CDs AND DVDs

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

A compact disc or CD is a form of digital media. It is an optical device which can be encoded with digital data. When you examine a CD you can tell it is mainly plastic. In fact, a CD is almost pure polycarbonate plastic. There is a spiral track molded into the top of the plastic.
The surface of a CD is reflective because the disc is coated with a thin layer of aluminum or sometimes gold. The shiny metal layer reflects the laser that is used to read or write to the device. A layer of lacquer is spin-coated onto the CD to protect the metal. A label may be screen-printed or offset-printed onto the lacquer. Data is encoded by forming pits in the spiral track of the polycarbonate (though the pits appear as ridges from the perspective of the laser). A space between pits is called a
land . A change from a pit to a land or a land to a pit is a “1” in binary data, while no-change is a “0”.

Scratches Are Worse on One Side than the Other
Pits are closer to the label side of a CD, so a scratch or other damage on the label side is more likely to result in an error than one occurring on the clear side of the disc. A scratch on the clear side of the disc often can be repaired by polishing the disc or filling the scratch with a material with a similar refractive index.
Most of a CD is composed of a plastic called polycarbonate . The bottom layer is a polycarbonate layer where data is encoded by using tiny bumps on the surface. Above this layer is a reflective layer, which is typically made of aluminum (gold is also used, although quite rarely).
Above the reflective layer is a protective layer of lacquer and plastic, which shields the layers below it. The artwork or label is printed on the lacquer layer (i.e., on top of the CD) via offset printing or screen printing.
CDs store information digitally, i.e., with the help of millions of 1s and 0s. Data on a CD is encoded with the help of a laser beam that etches tiny indentations (or bumps, if you will) on its surface. A bump, in CD terminology, is known as a
pit, and represents the number 0. Similarly, the lack of a bump (known as a land ) represents the number 1. Hence, a laser beam can encode the required data into a compact disc by using pits and lands (0 and 1, respectively).
Now that you know how a CD is encoded with data, let’s take a look at how a CD player actually reads that stored data.

How does a CD player work?

There are two main components inside a CD player that help read a CD: a tiny laser beam (known as a semiconductor diode laser) and an electronic light detector (basically, a tiny photoelectric cell). When you switch on the CD player, an electric motor inside the player makes the CD rotate at a very high speed (the outer edge rotates at 200 RPM , while the inner edge spins at 500 RPM).

Electromagnetism

by Abhijith.A.D(2016-2019)

https://www.facebook.com/abhijith.vjmd

Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually exhibits electromagnetic fields such as electric fields, magnetic fields and light, and is one of the four fundamental interactions (commonly called forces) in nature. The other three fundamental interactions are the strong interaction, the weak interaction and gravitation.

Lightning is an electrostatic discharge that travels between two charged regions.

The word electromagnetism is a compound form of two Greek terms, ἤλεκτρον ēlektron, “amber“, and μαγνῆτις λίθος magnētis lithos, which means “Μagnesian stone”, a type of iron ore. Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called theLorentz force, which includes both electricity and magnetism as different manifestations of the same phenomenon.

The electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life. Ordinary matter takes its form as a result of intermolecular forces between individual atoms and molecules in matter, and is a manifestation of the electromagnetic force.Electrons are bound by the electromagnetic force to atomic nuclei, and their orbital shapes and their influence on nearby atoms with their electrons is described by quantum mechanics. The electromagnetic force governs the processes involved in chemistry, which arise from interactions between the electrons of neighboring atoms.

There are numerous mathematical descriptions of the electromagnetic field. In classical electrodynamics, electric fields are described as electric potential and electric current. In Faraday’s law, magnetic fields are associated with electromagnetic induction and magnetism, and Maxwell’s equationsdescribe how electric and magnetic fields are generated and altered by each other and by charges and currents.

The theoretical implications of electromagnetism, particularly the establishment of the speed of light based on properties of the “medium” of propagation (permeability and permittivity), led to the development of special relativity by Albert Einstein in 1905.

Although electromagnetism is considered one of the four fundamental forces, at high energy the weak force and electromagnetic force are unified as a single electroweak force. In the history of the universe, during the quark epoch the unified force broke into the two separate forces as the universe cooled.

 

 

Electronics

 

Electronics is the science of controlling electrical energy electrically, in which the electrons have a fundamental role. Electronics deals with electrical circuits that involve active electrical components (such as vacuum tubes, transistors, diodes, integrated circuits, optoelectronics, and sensors), associated passive electrical components, and interconnection technologies. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements; such a circuit is described as an electronic circuit.

The science of electronics is considered to be a branch of physics and electrical engineering.

The nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible. Electronics is widely used in information processing, telecommunication, and signal processing. The ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system.

Electronics is distinct from electrical and electro-mechanical science and technology, which deal with the generation, distribution, switching, storage, and conversion of electrical energy to and from other energy forms using wires, motors, generators, batteries, switches, relays, transformers, resistors, and other passive components. This distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification of weak radio signals and audio signals possible with a non-mechanical device. Until 1950 this field was called “radio technology” because its principal application was the design and theory of radio transmitters, receivers, and vacuum tubes.

Today, most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid-state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering. This article focuses on engineering aspects of electronics.

3D Printing

by Anaswara.J.S.(2016-2019)

anaswarajs@gmail.com

3 D Printing  is an additive manufacturing process that creates a physical object from a digital design.

Principle:

a digital model is turned into a solid three-dimensional physical object by adding material layer by layer.

How does 3D printing work?

Every 3D print starts as a digital 3D design file – like a blueprint – for a physical object. Trying to print without a design file is like trying to print a document on a sheet of paper without a text file. This design file is sliced into thin layers which is then sent to the 3D printer.
From here on the printing process varies by technology , starting from desktop printers that melt a plastic material and lay it down onto a print platform to large industrial machines that use a laser to selectively melt metal powder at high temperatures. The printing can take hours to complete depending on the size, and the printed objects are often post-processed to reach the desired finish.
Available materials also vary by printer type, ranging from plastics to rubber, sandstone, metals and alloys – with more and more materials appearing on the market every year.

History of 3D Printing

Although 3D printing is commonly thought of as a new ‘futuristic’ concept, it has actually been around for more than 30 years.

SLA-1 is the first 3D printer invented by Chuck Hull in 1983

Chuck Hull invented the first 3D printing process called ‘stereolithography’ in 1983. In a patent, he defined stereolithography as ‘a method and apparatus for making solid objects by successively “printing” thin layers of the ultraviolet curable material one on top of the other’. This patent only focuses on ‘printing’ with a light curable liquid, but after Hull founded the company ‘3D Systems’, he soon realized his technique was not limited to only liquids, expanding the definition to ‘any material capable of solidification or capable of altering its physical state’. With this, he built the foundation of what we now know today as additive manufacturing (AM) – or 3D printing.

3D printing  -today

Until 2009 3D printing was mostly limited to industrial uses, but then the patent for fused deposition modeling (FDM) – one of the most common 3D printing technologies – expired.
Through the RepRap project’s mission to build a self-replicating machine, the first desktop 3D printer was born. As more and more manufacturers followed, what once cost $200,000 suddenly became available for below $2000, and the consumer 3D printing market took off in 2009.

3D printer sales have been growing ever since, and as additive manufacturing patents continue to expire. More innovations can be expected in the years to come. There are now roughly 300,000 consumer 3D printers in the world – and this figure is doubling every year.
Carbon 3D , one of the fastest 3D printing technologies is currently under development

                                                             

• Traditional manufacturing works by taking a material such as metal, glass or plastic and reducing and manipulating it into a solid object. This requires expensive tools and can be a very wasteful process, as often much of the original raw material is thrown away during the manufacture of the product.
• Additive manufacturing. Three dimensional objects are created from a digital file, so there is no waste.
• Ability to produce customised goods quickly and relatively cheaply. Customisation is increasingly important, as consumers and businesses want to personalise and set their products and goods apart. In an industrial environment, components may need to be marked with instructions, or codes to differentiate parts.
• 3D printing puts the power in the hands of the creator and that means that it is easier to generate customised products. The same build chamber can be used to produce multiple products that are identical apart from their customised components without adding the processing costs associated with more traditional techniques.
• Because the product is created direct from the printer, both labour time and therefore costs can be dramatically reduced. This is important in a competitive environment where products have to be delivered to tight time schedules and budgets.
• Traditional mass production techniques involve stockpiling components and parts, which can be expensive to produce, ship and house.
• Employing people to manage these processes can be expensive and finding warehouse space to hold goods and transporting them is costly, not to mention damaging to the environment.
• With 3D printing, manufacturers can follow the principals of lean manufacturing by cutting out waste generated by transportation, inventory, motion, waiting, over-processing, over-production and defects
• ECO FRIENDLY

• The first and most obvious one is the fact that as a technology it is still very much in its infancy. In time, it may well address limitations such as the type of material that can be produced in a 3D environment, or it may be that it sits alongside other manufacturing techniques.
• Print speed is another potential limitation and one that could be improved over time, but means that the process is not as timely as it might be. Other computer-based manufacturing techniques may sometimes be preferable if time is a vital factor.
•  They are not always easy to master, and in-depth training is often required to manage these complex machines.
• This can of course be costly to manufacturers and these costs may end up being absorbed by the consumer.

Because objects can be produced without tools, there is also the possibility that operators will produce too many components without considering the waste.

 The Future of 3-D Printing

3-D printing is moving in several directions at this time and all indications are that it will continue to expand in many areas in the future. Some of the most promising areas include medical applications, custom parts replacement, and customized consumer products. As materials improve and costs go down, other applications we can barely imagine today will become possible.