Switching Power Supply Design & Optimization
The design of switching power supplies has become one of the most crucial aspects of electronics, particularly in the fast-growing market for portable devices. Whether you’re a newcomer to power supply design or an experienced hand, this book belongs on your shelves. Rigorous and carefully explained, expert Sanjaya Maniktala’s Switching Power Supply Design and Optimization gives you both a practical tutorial and a handy quick reference. Delivering easy-to-understand converter design strategies, this book features:
- Key design equations in a special reference section
- Concise switching-power-supply-design FAQ
- Thermal management techniques
- Designing for printed circuit boards
- A fully reasoned, easy-to-follow guide to designing cooler, reliable, and more cost-effective power supplies
THE INSIDE EDGE ON SWITCHING POWER SUPPLY DESIGN
- Introduction * Power Supply Topologies * Non-Isolated Topologies * A/C Line Input * Power Supply Magnetics * Thermal Management * EMI Filter Design * Discontinuous Conduction Mode (DCM) * Inductors for Current Mode Control * PCB Design Procedure * Key Regulatory Issues * Key Design Equations * Power Supply Design FAQ
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Tricks and Tips for Using Your Network Printer
The printing processes in Windows run smoothly and automatically most of the time, even across a network. However, knowing a few tricks makes network printing easier for all the users on your network.
Using a printer shortcut on the desktop
Sometimes you just need a printed copy of an existing document and you don’t want to open the software, open the document, and use the commands that are required to print the document. If you put a shortcut to the printer on your desktop, you can drag documents to the shortcut icon to print them effortlessly. Follow these steps to create a printer shortcut on your desktop:
1. Choose Start –> Settings –> Printers.
The Printers folder opens.
2. Right-drag the printer icon to the desktop.
When you release the right mouse button, a shortcut menu appears.
3. Choose Create Shortcut(s) Here from the shortcut menu.
A printer shortcut appears on your desktop.
Using the printer shortcut is easy and timesaving. You can use it whenever you have any folder or window open (such as Windows Explorer, My Computer, or My Documents) that contains document files. Just drag a document file to the printer shortcut on the desktop. That’s all you have to do – Windows does the rest.
If you right-click a document file instead of dragging it to a desktop shortcut, you can choose Print from the shortcut menu that appears. Again, Windows takes care of the rest.
Using separator pages to identify users
If everyone in your household uses the printers, you are likely to experience a lot of printer traffic. It’s less messy if each job comes out of the printer with a form that displays the name of the owner. Luckily, such a form exists in Windows, and it’s called a separator page. A separator page (sometimes called a banner) automatically prints ahead of the first page of each document.
The downside of separator pages is that they can be a huge waste of paper. They work best if most of your print jobs are made up of multiple pages. You may end up spending the money you save on ink purchasing ream after ream of paper. Also, if your household is filled with people who don’t believe that “neatness counts,” you’ll just have one extra piece of paper per print job to get shuffled around in a big ugly pile.
Adding separator pages in Windows 95, 98, and Me
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For a Windows 95, Windows 98, or Windows Me print server, go to the computer that has the printer attached to turn on separator pages using these steps:
1. Choose Start –> Settings –> Printers.
The Printers folder opens.
2. Right-click the appropriate printer icon and choose Properties from the shortcut menu that appears.
The printer Properties dialog box opens, with the General tab in the foreground.
3. Click the arrow to the right of the Separator page list box and choose a Separator page type.
The Separator page choices are None, Full, and Simple. Both the Full and Simple separator pages contain the document name, the user name, and the date and time that the document was printed. The Full option uses large, bold type, whereas Simple uses the Courier typeface that’s built into the printer.
4. Click OK.
Adding separator pages in Windows 2000 and Windows XP
If you have a Windows 2000 Professional print server, follow Steps 1 and 2 in the previous section “Adding separator pages in Windows 95, 98, and Me,” and then follow these steps:
1. Click the Advanced tab.
2. Click the Separator Page button.
The Separator Page dialog box appears.
3. Click Browse to select a separator file.
Separator files have the .sep extension. Choose Sysprint.sep for PostScript printers or Pcl.sep for non-PostScript printers.
4. Click OK twice to close the dialog box.
Troubleshooting network printing
Sometimes when you’re printing to a remote printer, you see an error message indicating that there was a problem printing to the port. (The port is the path to the remote computer that has the printer attached.) Before you panic, check the condition of all the hardware.
Check the print server
Computers that have printers attached (called print servers) have to be turned on if you want to print from a remote computer. If the computer is turned off, turn it on.
It doesn’t matter whether you know the logon password for the user name that appears during the logon process; nobody has to be logged on to a computer to use its shared printer. The Windows operating system on that computer simply must be started.
Check the printer
Make sure that the printer is turned on. Check any buttons, indicator lights, or message windows that may be trying to tell you that something is amiss. When the printer’s “ready” light isn’t on, the most common problems are that the printer is out of paper, a paper jam has occurred, or the cartridge is out of toner (or ink).
Check the network cable
If the computer is on and the printer is fine, check the network cable. A cable that isn’t connected properly can’t send data.
Check the Windows XP SP2 Firewall
If a shared printer is on a computer running Windows XP SP2, make sure that the firewall is configured to allow access to the printer by remote computers. Use the following steps to view or change the firewall’s settings:
1. Open the Properties dialog box for the network adapter.
2. Click the Advanced tab.
3. Click the Settings button.
4. Click the Exceptions tab.
5. Be sure a check mark appears in the File and Printer Sharing option.
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Source : http://tech.yahoo.com/gd/tricks-and-tips-for-using-your-network-printer/
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Make a solar cell in your kitchen
| Source : http://sci-toys.com/scitoys/scitoys/echem/echem2.html�A solar cell is a device for converting energy from the sun into electricity. The high-efficiency solar cells you can buy at Radio Shack and other stores are made from highly processed silicon, and require huge factories, high temperatures, vacuum equipment, and lots of money. |
| If we are willing to sacrifice efficiency for the ability to make our own solar cells in the kitchen out of materials from the neighborhood hardware store, we can demonstrate a working solar cell in about an hour. |
| Our solar cell is made from cuprous oxide instead of silicon. Cuprous oxide is one of the first materials known to display the photoelectric effect, in which light causes electricity to flow in a material. |
| Thinking about how to explain the photoelectric effect is what led Albert Einstein to the Nobel prize for physics, and to the theory of relativity. |
Materials you will need |
The solar cell is made from these materials:
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How to build the solar cell |
| My burner looks like this: |
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| The first step is to cut a piece of the copper sheeting that is about the size of the burner on the stove. Wash your hands so they don’t have any grease or oil on them. Then wash the copper sheet with soap or cleanser to get any oil or grease off of it. Use the sandpaper or wire brush to thoroughly clean the copper sheeting, so that any sulphide or other light corrosion is removed. |
| Next, place the cleaned and dried copper sheet on the burner and turn the burner to its highest setting. |
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| As the copper starts to heat up, you will see beautiful oxidation patterns begin to form. Oranges, purples, and reds will cover the copper. |
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| As the copper gets hotter, the colors are replaced with a black coating of cupric oxide. This is not the oxide we want, but it will flake off later, showing the reds, oranges, pinks, and purples of the cuprous oxide layer underneath. |
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| The last bits of color disappear as the burner starts to glow red. |
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| When the burner is glowing red-hot, the sheet of copper will be coated with a black cupric oxide coat. Let it cook for a half an hour, so the black coating will be thick. This is important, since a thick coating will flake off nicely, while a thin coat will stay stuck to the copper. |
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| After the half hour of cooking, turn off the burner. Leave the hot copper on the burner to cool slowly. If you cool it too quickly, the black oxide will stay stuck to the copper. |
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| As the copper cools, it shrinks. The black cupric oxide also shrinks. But they shrink at different rates, which makes the black cupric oxide flake off. |
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| The little black flakes pop off the copper with enough force to make them fly a few inches. This means a little more cleaning effort around the stove, but it is fun to watch. |
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| When the copper has cooled to room temperature (this takes about 20 minutes), most of the black oxide will be gone. A light scrubbing with your hands under running water will remove most of the small bits. Resist the temptation to remove all of the black spots by hard scrubbing or by flexing the soft copper. This might damage the delicate red cuprous oxide layer we need to make to solar cell work. |
| The rest of the assembly is very simple and quick. |
| Cut another sheet of copper about the same size as the first one. Bend both pieces gently, so they will fit into the plastic bottle or jar without touching one another. The cuprous oxide coating that was facing up on the burner is usually the best side to face outwards in the jar, because it has the smoothest, cleanest surface. |
| Attach the two alligator clip leads, one to the new copper plate, and one to the cuprous oxide coated plate. Connect the lead from the clean copper plate to the positive terminal of the meter. Connect the lead from the cuprous oxide plate to the negative terminal of the meter. |
| Now mix a couple tablespoons of salt into some hot tap water. Stir the saltwater until all the salt is dissolved. Then carefully pour the saltwater into the jar, being careful not to get the clip leads wet. The saltwater should not completely cover the plates — you should leave about an inch of plate above the water, so you can move the solar cell around without getting the clip leads wet. |
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| The photo above shows the solar cell in my shadow as I took the picture. Notice that the meter is reading about 6 microamps of current. |
| The solar cell is a battery, even in the dark, and will usually show a few microamps of current. |
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| The above photo shows the solar cell in the sunshine. Notice that the meter has jumped up to about 33 microamps of current. Sometimes it will go over 50 microamps, swinging the needle all the way over to the right. |
How does it do that? |
| Cuprous oxide is a type of material called a semiconductor. A semiconductor is in between a conductor, where electricity can flow freely, and an insulator, where electrons are bound tightly to their atoms and do not flow freely. |
| In a semiconductor, there is a gap, called a bandgap between the electrons that are bound tightly to the atom, and the electrons that are farther from the atom, which can move freely and conduct electricity. |
| Electrons cannot stay inside the bandgap. An electron cannot gain just a little bit of energy and move away from the atom’s nucleus into the bandgap. An electron must gain enough energy to move farther away from the nucleus, outside of the bandgap. |
| Similarly, an electron outside the bandgap cannot lose a little bit of energy and fall just a little bit closer to the nucleus. It must lose enough energy to fall past the bandgap into the area where electrons are allowed. |
| When sunlight hits the electrons in the cuprous oxide, some of the electrons gain enough energy from the sunlight to jump past the bandgap and become free to conduct electricity. |
| The free electrons move into the saltwater, then into the clean copper plate, into the wire, through the meter, and back to the cuprous oxide plate. |
| As the electrons move through the meter, they perform the work needed to move the needle. When a shadow falls on the solar cell, fewer electrons move through the meter, and the needle dips back down. |
A note about power |
| The cell produces 50 microamps at 0.25 volts. This is 0.0000125 watts (12.5 microwatts). Don’t expect to light light bulbs or charge batteries with this device. It can be used as a light detector or light meter, but it would take acres of them to power your house. |
| The 0.0000125 watts (12.5 microwatts) is for a 0.01 square meter cell, or 1.25 milliwatts per square meter. To light a 100 watt light bulb, it would take 80 square meters of cuprous oxide for the sunlit side, and 80 square meters of copper for the dark electrode. To run a 1,000 watt stove, you would need 800 square meters of cuprous oxide, and another 800 square meters of plain copper, or 1,600 square meters all together. If this were to form the roof of a home, each home would be 30 meters long and 30 meters wide, assuming all they needed electricity for was one stove. |
| There are 17,222 square feet in 1,600 square meters. If copper sheeting costs $5 per square foot, the copper alone would cost $86,110.00 USD. Making it one tenth the thickness can bring this down to $8,611.00. Since you are buying in bulk, you might get it for half that, or about $4,300.00. |
| If you used silicon solar panels costing $4 per watt, you could run the same stove for $4,000.00. But the panels would only be about 10 square meters. |
| Or, for about a dollar, you can build a solar stove out of aluminum foil and cardboard. For about $20, you can build a very nice polished aluminum parabolic solar cooker. |
Categories: Basic electronics, News Technology Tags: Basic electronics, News Technology
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