Power-Tracking Battery-Charger IC Supports Solar-Power Systems

In non-utility grid applications solar panels produce dc power for emergency roadside telephones, navigation buoys, and other remote loads. Virtually all 12-V-system solar panels comprise a series of photovoltaic cells that have a maximum output power of less than 25 W. In producing this power the solar-panel system uses a battery to provide power when the panel is “dark.” The rechargeable battery can supply power for long periods of time, requiring a charger that can properly operate a solar panel.

Meeting this need is Linear Technology's LT3652 monolithic buck-charger IC, which operates with a single solar panel. The IC uses average-current-mode control-loop architecture to provide constant current/constant voltage (CC/CV) charge characteristics with a programmable charge current. The charger can be programmed to produce a 14.4-V float voltage. Housed in a 3- × 3-mm DFN-12 package, the IC can charge a variety of battery configurations, including up to three Li-Ion/Polymer cells in series, up to four Lithium Iron Phosphate (LiFePO₄) cells in series, and sealed lead-acid batteries up to 14.4 V.

Depending on panel characteristics, the LT3652 can produce peak power in excess of 95%, with panel output voltages from 12.5 V to 18.5 V. Its input-voltage-regulation loop controls the solar-panel output voltage to produce peak output power while charging the associated battery, delivering nearly the same efficiency as more complex and expensive Maximum Peak Power Tracking (MPPT) techniques.

Fig. 1 shows a typical solar panel-charger application circuit with a 7.2-V LiFePO ₄ battery pack. Connecting a resistor divider from V_IN (pin 1) to V_{IN_REG} (pin 2) programs the minimum operational input voltage, which in turn programs the peak power voltage for the solar panel. The LT3652 controls the maximum charge current required to maintain the programmed operational V_IN voltage by maintaining the voltage on V_{IN_REG} at or above 2.7 V. If V_{IN_REG} goes below 2.7 V it reduces the maximum charge current and maintains the panel at the output voltage corresponding to its peak output power point. Fig. 2 plots the LT3652's maximum charger-output current vs. input voltage from a solar panel.

The LT3652 accepts inputs from 4.95 V to 32 V, with a 40-V maximum rating. Its input-voltage-regulation loop also allows optimized charging from poorly regulated sources where the input can collapse in overcurrent conditions. An integrated 2-A switch driven by a bootstrapped supply maximizes efficiency during charging.

The LT3652 can be configured to charge at average currents to 2 A. The user sets the max charge current by choosing an inductor sense resistor, so that the max average current through the sense resistor creates a 100-mV drop. The sense resistor in Fig. 1 is 0.05 Ω. Besides having the appropriate inductance, the selected inductor must have a saturation current equal to or exceeding maximum peak current.

CHARGING THE BATTERY

The charge and discharge capacity of a battery is in terms of “C,” given as ampere-hours (Ah). The actual battery capacity depends on the C-rate and temperature. Most batteries are rated at 1 C. A discharge of 1 C draws a current equal to the rated capacity. For example, a battery rated at 1,000 mAh provides 1,000 mA for one hour if discharged at a 1-C rate.

The LT3652 charger IC uses a charge-current-based C/10 termination scheme to end a charge cycle when the battery charge current falls to one-tenth of its programmed maximum charge current. It also contains an internal charge-cycle control timer for timer-based termination. When using the internal timer, the IC combines C/10 detection with a programmable time constraint, during which the charging cycle can continue beyond the C/10 level to top-off a battery.

A capacitor connected from Timer pin 6 to ground sets the end-of-charge (EOC) time. A 0.68-µF capacitor generates a three-hour timer EOC and a precondition limit time of 22.5 min. When using the timer-based scheme, the IC also supports bad battery detection, which triggers a system fault if a battery stays in precondition mode for more than one-eighth of the total charge-cycle time.

If a timer-based termination is not desired, you can disable the timer function by connecting the TIMER pin to ground (Fig. 1). With the timer function disabled, charging terminates when the charge current drops below a C/10 threshold.

After terminating the charge, the LT3652 automatically enters a low-current standby mode where supply bias currents drop to 85µA. The IC continues to monitor the battery voltage while in standby, and if that voltage falls 2.5% from the full-charge float voltage, the LT3652 engages an automatic charge-cycle restart. The IC also automatically restarts a new charge cycle after a bad battery fault once the failed battery is removed and replaced with another battery.

The IC contains provisions for a battery-temperature monitoring circuit using a thermistor during the charging cycle. If the battery temperature moves outside the safe charging range (0° to 40°C), the IC suspends charging and signals a fault condition until the temperature returns to the safe range.

A shutdown mode can disable all charging functions. This precision threshold allows the use of the SHDN pin 3 to incorporate UVLO (undervoltage lockout) functions. Pulling the SHDN pin below 0.4 V causes the IC to enter a low-current shutdown mode where V_IN current reduces to 15 µA. Typical SHDN input bias current is 10 nA. When not charging, the IC draws less than 1 µA from the battery.

The open-collector CHRG pin 4 and the FAULT pin 5 usually use a resistor pulled up to a reference voltage. These status pins can be pulled up to voltages as high as V_IN when disabled, and can sink currents up to 10 mA when enabled.

During a battery charging cycle, if the required charge current is greater than 1/10 of the programmed max current (C/10), CHRG pin 4 is pulled low. A temperature fault also causes this pin to be pulled low. After C/10 charge termination, or if the internal timer is used for termination and charge current is less than C/10, the pin stays at high-impedance.

FAULT pin 5 indicates fault conditions during a battery charging cycle. A temperature fault causes this pin to be pulled low. If the internal timer is used for termination, a bad battery fault also causes this pin to be pulled low. If no fault conditions exist, this pin remains high-impedance.

SEALED LEAD-ACID BATTERY APPLICATION

Fig. 3 shows a sealed lead-acid battery using the LT3652. This 1-A circuit fast-charges with CC/CV characteristics up to 14.4 V. If the charge current falls to 0.1 A, the charger switches to 13.5-V float-charge mode.

The charger re-initiates the 14.4-V fast-charge mode if the battery voltage falls below 13.2 V and trickle charges at 0.15 A if the battery voltage is below 10 V. A resistor divider between BAT pin 9 and V_FB pin 7 programs the output battery float voltage.

Nokia N81 with its great performance

Nokia’s N-series is knows to everyone. Nokia N81 is an innovative mobile phone that will simply give you the best experience all the time. This phone comes with the advanced features that offer you great utility and style. If you want entertainment and great performance, then nothing else but the N81 can satisfy you. The handset has an advance camera phone that offers high quality pictures. Now you can capture the most memorable moments of your life in the most resplendent shades.
Nokia N81 has a high definition 2.4 inch large screen that offers crystal clear display. Pictures come to life on its screen which offers 16 million colours for that awe inspiring visuals.The Bluetooth wireless technology is one of the most useful features of the phone.
Now you can easily connect with other compatible devices like a headset etc. You can share files and images with other Bluetooth compatible phones wirelessly without any hassle.

Samsung G600- 5 Megapixel

Samsung Mobile have been at the forefront of mobile communications for the past five years due in no small part to the fact that the manufacturer consistantly delivers new and exciting features and technology to the mobile phone market place.

Gone are the days when you would have to squint at your small mobile phone screen to make out a picture before capturing it using a small VGA camera, these days Samsung consumers have the luxury of large full colour screens and multi megapixel cameras making for close to professional photography.

Samsungs newest edition offers these features but with their very latest technology - a five megapixel camera. There are only two other mobile phones currently offering this high quality camera, the LG KG920 Leo and the Nokia N95. The new Samsung G600 may sound like it already has competition but on closer examination it is easy to see why consumers will opt for this phone over its rivals. Firstly their is the sleek design, the outer casing is finished in a matt black paint and features Samsung’s trademark smooth slide. The exterior buttons almost fall into the central multikey allowing for easy navigation of the menu system.

The display screen is a large 2.2 inch QVGA offering sixteen million colours which compliments the high quality pictures when viewed on-screen. The most surprising thing about the new G600 is that it is a mere 14mm thick, this is astonishing when compared to its competitors like the LG KG920 at 18mm and the at 21mm proving that Samsung have really thought about the overall design and how they could squeeze this amount of technology into a phone without bulking out the dimensions.

The camera also offers autofocus, digital zoom and photolight (flash), as well as one of the best video recording resolutions available with 352 x 288 pixels at 30 frames per second.

The Samsung G600 also offers an MP3 player for uploading new music either direct from a PC or via the internet and creating playlists with your favourite music tracks and artists, and with 1GB of onbaord memory there is no need to take a second standalone music player with you, there is even a built-in FM Radio for tuning into local and national radio station whilst out and about.

Other important features in the Samsung G600 include Bluetooth technology for wireless conenction to compatible devices for file transfer and safe hands-free driving, internet and email access for browsing, downloading and keeping in touch whilst out of the office and built-in hands-free speakerphone for either talking hands-free or sharing your music and sound recordings with friends. Overall, the O2 Samsung G600 is a stylish, spohisticated, if not a little masculine photographic masterpiece that outshines it closest rivals with its array of new technology and features.

LG KU990

LG isn’t renowned for high-end camera phones but that doesn’t mean that the company behind the fashion-centric Chocolate phone can’t make one. In fact it can and it has — and no, we’re not talking about the

The LG KU990 Viewty, formerly know as the NYX, might have an awful name but it features a whopping 5-megapixel camera with a nifty touchscreen interface and YouTube functionality. Similar to the LG Prada phone, the LG Viewty comes in a glossy black casing and features a large display. The touchscreen interface produces small vibrations that make it easier to sense when you’ve touched it, a system that Motorola also uses in its Motorola Razr 2 V8, and one we think works really well.

The 5-megapixel camera on the back comes with a Schneider Kreuznach lens, autofocus and manual focus, image stabilisation and LED photo light, but more interestingly — or curiously — it can shoot video at up to 120 frames per second. The reason we’re curious about the high frame rate is because it’s about four times higher than a standard camcorder and is usually intended for viewing videos in slow motion or shooting fast-moving action footage.

Whether or not viewing slow-motion clips is your thing, the KU990 does one thing that’ll please many: it has the ability to upload videos directly to YouTube, a feature that many iPhone users would love to see. You can also watch YouTube videos on the handset.

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The LG KU990 viewty is set to come out soon on 3 and other major networks. Pricing has yet to be announced and we’re uncertain on all the final specs, but we’re getting one in very soon. We’ll post a hands-on with more juicy details as soon as we do — watch this space

Motorola Mobile Phones

Today mobiles mobiles are best way to contact people to people. I don’t think, without mobile phones we can make a friendly relation because many relations are broken by communication gapping.

Mobile Phone Accessories

So mobiles are also a means of communication fulfillment. In this way Motorola mobiles are good because I like and most users want to go with this manufacturers.

Now a day Motorola has launched great look and stylish mobile phones. Anybody can attract with this by its features and style.

You can go with this phone a contract like - Deals contract, Sim free, contract, 12 months line rental or PAYG phone deals. These are some deals which is famous in UK.

Mobile Phones - Buy cheap mobile phone deals and compare latest mobile phones Offer.
Compare cheap contract deals from O2, Vodafone, Orange, 3 Mobiles.

Call India - Make cheap VoIP calls to India from PC to mobile phone or landline. Cheap India calling plans with cheapest VoIP calling rates to India.

What do you think about this great looking mobile? Anybody would like to buy this phone.

Periscope from the Amazon Kindle

I just want to clarify the title of this article. I am not implying that the chair that you see here on the left costs six million dollars, but uses a bionic leg to support your weight similar to that of the Six-Million Dollar Man.

The Leopard is under development by the Oki Electric Industry and the Okamura Corporation, and it is designed to rise up and meet your backside as you go and sit down. It will also rise up when you want to get up.

You might ask yourself why someone would make a chair like this. Perhaps someone feels a need to create comfort that is “akin to being held in someone’s arms”. It sounds to me like the inventor of this chair may have some dependency issues, but I’m all for any device that can make you more comfortable, especially if it is an office chair.Gadget Post
News on todays hottest electronic mobile gadgets
Samsung Upstage Accessories Order body glove, jabra, headset, faceplate, cases, and batteries. Also has cellular phone accessory for Nokia, Samsung, Nextel, Motorola, Sanyo, LG, Audiovox and more.

Periscope from the Amazon Kindle

Application Development Software India

This isn’t the first time we have reported on Amazon Kindle accessories, and I’m sure it won’t be the last. At first glance, you may think the Periscope is just a clip-on light, but it is many things, including a cover for the Kindle, notepad, and pen holder.

mobile watch

The cover itself is not genuine leather, but leatherette. There are some that would not like the cover, as it can make the not-so-mini Kindle even bigger. However, for those who like to take to notes as they read, you might as well have a notepad and pen holder.

Wall Water Fountains

As for the light itself, it uses two LEDs for illumination. Unfortunately, these two LEDs are not powered by what powers the Kindle, but three not included AAA batteries. These batteries are good for about 40 hours worth of power.

azon Kindle

car bodywork could used to power future cars

Winchester, UK - Researchers from Imperial College London and their European partners, including Volvo Car Corporation, are developing parts of a car's bodywork to enable it to double up as a battery source.

The researchers, which are part in a new Euros 3.4 million project, are developing a prototype material that can store and discharge electrical energy and which is also strong and lightweight enough to be used for car parts.

The material could be used in hybrid petrol/electric vehicles to make them lighter, more compact and more energy efficient, enabling drivers to travel for longer distances before needing to recharge their cars.

In addition, the researchers believe the material, which has been patented by Imperial, could potentially be used for the casings of many everyday objects such as mobile phones and computers, so that they would not need a separate battery. This would make such devices smaller, more lightweight and more portable.

The project co-ordinator, Dr Emile Greenhalgh, from the Department of Aeronautics at Imperial College London, said: “We are really excited about the potential of this new technology. We think the car of the future could be drawing power from its roof, its bonnet or even the door, thanks to our new composite material. Even the Sat Nav could be powered by its own casing. The future applications for this material don't stop there - you might have a mobile phone that is as thin as a credit card because it no longer needs a bulky battery, or a laptop that can draw energy from its casing so it can run for a longer time without recharging. We’re at the first stage of this project and there is a long way to go, but we think our composite material shows real promise.”

In the new project, the scientists are planning to develop the composite material so that it can be used to replace the metal flooring in the car boot, called the wheel well, which holds the spare wheel. Volvo is investigating the possibility of fitting this wheel well component into prototype cars for testing purposes. By replacing a metal wheel well with a composite equivalent could enable Volvo to reduce the number of batteries needed to power the electric motor and could lead to a 15 per cent reduction in the car's overall weight, which should improve the range of future hybrid cars.

The researchers say that the composite material that they are developing, which is made of carbon fibers and a polymer resin, will store and discharge large amounts of energy much more quickly than conventional batteries. In addition, the material does not use chemical processes, making it quicker to recharge than conventional batteries. Furthermore, this recharging process causes little degradation in the composite material, because it does not involve a chemical reaction, whereas conventional batteries degrade over time.

The material could be charged by plugging a hybrid car into household power supply. The researchers are also exploring other alternatives for charging it such as recycling energy created when a car brakes.

For the first stage of the project, the scientists are planning to further develop their composite material so that it can store more energy. The team will improve the material’s mechanical properties by growing carbon nanotubes on the surface of the carbon fibers, which should also increase the surface area of the material, which would improve its capacity to store more energy.

The research team is also planning to investigate the most effective method for manufacturing the composite material at an industrial level.

The three-year European Union funded project includes researchers from the Departments of Chemistry, Aeronautics and Chemical Engineering and Chemical Technology at Imperial College London. European academic and industrial partners include Swerea SICOMP, INASCO Hella, Chalmers, Advanced Composites Group, Nanocyl, Volvo Car Corporation, Bundesanstalt Fur Materialforschung undprufung, ETC Battery and Fuel Cells Sweden. >

How Electronics Gates Works?

If you have read the HowStuffWorks article on Boolean logic, then you know that digital devices depend on Boolean gates. You also know from that article that one way to implement gates involves relays. However, no modern computer uses relays -- it uses "chips."

What if you want to experiment with Boolean gates and chips? What if you would like to build your own digital devices? It turns out that it is not that difficult. In this article, you will see how you can experiment with all of the gates discussed in the Boolean logic article. We will talk about where you can get parts, how you can wire them together, and how you can see what they are doing. In the process, you will open the door to a whole new universe of technology.

Apple iPad

Welcome to the new Apple iPad. Unveiled in San Francisco, the iPad is designed for browsing the web, reading and sending email, seeing photos, watching videos, listening to music, playing games, and reading e-books, says Apple. It is powered by A4, Apple’s system-on-a-chip. Designed by Apple, the new A4 chip supports a battery life of up to 10 hours, claims Apple.

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