Electronicsunit Blog

Optical fiber refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic strand or fiber. Optical fiber carries much more information than conventional copper wire and is in general not subject to electromagnetic interference and the need to retransmit signals. Most telephone company long-distance lines are now made of optical fiber. Transmission over an optical fiber cable requires repeaters at distance intervals, and because the installation of any new cabling is labor-intensive, for these reasons, few communities have installed optical fiber cables from the phone company’s branch office to local customers (known as local loops). A type of fiber known as single mode fiber is used for longer distances; multimode fiber is used for shorter distances.

Suppose you want to shine a flashlight beam down a long, straight hallway. Just point the beam straight down the hallway — light travels in straight lines, so it is no problem. What if the hallway has a bend in it? You could place a mirror at the bend to reflect the light beam around the corner. What if the hallway is very winding with multiple bends? You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical fiber.

The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called total external inflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances.

Why are fiber-optic systems revolutionizing telecommunications? Compared to conventional metal wire (copper wire), optical fibers are:

  • Less expensive – Several miles of optical cable can be made cheaper than equivalent lengths of copper wire. This saves your provider (cable TV, Internet) and you money.
  • Thinner – Optical fibers can be drawn to smaller diameters than copper wire.
  • Higher carrying capacity – Because optical fibers are thinner than copper wires, more fibers can be bundled into a given-diameter cable than copper wires. This allows more phone lines to go over the same cable or more channels to come through the cable into your cable TV box.
  • Less signal degradation – The loss of signal in optical fiber is less than in copper wire.
  • Light signals – Unlike electrical signals in copper wires, light signals from one fiber do not interfere with those of other fibers in the same cable. This means clearer phone conversations or TV reception.
  • Low power – Because signals in optical fibers degrade less, lower-power transmitters can be used instead of the high-voltage electrical transmitters needed for copper wires. Again, this saves your provider and you money.
  • Digital signals – Optical fibers are ideally suited for carrying digital information, which is especially useful in computer networks.
  • Non-flammable – Because no electricity is passed through optical fibers, there is no fire hazard.
  • Lightweight – An optical cable weighs less than a comparable copper wire cable. Fiber-optic cables take up less space in the ground.

Because of these advantages, you see fiber optics in many industries, most notably telecommunications and computer networks. For example, if you telephone Europe from the United States (or vice versa) and the signal is bounced off a communications satellite, you often hear an echo on the line. But with transatlantic fiber-optic cables, you have a direct connection with no echoes.

off How does transformer works ?

dixon to Uncategorized — Tags:  

A transformer is an electrical device that takes electricity of one voltage and changes it into another voltage which could be higher or lower than the first one. A basic transformer consists of two sets of coils or windings. Each set of windings is simply an inductor. AC voltage is applied to one of the windings, called the primary winding. The other winding, called the secondary winding, is positioned in close proximity to the primary winding, but is electrically isolated from it.

A transformer takes in electricity at a higher voltage and lets it run through lots of coils wound around an iron core. Because the current is alternating, the magnetism in the core is also alternating. Also around the core is an output wire with fewer coils. The magnetism changing back and forth makes a current in the wire. Having fewer coils means less voltage. So the voltage is “stepped-down.”

The following are three different kinds of transformers:

l       Three-phase transformers.

A basic 3-phase transformer consists of three sets of primary windings, one for each phase, and three sets of secondary windings wound on the same iron core. Separate single phase transformers can be used and externally interconnected to yield the same results as a 3-phase unit.

The primary windings are connected in one of several ways. The two most common configurations are the delta, in which the polarity end of one winding is connected to the non-polarity end of the next, and the wye, in which all three non-polarity (or polarity) ends are connected together. The secondary windings are connected similarly. This means that a 3-phase transformer can have its primary and secondary windings connected the same (delta-delta or wye-wye), or differently (delta-wye or wye-delta). It’s important to remember that the secondary voltage waveforms are in phase with the primary waveforms when the primary and secondary windings are connected the same way. This condition is called “no phase shift.” But when the primary and secondary windings are connected differently, the secondary voltage waveforms will differ from the corresponding primary voltage waveforms by 30 electrical degrees. This is called a 30? phase shift. When two transformers are connected in parallel, their phase shifts must be identical; if not, a short circuit will occur when the transformers are energized.

l       Autotransformers.

An autotransformer is a transformer with an electrical connection between the primary and secondary windings. Autotransformers have considerably more MVA capacity per pound of core iron and winding conductor than standard power transformers, but are limited to small turns rations — ideally 2:1.

Although the designs of different transformers vary extensively, their basic operation remains the same.

l       Special transformers.

Transformers can have more than two windings per phase. These designs help reduce fault current levels. Other transformers have been built to operate at relatively low voltages but extremely high currents. Arc furnace transformers fall into this category, and can have secondary current ratings in excess of 150,000A. Regulating transformers are designed to maintain their secondary voltage within specific limits as the primary voltage fluctuates. Transformers can also be built to shift phase a specified amount to control the flow of real power in a networked system.

off How to charge my own MP3 player ?

dixon to Battery — Tags: ,  

Battery powered MP3 players typically get their power in one of three different ways:

(1) regular alkaline batteries, e.g. AAA or AA.

(2) rechargeable alkaline batteries usually also AA or AA.

(3) lithium-ion batteries such as those found in almost all cell phones.

MP3 players with no battery compartment are most certainly powered by a lithium-ion battery. An example of this is Apple’s famous iPod line of MP3 players. These batteries are designed to be recharged and used throughout the life of the device. This is great for the consumer because lithium-ion batteries are typically going to give you a longer battery life than alkaline batteries.

As mentioned above, it is usually not necessary to change batteries, in the device unless the battery has reached the end of its life which is not the case with your MP3 player. Lithium-ion batteries in MP3 players are typically charged in three different ways:

1) Through a charger that plugs into a wall outlet and connects to the player. Buy a charging kit made specifically for your MP3 player. Some manufacturers like Sansa make charging kits for specific MP3 players. The kits are available at major electronics stores. They come with a charger that plugs directly into the outlet. You plug the USB cord into the port in the back of a charger and then into your MP3 player.

2) Through a USB (or FireWire) cable that is used to connect it to your computer. Get a USB wall charger. These are AC adapters that plug directly into the outlet. You then plug the USB from your MP3 into the port on the adapter. Since it sounds like you did not receive a charger with your MP3 player, your MP3 player probably charges via a USB cable that came with the device. Plug the USB cable into your MP3 player and the other end into your computer and you should see a message that the MP3 player is charging

3) Charge your MP3 player on the go. There are also charging kits that plug into the cigarette lighter or power plug in your car. These kits come with a DC power adapter that has a port on the end for you to plug in your MP3.

AC power plugs and sockets are devices for connecting electrically operated devices to the power supply at any place.

An electric plug is a male electrical connector with contact prongs to connect mechanically and electrically to slots in the matching female socket.

Wall sockets are female electrical connectors that have slots or holes which accept and deliver current to the prongs of inserted plugs. To reduce the risk of injury or death by electric shock, some plug and socket systems incorporate various safety features. Sockets are designed to accept only matching plugs and reject all others.

Electrical plugs and their sockets differ by country in shape, size and type of connectors. The type used in each country is set by national standards legislation. As is known to all, each type is designated by a letter designation from a U.S. government publication, plus a short comment in parentheses giving its country of origin and number of contacts. Subsections then detail the subtypes of each type as used in different parts of the world.

IEC Classes are assigned to electrical devices depending on whether or not they are earthed and the degree of insulation they incorporate. Class I, for example, refers to earthed equipment, while class II refers to unearthed equipment protected by double insulation.

Special purpose sockets may be found in residential, industrial, commercial or institutional buildings. These may be merely labeled or colored, or may have different arrangements of pins or keying provisions. Some special-purpose systems are incompatible with general-purpose lighting and appliances. Examples of systems using special purpose sockets include:

  • “clean” ground for use with computer systems,
  • emergency power supply,
  • uninterruptible power supply, for critical or life-support equipment,
  • isolated power for medical instruments,
  • “balanced” or “technical” power used in audio and video production studios,
  • theatrical lighting
  • outlets for electric clothes dryers, electric ovens, and air conditioners with higher current rating.

Depending on the nature of the system, special-purpose sockets may just identify a reserved use of a system (for example, computer power) or may be physically incompatible with utility sockets to prevent use of unintended equipment which could create electrical noise or other problems for the intended equipment on the line.

off Introduction to remote control cars

dixon to Remote Control — Tags:  

Do you love cars, engines, and engineering? Can you remember the first time you took control of a remote controlled car and became fascinated by it’s simple yet gripping play? I sure can, and I couldn’t put it down! 

For many decades now, remote controlled cars have fascinated and inspired multiple generations.   

There is something truely exhilarating about remotely piloting a highly complicated piece of machinery at 60 mph!  

Even though they’ve been around since the 1960′s, these gadgets have evolved into something far more than just toys.

And today there are competitions all over the nation dedicated to this thrilling hobby! 

Whether you’re new to remote controlled cars or a die hard fan who wants to start building their own cars, you want to read this…

No matter your expertise, age, or experience, you’ll find there is a lot to love about these high-tech gadgets!

You can go to the store, pick your model, and start racing today, or you can spend just a little bit more time learning about RC cars…

…and build your own high speed racing machine!

Learning all there is to know about RC cars and racing can be expensive if you don’t know what’s involved. 

You can learn things like this for avoiding spending so much money on RC cars and racing.

• The different kinds of remote controlled car models… always know which kinds are most enjoyable and which to avoid!

Racing guidelines and pointers… you’ll have the “edge” over your competitors.

• How to design your own car… your car will display your personality and skill for all to see!

The Pros and Cons of different engine systems… your car will have the most power for that all important race. 

In a very short time you can be enjoying the exhilarating hobby of remote controlled car racing, faster than you ever thought possible!

A rechargeable battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to megawatt systems connected to stabilize an electrical distribution network. Several different combinations of chemicals are commonly used, including: lead-acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer).

Rechargeable batteries have lower total cost of use and environmental impact than disposable batteries. Some rechargeable battery types are available in the same sizes as disposable types. Rechargeable batteries have higher initial cost, but can be recharged very cheaply and used many times.

Rechargeable batteries are used for applications such as automobile starters, portable consumer devices, light vehicles (such as motorized wheelchairs, golf carts, electric bicycles, and electric forklifts), tools, and uninterruptible power supplies. Emerging applications in hybrid electric vehicles and electric vehicles are driving the technology to reduce cost and weight and increase lifetime.

Normal new rechargeable batteries have to be charged before use; newer low self-discharge batteries hold their charge for many months, and are supplied charged to about about 70% of their rated capacity.

Grid energy storage applications use industrial rechargeable batteries for load leveling, where they store electric energy for use during peak load periods, and for renewable energy uses, such as storing power generated from photovoltaic arrays during the day to be used at night. By charging batteries during periods of low demand and returning energy to the grid during periods of high electrical demand, load-leveling helps eliminate the need for expensive peaking power plants and helps amortize the cost of generators over more hours of operation.

Credit and debit cards in the U.S. use old magnetic stripe technology. The magnetic stripe is the black or brown band on the back of your credit or debit card. Tiny, iron-based magnetic particles in this band store data such as your account number. When the card is swiped through a “reader,” the data stored on the magnetic stripe is accessed. Card readers and magnetic stripe technology are inexpensive and readily available, making the technology highly vulnerable to fraud.

One extremely prevalent example of such fraud is ATM skimming. Skimming occurs when a criminal copies the data stored on your card’s magnetic stripe and burns the stolen data onto a blank card, creating a clone can that be used like any normal credit or debit card.

According to the Smart Card Alliance, twenty-two countries, including China, India, Japan, Mexico, Canada, and many in Western Europe and Latin America, are migrating to encrypted microprocessor chip and PIN technology for credit and debit payments. These new “smart cards” contain an embedded microchip and are authenticated using a personal identification number, or PIN. When a customer uses a smart card to make a purchase, the card is placed into a “PIN pad” terminal or a modified swipe-card reader, which accesses the card’s microchip and verifies the card’s authenticity. The customer then enters a four digit PIN, which is checked against the PIN stored on the card.

U.S. travelers are encountering difficulties when attempting to use old magnetic stripe credit and debit cards abroad, since their cards do not contain the new microchips. This is especially problematic at automated kiosks, which are common in Europe. Vending machines at regional rail stations, bicycle rental racks in Paris, parking meters in parts of London, toll roads, and gas stations only accept chip and PIN cards. Visa claims that most payment terminals in countries that have adopted chip payment technology can still process old magnetic stripe U.S. cards, and, “in the rare instance that a card holder encounters a problem” at a self-service machine, Visa advises American travelers to present their cards to attendants.

In the meantime, if you travel to Europe, make sure to carry cash. And if you are likely to use a kiosk that can only process cards with chip and PIN technology, do your homework ahead of time to determine whether an alternative payment method is available.

 

off Introduction of smart card

dixon to Smart Card  

A smart card, chip card, or integrated circuit card (ICC), is any pocket-sized card with embedded integrated circuits. There are two broad categories of Integrated Circuit Cards. Memory cards contain only non-volatile memory storage components, and perhaps dedicated security logic. Microprocessor cards contain volatile memory and microprocessor components. The card is made of plastic, generally polyvinyl chloride, but sometimes acrylonitrile butadiene styrene or polycarbonate. The card may embed a hologram to prevent counterfeiting. Smart cards may also provide strong security authentication for single sign-on within large organizations. Smart cards can be used for identification, authentication, data storage and application processing

l              Contact smart card

Contact smart cards have a contact area of approximately 1 square centimetre (0.16 sq in), comprising several gold-plated contact pads. These pad provide electrical connectivity when inserted into a reader.

Cards do not contain batteries; energy is supplied by the card reader.

Signals

l              VCC 

Power supply input.

l              RST 

Reset signal, used to reset the card’s communications.

l              CLK 

Provides the card with a clock signal, from which data communications timing is derived.

l              GND 

Ground (reference voltage).

l              VPP 

Programming voltage input – originally an input for a higher voltage to program persistent memory (e.g. EEPROM, but now deprecated.

l              I/O 

Serial input and output (half-duplex).

l              C4, C8 

The two remaining contacts are AUX1 and AUX2 respectively, and used for USB interfaces and other uses.

 

 Reader

Contact smart card readers are used as a communications medium between the smart card and a host, e.g. a computer, a point of sale terminal, or a mobile telephone.

Because the chips in financial cards are the same Subscriber Identity Module (SIM) as in mobile phones, programmed differently and embedded in a different piece of PVC, chip manufacturers are building to the more demanding GSM/3G standards. So, for example, although EMV allows a chip card to draw 50 mA from its terminal, cards are normally well below the telephone industry’s 6 mA limit. This allows smaller and cheaper financial card terminals.

l              Contactless smart card

A second card type is the contactless smart card, in which the card communicates with and is powered by the reader through RF induction technology (at data rates of 106 to 848 kilobits/second). These cards require only proximity to an antenna to communicate. They are often used for quick or hands-free transactions such as paying a mass transit without removing the card from a wallet.

Examples of widely used contactless smart cards are Hong Kong’s Octopus card, Shanghai’s Public Transportation Card, Moscow’s Transport/Social Card, South Korea’s T-money (bus, subway, taxi), Melbourne’s myki, the Netherlands’ OV-chipkaart, Milan’s Itinero, London’s Oyster card, London’s sQuidcard which is used for small payments in Thames Ditton, Bolton and Dundee, Japan Rail’s Suica card, Israel’s Rav-Kav, Mumbai’s Brihanmumbai Electric Supply and Transport and Beijing’s Municipal Administration and Communications Card. All of them are primarily designed for public transportation payment and other electronic purse applications.

Like smart cards with contacts, contactless cards do not have a battery. Instead, they use a built-in inductor to capture some of the incident radio-frequency interrogation signal, rectify it, and use it to power the card’s electronics.

You may notice that your home is suddenly too hot or too cold. Perhaps the fan runs constantly, but the temperature gauge does not register a change. This could be a sign of aging equipment or could simply be the fault of the thermostat.

If your heating and air conditioning unit is more than fifteen years old, you may certainly be looking at replacement. First, though you should look at the options.

Before troubleshooting your thermostat

, check to see if all filters are clean and all hoses to and from the units themselves are free of wear.

If these are not causing problems, then it is time to look at specific issues and possible solutions. Your thermostat could have aging wiring that is faulty or the transformer may require replacing.

Always check the owner’s manual for the system first, if it is available.

For a wireless system, make sure you are using the correct batteries: AA Lithium. If the system is running at inconsistent times, then you may have inadvertently installed alkaline batteries. Regular batteries will run out of juice quickly in a wireless system, especially if the backlight is on or used frequently to check the readings.

Does the heater or air conditioning fail to come on when the home’s temperature is too cold or too warm? Or does it trigger on when there is no need? There are several different reasons for this to occur.

First, study the location of the thermostat. Is it in a drafty hallway? Is it too near a heat source? If no outside sources are to blame, you will need to check behind the thermostat and in the wall itself.

Thermostats run on very low voltage, but it is always a good idea to turn off power, both to the unit and to the thermostat. Remove the thermostat cover by either prying off or removing the screws, depending on the model. When the cover is off, can you detect any unusually cool or warm air coming through from the wall space? If so, remove the entire unit and caulk or add extra insulation around the opening.

If you have a regular, house-type thermometer that you know to be accurate, hang it next to the thermostat. Check the readouts every hour or so for a comparison. This will help you to determine its operation, both before and after trying simple repairs and cleaning.

Give the thermostat’s interior a light dusting with a small, soft paintbrush. Be sure to clean the contacts, which are small metal plates within the unit. The wires coming from the transformer attach to the contacts. Do not touch any of the interior parts with fingers.

You may need to test the transformer if nothing seems wrong with the thermostat. You can use a voltmeter or a multitester. If you are using a multitester, set the dial to ACV 50 and connect a probe to each of the terminals. This step will allow you to test for current. If there is none, one final step should be to check power coming in to the transformer. Use the multitester or voltmeter to probe the hot wires and the neutral wires and tighten the contacts if necessary.

If the problem is with an older thermostat, and the system is not on a heat pump

, you should consider replacing the thermostat with a digital model. It will increase the efficiency of your unit and many styles are available that can be programmed to suit your daily schedule.

If you are not comfortable working on the inside of your thermostat, do not hesitate to call a professional. Certainly, if these suggestions do not seem to help, then it is time to place that call.

Even if your system seems to be having problems not listed here, try the troubleshooting tips first. You may be able to solve the problem and avoid the expense of calling an outside professional

Remote controlled aeroplanes can be fun for both children and adults. For adults, these R.C. aeroplanes can bring back fond memories of when you were a child growing up. In today’s society, R.C. aeroplanes have come a long way with the addition of modern technology, making the much more strategic than in the past years. Whether you are flying like a pro or crashing every 30 seconds, you will absolutely be having fun while you’re doing it. If you are still a rookie, or new to flying R.C. aeroplanes, then you should be advised to go with a lower end (price) product, to ensure that you don’t waste a lot of money because if you are new to this, you will crash. Remote controlled aeroplanes come in many different shapes and sizes, as well as price tags. You may find that lower priced R.C. aeroplanes cost in the neighborhood of $100 and rise in price to an upwards of $10,000. The higher end aeroplanes are generally of great size, therefore, depending on your location, you may need to contact your local airport for licenses and restriction. Sometimes you will be forced to fly these large planes in designated areas as well. There are generally no restrictions on the smaller, less expensive R.C. aeroplanes with the exception of not being able to fly the in public places. Open fields and back yards will be ideal for this situation. Either way, R.C. aeroplanes can be fun. It takes a lot of practice to master the art of controlling on these remote controlled aeroplanes but when you do, you will have a great time with this outdoor recreation. There are many different styles of R.C. aeroplanes to choose from. It is ultimately up to the consumer and his or her preference as to how realistic and custom that they would want this plane. The feeling you get as you succeed in aviation flight through a remote controlled censored aeroplane will be well worth your invested time.