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In todays increasing environmentally conscious society, reducing our carbon footprint is seen as a social responsibility. Furthermore, as traditional sources of power become evermore expensive, energy derived from renewable sources are becoming more attractive and sought after.

Herein lies the beauty of using the most efficient solar panels we can find as a means of providing some or all of our electrical power. Furthermore, the accessibility and affordability of efficient solar panels means that they are no longer looked upon as quirky but rather as innovative, sensible and ultimately cost-effective.

It is estimated, given the world governments' increasing commitment to the use of renewable energy sources, that by the year 2030 some 14% of the world's energy will be provided by solar power.

The term solar panel actually describes two types of device, to give them their technical names:

1. Solar photovoltaic modules

2. Solar thermal collectors.

Solar thermal collectors use the sun's energy to heat water (in domestic use) or other fluids. A good solar hot water panel is able to provide an average household with around a third of its annual hot water supply.

However, it is with the photovoltaic modules (solar panels to you and I) that we will concentrate on here. These panels use solar sensitive cells to convert light energy from the sun into electricity and thereby provide a clean source of energy with no waste by-products.

For the science minded, photons from sunlight knock the electrons into a higher state of energy thereby creating electricity, passing the current so produced through a photodiode to power equipment or to recharge batteries.

Solar cells are interconnected and assembled into panels which require protection form the environment to allow them to continue to work effectively. Consequently, these panels are placed into a frame made of metal, plastic or fibreglass and glass fronted. The construction of the frame within which the solar cells are housed is vital. This is because the solar cells themselves are commonly made of wafer-based silicon and due to their being brittle they need protection from the elements, particularly impact from hail, wind and snow and from moisture, which would corrode the metal contacts and connections. A solar panel installation usually consists of multiple panels called an array.

The use of solar panels is becoming evermore popular and production has been doubling every two years, increasing by an average of 48% each year since 2002.

Building integrated photovoltaics (BIPV) are increasingly being integrated into new domestic and industrial buildings either as a principal or an ancillary source of electrical power. In new builds, the arrays are incorporated into the roof or walls of the building and roof tiles with integrated PV cells can now be purchased.

For existing buildings, arrays can be retrofitted usually on top of the existing roof structure. Alternatively, arrays can be located separately and connected by cable to provide the power supply for the building. Arrays are usually installed in a position angled so as to allow access to as much sunlight as possible to increase their efficiency.

This article was written by A R Forshaw.

For more information please see http://most-efficient-solar-panels.blogspot.com/

Digital Camera Basics-Images

In the past twenty years, most of the major technological breakthroughs in consumer electronics have been built around the same basic process: converting conventional analog information (represented by a fluctuating wave) into digital information (binary information represented by ones and zeros, or bits). This fundamental shift in technology has changed how we handle visual and audio information -- it completely redefined what is possible.

The digital camera is one of the most notable examples of this shift because it is so truly different from its predecessor. Conventional film cameras depend entirely on chemical and mechanical processes -- you don't need any electricity whatsoever to operate them, other than for a flash. On the other hand, all digital cameras have a built-in computer, and all of them record images electronically.

The new approach has been enormously successful. Since film usually provides better picture quality, digital cameras have not completely replaced conventional cameras. But, as digital imaging technology has improved, and prices dramatically decreased, digital cameras have rapidly become more popular.

In this article, we'll find out exactly what's going on inside these amazing digital-age devices.

Understanding the Basics

Let's say you want to take a picture and e-mail it to a friend. To do this, you need the image to be represented in the language that computers recognize -- bits and bytes, or binary information. Essentially, a digital image is just a long string of 1s and 0s that represent all the tiny colored dots -- or pixels -- that collectively make up the image. If you want to get a picture into this form, you have two options:

1) You can take a photograph using a conventional film camera, take the film to a developing lab that processes the film chemically, prints it onto photographic paper, and then place the picture on a digital scanner to sample the print (record the pattern of light as a series of pixel values).

2) You can directly sample the original light that bounces off your subject, immediately breaking that light pattern down into a series of pixel values -- in other words, you can use a digital camera.

At its most basic level, this is all there is to a digital camera. Just like a conventional film camera, it has a series of lenses that focus light to create an image of a scene. But instead of focusing this light onto a piece of film, it focuses it onto a semiconductor device that records light electronically. A computer then breaks this electronic information down into digital data. All the fun and interesting features of digital cameras come as a direct result of this process.

Instead of film, a digital camera has a sensor that converts light into electrical charges.

The image sensor employed by most digital cameras is a charge coupled device (CCD). Some cameras use complementary metal oxide semiconductor (CMOS) technology instead. Both CCD and CMOS image sensors convert light into electrons. Without getting too technical, a simplified way to think about these sensors is to think of a 2-dimentional array of thousands or millions of tiny solar cells.

Once the sensor converts the light into electrons, it reads the value (accumulated charge) of each cell in the image. This is where the differences between the two main sensor types become a factor:

A CCD transports the charge across the chip and reads it at one corner of the array. An analog-to-digital converter (ADC) then turns each pixel's value into a digital value by measuring the amount of charge at each photosite and converting that measurement to binary form. CCD sensors create high-quality, low-noise images. CCD sensors have been mass produced for a longer period of time, so they are more mature. They tend to have higher quality pixels, and more of them.

CMOS devices use several transistors at each pixel to amplify and move the charge using ordinary wires. The CMOS signal is digital, so it needs no ADC. Because each pixel on a CMOS sensor has several transistors located next to it, the light sensitivity of a CMOS chip is lower (many of the photons hit the transistors instead of the photodiode.) CMOS sensors traditionally consume little power. CCDs, on the other hand, use a process that consumes lots of power.

Resolution

The amount of detail that the camera can capture is called the resolution, and it is measured in pixels. The more pixels a camera has, the more detail it can capture and the larger pictures can be without becoming blurry or "grainy." High-end consumer cameras can capture over 12 million pixels. Some professional cameras support over 16 million pixels, or 20 million pixels for large-format cameras. For comparison, Hewlett Packard estimates that the quality of 35mm film is about 20 million pixels.

Exposure and Focus

Just as with film, a digital camera has to control the amount of light that reaches the sensor. The two components it uses to do this, the aperture and shutter speed, are also present on conventional cameras.

Aperture: The size of the opening in the camera. The aperture is automatic in most digital cameras, but some allow manual adjustment to give professionals and hobbyists more control over the final image.

Shutter speed: The amount of time that light can pass through the aperture. Unlike film, the light sensor in a digital camera can be reset electronically, so digital cameras have a digital shutter rather than a mechanical shutter.

These two aspects work together to capture the amount of light needed to make a good image. In photographic terms, they set the exposure of the sensor.

About the Author

By Brian Lee

Can anyone help me with some electronics?

I need to describe the construction, explain the opperation and give one detailed example of teh use of a large area photodiode.

A large area photo-diode is one with about 1 cm^2 area. They are often used for light measurement, and have a clearly defined area like 1cm^2 so it relates more directly to the measurement. Some I have seen have a built in filter so they have a photopic spectral response. Others may be enhanced in the blue region etc. The capacitance is like 100pF.

In a sense a solar panel is made up of larger area photo-diodes. I have used small solar cells for that exact reason, as well as commercial large area diodes. I have seen them used in various commercial instruments too. No doubt a purist could find arguments that the construction and doping are different. I would like to buy an argument on that sort of nit picking, but maybe the intention was explained somewhere in the course work and you missed it?

The reason I used large area photo-diodes was to simplify the optics. I had a LED with 5 degree beam as the source, and the entire beam fell on the cell, so needed no focusing at the detector end to maximise illumination. However they are not much good at low illumination levels and pulsed excitation, because of the capacitance.

The link below shows the differences from the amplifier point of view, and how to overcome some of the problems.

Because the larger ones can source a lot of current (more than the op-amp) I sometimes used them with a load of a few ohms (depending on the illumination and current so that there is about 10mV) and an instrumentation amplifier. This can be filtered easily so is less prone to interference (such as a radio transmitter) and can have a long cable with little impact, being balanced.

Enablence to showcase new PLC and photodiode products at OFC/NFOEC
MARCH 21, 2010 -- Enablence Technologies Inc. (TSX-V: ENA) will unveil two products for its Components and Subsystems Division, including new tunable optical filter array and photodiode products, at OFC/NFOEC 2010.

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