Saturday, November 26, 2011

Induccion mutua entre bobinas (fundamento transformador y antenas radio)

En este vídeo se puede ver el principio básico del transformador. Una bobina por la que pasa una corriente variable crea un campo magnético variable. En su proximidad, otra bobina está conectada a unos leds para comprobar que, cuando las dos bobinas están cerca, se produce transferencia de energía entre ellas. www.youtube.com www.youtube.com También se puede observar que cuando las espiras se colocan de forma que el flujo magnético concatenado es nulo (por ejemplo, disponiendo las espiras perpendiculares), los leds no se encienden ya que no existe fuerza electromotriz sobre la segunda espira (ley de Faraday-Lenz) Aunque por la distancia a la que están las bobinas el campo electromagnético no corresponde a la aproximación lejana (onda electromagnética), también puede servir para explicar el funcionamiento de antenas como las que se utilizan en los receptores de radio AM (la típica barra de ferrita) y de tipo LOOP (para bajas frecuencias) ======================================== Nota sobre la construcción: En este vídeo, la bobina se alimenta con un transformador ELECTRÓNICO de foco halógeno que proporciona 12 V a unos 44 kHz (en realidad la tensión que da este este tipo de transformadores es la señal de 50 Hz chopeada a unos 42-44 kHz, dependiendo del modelo). Esto permite utilizar bobinas de menos vueltas (la fuerza electromotriz inducida es proporcional a la frecuencia). La bobina del vídeo es de cable barnizado (aislado) de aluminio y 0,78 mm2 dispuesto en 11 vueltas ...

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Sunday, November 20, 2011

Schumacher AC Arc Welder - 120 Volt, 70 Amp, Model# 94070

!: Wholesale Schumacher AC Arc Welder - 120 Volt, 70 Amp, Model# 94070 order


Rate : | Price : $148.88 | Post Date : Nov 20, 2011 19:21:45
Usually ships in 1-2 business days

Basic stick welder for general repairs and fabrication. 120V, 60 Hz, single phase. 2-year limited warranty; 5-year limited warranty on transformer.

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Friday, November 18, 2011

Ultrafire Wf-139 - Duel Channel Charger for Ultrafire Flashlights

!: Ultrafire Wf-139 - Duel Channel Charger for Ultrafire Flashlights

Ultrafire wf-139 is an impressive charges and a powerful new model that aims at providing customers with one of the highest levels of power available on the market. The main difference between this model and the DSD chargers is related to the fact that Ultrafire has provided their gadget with two different channels for charging. This is very important, because in this way users are now able to charge batteries with two different capacities without worrying that something bad could happen.

On the other hand, a disadvantage of this model is that the unit requires a pretty impressive spacer if you are intending to charge batteries designed for CR123A and CR2. This kind of spacer is not even available on the market yet, but Ultrafire has announced that they will release one as soon as possible. Meanwhile, you can opt for the use of a paper clip or other similar metal instead of a spacer.

Ultrafire wf-139 is able to use a power source of 110V/220V, being provided with an auto AC switch. Moreover, there is a wide range of compatible batteries, so the level of portability has been seriously increased. You can use 3.6/3.7V models for CR123A, 18650, 14500, 18500, 17500 or CR2 rechargeable batteries, but be aware of the spacer situation described above.

For a reason that is currently unknown, the manufacturer has disabled the horizontal contacts. However, if you really want to re-activate them then you have the possibility to do so by following the steps presented in a great number of tutorials available online. If you never modded something like this before, maybe you should consider having a specialist to assist you in this process. The basic idea is that you have to connect some soldering points. After reactivation, you will be able to charge CR123A batteries without a spacer.

The output of this charger is 4.2V at approximately 450 mA. You must also know that the charging time can take between an hour and two for the CR123A batteries, whereas for 18650 and other similar models, it can take even 4 hours to complete. As for the design, the size of this gadget is 5.31 x 2.36 x 1.18 (L X H X W). It only weights about 7.5 oz, pretty impressive considering the quality provided.

Another possible problem is that you will have to purchase your own EU cable, because it is not provided by default in the bundle. Furthermore, the high voltage can sometimes prove to be a little higher in respect to the lifetime of the batteries charged, while the process of putting the batteries in with protection is a rather hard one but in the end, it is possible.

All in all, Ultrafire wf-139 is a model you should consider buying if it fits your budget.

For more information about the ultrafire flashlight models for sale, visit this dedicated online resource for ultrafire flashlight.


Ultrafire Wf-139 - Duel Channel Charger for Ultrafire Flashlights

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Monday, November 14, 2011

Types and Brands of Voltage Converters and Adapters

!: Types and Brands of Voltage Converters and Adapters

When traveling to another country, you'll need to know what type of voltage converters, or voltage transformers, and plug adapters to take for your electrical products. Items such as hair dryers, electric shavers, irons, coffee makers, TV, VCR, or DVD players all require power to operate. Unfortunately, the power voltage available is not always what's needed. In this case, you'll need either an 110v to 220v voltage converter or a 220v to 110v converter.

Let's take a look at the various types of converters and adapters available today.

Type of Voltage Converters

There are two main types of voltage converters - step up or step down. Step up converters will convert the power to a higher voltage than what is shown on the appliance. For instance, an electric shaver made in the U.S. works with the standard 110 volt outlet. With a step up converter, it can be used with a 220 volt outlet in another country. Step down converters do just the opposite.

Wattage and Voltage Converters

Wattage typically determines what type of voltage converter you will need in terms of power. For smaller electronics such as electric shavers that are non-heating products, a 50-watt converter will do. For heated electronics such as curling irons, hair dryers, irons, and coffee makers, a 1600-watt converter will be needed. If you feel the quality of power will be an issue, it's a good idea to buy a universal surge suppressor along with your voltage converter.

For your computer, CD player, camcorder, TV, VCR, or DVD, voltage converters can be used according to the wattage power needed. But keep in mind that there are various formats used for television programming and films (VHS or DVD) that may not work with your product.

A TV will need a more powerful voltage converter than what is indicated on the back of the set because a TV causes a power surge when it is first turned on. Many newer electronics in these categories are able to work with multiple voltage outlets. Some electronics contain a simple switch that controls the voltage output. Just be sure to turn the switch to the correct voltage for the country you're visiting - BEFORE plugging it in. There are also code free and region free players and TVs that will work fine in other countries.

A Variety of Adapters

Not only will you need voltage converters for traveling overseas, but plug end adapters as well. Since many countries have numerous types of outlets, it's wise to carry a variety of adapters with you. Some adapter types you might encounter include flat blade, flat blade with grounding pin, round pin, round pins with ground, round pin plug and receptacle with male grounding pin, "Schuko" plug, rectangular blade plug, oblique flat blades, round pins with spade ground, "South African" plug with oversized pin. Though adapters make the plug fit properly into the outlet, they will not convert the voltage.

Some popular brand names for voltage converters and adapters include Franzus, Tripplite, Kensington, Electro-Sensors, Horlick, Devar, Visicomm, Travelarts, Dataforth, Avtron, and many others.

With so many great online resources, you can easily surf the Web to find the voltage converters and adapters you need. Now you can travel without leaving your frequently used electronics behind!


Types and Brands of Voltage Converters and Adapters

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Wednesday, November 9, 2011

5 Argentina Travel Tips for the Foreign Study Traveler

!: 5 Argentina Travel Tips for the Foreign Study Traveler

Have you ever thought of hopping a plane for spring break in Argentina? Maybe you want to study Spanish in Buenos Aires or learn the Tango in Mendoza? Too difficult, you say? No way, but there are a few things you need to know when traveling abroad. Take advantage of the following top five travel tips for your next trip to Argentina and make it an experience to remember.

1. PASSPORTS - Argentina visitors that are citizens of the US, Canada, the United Kingdom, Australia, New Zealand and South Africa will require a passport for entry. US Passport applications can be obtained at http://travel.state.gov/passport/passport_1738.html, with routine services taking up to 10-12 weeks from the date you applied. A Visa is not required for a tourist stay up to 90 days, for longer stays contact your local embassy for information. In the U.S. -- Contact the Consular Section of the Argentine Embassy, 1718 Connecticut Ave. NW, Washington, DC 20009 (tel. 202/238-6460). For more information, try http://www.uic.edu/orgs/argentina. In Canada -- Contact the Embassy of the Argentine Republic, Suite 910, Royal Bank Center, 90 Sparks St., Ottawa, Ontario K1P 5B4 (tel. 613/236-2351; fax 613/235-2659). In the U.K. -- Contact the Embassy of the Argentine Republic, 65 Brooke St., London W1Y 4AH (tel. 020/7318-1300; fax 020/7318-1301; seruni at mrecic.gov.ar).

2. CURRENCY - The current exchange rate is 3 to 1 for the US dollar to the Argentina Peso. The Peso is made up of 100 centavos. Money is denominated in notes of 2, 5, 10, 20, 50, and 100 pesos; and coins of 1, 2, and 5 pesos, and 1, 5, 10, 25, and 50 centavos. US dollars are widely accepted in Buenos Aires, but in the rural areas of the country pesos are the currency of choice and exchange locations are less abundant. American Express traveler's checks can be exchanged at offices located in Buenos Aires at Arenales 707 (tel. 11/4130-3135), Bariloche, Salta, San Martan, and Ushuaia. Outside of these locations there are very few American Express exchange offices, so when traveling to remote locations be sure to plan ahead. Many of the hotels do not accept credit cards, so check in advance before you assume you can pay your bill that way.

3. CAR RENTALS - Argentines drive very fast in comparison to U.S. drivers and do not always obey traffic lights or lanes. The seat belt law is in effect, though few locals actually wear them. U.S. driver's licenses are valid in greater Buenos Aires, but you need an Argentine or international license to drive in most other parts of the country. When driving outside the city, remember that autopista means motorway or highway, and paso means mountain pass. It is not advised to drive in rural areas at night as cattle roam free and are hard to see in the dark. Fuel is about per liter, or per gallon. Car rentals are available at Hertz, Paraguay 1122 (tel. 800/654-3131 in the U.S., or 11/4816-8001 in Buenos Aires); Avis, Cerrito 1527 (tel. 800/230-4898 in the U.S., or 11/4300-8201 in Buenos Aires); Dollar, Marcelo T. de Alvear 523 (tel. 800/800-6000 in the U.S., or 11/4315-8800 in Buenos Aires); and Thrifty, Av. Leandro N. Alem 699 (tel. 800/847-4389 in the U.S., or 11/4315-0777 in Buenos Aires). Car rentals are more expensive in Argentina with compacts starting at to per day, ask for special promotions.

4. ELECTRICITY - Electricity in Argentina runs on 220v. Most U.S. laptops run on either 110v or 220v, check yours to determine which one you have. A transformer and a European style adapter will be necessary for any other small appliances. While most luxury hotels will have these items for your use, some smaller or rural hotels will not. Cyber cafes called "Locuturios" are common in Buenos Aires and other major cities, where you can connect for an average of .00US per hour.

5. SEASONS - While those of us here in the Northern Hemisphere are used to the seasons that we have come to know, you must remember that things are in reverse south of the equator. The summer months in Argentina are December thru February, perfect for a trip to Santa Cruz. However, Buenos Aires has a very hot, humid summer so it is therefore better to visit in the spring and fall (November or March). If winter sports are what you are looking for, then the winter months of June thru October would be when to plan your next trip.

These tips will certainly give you a leg up when planning a trip to exotic Argentina. Traveling to a foreign county does require a little effort, but the experiences you will gain will last a lifetime. The world is such a global community that visiting and understanding another country's culture only brings people closer together.

Argentina is waiting for you, use the tips above to plan a successful trip there today!


5 Argentina Travel Tips for the Foreign Study Traveler

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