author

Matthew Pawlina is a writer for Surveillance Cameras , the premier website to find surveillance cameras, wireless surveillance cameras, home surveillance cameras, wireless home surveillance cameras, digital surveillance cameras and many more.

I broke my digital camera monitor/viewing screen - can this be fixed?

I stood on my camera Nikon Coolpix 4600 and the monitor has cracked and is unusable (though I have been able to turn it on and download my photos, so presumably everything else works). I'm wondering can it be fixed? If so any idea how much this would cost or would I be better just to replace the camera?
btw I'm in the UK

that sux huh? well,it can be fixed but you're better off buying a new camera!!!!!!!!! peace tom!!!!!

Focus: Wireless Internet Camera Monitor Kit TV-M7110WK (IP) TRENDnet TV

	Cobra CPI 1575 1500 Watt 12 Volt DC to 120 Volt AC Power Inverter List Price: $189.95 Sale Price: $93.10 You save: $96.85 (51%)
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Car Security & Surveillance Systems

Car theft is big business throughout the world. A car is stolen every 25 seconds in the United States, costing Car owners and the insurance industry over $8 billion dollars a year.

Your car is possibly one of your most beloved, possessions. When your car is stolen, your life is turned upside down. Aside from losing your most valuable possession, you may also incur the following expenses:

* Increased insurance premiums

* Replacing valuables left in your car

* Missed work

* Time spent filing police reports, purchasing a new vehicle etc.,

Car security and surveillance systems come in many forms. While most people think of car security as a simple alarm system that is really loud, more often than not, they don't have the same impact on security as they once did. The most basic car alarm systems start at around $40 or $50 and come with a shock sensor or two, an alarm controller module, a remote control, siren, and wiring harness. More expensive alarms are starter alarms. These car alarms allows 2-way communication between your car a handheld monitoring device, letting you know if you car has been started and allowing you to disable it at the click of a button. Car surveillance using an internal car camera recorder and GPS vehicle tracking systems provide the ultimate in car security.

Car alarms and Sensors, motion detectors, and pressure sensors are wired into your car's electrical system and monitor such things as vibrations, doors or windows being opened while locked, and any tampering with the ignition system. Higher end systems come with microphone sensors which detect breaking windows and other sounds.

A Car tracking system can also be secretly installed into cars in some hidden, remote location. After a Car theft takes place, police can activate the radio transmitter on the device and it will begin broadcasting a signal, showing its location. This allows for complete recovery of the vehicle, hopefully before any damage has been done to it.

About the Author

Buy new and Used Cars in India, Buy or sell Bikes, Car Reviews, New and Used Car Prices, Compare new cars online, automobile industry, auto accessories at http://www.autoindia.com.

Who's in car camera showed us the incident between Moraes & Carpenter? in the indycar race today?

its for the indycar nation fantasy racing question of the day, please help.

That was Dario's cam.

In Car Camera with Todd Tutterow at Piedmont Dragway

	Epson Premium Canvas Matte - Fine art heavy-weight high resolution matte poly-cotton coated canvas paper - 19 mil - Roll (36 in x 40 ft) - 375 g/m2 - 1 roll(s) Sale Price: Too low to display
	Description Whether the application is photographic portraiture or fine art reproduction, Piezo Pro Water Resistant Matte Canvas for Epson will satisfy even the most demanding professional by providing both the finest image quality as well as a vehicle for enhanced artistic creativity...

	Quickcount High Resolution Counting Scale - 2.2lb X 0.00002lb
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	Topsy-Turvy - The Music of Gilbert & Sullivan: From the Original Motion Picture Soundtrack List Price: $8.99 Sale Price: $8.98 You save: $0.01 (%)
	Description The producers of Mike Leigh's vibrant Topsy-Turvy took many big studio meetings seeking financing for their film. Word has it all went swimmingly until time for the pitch came--there are apparently no two words as unsettling to Hollywood film execs as "Gilbert & Sullivan...

	The Live Anthology: Ultimate Collector's Edition Boxed Set (5 CDs + 1 Blu-ray + 2 DVDs + 1 LP) Sale Price: $135.99
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	Live at Trinity Church Sale Price: $19.98
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Old Fashioned High Resolution Photo Camera

Tired of trying to keep updated with the highest mega pixel resolution digital camera? Well even if one has tried to do that, most certainly he will soon find out that his few months old digital camera is outdated in terms of mega pixel resolution. It’s an ever changing kind of product that has become very hard to keep updated, unless one is willing to spend more money by making purchases every six to twelve months.

If the main intention of purchasing a photo camera is enlarging the image, then mega pixel resolution indeed will become the main factor. In this case one might consider a different option, which will keep his product updated for years to come. I’m talking about a used 4x5" film photo camera, together with a high resolution flat bed film scanner. All of this for less than one thousand US dollars. With all of this, one will get over 100 mega pixels in fine detailed film resolution and fine scanned digital images that can be enlarged up to 30x40" in size with professional quality. These 4x5" film cameras have done a remarkable job in general personal and commercial photography such as wedding, portraiture, product, documentary, advertising and landscape for nearly a hundred years.

Where to find 4x5" used film cameras? Since some of these cameras were mostly used in the past, until the 1960’s, it should be no problem in finding them in American auction web sites. Anyway, a good used 4x5" camera with lens can be found for less than four hundred US dollars.

As for the flat bed film scanner, one can find brand new ones for less than five hundred US dollars. Just make sure the scanner is able to scan films.

Whenever purchasing a 4x5" film camera, one should look for the following features: folds into a compact box, flexible bellows, lenses that can be easily interchanged, accepts sheet film, ground glass focusing screen, easily handheld and optical viewfinder accessory.

As for the lenses, there are four main categories: 1 - general purposes; 2 - wide field (mostly used for close up work and landscape); 3 – extreme wide angles lenses; 4 – special effects lenses (telephoto). However, one might use a general purpose 127 or 152mm lens for most of his photograph sessions. In cases where it requires special lenses, such as architecture or macro photography, one will still find lots of them available in auction sites. Used lenses for 4x5” cameras made after world word II have excellent performances comparable to today’s modern lenses.

Whenever making a purchase of a 4x5" camera make sure that: 1 - the bellows have no light leaks, 2 – the lens shutter works accurate at all speeds; 4 – the lens elements have no fungus and scratches of any kind; 4 – the focus is working properly between the ground glass and the film.

The option of using a 4x5" film camera, together with a flat bed film scanner, for enlarging images with professional quality is viable and accessible. Cheaper than top digital cameras, the 4x5" film camera offers better image quality and will always be updated in the future, maintaining its original value.

For those who wishes the very most detailed image enlargement, one can always use the 8x10" film camera. Four times the physical film size of the 4x5", this option offers so much film resolution that it is considered by many as the ultimate step for photo image enlargement.

Sometimes analog products deliver better results that its digital counter parts. If you are doing the job of enlarging photo images, you should give it a try with a 4x5" camera. You might just surprise yourself.

Roberto Sedycias

IT Consultant for PoloMercantil

This article is under GNU FDL license and can be distributed without any previous authorization from the author. However the author´s name and all the URL´s (links) mentioned in the article and biography must be kept.

About the Author

This article can also be accessed in portuguese language from the News Articles section of page PoloMercantil.
Roberto Sedycias has a bachelor degree in Business Administration and over 20 years experience in systems analysis and computer programming. Currently working as IT consultant/chief software engineer for www.PoloMercantil.com.br.

Where can I find good high resolution pictures of battleships?

I'm doing a project for class and need to make a 3D model of a battleship. I'm looking for high resolution pictures of older battleships, preferably from WWI/Pearl Harbor. Any kind will help, even new ones. Thanks

i'm not sure if this helps, but if you go onto google and type in battleships under pictures. once the page loads, you can choose the size of the pictures you want to come up. aka (small, medium, large, extra large)

PlayStation 3 - High-Resolution Image Enlargement Technology : DigInfo

	AC Adapter For Camcorders List Price: $142.95 Sale Price: $63.40
	Description Works with VDR-D100/D105/D200/D210/D220/D230/D250/D300/D310 DVD camcordersWorks with SDR-H200 and SDR-H20 SD camcordersWorks with PV-GS180/GS19/GS29/GS300/GS320/GS36/GS39/GS500/GS59/GS80/GS83/GS85 digital camcordersIncludes AC adapter, AC cord and DC cables

	TechFuel® DC Adapter for Panasonic Toughbook CF-29 Laptop List Price: $59.95 Sale Price: $39.95
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	Panasonic TV Adapter For Panasonic Network Cameras - Model BL-WV10A Observation System Accessories Sale Price: $599.99
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	175 Watt Power Inverter Car Adapter for the Panasonic Toughbook 30 - Core 2 Duo L7500 1.6 GHz - 13.3" TFT, 52, CF-52, W7 and Y7 - Core 2 Duo L7500 1.6 GHz - 14.1" TFT (by Wasabi Power®) List Price: $78.99 Sale Price: $44.99
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	TechFuel® DC Adapter for Panasonic Toughbook CF-18 Laptop List Price: $59.95 Sale Price: $39.95
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Panasonic Toughbook 74

This laptop comes in a ruggedized case, inbuilt WWAN, a handle for carriage, ports covers, extended battery life of about 7 hours.

But it is bulky, expensive, with a heavy adapter, and it doesn't have a multimedia control. The Panasonic ToughBook 74 happens to be uniquely durable in features and also a fantastic warranty.

This laptop is very rugged and can withstand unfriendly conditions in businesses and whatsoever.

The Panasonic Toughbook 74 has durability and mobility characteristics which includes a magnesium-alloy case, a spill-resistant keyboard, an outside readable screen, etc.

panasonic toughbook 74

The toughbook 74 has a processor of 1.8GHz Core Duo, 80GB with 5,400rpm HDD, 512MB of average 533MHz RAM, with an inbuilt graphics card that uses up to 128MB system memory. As regards battery life, this laptop has an extended battery life of averagely 7 hours 18 minutes. It uses an operating system of Windows XP Professional.

Other features includes two USB 2.0 ports, with VGA and serial ports, microphone and headphone jacks, a PC Card, SD card, and ExpressCard/54 slots, with an additional smart card reader. It also has a DVD burner which is swappable. In addition, all ports are covered with a flap for protection.

Its network features are 56Kbps modem, Gigabit Ethernet, and 802.11abg, Bluetooth is also inclusive, with an EV-DO WWAN radio.

It has a dimension of 12 inches width, 11.6 inches depth, and 2 inches thick, with a weight of about 6 pounds, plus an additional weight with its adapter.

The screen display is 13.3 inch with a touch screen function, and a 1,024x768 native resolution. It has a bright screen which is reader during bright daylight.

This laptop is rugged enough for rugged users.

About the Author

Visit my BLOGS: Buy Computers Online, Mesothelioma Info Online

i got Panasonic receiver and i dont have a optic on it. Got music port can you buy the monster cable adapter?

the model is SC-HT740 and i want to buy the monster cable opticl adpter for my xbox360 it has the music port will this work.the music port is a 3.5 same as the adpter.

best thing to do is call PANASONIC Customer Toll-Free Hotline. if i'm not mistaken, they're open 24 hours. they'd be happy to assist you with what ever problem you encounter with that Panasonic receiver.

SDR-S150 Adapter USB Battery Panasonic

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	Crimestopper SV-5400 License Plate Frame Compact CCD Reverse Camera with Infra Red LED and 70 Angle (1 Each) Sale Price: $140.80
	Description Crimestopper SV-5400 License Plate Frame Compact CCD Reverse Camera with Infra Red LED and 70 Angle (1 Each)

	58mm Reverse Mount Adapter for Canon EOS 1d, 1ds, Mark II, III, 5D, Mark II, 10D, 20D, 30D, 40D, 50D, Rebel t1i, xt, xti, xs, xsi 300D, 350D, 400D, 450D, 500D, 1000D List Price: $19.90 Sale Price: $8.95
	Description By mounting the lens backward on a camera body, you can create amazing macro images. It is extremely fun to turn you lens into a macro lens.

	Fotodiox 52mm Macro Reverse Lens Mount Adapter for Nikon D1, D1x, D1h, D2, D2x, D2h, D3, D3x, D3h, D100, D200, D300, D300s, D700, D40, D40x, D50, D60, D70, D70s, D80, D90, D5000, D3000 List Price: $19.90 Sale Price: $9.95
	Description By mounting the lens backward on a camera body, you can create amazing macro images. It is extremely fun to turn you lens into a macro lens.

	Fotodiox 52mm Macro Reverse Mount Adapter for Canon EOS 1d,1ds, Mark II, III, 5D, 5D Mark II, 10D, 20D, 30D, 40D, 50D, Digital Rebel xt, xti, xs, xsi x1i, 300D, 350D, 400D, 450D, 500d, 1000d List Price: $19.90 Sale Price: $9.95
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	Marshall 5.6" LCD Color Monitor (Audio and Reverse Image) Kit, with Battery Pack and Case List Price: $429.00
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Reversing Camera And Parking Sensors Should Be Accompanied By Mobile DVR

When it comes to automotive industry, you can see a diverse range of devices and products that are now available to make your car look and work good. But as no to people think the same, you can find a great deal of variation in the demand for these products and devices.

Actually, there are some people who believe that you must install parking sensors in your car as they are essential for parking. Since these parking sensors come in sensor kits containing 2 to 6 sensors, so a lot of people go for them as they provide an inexpensive way to hassle-free parking.

On the other hand, you can find people who argue about the importance and benefits of reversing camera as they believe it to be extremely useful in case you need to drive in the dark. Since they use a highly sophisticated technology, it becomes easier for you to detect an obstruction even in the dark.

It is fact that your major emphasis should be on making your car more functional so that you may become able to stay away from accidents but you must try to install some other devices as well . That’s the situation when you can consider buying a mobile DVR.

Mobile DVR or a mobile Digital Video Recorder has now become an integral part of most vehicles running on the road. The great thing is that the prices of these recorders have come down to a great extent, making it possible for all to buy one. If you are also interested in buying a recorder for you, then you must understand that different options are available for you to choose from. You can now pick one model from a wide variety of DVRs ranging from basic 4-channel stand alone units to 32 full multiplex PTZ recorders.

Generally though, you can opt for any one of the following;

•    4 camera DVR, which is perfect for those who don’t want to compromise over quality as this recorder can withstand a shock of 8GB. With 30/25 frames per channel and four alarm inputs, most of these DVRs are perfect for all.

•    Mobile DVR with audio, which comes with GPS video overlay and helps you in recording speed, direction position.

•    SD card mini DVR is also available which is perfect to take anywhere you want.

Apart from these, you can find several other options to consider but do make sure that you are buying from a right place as that’s the only way to get the best value for your money.

So, the bottom line is that though you must go for parking sensors and reversing cameras but you must never overlook the need of installing DVRs in your vehicle as that’s the latest trend. So, follow it!

About the Author

Because of the years of experience in automotive industry, regentrange.co.uk is now able to provide you with all important devices like parking sensors, CCTV, reversing camera, mobile dvr and much more. So, pay a visit to see what can be bought to make your driving life more convenient.

The Eye Shutter On My Camera Is In Reverse Can Someone PLEASE HELP!?

I Am Having Difficulties With My Sanyo Camera. The Shutter Eye Seems To Be In Reverse. When The Camera Is Powered Off The Eye Shutter Is Open When The Camera Is Powered On The Shutter Closes And I Am Unable To Take Photos

It sounds like the shutter was some how opened when the camera was off and it wasn't closed before it was turned back on. So now the mechanism inside is working in the opposite way.

I think I would take the camera to a camera repair shop, they should be able to fix it up with no problems.

If you want to try and do it yourself and save some money, then you could try opening the shutter on your own when the camera is turned on. If you are lucky, this may fix the problem.

6er Reversing camera

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	Description CASE LOGIC IN-CAR DVD

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Are you thinking of using a spy camera? Think again?

Do you think the use of a spy camera could play a significant role in your life? A few days ago, I was involved in a road accident. My car was hit by a van driver who, in the early hours of Monday morning, was thinking more about how short his weekend had been rather than paying attention to the road conditions. Subsequently, he jumped a red light and hit the front of my car. Fortunately no one was hurt although my car came out worse. We exchanged details and parted company.

Later in the day as I reported the incident to the driver’s insurance company, it quickly dawned on me that the other driver may be dishonest and claim that it was I who had jumped the red light. Although I have an independent witness, the other driver could later produce a friend to act as an “independent witness”. So how does an insurance company ascertain who is at fault when both parties produce their own witnesses? The answer is simple; which outcome will minimise their loss? That judgement may not necessarily be the just one for the wronged party!

How do you therefore ensure your “independent witness” is the one who is irrefutably believed? This is where the latest car recorder spy cameras come into their own. By definition, a spy camera is a device that is “hidden” in plain view. This may be in a tissue box, alarm clock or teddy bear. A car recorder on the other hand is not hidden and looks like what it is, a video recording device.

There are a number of car recorders in the market with varying functionalities that will make an ideal independent witness. Some record audio and vision of the internal and external of the car simultaneously, day and night. They record on to SD cards in AVI file format with recording times, in some cases, of up to 144 hours.

These very clever devices will record in infrared mode at night if desired. Some car recorders are very much like CCTV security systems that have vehicle DV recorders. They have a loop circular recording function recording in a one-hour loop with 2GB mini SD card. Their functions include repeat storage by section, date and time stamp, microphone and USB/AV interface. Red laser light points to the area being recorded. These devices can be mounted on the car’s dashboard or stuck to the windscreen. They usually come with 12v car cigarette lighter adaptors, batteries and TV out functions.

The video quality is of a very high standard. Video evidence is objective and is ideal for insurance purposes. However, it is not just for accidents that these recorders are being used. Taxi and mini cab drivers are quickly appreciating the benefits of these devices in recording passenger behaviour in their vehicles.

The burden of proof is firmly on the shoulders of the plaintiff. The financial loss due to failed litigation can be prohibitive. Do you not think you deserve all the advantages you can get?

About the Author

Patrick Etefia is a security and surveillance specialist. To see the latest spy cameras, hidden cameras and other surveillance devices available visit http://www.spyultimatum.com

Anyone know how to mount a camera to a dashboard, car's roof/hood/wheel well, and more?

I have an HDR-XR520 and need to mount it to the corner of the interior of the car, the dashboard, one on the roof, and one near the wheel well facing front and back. Anyone got any ideas on how to find camera mounts? The ones I have found are incredibly bulky and they are not meant for sports. I need them for sport races.

check out smc-corp.com
they have all the mounting hardware you need
they have real good suction cup mounts that will latch onto any smooth surface (window, hood, etc.)

The best of the best CAMERACAR in italia - crash e risate on board

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Open Loop Solutions and Current Limiting for Stepping Motors

There is good reason to run a stepping motor at a supply voltage above that needed to push the maximum rated current through the motor windings. Running a motor at higher voltages leads to a faster rise in the current through the windings when they are turned on, and this, in turn, leads to a higher cutoff speed for the motor and higher torques at speeds above the cutoff.

Microstepping, where the control system positions the motor rotor between half steps, also requires external current limiting circuitry. For example, to position the rotor 1/4 of the way from one step to another, it might be necessary to run one motor winding at full current while the other is run at approximately 1/3 of that current.

The remainder of this section discusses various circuits for limiting the current through the windings of a stepping motor, starting with simple resistive limiters and moving up to choppers and other switching regulators. Most of these current limiters are appropriate for many other applications, including limiting the current through conventional DC motors and other inductive loads.

Resistive Current Limiters

The easiest to understand current limiter is a series resistor. Most motor manufacturers recommended this approach in their literature up until the early 1980's, and most motor data sheets still give performance curves for motors driven by such circuits. The typical circuits used to control the current through one winding of a permanent magnet or hybrid motor are shown in Figure 4.1.

Figure 4.1

R1 in this figure limits the current through the motor winding. Given a rated current of I and a motor winding with a resistance Rw, Ohm's law sets the maximum supply voltage as I(Rw+R1). Given that the inductance of the motor motor winding is Lw, the time constant for the motor winding will be Lw/(Rw+R1). Figure 4.2 illustrates the effect of increasing the resistance and the operating voltage on the rise and fall times of the current through one winding of a stepping motor.

Figure 4.2

R2 is shown only in the unipolar example in Figure 4.1 because it is particularly useful there. For a bipolar H-bridge drive, when all switches are turned off, current flows from ground to the motor supply through R1, so the current through the motor winding will decay quite quickly. In the unipolar case, R2 is necessary to equal this performance. When the switches in the H-bridge circuit shown in Figure 4.1 are opened, the direction of current flow through R1 will reverse almost instantaneously! If R1 has any inductance, for example, if it is wire-wound, it must either be bypassed with a capacitor to handle the voltage kick caused by this current reversal, or R2 must be added to the H-bridge.

Given the rated maximum current through each winding and the supply voltage, the resistance and wattage of R1 is easy to compute. R2 if it is included, poses more interesting problems. The resistance of R2 depends on the maximum voltage the switches can handle. For example, if the supply voltage is 24 volts, and the switches are rated at 75 volts, the drop across R2 can be as much as 51 volts without harming the transistors. Given an operating current of 1.5 amps, R2 can be a 34 ohm resistor. Note that an interesting alternative is to use a zener diode in place of R2.

Figuring the peak average power R2 must dissipate is a wonderful exercise in dynamics; the inductance of the motor windings is frequently undocumented and may vary with the rotor position. The power dissipated in R2 also depends on the control system. The worst case occurs when the control system chops the power to one winding at a high enough frequency that the current through the motor winding is effectively constant; the maximum power is then a function of the duty cycle of the chopper and the ratios of the resistances in the circuit during the on and off phases of the chopper. Under normal operating conditions, the peak power dissipation will be significantly lower.

Linear Current Limiters

A pair of high wattage power resistors can cost more than a pair of power transistors plus a heat sink, particularly if forced air cooling is available. Furthermore, a transistorized constant current source, as shown in Figure 4.3, will give faster rise times through the motor windings than the current limiting resistor shown in Figure 4.1. This is because a current source will deliver the full supply voltage across the motor winding until the current reaches the rated current; only then will the current source drop the voltage.

Figure 4.3

In Figure 4.3, a transistorized current source (T1 plus R1) has been substituted for the current limiting resistor R1 used in the examples in Figure 4.1. The regulated voltage supplied to the base of T1 serves to regulate the voltage across the sense resistor R1, and this, in turn, maintains a constant current through R1 so long as any current is allowed to flow through the motor winding. Typically, R1 will have as low a resistance as possible, in order to avoid the high cost of a power resistor. For example, if the forward voltage drops across the diode in series with the base T1 and VBE for T1 are both 0.65 volts, and if a 3.3 volt zener diode is used for a reference, the voltage across R1 will be maintained at about 2.0 volts, so if R1 is 2 ohms, this circuit will limit the current to 1 amp, and R1 must be able to handle 2 watts. R3 in Figure 4.3 must be sized in terms of the current gain of T1 so that sufficient current flows through R1 and R3 to allow T1 to conduct the full rated motor current.

The transistor T1 used as a current regulator in Figure 4.3 is run in linear mode, and therfore, it must dissipate quite a bit of power. For example, if the motor windings have a resistance of 5 ohms and a rated current of 1 amp, and a 25 volt power supply is used, T1 plus R1 will dissapate, between them, 20 watts! The circuits discussed in the following sections avoid this waste of power while retaining the performance advantages of the circuit given here.

When an H-bridge bipolar drive is used with a resistive current limiter, as shown in Figure 4.1, the resistor R2 was not needed because current could flow backwards through R1. When a transistorized current limiter is used, current cannot flow backwards through T1, so a separate current path back to the positive supply must be provided to handle the decaying current through the motor windings when the switches are opened. R2 serves this purpose here, but a zener diode may be substituted to provide even faster turn-off.

The performance of a motor run with a current limited power supply is noticably better than the performance of the same motor run with a resistively limited supply, as illustrated in Figure 4.4:

Figure 4.4

With either a current limited supply or a resistive current limiter, the initial rate of increase of the current through the inductive motor winding when the power is turned on depends only on the inductance of the winding and the supply voltage. As the current increases, the voltage drop across a resistive current limiter will increase, dropping the voltage applied to the motor winding, and therefore, dropping the rate of increase of the current through the winding. As a result, the current will only approach the rated current of the motor winding asymptotically In contrast, with a pure current limiter, the current through the motor winding will increase almost linearly until the current limiter cuts in, allowing the current to reach the limit value quite quickly. In fact, the current rise is not linear; rather, the current rises asymptotically towards a limit established by the resistance of the motor winding and the resistance of the sense resistor in the current limiter. This maximum is usually well above the rated current for the motor winding.

Open Loop Current Limiters

Both the resistive and the linear transistorized current limiters discussed above automatically limit the current through the motor winding, but at a considerable cost, in terms of wasted heat. There are two schemes that eliminate this expense, although at some risk because of the lack of feeback about the current through the motor.

Use of a Voltage Boost

If you plot the voltage across the motor winding as a function of time, assuming the use of a transistorized current limiter such as is illustrated in Figure 4.3, and assuming a 1 amp 5 ohm motor winding, the result will be something like that illustrated in Figure 4.5:

Figure 4.5

As long as the current is below the current limiter's set point, almost the full supply voltage is applied across the motor winding. Once the current reaches the set point, the voltage across the motor winding falls to that needed to sustain the current at the set point, and when the switches open, the voltage reverses briefly as current flows through the diode network and R2. An alternative way to get this voltage profile is to use a dual-voltage power supply, turning on the high voltage for as long as it takes to bring the current in the motor winding up to the rated current, and then turning off the high voltage and turning on the sustaining voltage. Some motor controllers do this directly, without monitoring the current through the motor windings. This provides excellent performance and minimizes power losses in the regulator, but it offers a dangerous temptation.

If the motor does not deliver enough torque, it is tempting to simply lengthen the high-voltage pulse at the time the motor winding is turned on. This will usually provide more torque, although saturation of the magnetic circuits frequently leads to less torque than might be expected, but the cost is high! The risk of burning out the motor is quite real, as is the risk of demagnitizing the motor rotor if it is turned against the imposed field while running hot. Therefore, if a dual-voltage supply is used, the temptation to raise the torque in this way should be avoided!

The problems with dual voltage supplies are particularly serious when the time intervals are under software control, because in this case, it is common for the software to be written by a programmer who is insufficiently aware of the physical and electrical characteristics of the control system.

Use of Pulse Width Modulation

Another alternative approach to controlling the current through the motor winding is to use a simple power supply controlled by pulse width modulaton (PWM) or by a chopper. During the time the current through the motor winding is increasing, the control system leaves the supply attached with a 100% duty cycle. Once the current is up to the full rated current, the control system changes the duty cycle to that required to maintain the current. Figure 4.6 illustrates this scheme:

Figure 4.6

For any chopper or pulse width modulator, we can define the duty-cycle D as the fraction of each cycle that the switch is closed:

D = Ton / (Ton + Toff)

Where

Ton -- time the switch is closed during each cycle

Toff -- time the switch is open during each cycle

The voltage curve shown above indicates the full supply voltage being applied to the motor winding during the on-phase of every chopper cycle, while when the chopper is off, a negative voltage is shown. This is the result of the forward voltage drop in the diodes that are used to shunt the current when the switches turn off, plus the external resistance used to speed the decay of the current through the motor winding. For large values of Ton or Toff, the exponential nature of the rise and fall of the current through the motor winding is significant, but for sufficiently small values, we can approximate these as linear. Assuming that the chopper is working to maintain a current of I and that the amplitude is small, we will approximate the rates of rise and fall in the current in terms of the voltage across the motor winding when the switch is closed and when it is open:

Von = Vsupply - I(Rwinding + Ron)

Voff = Vdiode + I(Rwinding + Roff)

Here, we lump together all resistances in series with the winding and power supply in the on state as Ron, and we lump together all resistances in the current recirculation path when the switch(es) are open as Roff. The forward voltage drops of any diodes in the current recirculation path have been lumped as Vdiode; if the off-state recirculation path runs from ground to the power supply (H-bridge fast decay mode), the supply voltage must also be included in Vdiode. Forward voltage drops of any switches in the on-state and off-state paths should also be incorporated into these voltages.

To solve for the duty cycle, we first note that:

dI/dt = V/L

Where

I -- current through the motor winding

V -- voltage across the winding

L -- inductance of the winding

We then substitute the specific voltages for each phase of operation:

Iripple / Toff = Voff / L

Iripple / Ton = Von / L

Where

Iripple -- the peak to peak ripple in the current

Solving for Toff and Ton and then substituting these into the definition of the duty cycle of the chopper, we get:

D = Ton / (Ton + Toff) = Voff / (Von + Voff)

If the forward voltage drops in diodes and switches are negligable, and if the only significant resistance is that of the motor winding itself, this simplifies to:

D = I Rwinding / Vsupply = Vrunning / Vsupply

This special case is particularly desirable because it delivers all of the power to the motor winding, with no losses in the regulation system, without regard for the difference between the supply voltage and the running voltage.

The AC ripple Iripple superimposed on the running current by a chopper can be a source of problems; at high frequencies, it can be a source of RF emissions, and at audio frequencies, it can be a source of annoying noise. For example, with audio frequency chopping, most stepper controlled systems will "squeel", sometimes loudly, when the rotor is displaced from the equilibrium position. For small systems, this is usually no more than a minor nuisance, but in systems with large numbers of high power steppers, the ripple currents can induce dangerous AC voltages on nearby signal lines and dangerous currents in nearby ground lines. To find the ripple amplitude, first recall that:

Iripple / Toff = Voff / L

Then solve for Iripple:

Iripple = Toff Voff / L

Thus, to reduce the ripple amplitude at any particular duty cycle, it is necessary to increase the chopper frequency. This cannot be done without limit because switching losses increase with frequency. Note that this change has no significant effect on AC losses; the decrease in such losses due to decreased amplitude in the ripple is generally offset by the effect of increasing frequency.

The primary problem with use of a simple chopping or pulse-width modulation control scheme is that it is completely open loop. Design of good chopper based control systems requires knowledge of motor characteristics such as inductance that are frequently poorly documented, and as with dual-voltage supplies, when motor performance is marginal, it is very tempting to increase the duty-cycle without attention to the long-term effects of this on the motor. In the designs that follow, this weakness will be addressed by introducing feedback loops into the low level drive system to directly monitor the current and determine the duty cycle.

One-Shot Feedback Current Limiting

The most common approach to automatically adjusting the duty cycle of the switches in the stepper driver involves monitoring the current to the motor windings; when it rises too high, the winding is turned off for a fixed interval. This requires a current sensing system and a one-shot, as illustrated in Figure 4.7:

Figure 4.7

Figure 4.7 illustrates a unipolar drive system. As with the circuit given in Figure 4.3, R1 should be as small as possible, limited only by the requirement that the sense voltage provided to the comparator must be high enough to be within its operating range. Note that when the one-shot output (¬Q) is low, the voltage across R1 no-longer reflects the current through the motor winding. Therefore, the one-shot must be insensitive to the output of the comparator between the time it fires and the time it resets. Practical circuit designs using this approach involve some complexity to meet this constraint! Selecting the value of R2 for the circuit shown in Figure 4.7 poses problems. If R2 is large, the current through the motor windings will decay quickly when the higher level control system turns off this motor winding, but when the winding is turned on, the current ripple will be large and the power lost in R2 will be significant. If R2 is small, this circuit will be very energy efficient but the current through the motor winding will decay only slowly when this winding is turned off, and this will reduce the cutoff speed for the motor.

The peak power dissipated in R2 will be I2R2 during Toff and zero during Ton; thus, the average power dissipated in R2 when the motor winding is on will be:

P2 = I2R Toff / (Ton + Toff)

Recall that the duty cycle D is defined as Ton/(Ton+Toff) and may be approximated as Vrunning/Vsupply. As a result, we can approximate the power dissipation as:

P2 = I2R2 (1 - Vrunning/Vsupply).

Given the usual safety margins used in selecting power resistor wattages, a better approximation is not necessary.

When designing a control system based on pulse width modulation, note that the cutoff time for the one-shot determines Toff, and that this is fixed, determined by the timing network attached to the one-shot. Ideally, this should be set as follows:

Toff = L Iripple / Voff

This presumes that the inductance L of the motor winding is known, that the acceptable magnitude of Iripple is known, and that Voff, the total reverse voltage in the current recirculation path, is known and fixed. Note that this scheme leads to a variable chopping rate. As with the linear current limiters shown in Figure 4.3, the full supply voltage will be applied during the turn-on phase, and the chopping action only begins when the motor winding reaches the current limit set by Vref. This circuit will vary the chopping rate to compensate for changes in the back EMF of the motor winding, for example, those caused by rotor motion; in this regard, it offers the same quality of regulation as the linear current limiter. The one-shot current regulator shown in Figure 4.7 can also be applied to an H-bridge regulator. The encoded H-bridge shown in Figure 3.13 is an excellent candidate for this application, as shown in Figure 4.8:

Figure 4.8

Unlike the circuit in Figure 4.7, this circuit does not provide design tradeoffs in the selection of the resistance in the current decay path; instead, it offers the same selection of decay paths as was available in the original circuit from Figure 3.13. If the X and Y control inputs are held in a running mode (01 or 10), the current limiter will alternate between that running and slow decay modes, maximizing energy efficiency. When the time comes to turn off the current through the motor winding, the X and Y inputs may be set to 00, using fast decay mode to maximize the cutoff speed, while if the damping effect of dynamic braking is needed to control resonance, X and Y may be set to 11.

Note that the current recirculation path during dynamic braking does not pass through R1, and as a result, if the motor generates a large amount of power, burnt out components in the motor or controller are likely. This is unlikely to cause problems with stepping motors, but when dynamic braking is used with DC motors, the current limiter should be arranged to remain engaged while in braking mode!

Practical Examples

SGS-Thompson (and others) L293 (1A) and L298 (2A) dual H-bridges are designed for easy use with partial feedback current limiters. These chips have enable inputs for each H-bridge that can be directly connected to the output of the one-shot, and they have ground connections for motor-power that are isolated from their logic ground connections; this allows sense resistors to be easily incorporated into the circuit. The 3952 H-bridge from Allegro Microsystems can handle up to 2-amps at 50 volts and incorporates all of the logic necessary for current control, including comparators and one-shot. This chip is available in many package styles; Figure 4.9 illustrates the DIP configuration wired for a constant current limit:

Figure 4.9

If Rt is 20 Kohm, and Ct is 1000pF, Toff for the pulse-width modulation will be fixed at 20 (±2) microseconds. The 3952 chip incorporates a 10 to 1 voltage divider on the Vref input, so attaching Vref to the 5 volt logic supply sets the actual reference voltage to 0.5 V. Thus, if the sense resistor Rs is 0.5 ohms, this arrangement will attempt to maintain a regulated current through the load of 1 A.

Note that all power switching chips are potentially serious sources of electromagnetic interfence! The 47µF capacitor shown between the motor power and ground should be as close to the chip as possible, and the path from the SENSE pin through Rs to ground and back to a ground pin of the chip should be very short and with a very low resistance.

On the 5 volt side, because Vref is taken from Vcc, a small decoupling capacitor should be placed very close to the chip. It may even be appropriate to isolate the Vref input from Vcc with a small series resistor and a separate decoupling capacitor. If this is done, note that the resistance from the Vref pin to ground through the chip's internal voltage divider is around 50 Kohms.

One of the more dismaying features of the 3952 chip, as well as many of its competitors, is the large number of control inputs. These are summarized in the following table:

BRAKE ENABLE PHASE  MODE  OUTa OUTb Notes 

0  -  -  0   0  0  Brake 

0  -  -  1   0  0  Limited Brake 

1  1  -  0   -  -  Standby 

1  1  -  1   -  -  Sleep 

1  0  0  0   0  1  Reverse, Slow 

1  0  0  1   0  1  Reverse, Fast 

1  0  1  0   1  0  Forward, Slow 

1  0  1  1   1  0  Forward, Fast 

In the forward and reverse running modes, the mode input determines whether fast or slow decay modes are used during Toff. In the dynamic braking modes, the mode input determines whether the current limiter is enabled. This is of limited value with stepping motors, but use of dynamic braking without a current limiter can be dangerous with DC motors. In sleep mode, the power consumption of the chip is minimized. From the perspective of the load, sleep and standby modes put the load into fast decay mode (all switches off) but in sleep mode, the chip draws considerably less power, both from the logic supply and the motor supply.

Hysteresis Feedback Current Limiting

In many cases, motor control systems are expected to operate acceptably with a number of different stepping motors. The one-shot based current regulators illustrated in Figures 4.7 to 4.9 have an accuracy that depends on the inductance of the motor windings. Therefore, if fixed accuracy is required, any motor substation must be balanced by changes to the RC network that determines the off-time of the one-shot.

This section deals with alternative designs that eliminate the need for this tuning. These alternative designs offer fixed precision current regulation over a wide range of load inductances. The key to this approach is arrange the recirculation paths so that the current-sense resistor R1 is always in the circuit, and then turn the switches on or off depending only on the current.

The usually way to build this type of controller is to use a comparator with a degree of hysteresis, for example, by feeding the output of the comparator back into one of its inputs through a resistor network, as illustrated in Figure 4.10:

Figure 4.10

To compute the desired values of R2 and R3, we note that:

Vripple > Vhysteresis

Where:

Vripple = Iripple R1

Iripple -- the maximum ripple allowed in the current

and:

Vhysteresis = Vswing R2 / (R2 + R3)

Vswing -- the voltage swing at the output of the comparator

We can solve this for the ratio of the resistances:

R2 / (R2 + R3)

For example, if R1 is 0.5 ohms and we wish to regulate the current to within 10 milliamps, using a comparator with TTL compatable outputs and a voltage swing of 4 volts, the ratio must be no greater than .00125.

Note that the sum R2 + R3 determines the loading on Vref, assuming that the input resistance of the comparator is effectively infinite. Typically, therefore, this sum is made quite large.

One problem with the circuit given in Figure 4.10 is that it does not limit the current through the motor in dynamic braking or slow decay modes. Even if the current through the sense resistor vastly exceeds the desired current, switches B and D will remain closed in dynamic braking mode, and if the reference voltage is variable, rapid drops in the reference voltage will not be enforced by this control system.

The designers of the Allegro 3952 chip faced this problem, and passed the solution back to the user, providing a MODE input to determine whether the chopper alternated between running and fast decay mode or running and slow decay mode. Note that this chip uses a fixed off-time set by a one-shot, and therefore, switching between the two decay modes will change the precision of the current regulator. Given that such a change in precision is acceptable, we can modify the circuit from Figure 4.10 to automatically thrown the system into fast-decay mode if the running or dynamic braking current exceeds the set-point of the comparator by too great a margin. Figure 4.11 illustrates how this can be done using a second comparator:

Figure 4.11

As shown in Figure 4.11, the lower comparator directly senses the voltage across R1, while the upper comparator senses a higher voltage, determined by a resistor network. This network should hold the negative inputs of the two comparators just far enough apart to guarantee that, as the voltage across R1 rises, the top comparator will always open the top switches before the bottom comparator opens the bottom switches, and as the voltage across R1 falls, the bottom comparator will always close the bottom switches before the top comparator closes the top switches.

As a result, this system has two basic steady-state running modes. If the motor winding is drawing power, one of the bottom switches will remain closed while the opposite switch on the top is used to chop the power to the motor winding, alternating the state of the system between running and slow-decay mode.

If the motor winding is generating power, the top switches will remain open and the bottom switches will do the chopping, alternating between fast-decay and slow-decay modes as needed to keep the current within limits. If the two comparators have accuracies on the order of a millivolt with hysteresis on the order of 5 millivolts, it is reasonable to use a 5 millivolt difference between the top and bottom comparator. If we use the 5 volt logic supply as the pull-up supply for the resistor network, and we assume a nominal operating threshold of around 0.5 volts, the resistor network should have a ratio of 1:900; for example, a 90k resistor from +5 and a 100 ohm resistor between the two comparator inputs.

Practical Examples

The basic idea described in this section is also applicable to unipolar stepping motor controllers, although in this context, it is somewhat easier to apply if the reference voltage is measured with respect to the unregulated motor power supply. Figure 4.12 illustrates a practical example, using the forward voltage drop across an ordinary silicon diode as the reference voltage.

Figure 4.12

The circuit shown in Figure 4.12 uses a 2.4K resistor to provide a bias current of 10ma to the reference diode. A small capacitor should be added across the reference diode if the motor power supply is minimally regulated.

The 0.6 ohm value used for the current sensing resistor sets the regulator to 1 amp, assuming that the reference voltage is 0.6 volts. The 1000 to 1 ratio on the feedback network around the comparator sets the allowed ripple in the regulated current to around 8 ma.

The comparator shown in Figure 4.12 can be powered from the minimally regulated motor power supply, but only if it is able to operate with the inputs very close to its positive supply voltage. Although I have not tried it, the Mitsubishi M5249L comparator appears to be ideally suited to this job; it can work from a positive supply of up to 40 volts, and the input voltages are allowed to slightly exceed the positive supply voltage! The output of this comparator is open collector, so the hysteresis network shown in the figure also acts as a pull-up network, providing a pull-up current of a few milliamps. The diode to +5 shown in the figure clamps the comparator output to the logic supply voltage, protecting the and gate inputs from overvoltage.

Other Current Sensing Technologies

The feedback loops of all of the current limiters given above use the voltage drop across a small resistor to measure the current. This is an excellent choice for small motors, but it poses difficulties for large high-current motors! There are other current sensing technologies appropriate for such settings, most notably those that deliver only a fraction of the motor current to the sensing resistor, and those that measure the current by sensing the magnetic field around the conductor.

National Semiconductor had incorporated a very clever current sensor into a number of their H-bridges. This delivers a current to the sense resistor that is proportional to the current through the motor winding, but far lower. For example, on the LMD18200 H-bridge, the sense resistor receives exactly 377 micro amps per ampere flowing through the motor winding.

The key to the current sensing technology used in the National Semiconductor line of H-bridges is found in the internal structure of the DMOS power switching transistors they use. These transistors are composed of thousands of small MOSFET transistor cells wired in parallel. A small but representative fraction of these cells, typically 1 in 4000, is used to extract the sense current while the remainder of the cells controls the motor current. The data sheet for the National LMD18245 H-bridge contains an excellent write-up on how this is done.

When very high currents are involved, precluding use of an integrated H-bridge, an appealing and well established current sensing technology involves the use of a split ferrite core and a hall effect sensor, as illustrated in Figure 4.13:

Figure 4.13

Simple linear Hall effect sensors require a small regulated bias current between two of their terminals, and they generate a DC voltage proportional to the magnetic field on a third terminal. The magnetic field across the gap sawed in the ferrite core is proportional to the current through the wire, and therefore, the voltage reported by the Hall effect sensor will be proportional to the current.

Allegro Microsystems and others make a full lines of Hall effect sensors, but pre-calibrated hall effect current sensors are available; these include the split core, the hall effect sensor, and auxiliary components, all mounted on a small PC board or potted as a unit. Newark Electronics lists a few sources of these, including Honeywell, F. W. Bell and LEM Instruments.

An intriguing new current sensor is just becoming available, as of 1998, based on a thin-film magneto resistive sensor; the sensitivity of this technology eliminates the need for the ferrite core and the result is a very compact current sensor. The NT series sensors made by F. W. Bell use this technology.

About the Author

Assistant professor in lord venkateswara engineering college.I am doing phd in sathyabama university, Tamil Nadu,India.

How will current high school credits switch over if I were to start Penn Foster?

Hi, I'm halfway through my junior year and am really leaning toward starting the Penn Foster High School program, and I just want to know how my previous credits would be affected (if they'd still count, or if I'd have to take classes over again), and if I'd have to pay full tuition or just part of it since I've already taken a little more than two years of regular highschool. Any help would be great in the regard.

I know that the credits you earn will not be dropped. They will stay on your transcript and will show how many credits you have completed. I am not sure how you show Penn Foster that you have those credits, but I am sure if you call their phone number (help line?) They can help you with that... Good luck!

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Is setting up a home theater system just a matter of putting in a television, dvd player and setting up a few speakers? Well, technically yes but if you really want to experience all the viewing benefits home theater offers then you need to consider some viewing aesthetics.

TV Viewing Distance

Have you ever considered the importance of TV viewing distance? Not many people do. I've lost count of the number of times I've walked into a home theater room and cringed at the distance the TV is set up from the viewing platform. Sure, personal preferences come into play here and I'll admit, my idea of the right viewing distance will vary from others but if you follow some well worn guidelines then you can enhance your viewing experience no end.

What Do You Need To Consider For Best Viewing Position?

When planning and setting up a home theater room consider the size of the room. This will be in proportion to the size of television you intend to install. Issues such as distance from the TV plus viewing angle will come into play. Set the viewing platform too close to the TV and you risk seeing details you don't normally see such as image build up. If you are too far away, then other than losing the effect of the image output, it will be harder to become immersed in the program because at too far a distance, you immediately invite the risk of being distracted by influences other than the creen you are watching.

Suggested Viewing Distance Guidelines

What you want is a distance you are comfortable with and where your eye to detail ratio will not be lost. Recommended guidelines suggest that between two to five times the length of your television screen will get you somewhere "in the ball park." Again this depends on your vision strength so if you have 20/20 vision, then the distance between you and your Tv will probably be further than say a person with less vision strength.

In the end, TV viewing distance comes down to personal choice so you'll probably want to spend a little time adjusting and testing distance levels. Sounds technical doesn't it? Also consider if you are a frequent home theater host: what about your guests? I guess not huh! My philosophy in this instance is "Hey, I'm providing the theater center for your enjoyment. You work out where you want to sit."

Next time you walk into a cinema go in as early as possible and watch the seating habits of people as they walk in. It will give you some idea of how individual viewing habits differ. Some will sit to the left, others to the right while the center aisle, usually at the highest level, is always a popular place to view from.

Viewing Angles

Taking TV viewing distance to the next level, the vertical viewing angle is another important part of the equation. The good news is that in a home theater set up, this shouldn't present too much of a problem because most rooms are not big enough to enable a discomfort level outside the recommended angle of 30-35 degrees. What is the vertical viewing angle? Simply put, it's the viewer's eye height from his/her seated position to the top of the screen.

When you are seated for a long time this becomes important because too high or too low and problems can arise such as physical discomfort like neck strain. So, if you're thinking of mounting your TV high on the wall think again, and pay particular attention to the 30-35 degree vertical viewing angle.

So what does all this mean? Probably nought if you "don't give a hoot" about TV viewing distance and viewing angles however, if you are going to the trouble and expense of setting up a quality home theater room, then wouldn't it make sense to do it right from the ground up?

About the Author

Dean Caporella is a professional broadcaster. Understanding the importance of TV viewing distance will enhance your home theater experience. Get the latest home theater tips and tricks at:http://www.hometheaterinfoline.com

How do i improve my viewing angle on xbox360?

How do i improve my viewing angle on xbox360?
i mean how much of the screen i can see on my xbox 360, how r the 180 degree HDTVs? any help plz. lots of points to be handed out.

That has nothing to do with the Xbox 360, it depends on your screen!!

You'll just have to check out different HDTVs, I find Samsung and Phillips are good, I usually look at my Xbox 360 display on a Phillips HDTV at an angle (from where I sit) and not straight on.

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