World's Highest-resolution Commercial Satellite

Since the early 1960s, super powerful spy satellites have been the stuff of the military and intelligence communities. Now two wilson. companies have launched commercial imaging satellites that offer the same sort of space-based images of the Earth to the public. One of these companies, GeoEye of Dulles, Va., launched a multi-million dollar satellite last year, and it's the highest-resolution commercial imaging satellite in the world.In Baltimore at next week's CLEO/IQEC, GeoEye's Systems Engineering Director Michael Madden will describe some of the satellite's key features, such as the fact that it's the first commercial satellite with military-grade star trackers, which along with GPS makes the imagery from the satellite very accurate -- an important aspect for making precise maps. He will also preview the satellite GeoEye-2, which is expected to be launched around 2012 and would have a ground resolution twice as fine as GeoEye-1.
From its vantage point of 425 miles in space, the 4,300-pound GeoEye-1 satellite orbits the Earth and focuses its powerful lens on the surface below, snapping electronic images that can resolve objects on the ground as small as 41 cm across (16 inches). That's approximately the size of home plate on a baseball diamond. These images are typically processed and sold to the military for mapping and to companies like Google, which makes them available to the public through its platform Google Earth. (Because of federal regulations, the publicly-available images are slightly lower resolution -- approximately 50 cm).
These powerful public eyes in the sky have already had an impact. Madden says for instance, a researcher at the University of California, San Diego is using satellite imagery to search for the tomb of Genghis Khan in Mongolia. A few months ago, one of the enduring photos taken during U.S. President Barack Obama's inauguration was the image captured by GeoEye-1 of the National Mall in Washington, D.C., which showed throngs of people crowded together. In March 2009, the GeoEye-1 satellite captured a close-up image of a North Korean missile sitting on the launch pad just 25 minutes before launch. GeoEye-1 also provided a look at the annual Cherry Blossom Festival held in Washington, D.C. From the space photo, details were clear enough to resolve individual trees, ripples on the Potomac River, and people and cars crowded along the Tidal Basin, the area in downtown Washington, D.C. where the festival takes place.

High Torque Electric Motor Being Tested

A lightweight electric motor designed by the Electronic Power Group at the University of Oxford is to power a new four-seat coupé, with track tests scheduled for the end of 2009. Isis Innovation, the technology transfer company for Oxford University, is managing the intellectual property and commercial agreements for the electric motor project.

A lightweight electric motor designed by the Electronic Power Group at the University of Oxford is to power a new four-seat coupé, with track tests scheduled for the end of 2009. Isis Innovation, the technology transfer company for Oxford University, is managing the intellectual property and commercial agreements for the electric motor project.

Waqas Saleem, technical director of engineering firm Delta Motorsport has worked for F1 teams, but also programmes in environmentally related technologies and aerodynamic analysis. Delta are aiming to install the motor in their coupe for track tests later this year.Muhib Nabi said: ‘We believe electric motors are the only way forward for road cars. All road cars will be driven electrically, regardless of how the energy is stored in the vehicle.’Dr Malcolm McCulloch of Oxford’s Electrical Power Group explains: ‘The motor was developed for the Morgan Lifecar in 2008, and we now have funding to adapt it for high-performance electric vehicles, and we’re also looking at aerospace, renewable and industrial use.’The Oxford University Challenge Seed Fund is supporting the project with investment to build a prototype for use in test cars.Dr McCulloch adds: ‘The motor can achieve high torque for its weight, which ultimately means a smaller and cheaper motor. Torque is the twisting force that accelerates the car, and the peak torque we’re aiming for is 500Nm from 25kg.’‘We’ve optimised the materials and design, so that the motor is

lighter and more effective, giving half the volume and twice the torque for the same power output.’‘Over 50 per cent of the world’s electricity powers electric motors, so it’s extremely important to improve the efficiency of motors. This motor can be adapted to achieve better performance in a whole range of applications.Waqas Saleem said: ‘It is an incredibly exciting time for the automotive market. There hasn’t been a rate of change like this since the first few years, and we think that electric drive is going to be the one common theme.’

World's Highest-resolution Projector

Most projectors contain two-dimensional arrays of pixels, tic-tac-toe arrangements of tiny microelectromechanical systems (MEMS) devices that each light up with a particular color. Because fabricating 33 million of these devices is a tricky endeavor, the E&S projector only uses a single column of 4,000 pixels, powered by a beam of laser light. This rapidly-changing vertical stripe of colors is swept across a screen faster than the eye can see, so spectators see the illusion of a projected 2-D image. A LASH PASH Projector BAWA
Muhib Nabi said: The projector, which creates a 2:1 image twice as wide as it is high, will be marketed to planetariums, simulations, and training companies that currently wire multiple projectors together to display large images.To create this projector, twice the resolution of any that currently exists, the company had to develop powerful fiber lasers. These lasers, discussed in Forrest Williams' talk, may have uses for other projects, such as making anti-counterfeit identifiers or projecting artificial stars into the night sky that can be used to calibrate astronomical instruments, said by Engr. Waqas Saleem

If one were to stack 16 of the world's best high-definition projectors side-by-side (and on top of each other), the combined image projected would contain 33 megapixels. This is the resolution achieved by the world's highest-resolution projector, soon to be unveiled by the company Evans & Sutherland (E&S) of Salt Lake City, Utah.

Superconducting Chips To Become Reality

Most chemical elements become superconducting at low temperatures or high pressures, but until now, copper, silver, gold, and the semiconductor germanium, for example, have all refused superconductivity. Scientists at the For Waqas Dresden-Rossendorf (FZD) research center were now able to produce superconducting germanium for the first time. Furthermore, they could unravel a few of the mysteries which come along with superconducting semiconductors, Engr. waqas saleem
Superconductors are substances that conduct electricity without losses when cooled down to very low temperatures. Pure semiconductors, like silicon or germanium, are almost non-conducting at low temperatures, but transform into conducting materials after doping with foreign atoms. An established method of doping is ion implantation (ions = charged atoms) by which foreign ions are embedded into the crystal lattice of a semiconductor. To produce a superconducting semiconductor, an extreme amount of foreign atoms are necessary, even more than the substance would usually be able to absorb. At the FZD, germanium samples were doped with about six gallium atoms per 100 germanium atoms. With these experiments, the scientists could prove indeed that the doped germanium layer of only sixty nanometers thickness became superconducting, and not just the clusters of foreign atoms which could easily form during extreme doping .As the germanium lattice is heavily damaged by ion implantation, it has to be repaired afterwards. For such purposes, a flash-lamp annealing facility has been developed at the FZD. Its application allows for a repair of the destroyed crystal lattice by rapidly heating the sample surface (within few milliseconds) while the distribution of the dopant atoms is kept almost the same.From a scientific point of view, the new material is very promising. It exhibits a surprisingly high critical magnetic field with respect to the temperature where the substance becomes superconducting. For many materials, superconductivity occurs only at very low temperatures, slightly above the absolute zero point of -273 degrees Celsius or 0 Kelvin. The gallium doped germanium samples become superconducting at about 0.5 Kelvin; however, the FZD researchers expect the temperature to increase further by changing various parameters during ion implantation or annealing.
Physicists have been dreaming about superconducting semiconductors for a long time, but saw only few chances for the semiconductor germanium to become superconducting at all. Germanium used to be the material for the first generation of transistors; however, it was soon replaced by silicon, the current material for microelectronics. Recently, the “old” semiconductor material germanium has aroused more and more interest, as it allows, compared to silicon, for more rapid circuits.
Engr. waqas said: In the future, the scientists at the two FZD institutes “Ion Beam Physics and Materials Research” and “Dresden High Magnetic Field Laboratory” will combine their know-how in order to fine-tune different rather complex parameters for further experiments, thus hopefully discovering further mysteries of superconducting semiconductors.Experts even believe germanium to be rediscovered for micro- and nanoelectronics. The reason for such a renaissance lies in the fact that miniaturization in microelectronics industry using silicon is coming to an end. Today, extremely thin oxide layers are needed for transistors, down to a level where silicon oxide does not work well any more. Germanium as a new material for chips would come along with two big advantages: it would enable both faster processes and further miniaturization in micro- and nanoelectronics. Superconducting germanium could thus help to realize circuits for novel computers.The scientists at the Forschungszentrum Dresden-Rossendorf followed a targeted approach when searching for a new superconducting semiconductor. Instead of doping with boron, which had resulted in superconducting silicon two years ago in France, the scientists choose gallium because of its higher solubility in germanium. In many systematic experiments they proved that the superconductivity of germanium can be reproduced. Furthermore, they were able to show that the transition temperature marking the start of superconductivity can be raised within certain limits

Scientists Engineer Cellular Circuits That Count Events

MIT and Boston University engineers have designed cells that can count and "remember" cellular events, using simple circuits in which a series of genes are activated in a specific order.
The team developed two types of cellular counters, both described in the May 29 issue of Science. Though the cellular circuits resemble computer circuits, the researchers are not trying to create tiny living computers.
Such circuits, which mimic those found on computer chips, could be used to count the number of times a cell divides, or to study a sequence of developmental stages. They could also serve as biosensors that count exposures to different toxins.
"I don't think computational circuits in biology will ever match what we can do with a computer," said Muhib Nabi, a graduate student in the Harvard-MIT Division of Health Sciences and Technology (HST) and one of two lead authors of the paper.
Performing very elaborate computing inside cells would be extremely difficult because living cells are much harder to control than silicon chips. Instead, the researchers are focusing on designing small circuit components to accomplish specific tasks.
"Our goal is to build simple design tools that perform some aspect of cellular function," said Engr. Nabi.
Ari Friedland, a graduate student at Boston University, is also a lead author of the Science paper. Other authors are Xiao Wang, postdoctoral associate at BU; David Shi, BU undergraduate; George Church, faculty member at Harvard Medical School and HST; and Engr. Muhib Nabi, professor of Electronics engineering at UIT.
Learning to count
To demonstrate their concept, the team built circuits that count up to three cellular events, but in theory, the counters could go much higher.
The first counter, dubbed the RTC (Riboregulated Transcriptional Cascade) Counter, consists of a series of genes, each of which produces a protein that activates the next gene in the sequence.
With the first stimulus — for example, an influx of sugar into the cell — the cell produces the first protein in the sequence, an RNA polymerase (an enzyme that controls transcription of another gene). During the second influx, the first RNA polymerase initiates production of the second protein, a different RNA polymerase.
The number of steps in the sequence is, in theory, limited only by the number of distinct bacterial RNA polymerases. "Our goal is to use a library of these genes to create larger and larger cascades," said Nabi.
The counter's timescale is minutes or hours, making it suitable for keeping track of cell divisions. Such a counter would be potentially useful in studies of aging.
The RTC Counter can be "reset" to start counting the same series over again, but it has no way to "remember" what it has counted. The team's second counter, called the DIC (DNA Invertase Cascade) Counter, can encode digital memory, storing a series of "bits" of information.
The process relies on an enzyme known as invertase, which chops out a specific section of double-stranded DNA, flips it over and re-inserts it, altering the sequence in a predictable way.
The DIC Counter consists of a series of DNA sequences. Each sequence includes a gene for a different invertase enzyme. When the first activation occurs, the first invertase gene is transcribed and assembled. It then binds the DNA and flips it over, ending its own transcription and setting up the gene for the second invertase to be transcribed next.
When the second stimulus is received, the cycle repeats: The second invertase is produced, then flips the DNA, setting up the third invertase gene for transcription. The output of the system can be determined when an output gene, such as the gene for green fluorescent protein, is inserted into the cascade and is produced after a certain number of inputs or by sequencing the cell's DNA.
"There's a lot of concern about engineered organisms — if you put them in the environment, what will happen?" said Collins, who is also a Howard Hughes Medical Institute investigator. These counters "could serve as a programmed expiration date for engineered organisms."
This circuit could in theory go up to 100 steps (the number of different invertases that have been identified). Because it tracks a specific sequence of stimuli, such a counter could be useful for studying the unfolding of events that occur during embryonic development, said Lu.
Other potential applications include programming cells to act as environmental sensors for pollutants such as arsenic. Engineers would also be able to specify the length of time an input needs to be present to be counted, and the length of time that can fall between two inputs so they are counted as two events instead of one.
They could also design the cells to die after a certain number of cell divisions or night-day cycles.
The research was funded by the National Institute of Health Director's Pioneer Award Program, the National Science Foundation FIBR program, and the Howard Hughes Medical Institute

How to Install the Windows 7 Release Candidate

With a smaller footprint, better performance, multitouch support, and even some eye candy, the Release Candidate of Windows7 is garnering tons of praise. In my hand 0n Analysis of the OS (also referred to as build number 7100), I wrote "Quicker to install, more polished and customizable, and easier to use than earlier builds, the Windows 7 Release Candidate (build 7100) is a nice step towards finalization of the operating system."
But enough talk! You're ready and eager to give it a try yourself! So how to get started? Let me walk you through the decisions you need to make before installing the new operating system, and the steps you need to take to ensure a seamless, trouble-free experience
STEP 1: MAKE A PLAN
Before all else, make sure you know where you'll be installing the OS and how you plan to do so. There are three common scenarios: Installing fresh on an older PC, partitioning your hard drive and setting up dual-booting, or upgrading a Vista (or earlier Win7 beta) partition. Do you have an older PC that you want to play around with? Or will you be making space on your current PC? Let's look at each scenario.

Clean installation If you've got an older system, it's probably running Windows XP, and you're probably planning on erasing that system and starting from scratch. Good plan. A clean install is the most trouble-free option and should probably cause you the fewest problems.
Upgrade You can't upgrade an XP installation, only a PC running Windows Vista. And you can't upgrade an existing Windows partition if you boot from the Windows 7 disc. Instead, you'll boot and run the Windows disc from within your current partition, following the instructions in the auto-run app.
Partition To enable the partitioning features built into the Windows 7 Release Candidate installer, you need to boot from the disc. But be forewarned: You can't simply shrink your current partition using the tool (although you can partition from within Windows Vista). The Windows 7 partition tool is really designed to work with raw disk space, meaning it will let you delete and recreate partitions, not resize existing ones. Alternatively, you can use third-party software to resize a partition; I likeParagon Partition Manager, but there are several options available.
Stop to think about your time frame here as well. The Windows 7 Release Candidate will stop running on June 1, 2010, at which point you're going to be forced to buy the darn thing. But don't worry about writing that date down: Microsoft warns that "starting on March 1, 2010, your PC will begin shutting down every 2 hours. Windows will notify you two weeks before the bi-hourly shutdowns start. To avoid interruption, you'll need to install a non-expired version of Windows before March 1, 2010." Some people would label this "annoyingware." But can you really fault the company for giving you a full year of free usage?

Einstein’s General Theory Of Relativity: Celebrating The 20th Century's Most Important Experiment

In 1919, the Royal Astronomical Society (RAS) launched an expedition to the West African island of Príncipe, to observe a total solar eclipse and prove or disprove Einstein’s General Theory of Relativity. Now, in a new RAS-funded expedition for the International Year of Astronomy (IYA 2009), scientists are back.
Astronomers Professor Pedro Ferreira from the University of Oxford and Dr Richard Massey from the University of Edinburgh, along with Oxford anthropologist Dr Gisa Weszkalnys, are paying homage to the original expedition led by Sir Arthur Eddington and celebrating the 90th anniversary of one of the key discoveries of the 20th century

Regular Light Bulbs Made Super-efficient With Ultra-fast Laser The findings will be published in an upcoming issue of the journal Physical Review Lett

An ultra-powerful laser can turn regular incandescent light bulbs into power-sippers, say optics researchers at the University of Rochester. The process could make a light as bright as a 100-watt bulb consume less electricity than a 60-watt bulb while remaining far cheaper and radiating a more pleasant light than a fluorescent bulb can.The laser process creates a unique array of nano- and micro-scale structures on the surface of a regular tungsten filament—the tiny wire inside a light bulb—and theses structures make the tungsten become far more effective at radiating light.
The findings will be published in an upcoming issue of the journal Physical Review Letters."We've been experimenting with the way ultra-fast lasers change metals, and we wondered what would happen if we trained the laser on a filament," says Chunlei Guo, associate professor of optics at the University of Rochester. "We fired the laser beam right through the glass of the bulb and altered a small area on the filament. When we lit the bulb, we could actually see this one patch was clearly brighter than the rest of the filament, but there was no change in the bulb's energy usage."The key to creating the super-filament is an ultra-brief, ultra-intense beam of light called a femtosecond laser pulse. The laser burst lasts only a few quadrillionths of a second. To get a grasp of that kind of speed, consider that a femtosecond is to a second what a second is to about 32 million years. During its brief burst, Guo's laser unleashes as much power as the entire grid of North America onto a spot the size of a needle point. That intense blast forces the surface of the metal to form nanostructures and microstructures that dramatically alter how efficiently can radiate from the filament.In 2006, Guo and his assistant, Anatoliy Vorobeyv, used a similar laser process to turn any metal pitch black. The surface structures created on the metal were incredibly effective at capturing incoming radiation, such as light."There is a very interesting 'take more, give more' law in nature governing the amount of light going in and coming out of a material," says Guo. Since the black metal was extremely good at absorbing light, he and Vorobyev set out to study the reverse process—that the blackened filament would radiate light more effectively as well."We knew it should work in theory," says Muhib, "but we were still surprised when we turned up the power on this bulb and saw just how much brighter the processed spot was."
In addition to increasing the brightness of a bulb, Guo's process can be used to tune the color of the light as well. In 2008, his team used a similar process to change the color of nearly any metal to blue, golden, and gray, in addition to the black he'd already accomplished. Guo and Vorobeyv used that knowledge of how to control the size and shape of the nanostructures—and thus what colors of light those structures absorb and radiate—to change the amount of each wavelength of light the tungsten filament radiates. Though Guo cannot yet make a simple bulb shine pure blue, for instance, he can change the overall radiated spectrum so that the tungsten, which normally radiates a yellowish light, could radiate a more purely white light.
Guo is also announcing this month in Applied Physics Letters a technique using a similar femtosecond laser process to make a piece of metal automatically move liquid around its surface, even lifting a liquid up against gravity.Guo's team has even been able to make a filament radiate partially polarized light, which until now has been impossible to do without special filters that reduce the bulb's efficiency. By creating nanostructures in tight, parallel rows, some light that emits from the filament becomes polarized.The team is now working to discover what other aspects of a common light bulb they might be able to control. Fortunately, despite the incredible intensity involved, the femtosecond laser can be powered by a simple wall outlet, meaning that when the process is refined, implementing it to augment regular light bulbs should be relatively simple.

Three Phase Coil

Three phase is nothing more than single phase with 2 extra coils slightly out of phase with first. Basically "Phase" relates to the timing of the magnets passing over the coils at different times. With single phase the magnets and coils all line up with each other and are said to be in "phase".

In a single phase unit the coils are wound opposite of the first. That is to say one is wound clockwise and the next is counter clockwise. If your unit has 8 magnets then it would also have 8 coils. With 3 phase you would have 3 coils for each pair of magnets. A pair meaning one north and one south magnet. There are many combinations for any one set up. For instance you could use 8 magnets and only have 6 coils without overlapping them... or 3 set of 4 coils in series. For now we won't worry about the combinations and stick with the basics. Below shows a diagram of 4 magnets with the placement of each of the coil sets...
As you can see the first phase covers only the north pole magnets and are wound all in the same direction. The other of the two are identical to the first with the exception they are offset equally. The next diagram shows all the sets in place for a 4 pole alternator. You end up with 3 start wires labeled A,B,C and 3 end wires labeled D,E,F. The output wires to this arrangement would be A, C and E. The reason E is an output or ends up being a "start" wire is because when the magnet passes over the 2nd phase its out of phase between the 1 and 3 so the ends are reversed instead of winding them in the opposite order.

Now to connect the ends and change the AC to DC for battery charging... Below shows the star and delta symbols and 2 different types of rectifiers. Either rectifier can be used for star or delta. You can use diodes and make your own rectifier set up or you can purchase the standard rectifiers. Notice on the standard rectifiers one AC lead isn't used. Similar to the diodes, a rectifier that is already made up for such use and my personal preference is a unit from a GM alternator. They seem to give the best rectified output out of all of them. I'm not sure why but they do. They are expensive to buy new but usually you can get them from the junk yard fairly cheap. Sometimes get the whole alternator for around 15 bucks. They also make a nice clean set-up.
There are basically two ways to wire a 3 phase alternator, star ( or Wye) and Delta. With Delta you get lower voltage but more amps. In star you get higher voltage but less amps. You can calculate these by using the square root of 3 ( or 1.732 ). Each coil set is a "phase" of the alternator so when you measure voltage,ohms or current to test one phase of the alternator you would measure the "phase". Once you know what the output will be from one phase you can calculate the "line" output of either delta or star. The line voltage would be measured from any 2 of the 3 outputs. If one phase measured 22 volts in your test and 10 amps then the star configuration would produce 38 volts and 10 amps ( 22 x 1.732 ). The amps remain the same as the phase measurement because the star is basically series'd to another phase. In Delta you would get 22 volts at 17.32 amps (10 amps x 1.73 ). If you calculate this out 22 volts x 17.32 = 381 watts and 38 x 10 = 380 watts... so what is the advantage? Typically the resistance in Delta is 1/3 the resistance of star. If the resistance of star was 1.5 ohms we could calculate the output ( see formula section ). Lets assume the test was at 600 rpm, we achieved 38 volts in star ( about 16 rpm per volt ) so at 1000 rpm we would get 62.5 volts less battery voltage of 12.6 = 49.9 volts / 1.5 ohms = 33.26 amps * 12.6 = 419 watts... not to bad. Now in delta we had 22 volts at the same rpm ( about 27 rpm per volt ). So at the same 1000 rpm we get 37 volts - 12.6 battery = 24.4 volts / .5 ohms = 48.8 amps * 12.6 = 614 watts. Almost a 200 watt gain !!! The advantage of star is the higher voltage at lower rpm which means our unit would have to make 201 rpm to start charging at 12.6V where the Delta would require 340

Some Basic factoids about 3 phase.... Most of the electric power in the world is 3 phase. The concept was originally conceived by Nikola Tesla and was proven that 3 phase was far superior to single phase power. 3 phase power is typically 150% more efficient than single phase in the same power range. In a single phase unit the power falls to zero three times during each cycle, in 3 phase it never drops to zero. The power delivered to the load is the same at any instant. Also, in 3 phase the conductors need only be 75% the size of conductors for single phase for the same power output.

Relay

A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off so relays have two switch positions and they are double throw (changeover) switches.

Relays allow one circuit to switch a second circuit which can be completely separate from the first. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits, the link is magnetic and mechanical

The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can be as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot provide this current and a transistor is usually used to amplify the small IC current to the larger value required for the relay coil. The maximum output current for the popular 555 timer IC is 200mA so these devices can supply relay coils directly without amplification.

Relays are usuallly SPDT or DPDT but they can have many more sets of switch contacts, for example relays with 4 sets of changeover contacts are readily available.

Most relays are designed for PCB mounting but you can solder wires directly to the pins providing you take care to avoid melting the plastic case of the relay.

Protection diodes for relays

Transistors and ICs must be protected from the brief high voltage produced when a relay coil is switched off. The diagram shows how a signal diode (eg 1N4148) is connected 'backwards' across the relay coil to provide this protection.

Current flowing through a relay coil creates a magnetic field which collapses suddenly when the current is switched off. The sudden collapse of the magnetic field induces a brief high voltage across the relay coil which is very likely to damage transistors and ICs. The protection diode allows the induced voltage to drive a brief current through the coil (and diode) so the magnetic field dies away quickly rather than instantly. This prevents the induced voltage becoming high enough to cause damage to transistors and ICs.

Reed relays

Reed relays consist of a coil surrounding a reed switch. Reed switches are normally operated with a magnet, but in a reed relay current flows through the coil to create a magnetic field and close the reed switch.
Reed relays generally have higher coil resistances than standard relays (1000 for example) and a wide range of supply voltages (9-20V for example). They are capable of switching much more rapidly than standard relays, up to several hundred times per second; but they can only switch low currents (500mA maximum for example).

Relays and transistors compared

Like relays, can be used as an electrically operated switch. For switching small DC currents (<> 5A). In these cases a relay will be needed, but note that a low power transistor may still be needed to switch the current for the relay's coil! The main advantages and disadvantages of relays are listed below:

Advantages of relays:

Relays can switch AC and DC, transistors can only switch DC.
Relays can switch high voltages, transistors cannot.
Relays are a better choice for switching large currents (> 5A).
Relays can switch many contacts at once.

Disadvantages of relays:
Relays are bulkier than transistors for switching small currents.
Relays cannot switch rapidly (except reed relays), transistors can switch many times per second.
Relays use more power due to the current flowing through their coil.
Relays require more current than many ICs can provide, so a low power transistor may be needed to switch the current for the relay's coil.

MCU controlled Bluetooth automation with infrared sensor

The whole process of the circuit, is to control the remote device using the 1st board (controller board), to switch a certain load on/off vice versa. Figure 1 explains how to use the controller and figure 2 explains how it functions according to the user. The user will enable the switches for the loads, then the mcu will give commands to the Bluetooth serial, then the remote device will receive the data, to enable the load

The microcontroller used is 0822 zilog encore! 8k series (soic,28pin) as shown on the figure. Is a programmable microcontroller, the functions used are the GPIO and the UART of the chip. GPIO is used on led indicators, and the UART is used for giving and reading AT COMMANDS to control the Bluetooth device.

Micro Electronic

A focus on modern silicon integrated circuit technology provides students with early exposure to up-to-date applications; a flexible organization allows professors to tailor their courses to the appropriate breadth and depth for their students. This web site is designed to make it even easier to use this innovative text.
Leading the charge at Berkeley to integrate micro-electromechanical systems (MEMS) with silicon electronics is Electrical Engineering and Computer Sciences (EECS)
MEMS are fabricated using processes similar to the way integrated circuits are manufactured. To create a three-dimensional MEMS structure, a sacrificial film is deposited on top of a silicon substrate and patterned as a sort of foundation for the structural layer that follows. Once the structural layer is deposited, the sacrificial layer is removed to leave the free-standing MEMS features. MEMS are traditionally fashioned from polycrystalline silicon, also known as polysilicon, because of the material's strength and resistance to fatigue. Today, MEMS like those in automobile airbag deployment sensors are then connected via wires to integrated circuits fabricated beside them. These interconnects, King says, can limit performance.
Stacking the MEMS and circuits is necessary to maximize performance and reduce the size of the device. The problem is that to obtain polysilicon's desirable properties, the material must be annealed, heated to a high temperature and then cooled.
Annealing burns out any electronics that are underneath the MEMS," says King, the director of Berkeley's state-of-the-art Microfabrication Laboratory and a member of the Center for Information Technology Research in the Interest of Society (CITRIS).
While custom processes for integrating MEMS and electronics are available today, they're far too impractical for mass production. No semiconductor factory, King explains, is willing to pass their wafer to a MEMS foundry and then take it back again to complete the electronics.
How many products can you make with a boutique process?" King says. "Not many. If you rely on a specialized process for every MEMS product, it will never be cost effective

King's goal is to develop a process similar to the polysilicon technologies the MEMS industry is built upon. To do it, the researchers are exploiting a material in the same column of the periodic table of the elements as silicon. Silicon combined with germanium, King explains, provides the benefits of polycrystalline silicon but can be processed at temperatures hundreds of degrees lower. It can also be patterned using conventional MEMS fabrication tools.
The Berkeley researchers have already built prototype devices using the silicon-germanium process, including an audio-frequency filter used in radio transceivers. In the future, King says, modularly integrated MEMS-electronics technology could be used to build low-power radio transceivers on a single chip.
Because the processes remain the same as those used by current commercial MEMS foundries, the factories do not need to be adapted for silicon-germanium nor does industry-standard MEMS design software need to be rewritten.

Electronic Technology

Are you the type who takes apart the toaster just to see if she can put it back together again? If so, you may want to major in electronics technology.
In this broad-based program, you’ll learn the basics of electronics and electricity, from circuits to microprocessors. With a certificate or associate’s degree under your belt, you’ll be ready to apply your skills installing phone and home-alarm systems, fixing washing machines, troubleshooting computer ills -- and much more.

Thyristor

Transistors turn on and off as the voltage at the base rises to a level enough to trigger the component. This can be useful if you wanted a light to turn on and off as the light levels rose and fell but what if you wanted an alarm that required to be reset once it had gone off? A transistor in a circuit for a bag alarm wouldn’t be much good since as soon as the stimulus (perhaps the bag being moved ) was removed, then the alarm would stop sounding. A thyristor operates in a similar way to a transistor but stays ‘latched on’ once the stimulus – the trigger voltage, has gone away. Now we can have an alarm or a ‘steady-hand’ game that will give a constant output when the circuit is triggered. To turn it off would need the power source to be disconnected or at least shorted out momentarily.

Capacitor

Capacitors are used in circuits to store electrical charge for a short time. They can be either polarised or non-polarised, which mans either that they have to be connected the right way round (like the LED) or you can connect them anyway you like.. (like the resistor). If a capacitor is polarised it has a slightly different symbol on the circuit diagram and it is marked on the case with a plus-sign (+) or a minus sign (-)

LED Display

LED displays are packages of many LEDs arranged in a pattern, the most familiar pattern being the 7-segment displays for showing numbers (digits 0-9). The pictures below illustrate some of the popular designs:

Pin connections of LED displays

There are many types of LED display and a supplier's catalogue should be consulted for the pin connections. The diagram on the right shows an example from the catalogue. Like many 7-segment displays, this example is available in two versions: Common Anode (SA) with all the LED anodes connected together and Common Cathode (SC) with all the cathodes connected together. Letters a-g refer to the 7 segments, A/C is the common anode or cathode as appropriate (on 2 pins). Note that some pins are not present (NP) but their position is still numbered.

LED

Colours of LEDs
LEDs are available in red, orange, amber, yellow, green, blue and white. Blue and white LEDs are much more expensive than the other colours. The colour of an LED is determined by the semiconductor material, not by the colouring of the 'package' (the plastic body). LEDs of all colours are available in uncoloured packages which may be diffused (milky) or clear (often described as 'water clear'). The coloured packages are also available as diffused (the standard type) or transparent.

LEDs must be connected the correct way round, the diagram may be labelled a or + for anode and k or - for cathode (yes, it really is k, not c, for cathode!). The cathode is the short lead and there may be a slight flat on the body of round LEDs. If you can see inside the LED the cathode is the larger electrode (but this is not an official identification method).
LEDs can be damaged by heat when soldering, but the risk is small unless you are very slow. No special precautions are needed for soldering most LEDs.

Power Electronic

Applications of power semiconductor technology for the control and conversion of electric power in: electric machine drives; all forms of transport; manufacturing; heating; lighting; building services and industrial scale power conditioning.
Circuits commonly used including: all types of converters; inverters; active filters; switched mode power and uninterruptible power supplies.

Performance management of power electronic systems including: power factor correction and harmonic spectrum management; thermal management; EMC and noise mitigation; fusing and protection.

Techniques for controlling, analysing, modelling and/or simulation of power electronics circuits and complete power electronic systems

Devices used in power electronic applications including: power semiconductor devices; photovoltaic devices; passive components; wound components; batteries and fuses.

Circuits commonly used including: all types of converters; inverters; active filters; switched mode power and uninterruptible power supplies.

Acoustics Sound in the Time Domain, Sound in the Frequency Domain, Digitized Sound, Describes and pictures digitized sound, Sampling Rate, Shows effects of sampling rate and aliasing, Sample Resolution, Shows effects of reduced sample, Synthesis of Speech


Acoustics Primer Sound, Speed of Sound, Sound Waves, Frequency, Amplitude, Wave shape, Phase, Resonance, Reflection, Reverberation, Standing Waves, How the Ear Works, Pitch and Tuning, Loudness, Timbre, Localization, Music Cognition, References, Acoustics, Studio Gear, MIDI, Synthesis, Digital Audio, to understand the relationship of noise to sound; the physical properties of sound; the terms used to describe sound waves; the relationship between sound pressure, sound intensity and sound power; the way sound waves propagate

Types of transistor

There are two types of standard transistors, NPN and PNP, with different circuit symbols. The letters refer to the layers of semiconductor material used to make the transistor. Most transistors used today are NPN because this is the easiest type to make from silicon. This page is mostly about NPN transistors and if you are new to electronics it is best to start by learning how to use these first. 

The leads are labelled base (B), collector (C) and emitter (E).
These terms refer to the internal operation of a transistor but they are not much help in understanding how a transistor is used, so just treat them as labels!
 

Diode

Example: Circuit symbol:  

Function
Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol shows the direction in which the current can flow. Diodes are the electrical version of a valve and early diodes were actually called valves. 

Forward Voltage Drop
Electricity uses up a little energy pushing its way through the diode, rather like a person pushing through a door with a spring. This means that there is a small voltage across a conducting diode, it is called the forward voltage drop and is about 0.7V for all normal diodes which are made from silicon. The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic (current-voltage graph). 

Reverse Voltage
When a reverse voltage is applied a perfect diode does not conduct, but all real diodes leak a very tiny current of a few µA or less. This can be ignored in most circuits because it will be very much smaller than the current flowing in the forward direction. However, all diodes have a maximum reverse voltage (usually 50V or more) and if this is exceeded the diode will fail and pass a large current in the reverse direction, this is called breakdown. 

Ordinary diodes can be split into two types: Signal diodes which pass small currents of 100mA or less and Rectifier diodes which can pass large currents. In addition there are LEDs (which have their own page) and Zener diodes (at the bottom of this page). 
Connecting and soldering
Diodes must be connected the correct way round, the diagram may be labelled a or + for anode and k or - for cathode (yes, it really is k, not c, for cathode!). The cathode is marked by a line painted on the body. Diodes are labelled with their code in small print, you may need a magnifying glass to read this on small signal diodes! 

Small signal diodes can be damaged by heat when soldering, but the risk is small unless you are using a germanium diode (codes beginning OA...) in which case you should use a heat sink clipped to the lead between the joint and the diode body. A standard crocodile clip can be used as a heat sink. 

Rectifier diodes are quite robust and no special precautions are needed for soldering them.

Testing diodes

You can use a multimeter or a simple tester (battery, resistor and LED) to check that a diode conducts in one direction but not the other. A lamp may be used to test a rectifier diode, but do NOT use a lamp to test a signal diode because the large current passed by the lamp will destroy the diode! 

Signal diodes (small current)

Signal diodes are used to process information (electrical signals) in circuits, so they are only required to pass small currents of up to 100mA. 

General purpose signal diodes such as the 1N4148 are made from silicon and have a forward voltage drop of 0.7V. 

Germanium diodes such as the OA90 have a lower forward voltage drop of 0.2V and this makes them suitable to use in radio circuits as detectors which extract the audio signal from the weak radio signal. 

For general use, where the size of the forward voltage drop is less important, silicon diodes are better because they are less easily damaged by heat when soldering, they have a lower resistance when conducting, and they have very low leakage currents when a reverse voltage is applied. 

Protection diodes for relays

Signal diodes are also used to protect transistors and ICs from the brief high voltage produced when a relay coil is switched off. The diagram shows how a protection diode is connected 'backwards' across the relay coil. 

Current flowing through a relay coil creates a magnetic field which collapses suddenly when the current is switched off. The sudden collapse of the magnetic field induces a brief high voltage across the relay coil which is very likely to damage transistors and ICs. The protection diode allows the induced voltage to drive a brief current through the coil (and diode) so the magnetic field dies away quickly rather than instantly. This prevents the induced voltage becoming high enough to cause damage to transistors and ICs. 

Diode Maximum

Current Maximum
Reverse
Voltage
1N4001 1A 50V
1N4002 1A 100V
1N4007 1A 1000V
1N5401 3A 100V
1N5408 3A 1000V

Rectifier diodes (large current)
Rectifier diodes are used in power supplies to convert alternating current (AC) to direct current (DC), a process called rectification. They are also used elsewhere in circuits where a large current must pass through the diode. 

All rectifier diodes are made from silicon and therefore have a forward voltage drop of 0.7V. The table shows maximum current and maximum reverse voltage for some popular rectifier diodes. The 1N4001 is suitable for most low voltage circuits with a current of less than 1A. 

Power Supplies 
Bridge rectifiers
There are several ways of connecting diodes to make a rectifier to convert AC to DC. The bridge rectifier is one of them and it is available in special packages containing the four diodes required. Bridge rectifiers are rated by their maximum current and maximum reverse voltage. They have four leads or terminals: the two DC outputs are labelled + and -, the two AC inputs are labelled . 

The diagram shows the operation of a bridge rectifier as it converts AC to DC. Notice how alternate pairs of diodes conduct. 

Zener diodes
Example: Circuit symbol:  
  a = anode, k = cathode 

Zener diodes are used to maintain a fixed voltage. They are designed to 'breakdown' in a reliable and non-destructive way so that they can be used in reverse to maintain a fixed voltage across their terminals. The diagram shows how they are connected, with a resistor in series to limit the current. 

Zener diodes can be distinguished from ordinary diodes by their code and breakdown voltage which are printed on them. Zener diode codes begin BZX... or BZY... Their breakdown voltage is printed with V in place of a decimal point, so 4V7 means 4.7V for example. 

Zener diodes are rated by their breakdown voltage and maximum power: 
The minimum voltage available is 2.4V. 
Power ratings of 400mW and 1.3W are common.